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Aircraft Measurements of Nitrogen and Phosphorus in and around the Lake Tahoe Basin: Implications for Possible Sources of Atmospheric Pollutants to Lake Tahoe
Abstract
Atmospheric deposition of nitrogen (N) and phosphorus (P) into Lake Tahoe appears to have been a major factor responsible for the shifting of the lake's nutrient response from N-limited to P-limited. To characterize atmospheric N and P in and around the Lake Tahoe Basin during summer, samples were collected using an instrumented aircraft flown over three locations: the Sierra Nevada foothills east of Sacramento ("low-Sierra"), further east and higher in the Sierra ("mid-Sierra"), and in the Tahoe Basin. Measurements were also made within the smoke plume downwind of an intense forest fire just outside the Tahoe Basin. Samples were collected using a denuder-filter pack sampling system (DFP) and analyzed for gaseous and water-soluble particle components including HNO3/ NO3-, NH3 /NH4+, organic N (ON), total N, SRP (soluble reactive phosphate) and total P. The average total gaseous and particulate N concentrations (+/- 1sigma) measured over the low- and mid-Sierra were 660 (+/- 270) and 630 (+/- 350) nmol N/m3-air, respectively. Total airborne N concentrations in the Tahoe samples were one-half to one-fifth of these values. The forest fire plume had the highest concentration of atmospheric N (860 nmol N/m3-air) and a greater contribution of organic N (ON) to the total N compared to nonsmoky conditions. Airborne P was rarely observed over the low- and mid-Sierra but was present at low concentrations over Lake Tahoe, with average +/- 1sigma) concentrations of 2.3 +/- 2.9 and 2.8 +/- 0.8 nmol P/m3-air under typical clear air and slightly smoky air conditions, respectively. Phosphorus in the forestfire plume was present at concentrations approximately 10 times greater than over the Tahoe Basin. P in these samples included both fine and coarse particulate phosphate as well as unidentified, possibly organic, gaseous P species. Overall, our results suggest that out-of-basin emissions could be significant sources of nitrogen to Lake Tahoe during the summer and that forest fires could be important sources of both N and P.
... In addition, due to high filter blank levels of phosphorus and potassium throughout the sampling campaign, these elements are not reported for either the aircraft or boat samples. (During a previous, shorter campaign in the summer of 2001 we found that P levels were typically 2 -3 nmol P m -3 above the lake, as described in Zhang et al., 2002.) Sampling was conducted under different meteorological conditions, allowing some insight into which conditions lead to high atmospheric concentrations of measured pollutants in the Tahoe Basin. ...
... This Oregon fire, which burned from 13 July to 09 November and was contained on 05 September, burned approximately 500,000 acres of forest in southwest Oregon. Our previous results (Zhang et al., 2002) suggested that organic nitrogen can be a tracer for aged forest fire emissions. These past results are consistent with this 2002 episode, especially on the second day, where it appears that emissions from the Biscuit fire contributed to N concentrations in the air above Lake Tahoe. ...
... Values < LOD were considered to be zero in the calculation of WSIN and TN Max WD error (deg) FIGURE 11. Average total gaseous and particulate nitrogen (TN g+p ) concentrations (± 1σ) and speciation for the 2002 sampling campaign (left pie) and during a smaller campaign during the summer of 2001 (right pie; Zhang et al., 2002). The 2002 TN average and speciation include only those DFP samples with both gaseous and particulate data (i.e., they do not include samples collected from July 17 -September 5, which had no particulate data). ...
... The eutrophication of Sierra Nevada lakes due to the atmospheric input of nutrients has been noted in several studies, the majority of the ecosystem effects having been attributed to nitrogen deposition (Jassby et al., 1994;Schuster and Grismer, 2004). However, there is some evidence that atmospheric inputs of P may also be driving long-term ecological changes in lakes of this region (Jassby et al., 1994;Zhang et al., 2002). In a 18year study of Emerald Lake, Sickman et al. (2003) observed a two-to three-fold increase in algal biomass and a shift from P limitation toward more frequent N limitation of phytoplankton abundance. ...
... Atmospheric TP concentrations during the study ranged from 11 to 75 ng m À3 (mean ¼ 37 AE 16 ng m À3 ), as shown in Fig. 2. Such values are nearly an order of magnitude higher than those observed in other locations in the Sierra Nevada (Mahowald et al., 2008), although they are similar to measurements made in the heavily urbanized Lake Tahoe basin (Zhang et al., 2002). TP maxima generally coincided with peaks in coarse PM concentration and the correlation between the two variables was statistically significant (r 2 ¼ 0.83, p < 0.001), suggesting that TP dynamics at Lower Kaweah are driven primarily by variability in the atmospheric burden of particles with aerodynamic diameters >1 mm, an observation in agreement with previous studies (Mahowald et al., 2008). ...
... Our observations during the Hidden Fire seem to be in disagreement with Zhang et al. (2002) who reported P values of up to 800 ng m À3 for samples collected from an aircraft 35 km downwind of an intense forest fire plume in the northern Sierra Nevada. They assert that forest fire emissions were rich in OP, particularly in aerosol particles larger than 3.2 mm, (which contributed 40% of atmospheric P in the forest fire samples), but also due to contributions from an unidentified volatile organophosphorus compound, which accounted for over 20% of the total P. ...
The dry deposition of atmospheric particulate matter can be a significant source of phosphorus (P) to oligotrophic aquatic ecosystems, including high-elevation lakes. In this study, measurements of the mass concentration and size distribution of aerosol particles and associated particulate P are reported for the southern Sierra Nevada, California, for the period July–October, 2008. Coarse and fine particle samples were collected with Stacked Filter Units and analyzed for Total P (TP) and inorganic P (IP) using a digestion-extraction procedure, with organic P (OP) calculated by difference. Particle size-resolved mass and TP distributions were determined concurrently using a MOUDI cascade impactor. Aerosol mass concentrations were significantly elevated at the study site, primarily due to transport from offsite and emissions from local and regional wildfires. Atmospheric TP concentrations ranged from 11 to 75 ng m−3 (mean = 37 ± 16 ng m−3), and were typically dominated by IP. Phosphorus was concentrated in the coarse (>1 μm diameter) particle fraction and was particularly enriched in the 1.0–3.2 μm size range, which accounted for 30–60% of the atmospheric TP load. Wildfire emissions varied widely in P content, and may be related to fire intensity. The estimated dry depositional flux of TP for each daily sampling period ranged between 7 and 118 μg m−2 d−1, with a mean value of 40 ± 27 μg m−2 d−1. Relative rates of dry deposition of N and P in the Sierra Nevada are consistent with increasing incidence of N limitation of phytoplankton growth and previously observed long-term eutrophication of lakes.
... Specifically, atmospheric deposition has been suggested as an important source of nutrients that support phytoplankton growth and affect water quality ( Brahney et al., 2014;Morales-Baquero et al., 2006). Accordingly, several studies including the Lake Tahoe Atmospheric Deposition Study (LTADS) by the California Air Resources Board (CARB) have been conducted to monitor gases (Tarnay, 2005;Zhang et al., 2002), atmospheric particulate matter (Gertler et al., 2006a;Sahoo et al., 2013;Zhang et al., 2002) and wet deposition ( Jassby et al., 1994) at representative sites throughout the Lake Basin. These along with other studies provided important information on total particle deposition ( Dolislager et al., 2012;Sahoo et al., 2013;VanCuren et al., 2012) and specifically on N ( Jassby et al., 1994;Tarnay et al., 2001) and phosphorus (P) inputs Jassby et al., 1994) and the distribution of these constituents within atmospheric ...
... Specifically, atmospheric deposition has been suggested as an important source of nutrients that support phytoplankton growth and affect water quality ( Brahney et al., 2014;Morales-Baquero et al., 2006). Accordingly, several studies including the Lake Tahoe Atmospheric Deposition Study (LTADS) by the California Air Resources Board (CARB) have been conducted to monitor gases (Tarnay, 2005;Zhang et al., 2002), atmospheric particulate matter (Gertler et al., 2006a;Sahoo et al., 2013;Zhang et al., 2002) and wet deposition ( Jassby et al., 1994) at representative sites throughout the Lake Basin. These along with other studies provided important information on total particle deposition ( Dolislager et al., 2012;Sahoo et al., 2013;VanCuren et al., 2012) and specifically on N ( Jassby et al., 1994;Tarnay et al., 2001) and phosphorus (P) inputs Jassby et al., 1994) and the distribution of these constituents within atmospheric ...
Atmospheric deposition can be an important source of nutrients and trace metals to oligotrophic alpine lakes, affecting their biogeochemistry. We measured trace metal concentrations and lead (Pb) isotope ratios in lake water, river water, ground water, and aerosol total suspended particles (TSP), as well as nutrient (NO 3⁻ , NH 4⁺ , PO 4³⁻ ) concentrations in TSP in the Tahoe Basin. The contribution of TSP deposition to the lake trace metal budget was assessed. Our results show seasonality in TSP and associated trace metal concentrations with higher concentrations during Oct – April. However, trace metal solubilities are higher during May – Sept, resulting in a higher contribution of soluble trace metals to the lake water. The source of most of the trace metals in TSP in the Lake Tahoe Basin is mineral dust; however, Zn, Cu, and Cd also have an anthropogenic origin. Among major nutrients, NO 3⁻ concentrations are slightly higher during Oct – April, while NH 4⁺ and soluble reactive phosphorus (SRP) are higher during May – Sept. The distributions of trace metal concentrations and Pb isotopic ratios are homogenous throughout the lake water column, suggesting that the residence time of the trace metals in the lake is longer than the lake water mixing time. The contribution of atmospheric TSP deposition to the upper 20 m of lake water trace metal inventory is low, ranging from 0.03% for V to 5.7% for Mn. A triple-isotopes plot of Pb indicates that riverine and groundwater inputs are the major Pb sources, but aerosols still contribute some Pb to the lake. This article is part of a special issue entitled: Conway GEOTRACES - edited by Tim M. Conway, Tristan Horner, Yves Plancherel, and Aridane G. González.
... As discussed in Burley et al. (2015), several studies have investigated the transport of ozone and ozone precursors in the Lake Tahoe Basin from upwind source regions using aircraft (Carroll and Dixon 2002;Zhang et al. 2002), and spatial and temporal ozone distributions (Bytnerowicz et al. 2004). These efforts have concluded that the Sierra Nevada mountains act as a barrier to prevent pollutants from entering the Lake Tahoe Basin. ...
... As discussed in Burley et al. (2015), several studies have investigated the transport of ozone and ozone precursors in the Lake Tahoe Basin from upwind source regions using aircraft (Carroll and Dixon 2002;Zhang et al. 2002), and spatial and temporal ozone distributions (Bytnerowicz et al. 2004). These efforts have concluded that the Sierra Nevada mountains act as a barrier to prevent pollutants from entering the Lake Tahoe Basin. ...
The Lake Tahoe Basin is located on the California-Nevada border and occasionally experiences elevated levels of ozone (O3) exceeding the California Air Resources Board ambient air quality standard (8-h average). Previous studies indicate that both the local generation and long-range transport from out-of-basin sources are important in contributing to O3 exceedances, but little is known about the impact of regional meteorology on O3 source regions. To develop a better understanding of the factors affecting O3 levels and sources in the Lake Tahoe Basin, a comprehensive field study was performed in the summer of 2010. Included in this effort was a meteorological analysis addressing potential regional meteorological influences leading to periods of elevated levels of O3. Three approaches were used to conduct the analysis: (1) regional atmospheric pressure difference (i.e., the Washoe Zephyr) to access potential transport, (2) back trajectory modeling using the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model to determine where the air masses originated and, (3) composite soundings to evaluate in-Basin atmospheric influences. These analyses indicate the Washoe Zephyr did not strongly impact O3 levels; however, higher O3 levels were found to correspond with both a more southerly wind component and a dip in dew point temperature around 400 hPa. The results also indicate that if transport does occur, it is more likely to come from the San Joaquin Valley and move to the southern part of the Basin, rather than originating in the large cities to the west (i.e., Sacramento and San Francisco).
... Molecular or functional group analysis allows for particular components to be investigated, but there remains a concern that this approach is not a representative sampling of the organic matter present in the bulk samples, and given the diversity of possible compounds to analyse in this approach, there are few comparable studies of any given compound group. In general, analysis of specific compounds in rain or aerosol has only been able to account for a small proportion of the total organic N (Shi et al., 2010;Zhang et al., 2002a). Bulk analysis gives the total concentration of the rain or aerosol organic N, so it can only give insights into the 'collective behaviour' of the organic matter. ...
... Seasonal patterns in the concentrations of organic N, or components of organic N, in particulates may show interesting differences from those of WSON in precipitation. However, concentrations are subject to variations caused by seasonal changes in the depth of the boundary layer (lower in winter (Zhang et al., 2002a)), so should be interpreted with care. Over the ocean, amines showed a peak in late summer (cf. ...
This review considers the ways in which atmospheric organic nitrogen has been measured and linked to potential sources. Organic N exists in gas, particle and dissolved phases and represents a large (ca. 30%) fraction of total airborne nitrogen, but with large variability in time and space. Although some components (e.g. amines) have been the subject of several studies, little information is available for the many other components of organic N that have been identified in individual measurements. Measurements of organic N in precipitation have been made for many decades, but both sampling and chemical analytical methods have changed, resulting in data that are not directly comparable. Nevertheless, it is clear that organic N is ubiquitous and chemically complex. We discuss some of the issues which have inhibited the widespread adoption of organic N as a routine analyte in atmospheric sampling, and identify current best practice. Correlation analysis is the most widely used technique for attributing likely sources, examining the co-variation in time and/or space of organic N with other components of precipitation or particulate matter, yet the shortcomings of such simple approaches are rarely recognised. Novel measurement techniques which can identify, if not yet quantify, many of the components of particulate or dissolved organic N greatly enhance the data richness, thereby permitting powerful statistical analyses of co-variation such as factor analysis, to be employed. However, these techniques also have their limitations, and whilst specific questions about the origin and fate of particular components of atmospheric organic N may now be addressed, attempts to quantify and attribute the whole suite of materials that comprise atmospheric organic N to their sources is still a distant goal. Recommendations are made as to the steps that need to be taken if a consistent and systematic approach in identifying and quantifying atmospheric organic N is to progress. Only once sources have been recognised can any necessary control measures to mitigate adverse effects of atmospheric organic N on human health or ecosystem function be determined.
... Additionally, the ash leachate chemistry results reported here differed from the Thomas Fire ash leachate reported by Harper et al. [22] which leached higher amounts of nitrate (3.7 versus 1.9 µmol g (ash) −1 ), phosphate (0.1 versus 0.01 µmol g (ash) −1 ) and iron (0.01 versus 0.0003 µmol g (ash) −1 ) compared with our results but was still nitrogen-rich relative to phosphorus, although not compared with iron (although nitrite concentrations were not measured) [22]. The lack of phosphate and organic phosphorus leached from Thomas Fire ash was surprising given that wildfires have been shown to increase concentrations of atmospheric phosphorus [36] and dissolved phosphorus in fire impacted watersheds [12,37]. Although ash may contain significant quantities of phosphorus containing compounds, phosphorus in wildfire ash has low aqueous solubility [34,[38][39][40] and the solubility of phosphorus is lower in seawater compared with freshwater [41,42]. ...
In December 2017, one of the largest wildfires in California history, the Thomas Fire, created a large smoke and ash plume that extended over the northeastern Pacific Ocean. Here, we explore the impact of Thomas Fire ash deposition on seawater chemistry and the growth and composition of natural microbial communities. Experiments conducted in coastal California waters during the Thomas Fire revealed that leaching of ash in seawater resulted in significant additions of dissolved nutrients including inorganic nitrogen (nitrate, nitrite and ammonium), silicic acid, metals (iron, nickel, cobalt and copper), organic nitrogen and organic carbon. After exposure to ash leachate at high (0.25 g ash l⁻¹) and low (0.08 g ash l⁻¹) concentrations for 4 days, natural microbial communities had 59–154% higher particulate organic carbon concentrations than communities without ash leachate additions. Additionally, a diverse assemblage of eukaryotic microbes (protists) responded to the ash leachate with taxa from 11 different taxonomic divisions increasing in relative abundance compared with control treatments. Our results suggest that large fire events can be important atmospheric sources of nutrients (particularly nitrogen) to coastal marine systems, where, through leaching of various nutrients, ash may act as a ‘food for all’ in protist communities.
... These included many of the conceptual model end points, such as increases in smoke and aerosols, 37−42 particulates, 43−46 nitrogen (N), sulfur (S) and carbon oxides, 39,47−52 ozone, 15,53,54 VOCs, 55−59 metals, 39,60−64 and other inorganic compounds. 38,39,45,62,65,66 These same studies highlighted the range of monitoring tools and modeling efforts employed to detect, characterize, and quantify atmospheric pollutant loads from wildfire. Thus, information about the types and loads of pollutants is generally not a limitation on insights into downwind exposures. ...
Wildfires have increased in frequency and area burned, trends expected to continue with climate change. Among other effects, fires release pollutants into the atmosphere, representing a risk to human health and downwind terrestrial and aquatic ecosystems. While human health risks are well studied, the ecological impacts to downwind ecosystems are not, and this gap may present a constraint on developing an adequate assessment of the ecological risks associated with downwind wildfire exposure. Here, we first screened the scientific literature to assess general knowledge about pathways and end points of a conceptual model linking wildfire generated pollutants and other materials to downwind ecosystems. We found a substantial body of literature on the composition of wildfire derived pollution and materials in the atmosphere and subsequent transport, yet little observational or experimental work on their effects on downwind ecological end points. This dearth of information raises many questions related to adequately assessing the ecological risk of downwind exposure, especially given increasing wildfire trends. To guide future research, we pose eight questions within the well-established US EPA ecological risk assessment paradigm that if answered would greatly improve ecological risk assessment and, ultimately, management strategies needed to reduce potential wildfire impacts.
... The largest increases in TP concentrations were found in the coarse mode at 3.3-4.7 and 7.0-11 μm, with 31% and 32% increases, respectively, and the increases in TP at other particle size classes ranged from 11% to 18%. It has been reported that biomass burning emission particles can not only emit fine particles directly into the atmosphere, but they can also increase surface exposure, thus causing soil dust to be more easily blown into the atmosphere (Echalar et al., 1995;Zhang et al., 2003). Therefore, the significant increase in TP over the coarse mode during biomass burning events may be simultaneously contributed by biomass burning emission particles and soil dust. ...
Atmospheric deposition is an important source for the P biological cycle, especially for P‐limited ecosystems. In the present study, 48 hr size‐segregated aerosol samples were collected at an urban site in Shanghai for one year from May 2019 to June 2020. Total phosphorus (TP) presented a bimodal distribution in four seasons, which was mainly contributed by mineral dust in the coarse mode, and was related to anthropogenic and combustion emissions in the fine mode. Dissolved inorganic phosphorus (DIP) and dissolved organic phosphorus (DOP) presented a bimodal distribution in spring and summer, and a unimodal distribution dominated by a fine mode in autumn and winter. Size distributions and correlation analysis showed that DIP in the fine and coarse modes originated from the acid processing of SO42‐ and NO3⁻, respectively, while DOP was mainly from biomass burning emissions. Positive Matrix Factor analysis showed that phosphorus (P) in atmospheric aerosols in Shanghai was mainly contributed by four sources, including crustal sources, sea‐salt, industry emissions and fossil fuel combustion, and biomass burning. Industry emissions and fossil fuel combustion, as well as biomass burning were important sources of TP in all particle sizes (50%–65%). Biomass burning was the most important source of DOP (>50%). The total deposition flux of total dissolved phosphorus (TDP) calculated based on the size‐weighted deposition velocity model averaged 75.2 ± 17.4 μg/m²/d. Assuming that all of TDP is bioavailable, TDP deposition can create a primary production of 8.0 mg C/m²/d, which can support 1.3%–4.4% of the new production in the East China Sea.
... Our empirical evidence of the responsiveness of phytoplankton to P suggests that they can serve as indicators of increasing deposition of P, which is of growing concern because of recent large wildfires that emit aeolian particles containing P (Zhang et al. 2002;Brahney et al. 2015;Wang et al. 2015). The primacy of P limitation in phytoplankton production has also been reported for lakes across Europe (Burpee et al. 2022), including those located in the Tatra Mountains (Kopáček et al. 2000) and parts of the French Alps (Jacquemin et al. 2018). ...
Remote mountain lakes in protected areas are sentinels of the ecological impacts of extreme and novel environmental changes occurring at broad regional scales. Ecosystem responses to such stressors are often first detected as shifts in community composition. We surveyed phytoplankton communities across 82 mountain lakes to test the hypothesis that taxonomic composition is indicative of more environmental changes than are aggregate properties, such as total biomass. Phosphorus was the only significant predictor of chlorophyll-inferred algal biomass, a correlative finding supported by evidence from our nutrient amendment bioassays. Interlake variances in taxonomically diagnostic algal pigments and 78 genera were indicative of changes in total phosphorus, glacial coverage, underwater light availability, and dissolved organic carbon. Lack of concordance was observed between ordinations of pigment- and genus-based data as environmental variables captured more variance in the pigment data. Our findings provide a baseline for future lake monitoring programs in the Canadian Rockies as they increasingly experience interactive effects involving climate change and landscape features, such as variation in turbid glacial meltwaters and aeolian phosphorus deposition from wildfires.
... In addition, BC can combine with nitrogenous compounds during combustion (Cornelissen et al., 2005), which can then be utilized by phytoplankton and algae and increase primary productivity (Paerl et al., 2002). For example, in Lake Tahoe, lacustrine productivity increased immediately after forest fires because the input of P complexed with BC triggered the change (Jaworski et al., 1997;Zhang et al., 2002). Bisiaux et al. (2011) indicated that refractory BC added into Lake Tahoe was rapidly degraded; the unexpected rapid turn-over prevented a build-up in lake sediments. ...
Lake Victoria, a lifeline for millions of people in East Africa, is affected by anthropogenic activities resulting in eutrophication and impacting the aquatic life and water quality. Therefore, understanding the ongoing changes in the catchment is critical for its restoration. In this context, catchment and lake sediments are important archives in tracing nutrient inputs and their dominant sources to establish causality with human activities and productivity shifts. In this study, we determine the 1) changes in concentrations of total organic carbon (TOC), black carbon (BC), total nitrogen (TN), C/N ratio, and phosphorous (P) fractions in catchment sediments and the open lake, 2) distribution of diatom population in the lake, and 3) land use and land cover changes in the catchment. The distribution of TOC, BC, TN, C/N, and P correlate while showing spatial and temporal variations. In particular, the steady increase in BC confirms atmospheric inputs from anthropogenic activities in the catchment. However, lake sediments show more variations than catchment-derived sediments in geochemical trends. Notably, the catchment has undergone dramatic land use changes since the 1960s (post-independence). This change is most evident in satellite records from 1985 to 2014, which indicate accelerated human activities. For example, urban growth (666-1022%) and agricultural expansion (23-48%) increased sharply at the expense of a decline in forest cover, grassland, and woodlands in the catchment. Cities like Kisumu and Homa Bay expanded, coinciding with rapid population growth and urbanization. Consequently, nutrient inputs have increased since the 1960s, and this change corresponds with the divergence of diatom communities in the lake. In addition, the transition to Nitzschia and cyanobacteria mark increasing cultural eutrophication in the lake. The geochemical trends and statistical data support our inference(s) and provide insights into urban development and agriculture practices, which propelled increased nutrients from the catchment and productivity shifts in the lake.
... In addition, BC can combine with nitrogenous compounds during combustion (Cornelissen et al., 2005), which can then be utilized by phytoplankton and algae and increase primary productivity (Paerl et al., 2002). For example, in Lake Tahoe, lacustrine productivity increased immediately after forest fires because the input of P complexed with BC triggered the change (Jaworski et al., 1997;Zhang et al., 2002). Bisiaux et al. (2011) indicated that refractory BC added into Lake Tahoe was rapidly degraded; the unexpected rapid turn-over prevented a build-up in lake sediments. ...
... In addition to N and S, fires are also a source of atmospheric phosphorous (P) (Zhang et al 2002, Mahowald et al 2005, Sundarambal et al 2010, Vicars et al 2010, Barkley et al 2019. Recent work suggests that P concentrations are increasing at remote monitoring sites across the country, and that atmospheric sources may contribute to this trend (Stoddard et al 2016). ...
Ecosystems require access to key nutrients like nitrogen (N) and sulfur (S) to sustain growth and healthy function. However, excessive deposition can also damage ecosystems through nutrient imbalances, leading to changes in productivity and shifts in ecosystem structure. While wildland fires are a known source of atmospheric N and S, little has been done to examine the implications of wildland fire deposition for vulnerable ecosystems. We combine wildland fire emission estimates, atmospheric chemistry modeling, and forest inventory data to (a) quantify the contribution of wildland fire emissions to N and S deposition across the U S, and (b) assess the subsequent impacts on tree growth and survival rates in areas where impacts are likely meaningful based on the relative contribution of fire to total deposition. We estimate that wildland fires contributed 0.2 kg N ha-1 yr-1 and 0.04 kg S ha-1 yr-1 on average across the U S during 2008-2012, with maxima up to 1.4 kg N ha-1 yr-1 and 0.6 kg S ha-1 yr-1 in the Northwest representing over ~30% of total deposition in some areas. Based on these fluxes, exceedances of S critical loads as a result of wildland fires are minimal, but exceedances for N may affect the survival and growth rates of 16 tree species across 4.2 million hectares, with the most concentrated impacts occurring in Oregon, northern California, and Idaho. Understanding the broader environmental impacts of wildland fires in the U S will inform future decision making related to both fire management and ecosystem services conservation.
... Burning sulfur-containing fuels and the production of NOx in internal combustion engines can produce sulfuric and nitric acids, respectively, after interactions with other oxidizers (such as ozone) and water in the environment. Wind-blown fertilizers containing nitrate, ammonia, and phosphorus have been shown to be carried for miles from croplands to high elevation where they deposit on trees, grass and rocks, or fall in rain and snow , Zhang et al. 2002, Vicars et al. 2010. For several decades, the concentrations of nutrients and alkalinity have been measured in samples collected from streams and lakes in Sequoia and Kings Canyon National Parks. ...
Assessment of 50 years of water quality data from research studies in Sequoia and Kings National Parks.
https://irma.nps.gov/DataStore/DownloadFile/474499
... Nevertheless, existing related studies suggested that P emitted from biomass burning generally in the form of organic P (OP). Zhang et al. (2002) performed a measurement within the smoke plume downwind of an intense forest fire in the northern Sierra Nevada and observed that OP dominated in the forest fire plume, accounting for~60% of the total P. In the meanwhile, they pointed that an unidentified volatile organophosphorus compound accounted for over 20% of the total P. Vicars et al. (2010) also observed maximum concentration of coarse and fine OP in the southern Sierra due to the transport of wildfire emissions from northern California; however, in the same study, they observed that only modest OP increases during a local wildfire of hidden fire. ...
Atmospheric deposition is considered as an important source of phosphorus (P) to P‐limited ecosystems. The PM2.5 samples were collected from a high alpine P‐limited forest of Gongga Mountain (Mt. Gongga), eastern Tibetan Plateau from May 2015 to May 2016. Total P (TP) exhibited a higher concentration in the dry season (November to April, 96 ± 30 ng/m³) than that in the wet season (May to October, 77 ± 21 ng/m³). Source apportionment exhibited that 22% and 44% of TP in the dry season were contributed by soil dust and biomass burning, respectively. During the wet season, soil dust, biomass burning, and anthropogenic sources were estimated to contribute to 19%, 26%, and 41% of TP, respectively. Dissolved organic P (DOP) was found to be the significant fraction of total dissolved P (TDP), accounting for 65% and 53% of TDP in the dry and wet season, respectively. The significant correlations between DOP and KBB⁺ suggested that the soluble P originating from biomass burning was possible mainly in the form of DOP. In addition, the acidification of apatite during the transport could explain the dissolved inorganic P level in the wet season. Supposing that all the soluble P was bioavailable, the atmospheric deposition of TDP was estimated to result in a fixation of 0.1394 kg C/m²/yr, accounting for 23% of net primary productivity in a forest of Mt. Gongga. The data showed herein highlighted the importance of atmospheric dry deposition of P to the long‐term fertility of high‐elevation soils.
... Dry deposition of P from aeolian dust has altered nutrient limitation of alpine phytoplankton in the Sierra Nevada Mountains of California and in the Spanish Pyrenees (Camarero and Catalan 2012). Further, P can be deposited as ash as a by-product of fires (Zhang et al. 2002;Brahney et al. 2015), which are predicted to increase in the number of active burning days (Wang et al. 2015). A greater than 50% increase in the number of fire spread days is predicted over the next century in Western Canada (Wang et al. 2017). ...
Deposition of nutrients over mountainous regions in many parts of the world is increasing due to human activities. To assess the level of agreement between chemically-inferred and experimental evidence of the potential sensitivity of alpine lake ecosystems along the Eastern Front range of the Canadian Rockies to increased deposition of nitrogen (N) and phosphorus (P), nutrient limitation was investigated in 29 sites using water chemistry and nutrient amendment bioassays of phytoplankton. The two lines of evidence agreed in 55% of all cases with discrepancies mainly involving instances of co-limitation. Dissolved inorganic N:total P (DIN:TP) mass ratios frequently suggested P limitation while the corresponding bioassays supported meta-analytical evidence of the prevalence of co-limitation of freshwater primary producers. Based on previous evidence of low DIN:TP mass ratios and experimental N amendments stimulating algal communities in shallower alpine sites, we hypothesized that nutrient limitation of phytoplankton shifts from being P- to N-driven with decreasing lake depth. However, we found little evidence of N limitation from bioassays of phytoplankton from the shallower (< 2-m deep) lakes. Most phytoplankton were co-limited by P plus N amendments (42%), while 38% responded to only P, 10% to only N, and 10% to neither nutrient. Overall, DIN:TP mass ratios and bioassay results showed that chromophytes and chlorophytes drove the greater responsiveness of whole communities to P relative to N. Since the short-term bioassay experiments often demonstrated the alpine phytoplankton to be NP-co-limited, our findings highlight a need for further research into potential synergistic fertilizing effects of anthropogenic N emissions and P deposition from forest fires on lake ecosystems at high elevations.
... Forest fires, which have long been a natural part of the prairie and boreal forest landscape, result in substantial nutrient deposition in regional lakes. This effect is most well-studied in nitrogen cycling, though there is evidence that it also causes an increase in phosphorus deposition that can, alongside the nitrogen, lead to a boost in microbial growth [73][74][75]. If one of the limiting factors for the growth of photosynthetic algae was the availability of nitrogen or phosphorus, then the 2016 Fort McMurray forest fire may result in an increased lake biomass and significantly affect microbial eukaryotic population dynamics going forward. ...
Reclamation of anthropogenically impacted environments is a critical issue worldwide. In the oil sands extraction industry of Alberta, reclamation of mining‐impacted areas, especially areas affected by tailings waste, is an important aspect of the mining life cycle. A reclamation technique currently under study is water‐capping, where tailings are capped by water to create an end‐pit lake (EPL). Base Mine Lake (BML) is the first full‐scale end pit lake in the Alberta oil sands region. In this study, we sequenced eukaryotic 18S rRNA genes recovered from 92 samples of Base Mine Lake water in a comprehensive sampling program covering the ice‐free period of 2015. The 565 operational taxonomic units (OTUs) generated revealed a dynamic and diverse community including abundant Microsporidia, Ciliata and Cercozoa, though 41% of OTUs were not classifiable below the phylum level by comparison to 18S rRNA databases. Phylogenetic analysis of five heterotrophic phyla (Cercozoa, Fungi, Ciliata, Amoebozoa and Excavata) revealed substantial novel diversity, with many clusters of OTUs that were more similar to each other than to any reference sequence. All of these groups are entirely or mostly heterotrophic, as a relatively small number of definitively photosynthetic clades were amplified from the BML samples. This article is protected by copyright. All rights reserved.
... Forest fires, which have long been a natural part of the prairie and boreal forest landscape, result in substantial nutrient deposition in regional lakes. This effect is most well-studied in nitrogen cycling, though there is evidence that it also causes an increase in phosphorus deposition that can, alongside the nitrogen, lead to a boost in microbial growth [73][74][75]. If one of the limiting factors for the growth of photosynthetic algae was the availability of nitrogen or phosphorus, then the 2016 Fort McMurray forest fire may result in an increased lake biomass and significantly affect microbial eukaryotic population dynamics going forward. ...
Hydrocarbon extraction and exploitation is a global, trillion-dollar industry. However, for decades it has also been known that fossil fuel usage is environmentally detrimental; the burning of hydrocarbons results in climate change, and environmental damage during extraction and transport can also occur. Substantial global efforts into mitigating this environmental disruption are underway. The global petroleum industry is moving more and more into exploiting unconventional oil reserves, such as oil sands and shale oil. The Albertan oil sands are one example of unconventional oil reserves; this mixture of sand and heavy bitumen lying under the boreal forest of Northern Alberta represent one of the world’s largest hydrocarbon reserves, but extraction also requires the disturbance of a delicate northern ecosystem. Considerable effort is being made by various stakeholders to mitigate environmental impact and reclaim anthropogenically disturbed environments associated with oil sand extraction. In this review, we discuss the eukaryotic microbial communities associated with the boreal ecosystem and how this is affected by hydrocarbon extraction, with a particular emphasis on the reclamation of tailings ponds, where oil sands extraction waste is stored. Microbial eukaryotes, or protists, are an essential part of every global ecosystem, but our understanding of how they affect reclamation is limited due to our fledgling understanding of these organisms in anthropogenically hydrocarbon-associated environments and the difficulties of studying them. We advocate for an environmental DNA sequencing-based approach to determine the microbial communities of oil sands associated environments, and the importance of studying the heterotrophic components of these environments to gain a full understanding of how these environments operate and thus how they can be integrated with the natural watersheds of the region.
... Few models include atmospheric F&T of P, which is a shortcoming given the emerging opinion that windblown P can contribute to nutrient loading in surface water. [13][14][15][16]73,74 CAMx and CMAQ are regional models that can be applied globally when linked with GEOS-Chem or other global models to provide initial boundary conditions. All models provide nested grid capability, which allows local areas of interest to be treated at a finer level of spatial and temporal resolution than surrounding regions. ...
This paper evaluates the current state of life cycle impact assessment (LCIA) methods used to estimate potential eutrophication impacts in freshwater and marine ecosystems, and presents a critical review of the underlying surface water quality, watershed, marine, and air fate and transport (F&T) models. Using a criteria rubric, the authors assess the potential of each method and model to contribute to further refinements of life cycle assessment’s (LCA’s) eutrophication mechanisms, and nutrient transformation processes, as well as model structure, availability, geographic scope, and spatial and temporal resolution. The authors describe recent advances in LCIA modeling, and provide guidance on the best available sources of fate and exposure factors, with a focus on midpoint indicators. The critical review identifies gaps in LCIA characterization modeling regarding availability and spatial resolution of fate factors in the soil compartment, and identifies strategies to characterize emissions from soil. Additional opportunities are identified to leverage detailed F&T models that strengthen existing approaches to LCIA, or that have the potential to link LCIA modeling more closely with the spatial and temporal realities of effects from eutrophication.
... Likewise, input of P via dry deposition has been suggested in Lakes Victoria, Tanganyika, Tahoe, Erie, and Baikal and the East China Sea [16][17][18]. Studies by Jaworski et al. [19] and Zhang et al. [20] in Lake Tahoe firmly establish the causality and provide better understanding about the relationship between BC and eutrophication. The authors reported that algal blooms increased in the lake immediately after large forest fires. ...
Eutrophication is a major ecological crisis in water bodies. This is mainly driven by anthropogenic activities in the catchment that incorporate various nutrients. Input of nutrients can also be driven by atmospheric deposition, which has a large footprint that goes beyond local point source(s). In particular, black carbon (BC) can be a carrier of various nutrients and increase primary productivity in lakes. We need to monitor the input of BC in large water bodies to fully understand its role in driving primary productivity and change in trophic status.
... Our UK average long-term N burial is 0.7 g m − 2 year − 1 , and N export via DON in runoff will be of the same order (0.5 based on N:C being 41:1, range 0.1 to 0.7 g m −2 year − 1 ). If we assume that N:P for preindustrial atmospheric deposition is 10:1 (rounded average of dust - Lawrence and Neff, 2009;vegetation and litter -Wang et al., 2015; forest fire smoke - Zhang et al., 2002), then based on the long-term mean atmospheric P loading calculated above we can expect 0.38 gN m −2year −1 from atmosphere. This leaves 0.8 g m −2 year −1 to be supplied through biological N fixation, rather lower than has been measured in Alberta peat bogs (Vile et al., 2014;1.7 to 3.4 g m − 2 year − 1 ). ...
In this paper we report new data on peat carbon (C), nitrogen (N) and phosphorus (P) concentrations and accumulation rates for 15 sites in the UK. Concentrations of C, N and P measured in peat from five ombrotrophic blanket mires, spanning 4000-10,000years to present were combined with existing nutrient data from ten Scottish ombrotrophic peat bogs to provide the first UK perspective on millennial scale macronutrient concentrations in ombrotrophic peats. Long-term average C, N and P concentrations (0-1.25m) for the UK are 54.8, 1.56 and 0.039wt%, of similar magnitude to the few published comparable sites worldwide. The uppermost peat (0-0.2m) is enriched in P and N (51.0, 1.86, and 0.070wt%) relative to the deeper peat (0.5-1.25m, 56.3, 1.39, and 0.027wt%). Long-term average (whole core) accumulation rates of C, N and P are 25.3±2.2gCm(-2)year(-)(1) (mean±SE), 0.70±0.09gNm(-2)year(-1) and 0.018±0.004gPm(-2)year(-1), again similar to values reported elsewhere in the world. The two most significant findings are: 1) that a regression model of N concentration on P concentration and mean annual precipitation, based on global meta data for surface peat samples, can explain 54% of variance in N concentration in these UK peat profiles; and 2) budget calculations for the UK peat cores yield an estimate for long-term average N-fixation of 0.8gm(-2)year(-1). Our UK results, and comparison with others sites, corroborate published estimates of N storage in northern boreal peatlands through the Holocene as ranging between 8 and 15Pg N. However, the observed correlation of N% with both mean annual precipitation and P concentration allows a potential bias in global estimates that do not take this into account. The peat sampling data set has been deposited at the NERC Data Centre (Toberman et al., 2016).
... Detection of phosphate in ambient samples is not widely reported in the literature. Measurements have been made in rural areas near Sierra Nevada, CA (Vicars et al., 2010) and Lake Tahoe, NV (Zhang et al., 2002), which have found coarse particle phosphate concen trations as high as 90 ng/m 3 , but measurements near cattle feedlots have shown elevated concentrations (Razote et al., 2006;McGinn et al., 2010) consistent with our measurements at COW. ...
The Desert Southwest Coarse Particulate Matter Study was undertaken to further our understanding of ambient concentrations and the composition of fine and coarse particles in rural, arid environments. Sampling was conducted in Pinal County, Arizona between February 2009 and February 2010. The goals of this study were to: (1) chemically characterize the coarse and fine fraction of the ambient particulate matter in terms of mass, ions, elements, bulk organic and elemental carbon; (2) examine the temporal and spatial variability of particles within the area using a series of three sampling locations and use this information to determine the contribution of local vs. regional sources; (3) collect, re–suspend, and chemically characterize various crustal sources within the area to identify differences which may isolate them (crustal sources) as independent sources, and; (4) use a receptor based modeling approach to identify particle sources and the relative impact of each on ambient PM concentrations. This work reviews the study objectives, design, site descriptions, and measurement techniques relevant to this research effort and presents the general characteristics of PM during the study period. This unique dataset will support efforts to reduce PM10 and PM2.5 concentrations in the area to below the National Ambient Air Quality Standards (NAAQS) for these pollutants.
... Similarly, ANs are calculated to consist of all alkyl and multifunctional nitrates present in the gas or aerosol phase. Inorganic nitrate aerosols were reported to contribute 25% to total measured inorganic nitrate (HNO 3 gas +NO − 3 particulate ) in the mid-Sierras during summer (Zhang, et al., 2002). However, measurements of NH 3 at UC-BFRS during summer 2006 (Fischer and Littlejohn, 2007) show that concentrations are too low and temperatures too high to support NH 4 NO 3 aerosol, providing an indication that any aerosol NO − 3 in the region is non-volatile and would not have been detected as part of our measurements of HNO 3 . ...
We describe observations of atmospheric reactive nitrogen compounds including NO, NO2, total peroxy nitrates, total alkyl nitrates, and HNO3 and their correlation with temperature. The measurements were made at a rural location 1315 m a.s.l. on the western slope of the Sierra Nevada Mountains in California during summer of 2001. The ratio of HNO3 to its source molecule, NO2, and the ratio of HNO3 to all other higher oxides of nitrogen (NOz) both increase with increasing temperature. Analysis of these increases suggests they are due to a steep increase in OH of between a factor of 2 and 3 over the range 18–32°C. Total peroxy nitrates decrease and total alkyl nitrates increase over the same temperature range. The decrease in the total peroxy nitrates is shown to be much less than expected if the rate of thermal decomposition were the sole important factor. This observation is consistent with the increase in OH inferred from the temperature trends in the HNO3/NO2 ratio.
... Similarly, ANs are calculated to consist of all alkyl and multifunctional nitrates present in the gas or aerosol phase. Inorganic nitrate aerosols were reported to contribute 25% to total measured inorganic nitrate (HNO 3 gas +NO − 3 particulate ) in the mid-Sierras during summer (Zhang, et al., 2002). However, measurements of NH 3 at UC-BFRS during summer 2006 (Fischer and Littlejohn, 2007) show that concentrations are too low and temperatures too high to support NH 4 NO 3 aerosol, providing an indication that any aerosol NO − 3 in the region is non-volatile and would not have been detected as part of our measurements of HNO 3 . ...
We describe observations of atmospheric reactive nitrogen compounds
including NO, NO2, total peroxy nitrates, total alkyl
nitrates, and HNO3 and their correlation with temperature.
The measurements were made at a rural location 1315 m a.s.l. on the
western slope of the Sierra Nevada Mountains in California during summer
of 2001. The ratio of HNO3 to its source molecule,
NO2, and the ratio of HNO3 to all other higher
oxides of nitrogen (NOz) both increase with increasing
temperature. Analysis of these increases suggests they are due to a
steep increase in OH of between a factor of 2 and 3 over the range
18-32°C. Total peroxy nitrates decrease and total alkyl nitrates
increase over the same temperature range. The decrease in the total
peroxy nitrates is shown to be much less than expected if the rate of
thermal decomposition were the sole important factor. This observation
is consistent with the increase in OH inferred from the temperature
trends in the HNO3/NO2 ratio.
... PMf phosphate concentrations, as well as PMc phosphate concentrations at the other sampling sites, were below the detection limit of 0.008 µg/m 3 of the ion chromatographic method. Phosphate is not typically observed in ambient samples but has been measured in PMc in rural areas near Sierra Nevada, California (Vicars et al., 2010), and Lake Tahoe, Nevada (Zhang et al., 2002), at concentrations as high as 90 ng/m 3 , much lower than the PMc phosphate levels observed at COW, which routinely exceeded 2 mg/m 3 . Comparison of PMc phosphate (by IC) and phosphorous (P by ICP-MS) at the COW site shown in Figure 6 (P ¼ 1.2 AE 0.2x; R 2 ¼ 0.91), strongly suggests that most measured P is present as water-soluble phosphate, which is more bioavailable and thus has implications to desert fertilization. ...
Unlabelled:
A year-long study was conducted in Pinal County, AZ, to characterize coarse (2.5 - 10 microm aerodynamic diameter, AD) and fine (< 2.5 microm AD) particulate matter (PMc and PMf, respectively) to further understand spatial and temporal variations in ambient PM concentrations and composition in rural, arid environments. Measurements of PMc and PMf mass, ions, elements, and carbon concentrations at one-in-six day resolution were obtained at three sites within the region. Results from the summer of 2009 and specifically the local monsoon period are presented. The summer monsoon season (July - September) and associated rain and/or high wind events, has historically had the largest number of PM10 NAAQS exceedances within a year. Rain events served to clean the atmosphere, decreasing PMc concentrations resulting in a more uniform spatial gradient among the sites. The monsoon period also is characterized by high wind events, increasing PMc mass concentrations, possibly due to increased local wind-driven soil erosion or transport. Two PM10 NAAQS exceedances at the urban monitoring site were explained by high wind events and can likely be excluded from PM10 compliance calculations as exceptional events. At the more rural Cowtown site, PM10 NAAQS exceedances were more frequent, likely due to the impact from local dust sources. PM mass concentrations at the Cowtown site were typically higher than at the Pinal County Housing and Casa Grande sites. Crustal material was equal to 52-63% of the PMc mass concentration on average. High concentrations of phosphate and organic carbon found at the rural Cowtown were associated with local cattle feeding operations. A relatively high correlation between PMc and PMf (R2 = 0.63) indicated that the lower tail of the coarse particle fraction often impacts the fine particle fraction, increasing the PMf concentrations. Therefore, reductions in PMc sources will likely also reduce PMf concentrations, which also are near the value of the 24-hr PM2.5 NAAQS.
Implications:
In the desert southwest, summer monsoons are often associated with above average PM10 (< 10 microm AD) mass concentrations. Competing influences of monsoon rain and wind events showed that rain suppresses ambient concentrations while high wind increase them. In this region, the PMc fraction dominates PM10 and crustal sources contribute 52-63% to local PMc mass concentrations on average. Cattle feedlot emissions are also an important source and a unique chemical signature was identified for this source. Observations suggest monsoon wind events alone cannot explain PM10 NAAQS exceedances, thus requiring these values to remain in compliance calculations rather than being removed as exceptional wind events.
... However, ammonia (NH 3 ) and the reactive nitrogen oxides (NO y =NO+NO 2 +PAN + other peroxy nitrates + alkyl nitrates + nitric acid + N 2 O 5 +. . . ) are significant contributors to N dry deposition, and 15 recent research indicates that surface interactions affect atmospheric concentrations and partitioning of these species. For example, extreme changes in the atmospheric reactive nitrogen budget following biomass burning or rain events have been observed (Zhang et al., 2002;Jaegle et al., 2004;Bertram et al., 2006). Few studies have investigated the magnitude and mechanisms of ecosystem-scale exchange of NO 2 , 20 peroxy nitrates, alkyl nitrates or HNO 3 , likely because of the absence of techniques for measurement of these reactive nitrogen oxide species with both adequate sensitivity and minimal day-to-day maintenance requirements to enable application to ecosystemscale flux measurements. ...
Nitrogen exchange between the atmosphere and biosphere directly influences atmospheric composition. While much is known about mechanisms of NO and N2O emissions, instrumentation for the study of mechanisms contributing to exchange of other major nitrogen species is quite limited. Here we describe the application of a new technique, thermal dissociation-laser induced fluorescence (TD-LIF), to eddy covariance measurements of the fluxes of NO2, total peroxy acyl and peroxy nitrates, total alkyl and multifunctional alkyl nitrates, and nitric acid. The technique offers the potential for investigating mechanisms of exchange of these species at the canopy scale over timescales from days to years. Examples of flux measurements at a ponderosa pine plantation in the mid-elevation Sierra Nevada Mountains in California are reported and used to evaluate instrument performance.
... Similarly, ANs are calculated to consist of all alkyl and multifunctional nitrates present in the gas or aerosol phase. Inorganic nitrate aerosols were reported to contribute 25% to total measured inorganic nitrate (HNO 3 gas +NO − 3 particulate ) in the mid-Sierras during summer (Zhang, et al., 2002). However, measurements of NH 3 at UC-BFRS during summer 2006 (Fischer and Littlejohn, 2007) show that concentrations are too low and temperatures too high to support NH 4 NO 3 aerosol, providing an indication that any aerosol NO − 3 in the region is non-volatile and would not have been detected as part of our measurements of HNO 3 . ...
We describe observations of atmospheric reactive nitrogen compounds including NO, NO2, total peroxy nitrates, total alkyl nitrates, and HNO3 and their correlation with temperature. The measurements were made at a rural location 1315 m a.s.l. on the western slope of the Sierra Nevada Mountains in California during summer of 2001. The ratio of HNO3 to its source molecule, NO2, and the ratio of HNO3 to all other higher oxides of nitrogen (NOz) both increase with increasing temperature. Analysis of these increases suggests they are due to a steep increase in OH of between a factor of 2 and 3 over the range 18-32°C. Total peroxy nitrates decrease and total alkyl nitrates increase over the same temperature range. The decrease in the total peroxy nitrates is shown to be much less than expected if the rate of thermal decomposition were the sole important factor. This observation is consistent with the increase in OH inferred from the temperature trends in the HNO3/NO2 ratio.
... The downward mixing of material transported over the Sierra Nevada to the Tahoe Basin may be limited by the likely presence of a temperature inversion above Lake Tahoe between 3000 and 3400 m MSL (indicated by a heavy dashed line). This inversion is frequently observed (w50% of afternoon observations from 1978 -see Fig. D in on-line Supplemental Material) by aircraft and sondes conducting deep vertical temperature profiles; unfortunately, these measurements are not frequently conducted (Unger, 1979;Zhang et al., 2002). This inversion is likely associated with descending (i.e., warming) air in lee waves east of the crest of the Sierra Nevada (Whiteman, 2000). ...
The Lake Tahoe Atmospheric Deposition Study (LTADS) was conducted by the Air Resources Board of the State of California (CARB) primarily to generate refined estimates of the atmospheric deposition of nitrogen, phosphorous, and particulate matter directly to Lake Tahoe, which straddles the border between the states of California and Nevada near Reno, Nevada. The enhanced air quality monitoring during LTADS also included ozone measurements, which yielded additional insights into atmospheric processes and the role of transport in determining ozone concentrations within the Lake Tahoe Air Basin.
... Elevated levels of reactive nitrogen in both the gaseous and particulate phase have been observed downwind of biomass burning episodes (Zhang et al., 2002). If these burning events occur within a five-hour transit time to the Tahoe Basin, they may be capable of delivering additional nitrogen to the atmosphere above the lake. ...
The Lake Tahoe Atmospheric Deposition Study (LTADS) was conducted by the California Air Resources Board (CARB) primarily to generate refined estimates of the atmospheric deposition of nitrogen (N), phosphorous (P), and particulate matter (PM) directly to Lake Tahoe, which straddles the boundary between the states of California and Nevada in the United States of America. LTADS estimated that approximately 185, 3, and 755 metric tons respectively of N, P, and PM being directly deposited to the lake from the atmosphere. Various measurements of emissions, meteorology, and air quality were made within and west (typically upwind) of the Lake Tahoe Air Basin to better understand the pollutant sources contributing to the atmospheric deposition. The data indicate that ammonia (NH3) contributes the bulk of the N loading. Aerosols with diameters greater than 2.5 μm contribute the bulk of the P and PM mass loadings. The emission sources of P and PM appear to be primarily local and associated with motor vehicles. However, construction, fires, and natural sources also contribute to the pollutant loadings. LTADS was part of a much larger research program to guide efforts to restore the remarkable water clarity of Lake Tahoe.
... While most NH 3 measurements have been made in urban areas in California, some measurements have been made in rural settings. Airborne measurements in the afternoon mixed layer showed that ammonium compounds (i.e., NH 3 + NH 4 + ) were the dominant component of the N budget with variable NH 3 concentrations corresponding to mixing ratios of 10 ± 7 and 2.5 ± 0.5 ppb in boundary layer above the foothills of the Sierra in the boundary layer above Lake Tahoe respectively (Zhang et al. 2002). In contrast, a ground-based study at Lake Tahoe measured significantly lower concentrations corresponding to approximate mixing ratios between 0.6 to 1.5 ppb and mean summer deposition rates between 3 to 11 ng N m -2 s -1 (Tarnay et al. 2001). ...
Ammonia is a reactive trace gas that is emitted in large quantities by animal agriculture and other sources in California, which subsequently forms aerosol particulate matter, potentially affecting visibility, climate, and human health. We performed initial measurements of NH at the Blodgett Forest Research Station (BFRS) during a 3 week study in June, 2006. The site is used for ongoing air quality research and is a relatively low-background site in the foothills of the Sierra Nevada. Measured NH mixing ratios were quite low (< 1 to 2 ppb), contrasting with typical conditions in many parts of the Central Valley. Eddy covariance measurements showed NH fluxes that scaled with measured NH mixing ratio and calculated aerodynamic deposition velocity, suggesting dry deposition is a significant loss mechanism for atmospheric NH at BFRS. A simple model of NH transport to the site supports the hypothesis that NH is transported from the Valley to BFRS, but deposits on vegetation during the summer. Further work is necessary to determine whether the results obtained in this study can be generalized to other seasons.
... [23] Atmospheric TP concentrations during the dry season ranged from 9 to 47 ng m −3 (mean = 24 ± 10 ng m −3 ) and 2 to 28 ng m −3 (mean = 11 ± 6 ng m −3 ) for coarse and fine particles, respectively. Such values are nearly an order of magnitude higher than those observed in other locations of the Sierra Nevada , although they are similar to P measurements made in the Lake Tahoe basin [Zhang et al., 2002], the Mediterranean region [Bergametti et al., 1992;Markaki et al., 2003;Migon et al., 2001] and Brazil [Artaxo et al., 2002;Fuzzi et al., 2007]. Atmospheric P is thought to be associated primarily with mineral dust [Graham and Duce, 1979;Mahowald et al., 2008], particularly at high-elevation sites [Morales-Baquero et al., 2006], and this assertion is generally supported by the observations made in our study. ...
The transport and deposition of aeolian dust represents an important material input pathway for many marine and terrestrial ecosystems and may be an ecologically significant source of exogenous phosphorus (P) to alpine lakes. In order to assess the abundance and elemental composition of atmospheric mineral dust over the Sierra Nevada of California, we collected size-fractionated atmospheric particulate matter (PM) samples during July 2008 to March 2009 at a mixed conifer site located in Sequoia National Park. PM concentrations were at their highest levels during the dry season, averaging 8.8 ± 3.7 and 11.1 ± 7.5 mug m-3 for the coarse (1 mum < Da < 15 mum) and fine (Da < 1 mum) fractions, respectively, while winter months were characterized by low (
... Basin population increases and the establishment of recreational activities have increased fertilizer usage within the basin and increased the potential for leakage from pipes that export sewage from the basin , both potential sources of available nitrogen and phosphorus (Burgy and Knight, 1974;Loeb and Goldman, 1979;Mitchell and Reisenauer, 1974). A large transient tourist population has contributed a significant amount nitrogen oxides, emitted from automobiles, and fixed nitrogen is also likely imported from urban pollution outside the basin (Jassby et al., 1995;Jassby et al., 1994;Tarnay et al., 2001;Tarnay, 2001;Zhang et al., 2002). Deposition studies suggest that a major component of lake nitrogen is derived from direct deposition of this atmospheric nitrogen to the lake surface (Jassby et al., 1994). ...
... However, ammonia (NH 3 ) and the reactive nitrogen oxides (NO y = NO + NO 2 + PAN + other peroxy nitrates + alkyl nitrates + nitric acid + N 2 O 5 + . . . ) are significant contributors to N dry deposition, and recent research indicates that surface interactions affect atmospheric concentrations and partitioning of these species. For example, extreme changes in the atmospheric reactive nitrogen budget following biomass burning or rain events have been observed (Bertram et al., 2005;Jaegle et al., 2004;Zhang et al., 2002). Few studies have investigated the magnitude and mechanisms of ecosystemscale exchange of NO 2 , peroxy nitrates, alkyl nitrates or Published by Copernicus GmbH on behalf of the European Geosciences Union. ...
Nitrogen exchange between the atmosphere and biosphere directly influences atmospheric composition. While much is known about mechanisms of NO and N<sub>2</sub>O emissions, instrumentation for the study of mechanisms contributing to exchange of other major nitrogen species is quite limited. Here we describe the application of a new technique, thermal dissociation-laser induced fluorescence (TD-LIF), to eddy covariance measurements of the fluxes of NO<sub>2</sub>, total peroxy acyl and peroxy nitrates, total alkyl and multifunctional alkyl nitrates, and nitric acid. The technique offers the potential for investigating mechanisms of exchange of these species at the canopy scale over timescales from days to years. Examples of flux measurements at a ponderosa pine plantation in the mid-elevation Sierra Nevada Mountains in California are reported and used to evaluate instrument performance.
... While most NH 3 measurements have been made in urban areas in California, some measurements have been made in rural settings. Airborne measurements in the afternoon mixed layer showed that ammonium compounds (i.e., NH 3 + NH + 4 ) were the dominant component of the N budget with variable NH 3 concentrations corresponding 15 to mixing ratios of 10±7 and 2.5±0.5 ppb in boundary layer above the foothills of the Sierra in the boundary layer above Lake Tahoe respectively (Zhang et al., 2002). In contrast, a ground-based study at Lake Tahoe measured significantly lower concentrations corresponding to approximate mixing ratios between 0.6 to 1.5 ppb and mean summer deposition rates between 3 to 11 ng N m −2 s −1 (Tarnay et al., 2001). ...
Ammonia is a reactive trace gas that is emitted in large quantities by animal agriculture and other sources in California, which subsequently forms aerosol particulate matter, potentially affecting visibility, climate, and human health. We performed initial measurements of NH<sub>3</sub> at the Blodgett Forest Research Station (BFRS) during a two week study in June, 2006. The site is used for ongoing air quality research and is a relatively low-background site in the foothills of the Sierra Nevada. Measured NH<sub>3</sub> mixing ratios were quite low (<1 to ~2 ppb), contrasting with typical conditions in many parts of the Central Valley. Eddy covariance measurements showed NH<sub>3</sub> fluxes that scaled with measured NH<sub>3</sub> mixing ratio and calculated aerodynamic deposition velocity, suggesting dry deposition is a significant loss mechanism for atmospheric NH<sub>3</sub> at BFRS. A simple model of NH<sub>3</sub> transport to the site supports the hypothesis that NH<sub>3</sub> is transported from the Valley to BFRS, but deposits on vegetation during the summer. Further work is necessary to determine whether the results obtained in this study can be generalized to other seasons.
... Similarly, ANs are calculated to consist of all alkyl and multifunctional nitrates present in the gas or aerosol phase. Inorganic nitrate aerosols were reported to contribute 25% to total measured inorganic nitrate (HNO 3 gas +NO − 3 particulate ) in the mid-Sierras during summer (Zhang, et al., 2002). However, measurements of NH 3 at UC-BFRS during summer 2006 (Fischer and Littlejohn, 2007) show that concentrations are too low and temperatures too high to support NH 4 NO 3 aerosol, providing an indication that any aerosol NO − 3 in the region is non-volatile and would not have been detected as part of our measurements of HNO 3 . ...
We describe observations of atmospheric reactive nitrogen compounds including NO, NO<sub>2</sub>, total peroxy nitrates, total alkyl nitrates, and HNO<sub>3</sub> and their correlation with temperature. The measurements were made at a rural location 1315 m a.s.l. on the western slope of the Sierra Nevada Mountains in California during summer of 2001. The ratio of HNO<sub>3</sub> to its source molecule, NO<sub>2</sub>, and the ratio of HNO<sub>3</sub> to all other higher oxides of nitrogen (NO<sub>z</sub>) all increase with increasing temperature. Analysis of these increases suggests they are due to a steep increase in OH of between a factor of 2 and 3 over the range 18–32°C. Total peroxy nitrates decrease and total alkyl nitrates increase over the same temperature range. The decrease in the total peroxy nitrates is shown to be much less than expected if the rate of thermal decomposition were the sole important factor and to be consistent with the increase in OH inferred from the temperature trends in the HNO<sub>3</sub>/NO<sub>2</sub> ratio.
Wildfire activity is increasing globally. The resulting smoke plumes can travel hundreds to thousands of kilometers, reflecting or scattering sunlight and depositing particles within ecosystems. Several key physical, chemical, and biological processes in lakes are controlled by factors affected by smoke. The spatial and temporal scales of lake exposure to smoke are extensive and under‐recognized. We introduce the concept of the lake smoke‐day, or the number of days any given lake is exposed to smoke in any given fire season, and quantify the total lake smoke‐day exposure in North America from 2019 to 2021. Because smoke can be transported at continental to intercontinental scales, even regions that may not typically experience direct burning of landscapes by wildfire are at risk of smoke exposure. We found that 99.3% of North America was covered by smoke, affecting a total of 1,333,687 lakes ≥10 ha. An incredible 98.9% of lakes experienced at least 10 smoke‐days a year, with 89.6% of lakes receiving over 30 lake smoke‐days, and lakes in some regions experiencing up to 4 months of cumulative smoke‐days. Herein we review the mechanisms through which smoke and ash can affect lakes by altering the amount and spectral composition of incoming solar radiation and depositing carbon, nutrients, or toxic compounds that could alter chemical conditions and impact biota. We develop a conceptual framework that synthesizes known and theoretical impacts of smoke on lakes to guide future research. Finally, we identify emerging research priorities that can help us better understand how lakes will be affected by smoke as wildfire activity increases due to climate change and other anthropogenic activities.
Wildfire activity is increasing globally. The resulting smoke plumes can travel hundreds to thousands of kilometers, reflecting or scattering sunlight and depositing ash within ecosystems. Several key physical, chemical, and biological processes in lakes are controlled by factors affected by smoke. The spatial and temporal scales of lake exposure to smoke are extensive and underrecognized. We introduce the concept of the lake-smoke day, or the number of days any given lake is exposed to smoke in any given fire season, and quantify the total lake-smoke day exposure in North America from 2019 - 2021. Because smoke can be transported at continental to intercontinental scales, even regions that may not typically experience direct burning of landscapes by wildfire are at risk of smoke exposure. We found that 99.3% of North America was covered by smoke, affecting a total of 1,333,687 lakes >=10 ha. An incredible 98.9% of lakes experienced at least 10 smoke-days a year, with 89.6% of lakes receiving over 30 lake-smoke days, and lakes in some regions experiencing up to 4 months of cumulative smoke-days. Herein we review the mechanisms through which smoke and ash can affect lakes by altering the amount and spectral composition of incoming solar radiation and depositing carbon, nutrients, or toxic compounds that could alter chemical conditions and impact biota. We develop a conceptual framework that synthesizes known and theoretical impacts of smoke on lakes to guide future research. Finally, we identify emerging research priorities that can help us better understand how lakes will be affected by smoke as wildfire activity increases due to climate change and other anthropogenic activities.
Biomass burning has been recognized as an important primary source of atmospheric phosphorus (P), but the measurements of P from biomass burning particles are lacking. In this work, emission factors of different P forms, including total P (TP), total dissolved P (TDP), dissolved inorganic P (DIP) and dissolved organic P (DOP), in emission particles from four types of crop residues burning were measured in a number of chamber experiments. Based on the measured emission factors and the amount of crop residue burned, a high-resolution (0.25° × 0.25°) emission inventory of P for China during 2011–2015 was firstly developed. The emission factors of TP, DIP and DOP were 0.23, 0.06 and 0.13 g/kg, 0.57, 0.17 and 0.27 g/kg, 0.52, 0.15 and 0.27 g/kg, 0.43, 0.13 and 0.25 g/kg for wheat, corn, soybean and rice straw burning, respectively. The total emissions of TP, TDP, DIP, and DOP from the four types of crop straw open burning were 72.0 × 10³ ± 6.7 × 10³ Tons, 56.3 × 10³ ± 5.5 × 10³, 20.9 × 10³ ± 2.0 × 10³ and 35.4 × 10⁴ ± 3.4 × 10³ Tons, respectively. TDP dominated the TP fraction, indicating that biomass burning was the important source of bioavailable P. The high P emission areas were mainly distributed in the Northeast and North China Plain, where were the main grain production areas in China, while P emission in economically developed areas such as Beijing and Shanghai and western areas such as Tibet and Qinghai was lower. Affected by the harvesting periods of crops, high P emissions peaked in March, April, June and October. The results herein can provide a dataset for modeling research in calculating the contribution of biomass burning sources to atmospheric P; therefore reduce uncertainties in estimating atmospheric P deposition.
The composition and concentrations of water-soluble gases and ionic aerosol components were measured from January to February 2013 in Fresno, CA, with a particle-into-liquid sampler with ion chromatography and annular denuders. The average (±1σ) ionic aerosol mass concentration was 15.0 (±9.4) µg m−3, and dominated by nitrate (61%), followed by ammonium, sulfate, chloride, potassium, nitrite, and sodium. Aerosol-phase organic acids, including formate and glycolate, and amines including methylaminium, triethanolaminium, ethanolaminium, dimethylaminium, and ethylaminium were also detected. Although the dominant species all came from secondary aerosol formation, there were primary sources of ionic aerosols as well, including biomass burning for potassium and glycolate, sea spray for sodium, chloride, and dimethylamine, and vehicles for formate. Particulate methanesulfonic acid was also detected and mainly associated with terrestrial sources. On average, the molar concentration of ammonia was 49 times greater than nitric acid, indicating that ammonium nitrate formation was limited by nitric acid availability. Particle water was calculated based on the Extended Aerosol Inorganics Model (E-AIM) thermodynamic prediction of inorganic particle water and κ-Köhler theory approximation of organic particle water. The average (±1σ) particle water concentration was 19.2 (±18.6) µg m−3, of which 90% was attributed to inorganic species. The fractional contribution of particle water to total fine particle mass averaged at 36% during this study and was greatest during early morning and night and least during the day. Based on aqueous-phase concentrations of ions calculated by using E-AIM, the average (±1σ) pH of particles in Fresno during the winter was estimated to be 4.2 (±0.2).
Surface ozone (O3) concentrations were measured in and around the Lake Tahoe Basin using both active monitors (2010) and passive samplers (2002, 2010). The 2010 data from active monitors indicate average summertime diurnal maxima of approximately 50-55 ppb. Some site-to-site variability is observed within the Basin during the well-mixed hours of 10:00 to 17:00 PST, but large differences between different sites are observed in the late evening and pre-dawn hours. The observed trends correlate most strongly with elevation, topography, and surface vegetation. High elevation sites with steeply sloped topography and drier ground cover experience elevated O3 concentrations throughout the night because they maintain good access to downward mixing of O3-rich air from aloft with smaller losses due to dry deposition. Low elevation sites with flat topography and more dense surface vegetation experience low O3 concentrations in the pre-dawn hours because of greatly reduced downward mixing coupled with enhanced O3 removal via efficient dry deposition. Additionally, very high average O3 concentrations were measured with passive samplers in the middle of the Lake in 2010. This latter result likely reflects diminished dry deposition to the surface of the Lake. High elevation Tahoe Basin sites with exposure to nocturnal O3-rich air from aloft experience daily maxima of 8-hour average O3 concentrations that are frequently higher than concurrent maxima from the polluted upwind comparison sites of Sacramento, Folsom, and Placerville. Wind rose analyses of archived NAM 12 km meteorological data for the summer of 2010 suggest that some of the sampling sites situated near the shoreline may have experienced on-shore “lake breezes” during daytime hours and/or off-shore “land breezes” during the night. Back-trajectory analysis with the HYSPLIT model suggests that much of the ozone measured at Lake Tahoe results from the transport of “polluted background” air into the Basin from upwind pollution source regions. Calculation of ozone exposure indices indicates that the two most polluted sites sampled by active monitors in 2010 - the highest Genoa Peak site, located on the eastern side of the Lake at an elevation of 2734 m above sea level, and Angora Lookout, located to the south-southwest (SSW) of the Lake at an elevation of 2218 m above sea level - likely experienced some phytotoxic impacts, while the other Tahoe Basin locations received lower ozone exposures.
Although organic nitrogen (ON) compounds are apparently ubiquitous in the troposphere, very little is known about their fate and transformations. As one step in addressing this issue, we have studied the transformations of bulk (uncharacterized) organic nitrogen in fogwaters and aerosol aqueous extracts during exposure to simulated sunlight and O-3. Our results show that over the course of several hours of exposure a significant portion of condensed-phase organic nitrogen is transformed into ammonium, nitrite, nitrate, and NOx. For nitrite, there was both photochemical formation and destruction, resulting in a slow net loss. Ammonium and nitrate were formed at initial rates on the order of a few micromolar per hour in the bulk fogwaters, corresponding to formation rates of similar to10 and 40 ng m(-3) h(-1), respectively, in ambient fog. The average initial formation rate (expressed as ng (m of air)(-3) h(-1)) of NH4+ in the aqueous extracts of fine particles (PM2.5) was approximately one-half of the corresponding fogwater value. Initial formation rates of NOx (i.e., NO + NO2) were equivalent to similar to2-11 pptv h(-1) in the three fogwaters tested. Although the formation rates of ammonium and nitrate were relatively small as compared to their initial concentrations in fogwaters (similar to200-2000 muM) and aerosol particles (similar to400-1500 ng m(-3)), this photochemical mineralization and "renoxification" from condensed-phase organic N is a previously uncharacterized source of inorganic N in the atmosphere. This conversion also represents a new component in the biogeochemical cycle of nitrogen that might have significant influences on atmospheric composition, condensed-phase properties, and the ecological impacts of N deposition.
[1] Biogeochemical studies show that the surface waters of the subtropical North Atlantic are highly phosphorus (P) stressed. Human activity may exacerbate phosphorus stress by enhancing atmospheric nitrogen (N) deposition and raising N/P ratios in deposition. However, the magnitude of this effect is unclear, in part, because atmospherically deposited phosphorus sources are not well known, particularly the contribution from organic phosphorus. Here we report measurements of phosphorus in aerosols and wet deposition at Miami and Barbados. African dust is the major aerosol P source at both Miami and Barbados, containing ~880 ppm total phosphorus and ~70 ppm soluble reactive phosphorus (SRP). Organic compounds contribute, on average, 28%–44% of soluble phosphorus in precipitation. Because of dust transport seasonality, phosphorus inputs to the North Atlantic are expected to be highly variable with 2–10 times more P deposition during summer than winter. Pollution is also an important contributor to total and soluble phosphorus in Miami aerosols and deposition. Estimated SRP deposition in Barbados and Miami is 0.21 and 0.13 µmol m−2 d−1 phosphorus, respectively. Inorganic nitrogen in excess of Redfield ratio expectations in deposition was very different between the sites, totaling 21–30 and 127–132 µmol m−2 d−1 nitrogen in Barbados and Miami, respectively; the high deposition rates at Miami are linked to pollutants. Including soluble organic nitrogen and phosphorus halved the estimates of excess nitrogen in Barbados wet deposition. Thus, the organic phosphorus fraction is important in the assessment of the magnitude of biogeochemical change of the North Atlantic caused by atmospheric deposition.
The concentrations of free amino acids were determined in atmospheric particulate matter from the city of Venice (Italy) in order to better understand their origin. The analysis of aerosol samples was carried out via high-performance liquid chromatography coupled to a triple quadrupole tandem mass spectrometric detector (HPLC/ESI-MS/MS). The internal standard method was used and the analytical procedure was validated by evaluating the trueness, the precision, the recovery, the detection and the quantification limits.The particulate matter was collected using quartz fiber filters and extracted in methanol; after filtration the extract was directly analyzed. Forty samples were collected from April to October 2007 and the average concentrations of free amino acids in the aerosol were: alanine 35.6pmolm−3, aspartic acid 31.1pmolm−3, glycine 30.1pmolm−3, glutamic acid 32.5pmolm−3, isoleucine 2.4pmolm−3, leucine 2.7pmolm−3, methionine, cystine and 3-hydroxy-proline below the limit of detection, phenylalanine 2.8pmolm−3, proline 43.3pmolm−3, serine 8.6pmolm−3, threonine 2.8pmolm−3, tyrosine 1.7pmolm−3, valine 3.8pmolm−3, asparagine 70.2pmolm−3, glutamine 38.0pmolm−3, 4-hydroxy-proline 2.5pmolm−3, methionine sulfoxide 1.1pmolm−3, and methionine sulfone 0.1pmolm−3. The total average concentration of these free amino acids in aerosol samples of Venice Lagoon was 334pmolm−3. The temporal evolution and multivariate analysis indicated the photochemical origin of 4-hydroxy-proline and methionine sulfoxide and for other compounds an origin further away from the site of sampling, presumably reflecting transport from terrestrial sources.
Atmospheric nitrogen deposition to the ocean has more than doubled in the past 150 years due to anthropogenic activity, reaching levels comparable with nitrogen fixation in the subtropical North Atlantic. Previous studies have suggested that atmospherically deposited N may increase export production, decrease surface water phosphate levels, and substantially impact geochemical estimates of nitrogen fixation. This dissertation reports on the magnitude and biogeochemical fate of soluble N and P deposition in the subtropical North Atlantic. Aerosol and wet deposition time-series samples were used to determine the fluxes, sources, and N:P ratios of atmospheric nutrient deposition. Based on the magnitudes of total soluble N and P deposition, atmospheric nutrients are estimated to supply ~10-50% of allochthonous N to the North Atlantic subtropical gyre. Samples gathered in Barbados, the Canary Islands, and Miami indicate that atmospheric N sources are primarily anthropogenic (and thus, increasing) and that P sources are primarily natural (and thus relatively steady). Because inorganic nutrient concentrations in surface waters are in the low nM range, increasing P stress in surface waters may occur as a result of increasing N deposition. This assessment is supported by modeling studies, which also indicate that deposition would enhance surface P depletion. Inorganic N contributes nearly all (85-87%) of atmospherically deposited soluble N; the majority (~60%) of the remaining soluble organic N is comprised of an incompletely characterized pool of volatile basic organic N. Water soluble organic P contributes ~20-50% of soluble P. Because organic P contributes a relatively higher portion of soluble P as compared to organic N, the inclusion of organic matter in deposition estimates could both enhance the expected level of export production and reduce the predicted levels of P stress induced by atmospheric deposition. Further modeling studies indicate that the fate of atmospheric nutrients in the subtropical North Atlantic is controlled by non-Redfieldian processes, and that atmospheric nutrients eventually accumulate in the main thermocline. The research presented here suggests that future increases in atmospheric N emissions could have long-term impacts on surface ocean biology and nutrient cycles in the subtropical North Atlantic.
There is growing evidence that organo-nitrogen compounds may constitute a significant fraction of the aerosol nitrogen (N) budget. However, very little is known about the abundance and origin of this aerosol fraction. In this study, the concentration of organic nitrogen (ON) and major inorganic ions in PM 2.5 aerosol were measured at the Duke Forest Research Facility near Chapel Hill, NC, dur-ing January and June of 2007. A novel on-line instrument was used, which is based on the Steam Jet Aerosol Collector (SJAC) coupled to an on-line total carbon/total nitrogen an-alyzer and two on-line ion chromatographs. The concentra-tion of ON was determined by tracking the difference in con-centrations of total nitrogen and of inorganic nitrogen (deter-mined as the sum of N-ammonium and N-nitrate). The time resolution of the instrument was 30 min with a detection limit for major aerosol components of ∼0.1 µgm −3 . Nitrogen in organic compounds contributed ∼33% on av-erage to the total nitrogen concentration in PM 2.5 , illustrating the importance of this aerosol component. Absolute concen-trations of ON, however, were relatively low (<1.0 µgm −3) with an average of 0.16 µgm −3 . The absolute and relative contribution of ON to the total aerosol nitrogen budget was practically the same in January and June. In January, the concentration of ON tended to be higher during the night and early morning, while in June it tended to be higher during the late afternoon and evening. Back-trajectories and correlation with wind direction indicate that higher concentrations of ON occur in air masses originating over the continental US, while marine air masses are characterized by lower ON concentra-tions. The data presented in this study suggests that ON has a Correspondence to: A. Khlystov (andrey@duke.edu) variety of sources, which are very difficult to quantify with-out information on chemical composition of this important aerosol fraction.
Atmospheric fine particles (PM2.5) collected during August 1997–July 1998 and wintertime fog waters collected during 1997–1999 at Davis, California were analyzed for free and combined amino compounds. In both PM2.5 and fog waters, the average concentrations of combined amino compounds (CAC, e.g., proteins and peptides) were generally 4–5 times higher than those of free amino compounds (FAC, i.e., amino acids and alkyl amines). Concentrations of total amino compounds (TAC=FAC+CAC) ranged from 1260 to 3650 pmol m−3 air in PM2.5, and from 1620 to 5880 pmol m−3 air in fog waters. Average values (±1σ) were 2500±879 and 3400±1430 pmol m−3 air, respectively. Concentrations of amino compounds in PM2.5 varied seasonally, with a peak during late winter and early spring. Ornithine was a major FAC component in both PM2.5 and fog waters (typically accounting for ∼20% of FAC), but these sample types otherwise had fairly different FAC distributions. FAC in PM2.5 were enriched in protein-type amino species such as glycine/threonine, serine and alanine, while fog water FAC had significantly higher levels of non-protein species such as methylamine, γ-aminobutyric acid and ethanolamine. The compositions of CAC in PM2.5 and fogs were fairly similar and were mainly protein-type. Mass concentrations of TAC in PM2.5 and fog waters were, on average, 302 and 399 ng m−3 air, respectively. Amino compounds were an important component of the organic carbon pool for both fog and particles, with TAC accounting for an average of 13% of the dissolved organic carbon in fog waters and ∼10% of the water-soluble organic carbon in PM2.5. At these levels amino compounds likely play important roles in the chemistry of fog drops and fine particles, for example by influencing their buffering capacity and basicity.
A recently developed algorithm (Zhang et al., 2005) has been applied to deconvolve the mass spectra of organic aerosols acquired with the Aerosol Mass Spectrometer (AMS) in Pittsburgh during September 2002. The results are used here to characterize the mass concentrations, size distributions, and mass spectra of hydrocarbon-like and oxygenated organic aerosol (HOA and OOA, respectively). HOA accounts for 34% of the measured organic aerosol mass and OOA accounts for 66%. The mass concentrations of HOA demonstrate a prominent diurnal profile that peaks in the morning during the rush hour and decreases with the rise of the boundary layer. The diurnal profile of OOA is relatively flat and resembles those of SO<sub>4</sub><sup>2?</sup> and NH<sub>4</sub><sup>+</sup>. The size distribution of HOA shows a distinct ultrafine mode that is commonly associated with fresh emissions while OOA is generally concentrated in the accumulation mode and appears to be mostly internally mixed with the inorganic ions, such as SO<sub>4</sub><sup>2?</sup> and NH<sub>4</sub><sup>+</sup>. These observations suggest that HOA is likely primary aerosol from local, combustion-related emissions and that OOA is secondary organic aerosol (SOA) influenced by regional contributions. There is strong evidence of the direct correspondence of OOA to SOA during an intense new particle formation and growth event, when condensational growth of OOA was observed. The mass spectrum of OOA of this new particle formation event is very similar to the OOA spectrum of the entire study, which strongly suggests that most OOA during this study is SOA. O<sub>3</sub> appears to be a poor indicator for SOA concentration while SO<sub>4</sub><sup>2?</sup> is a relatively good surrogate for this dataset. Since the diurnal averages of HOA tightly track those of CO during day time, oxidation/aging of HOA appears to be very small on the time scale of several hours. Based on extracted mass spectra and the likely elemental compositions of major m/z 's, the organic mass to organic carbon ratios (OM:OC) of HOA and OOA are estimated at 1.2 and 2.2 ?g/?g C, respectively, leading to an average OM:OC ratio of 1.8 for submicron OA in Pittsburgh during September. The C:O ratio of OOA is estimated at 1:0.8. The carbon contents in HOA and OOA calculated accordingly correlate well to primary and secondary organic carbon, respectively, estimated by the OC/EC tracer technique (assuming POC-to-EC ratio=1). In addition, the total carbon concentrations calculated from the AMS data agree well with those measured by the Sunset Laboratory Carbon analyzer ( r <sup>2</sup>=0.87; slope=1.01±0.11).
Ammonia is a reactive trace gas that is emitted in large quantities by animal agriculture and other sources in California, which subsequently forms aerosol particulate matter, potentially affecting visibility, climate, and human health. We performed initial measurements of NH3 at the Blodgett Forest Research Station (BFRS) during a two week study in June, 2006. The site is used for ongoing air quality research and is a relatively low-background site in the foothills of the Sierra Nevada. Measured NH3 mixing ratios were quite low (3 fluxes that scaled with measured NH3 mixing ratio and calculated aerodynamic deposition velocity, suggesting dry deposition is a significant loss mechanism for atmospheric NH3 at BFRS. A simple model of NH3 transport to the site supports the hypothesis that NH3 is transported from the Valley to BFRS, but deposits on vegetation during the summer. Further work is necessary to determine whether the results obtained in this study can be generalized to other seasons.
A recently developed algorithm (Zhang et al., 2005) has been applied to deconvolve the mass spectra of organic aerosols acquired with the Aerosol Mass Spectrometer (AMS) in Pittsburgh during September 2002. The results are used here to characterize the mass concentrations, size distributions, and mass spectra of hydrocarbon-like and oxygenated organic aerosol (HOA and OOA, respectively). HOA accounts for 34% of the measured organic aerosol mass and OOA accounts for 66%. The mass concentrations of HOA demonstrate a prominent diurnal profile that peaks in the morning during the rush hour and decreases with the rise of the boundary layer. The diurnal profile of OOA is relatively flat and resembles those of SO<sub>4</sub><sup>2−</sup> and NH<sub>4</sub><sup>+</sup>. The size distribution of HOA shows a distinct ultrafine mode that is commonly associated with fresh emissions while OOA is generally concentrated in the accumulation mode and appears to be mostly internally mixed with the inorganic ions, such as SO<sub>4</sub><sup>2−</sup> and NH<sub>4</sub><sup>+</sup>. These observations suggest that HOA is likely primary aerosol from local, combustion-related emissions and that OOA is secondary organic aerosol (SOA) influenced by regional contributions. There is strong evidence of the direct correspondence of OOA to SOA during an intense new particle formation and growth event, when condensational growth of OOA was observed. The fact that the OOA mass spectrum from this event is very similar to that from the entire study suggests that the majority of OOA in Pittsburgh is likely SOA. O<sub>3</sub> appears to be a poor indicator for OOA concentration while SO<sub>4</sub><sup>2−</sup> is a relatively good surrogate for this dataset. Since the diurnal averages of HOA track those of CO during day time, oxidation/aging of HOA appears to be very small on the time scale of several hours. Based on extracted mass spectra and the likely elemental compositions of major m/z 's, the organic mass to organic carbon ratios (OM:OC) of HOA and OOA are estimated at 1.2 and 2.2 μg/μgC, respectively, leading to an average OM:OC ratio of 1.8 for submicron OA in Pittsburgh during September. The C:O ratio of OOA is estimated at 1:0.8. The carbon contents in HOA and OOA estimated accordingly correlate well to primary and secondary organic carbon, respectively, estimated by the OC/EC tracer technique (assuming POC-to-EC ratio=1). In addition, the total carbon concentrations estimated from the AMS data agree well with those measured by the Sunset Laboratory Carbon analyzer ( r <sup>2</sup>=0.87; slope=1.01±0.11). Our results represent the first direct estimate of the OM:OC ratio from highly time-resolved chemical composition measurements.
Atmospheric deposition provides most of the dissolved inorganic nitrogen (DIN) and total nitrogen in the annual nutrient load of Lake Tahoe. Deposition also contributes significant amounts of soluble reactive phosphorus (SRP) and total phosphorus loading but plays less of a role than in the case of nitrogen. Most of the DIN probably originates outside of the drainage basin in urban and agricultural areas to the south and west. Spatial patterns of SRP deposition differ from those of DIN and suggest a within-basin terrestrial source, such as leachate from windblown dust or other particles. Because of atmospheric N deposition, the N:P (molar) ratio in combined loading is well above the Redfield ratio of 16 and consistent with an observed shift from colimitation by N and P to persistent P limitation in the lake phytoplankton.
BIOMASS burning is a primary source of many trace substances that are important in atmospheric chemistry1–6. More than 80% of the world's biomass burning takes place in the tropics3 as a result of savanna fires, forest-clearing activity, and the burning of agricultural waste and wood. Here we report results from laboratory studies on the emission of nitrogen-containing compounds from the burning of dry vegetation. We find that the emission rates of NOX, HCN and CH3CN are sufficient to contribute significantly to the global atmospheric budget of the compounds. Furthermore, possibly up to half of the biomass nitrogen can be converted to molecular nitrogen, N2, leading to an estimated annual loss of 12–28 x 1012g of biomass nitrogen ('pyrodenitrification'), equal to ~9–20% of the estimated global rate of terrestrial nitrogen fixation.
Algal bioassays using stream water additions from seven Lake Tahoe basin mountain creeks were used to assess short-term bioavailability of stream P to Lake Tahoe phytoplankton during the 1996 spring snowmelt. Results indicate that 75-90% of bioassay response is due to nutrients in the <0.45-μm range. Lake Tahoe phytoplankton are primarily P limited, although N colimitation has been observed during summer. Bioassay response did not correlate well with particulate P > 0.45 μm but was highly correlated with dissolved inorganic P. Dissolved organic P may also be stimulatory to Lake Tahoe phytoplankton. Bioassay response was relatively constant for each treatment during the study, due in part to a consistent diatom dominance of the phytoplankton community. The bioassay technique utilized is not sensitive enough to detect changes in land use along a single stream. Dissolved inorganic P was determined to best represent Lake Tahoe short-term (several days) stream bioavailable P at the present time. Physical bioavailability factors such as lake thermal dynamics and biological factors such as lake microbial dynamics should be addressed in addition to the chemical factors when considering lake biologically available P.
The rate of deposition of ammonia to sea water was observed in laboratory chamber experiments. Similar experiments using demineralised water and dilute sulphuric acid were also carried out, and information on the surface resistance for ammonia at the sea water surface was determined from the results. Estimates of the resistance for transfer through the air to the sea surface were added to the surface resistance in order to derive an estimation of the mean deposition velocity of ammonia to sea water around the British Isles of approximately 5 mm s-1, with an uncertainty range of 2–15 mm s-1. Despite the limitations of these preliminary experiments, the chamber method has been demonstrated successfully for ammonia. Further refinements should increase confidence and reduce uncertainty in the rates and direction of exchange of ammonia with the sea surface. The derived deposition velocity, and its uncertainty range was used in a modelling study to determine the likely fate of ammonia in air passing over the North Sea in both wet and dry conditions. In a dry eastward trajectory, about 40% of the ammonia emitted from the central lowlands of Scotland was deposited before reaching the coast. Some 1.5–4% was lost to the sea surface, and approximately 55% was advected to the continent. In wet conditions, however, 80% of the emissions were deposited over Scotland before reaching the coast, and the remainder was lost to the sea, chiefly in rain. These calculations assumed that the sea will act as a sink for ammonia in dry conditions rather than a source. In order to investigate this, the equilibrium concentration at the surface was calculated to be 0.07 μg m-3 for typical North Sea conditions, and measurements of atmospheric concentrations over the North Sea were made during a short ship-board campaign which showed air concentrations of ammonia in the range of 0.06–2.4 μg m-3. These and other measurements indicate that on occasions the North Sea may be a source, but more often represents a sink for ammonia.
This study utilized conditional sampling to identify three frequent wind
regimes in the lower Sacramento Valley. The major flow features of the
mean diurnal wind patterns in the southern Sacramento Valley and
surrounding areas were analyzed for each wind regime. Afternoon wind
directions at a pivotal observing site (Davis, CA) in the south-central
part of the valley were used to classify the regimes as south wind
(marine air intrusion), north wind (no marine air intrusion), and
transitional wind days. In the summer of 1991, these occurred 72%, 14%,
and 14% of the days, respectively. Daily data from 21 surface observing
stations were segregated by wind regime, then averaged for quarters of
the day to produce wind roses grouped by regime and time of day. These
data were then plotted on a base map. The most frequent direction in
each of these wind roses was used to construct streamlines for the area
by quarter of the day for each regime. These analyses provide a
climatology of the diurnal variation of the average wind flow for each
of these frequent flow regimes, providing a wind climatology with
greater spatial and temporal resolution than those in extant
publications. These analyses are especially useful for evaluating
transport patterns of air pollutants or contaminants.
For more than half a century, the trophic status of water bodies has been of interest to Iimnologists and oceanographers alike. This report demonstrates the close, inverse relationship between '4C-estimated primary productivity and transparency during the earliest stages of cultural eutro- phication. As the population in the Tahoe basin has rapidly increased, Lake Tahoe has been characterized by an increase in primary productivity that has averaged 5.6% yr- 1 for the last 28 yr. There has been a concomitant decline in transparency of 0.37 m yr". During winter months when transparency is highest, the average annual loss has been slightly greater (0.40 m yr- '). The average annual Secchi depth has decreased by 7 m during the last 19 yr of intensive monitoring. There has also"been a significant increase in the light extinction coefficient. Photosynthetic efficiency has increased while there has been a gradual shrinkage of the euphotic zone. During the same period the total NO~--N content of the lake has increased significantly, but total P content has not. Lake Tahoe primary production has become increasingly P sensitive during the last decade as N has accumulated in the system. A gradual increase in the N:P may prove to be a general evolutionary characteristic of oligotrophic lakes during the earliest stages of eutrophication. The importance of long-term studies in detecting gradual change that may be masked by considerable interannual variability is particularly evident from this study.
Three-dimensional analysis shows the sea-breeze front to be primarily a wind shift line in which the thermal discontinuity lags behind the shear line and becomes quasi-stationary in the afternoon. Two synoptic patterns control the temperature regime. On cool days, when a high level trough is present the sea-breeze front is weak, moves rapidly and penetrates far inland; the marine layer is deep and the sea breeze spills over the low mountain ridges. Warm days occur, when the Pacific high penetrates into Oregon and Washington; the marine layer is shallow and the sea-breeze front is intense and slow moving.
Secchi depth has been measured in Lake Tahoe an average of every 12 d since July 1967. Because of the unusual clarity of the lake, Secchi depth measurement is responsive to small changes in light-attenuating particles, and the record exhibits strong variability at the seasonal, interannual, and decadal scales. Using recently developed methods of applied time-series analysis, the mechanisms of change were delineated at each scale. The seasonal pattern is a bimodal one, with two minima at approximately June and December. The June minimum is due mostly to cumulative discharge of suspended sediments following melting of the snowpack. The December minimum is probably a result of mixed-layer deepening as the thermocline passes through layers of phytoplankton and other light-attenuating particles that reach a maximum below the summer mixed layer. The interannual scale exhibits two modes of variability, one during the weakly stratified autumn-winter period and the other during the more stratified spring- summer period. The first mode is a result of variable depth of mixing in this unusually deep lake, while the second results from year-to-year changes in spring runoff. A decadal trend also exists ( 20.25 m yr 21 ), resulting from accumulation of materials in the water column. It is not yet understood, however, how much of this change is due to phytoplankton or recent phytoplankton-derived materials and how much is due to other materials such as mineral suspensoids. Based on the available measurements and physical considerations, both categories may play a signif- icant role.
Wood ash is a residual material produced when wood is burned for energy production. It is a useful soil amendment because it raises soil pH and has the potential to supply plant nutrients. The two studies described in this paper were designed to assess the plant availability of P and K in wood ash. Both studies compared nutrient uptake by corn (Zea mays L.) grown in the greenhouse in wood ash-amended soils to nutrient uptake from fertilizer-amended soils. The wood ashes used were chemically characterized for available P and soluble K content by ammonium citrate extraction, as well as for total P and K. In addition wood ash- and fertilizer-amended soils from the P availability study were extracted with Bray-1, Olsen, and NH4OAc solutions after harvest. Wood ashes were found to be more similar to conventional P fertilizer materials when the amendments were compared on a citrate-extractable P basis than when they were compared on a total P basis. For K there was little difference between ash and fertilizer sources, whether they were compared on a total K or a citrate-extractable K basis. The buffered NH4OAc (pH 3.0) extract was adequate for determining K availability in wood ash-amended soils, but inadequate with regard to P availability in these soils. The buffered solution may have dissolved residual wood ash and released P that was not actually plant-available. Either the Bray-1 or the Olsen extract provided a relative measure of P availability that was consistent for both fertilizer- and wood ash-amended soils.
Atmospheric transport of organophosphate pesticides from California's Central Valley to the Sierra Nevada mountains was assessed by collecting air- and wet-deposition samples during December, January, February, and March, 1990 to 1991. Large-scale spraying of these pesticides occurs during December and January to control insect infestations in valley orchards. Sampling sites were placed at 114- (base of the foothills), 533-, and 1920-m elevations. Samples acquired at these sites contained chlorpyrifos [phosphorothioic acid; 0,0-diethyl 0 (3,5,6-trichloro-2-pyridinyl) ester), parathion [phosphorothioic acid, 0,0-diethyl (4-nitrophenyl) ester], diazinon {phosphorothioic acid, 0,0-diethyl 0-[6-methyl-2-(1-methylethyl)-4-pyrimidinyl] ester} diazinonoxon {phosphoric acid, 0,0-diethyl 0-[6-methyl-2-(1-methylethyl)-4-pyrimidinyl] ester}, and paraoxon [phosphoric acid, 0,0-diethyl 0-(4-nitrophenyl) ester] in both air and wet deposition samples. Air concentrations of chloropyrifos, diazinon and parathion ranged from 13 to 13 000 pg/m3 at the base of the foothills. At 533-m air concentrations were below the limit of quantification (1.4 pg/m3) to 83 pg/m3 and at 1920 m concentrations were below the limit of quantification. Concentrations in wet deposition varied with distance and elevation from the Central Valley. Rainwater concentrations at the base of the foot hills ranged from 16 to 7600 pg/mL. At 533-m rain and snow water concentrations ranged from below the limit of quantification (1.3 pg/ mL) to 140 pg/mL and at 1920 m concentrations ranged from below the limit of quantification to 48 pg/mL. These findings indicate that atmospheric transport of pesticides applied in the valley to the Sierra Nevada mountains is occurring, but the levels decrease as distance and elevation increase from the valley floor.
Three reduced forms of nitrogen are associated with ambient air pollution particulates: ammonium and two additional species assigned to amine and/or amide and to nitrile. Nitrogen species of the same type and behavior can be synthesized in soot (or graphite) interactions with NO or NH3. Volatile hydroxyl and carboxyl ammonium salts (and/or physically adsorbed ammonia species) are produced in soot-NO and soot-NH3 reactions at ambient temperatures, while amines, amides and nitriles are produced at higher temperatures. The proposed mechanism is in qualitative agreement with the field observations. The experiments were performed with the aid of X-ray photoelectron spectroscopy, ESCA.
The spatial variability of ozone climatology is described for six remote sites on the western slope of the Sierra Nevada. A statistical analysis was applied to determine relationships between ozone concentrations and atmospheric variables, as well as relationships among sites. The sites, whose locations vary in latitude, elevation, and topography, show considerable variability in climatological patterns and statistics. However, the stations fall into two general groups: those with a distinct diurnal ozone pattern and those with a flat diurnal ozone pattern. Diurnal variations among sites appear to depend primarily on topographic setting rather than on remoteness from urban sources.
During the 1991 and 1992 dry seasons (April to October), we collected and analyzed over 100 samples of smoke from savanna fires at the Kapalga Research Station (12°S, 132°E) in Kakadu National Park, Northern Territory, Australia. Samples collected from the ground and from a light aircraft flying at 50-700 m above the fires were analyzed for CO2, CO, CH4, C2H2, C6H6, CH2O, CH3CHO, NOx(=NO+NO2), NH3, HCN, and CH3CN using gas phase Fourier transform infrared (FTIR) spectroscopy, matrix isolation FTIR spectroscopy, and chemiluminescence techniques. In addition, we made detailed analyses of the mass, carbon, and nitrogen loads of the prefire fuel and the postfire ash residue. Molar emission ratios relative to emitted CO2 and CO, and emission factors relative to the fuel carbon or nitrogen burned were determined for the measured trace gases. Over 95% of the fuel carbon burned was released to the atmosphere, predominantly as CO2 (87+/-3% of fuel C) and CO (7.8+/-2.3%). The mean DeltaCO/DeltaCO2 emission ratio of 9.0+/-2.6% indicates efficient combustion in these fires of grasses and other light fuels. The main nitrogen-based emissions we measured were NOx (21+/-8% of fuel N) and NH3 (23+/-13%). The combined emissions of NOx, NH3, N2O, CH3CN, and HCN accounted for only 51+/-17% of the fuel N released to the atmosphere during combustion. We use these measurements to estimate the annual emissions of several important trace gases from savanna burning in Australia.
Measurements of ammonia and ammonium aerosol were made during straw and stubble burning experiments in the field. Factors were determined for the calculation of emissions of ammonia and ammonium ion, from this source, in the United Kingdom between 1981 and 1992. Emissions of NHx from straw burning were calculated to be equivalent to approximately 20 ktonnes N yr−1 in 1981 and have declined to 3.3 ktonnes N yr−1 in 1991 as a result of changes in agricultural practices in response to impending U.K. legislation. The fraction of total plant nitrogen released as NHx was estimated to be between approximately 40 and 80%. Emissions of ammonia from straw and stubble burning over a 6—8 week period over which this typically occurs were calculated to be 27% of the total U.K. emissions over the equivalent period in 1981 and 7% in 1991. We have identified straw and stubble burning as another source of ammonia currently not accounted for in European and North American emission inventories; these focus almost exclusively on emissions from animal sources.
Phenols are transformed into nitrophenols by the combined action of ozonized oxygen and nitrogen dioxide (Kyodai nitration) in different solvents. Dipole moments of the solvents were correlated with the ortho/para nitration ratio with phenol, showing an influence of the polarity of the solvent on the ortho/para nitration selectivity. A Hammett ρ of −0.72 was obtained in the Kyodai nitration of 4-substituted phenols. These facts suggest the formation of a charge-transfer complex which evolves to the addition of NO3 to phenols followed by elimination of nitric acid to give the final nitrophenols. The position of the nitro group in nitrophenols found in air samples may be indicative of a gas- or a liquid-phase nitration occurring in the troposphere.
This is a reference book on the occurrence, source, and genetic toxicology of ALL (the authors claim approx. 2500) of the chemical compounds reported in the atmosphere and public indoor situations (it excludes the workplace environment). There is a 55-p introductory chapter that briefly discusses the physical structure and properties of the atmosphere and the gases and particles in it; the causes of mutations and the bioassays used to test for them; and a brief outline of the content and organization of the tables. A 74-p summary chapter discusses the chemical reactions that take place in the indoor and outdoor atmosphere, in precipitation, and on environmental surfaces. It also summarizes the bioassay information. The major part of the book, Chapters 2-14, is the tables that list references to the compounds detected, their sources, and the bioassay results on them.
Residential wood combustion emissions were analyzed to determine emission rates and to develop chemical emissions profiles that represent the appliances and woods typically used in wood-burning communities. Over 350 elements, inorganic compounds, and organic compounds were quantified. A range of 4−9 g/kg dry fuel of particulate matter (<2.5 μm) and 5−22 g/kg volatile organic compounds were observed. Samples were collected using a dilution stack sampler equipped with a 2.5-μm particle selective cyclone. Emissions were diluted 20−70 times, cooled to ambient temperature, and allowed 80 s for condensation prior to collection. Wood type, wood moisture, burn rate, and fuel load were varied for different experiments. Fine particle and semivolatile organic compounds were collected on filter/PUF/XAD/PUF cartridges. Inorganic samples and mass were collected on Teflon and quartz filters. Volatile organic carbon compounds were trapped with Tenax (C8−C20), canister (C2−C12), and 2,4-dinitrophenylhydrazine impregnated cartridges (carbonyl compounds). Analysis of particle and semivolatile organic species was conducted by gas chromatography/mass spectrometry. Teflon filters were analyzed for mass by gravimetry, trace elements were analyzed by X-ray fluorescence, and ammonium was analyzed by automated colorimetry. Quartz filters were analyzed for organic and elemental carbon by thermal/optical reflectance, and ions were analyzed by ion chromatography. Select quartz filters were analyzed by accelerator mass spectrometry for carbon-12 and carbon-14 abundance. Canister and Tenax samples were analyzed by gas chromatography with a flame ionization detector, and carbonyl compounds were analyzed by high-performance liquid chromatography.
Aricultural activity in California's Central Valley may be an important source of pesticides that are transported in the air to the Sierra Nevada Mountain Range, USA. Pesticides applied to this intensive crop production area may volatilize under warm temperatures typical of the valley and be transported through the atmosphere to be deposited in the cooler, higher elevation regions of the Sierra Nevada Mountains. To determine the extent of summertime atmospheric transport of pesticides to this region, high-volume air, dry deposition, and surface water samples were collected in the Central Valley and at different elevations in California's Sequoia National Park. Results revealed that the highest residue concentrations were those of compounds with heavy summertime agricultural use. A significant drop in pesticide concentrations in both air and water samples was observed within a few 100-m elevation from the valley; however, levels remained relatively constant between ∼500 and 2,000 m. Water concentrations from two areas above 3,000 m contained levels less than a tenth as high as those at lower elevations. Possible effects of the pesticides were estimated using measured water concentrations to calculate total exposure of three aquatic species to organophosphate insecticides. Aggregate exposure calculations showed concentrations were well below 96-h LC50 values for rainbow trout and stonefly but concentrations may be harmful to amphipods.
Wood ash is a residual material produced during biomass burning. In the northeastern United States up to 80 % of the ash is spread on agricultural lands as a liming amendment with the remainder being disposed of in landfills. As well as raising soil pH, wood ash also adds plant nutrients to soil. This study is an examination of the plant availability of the P in 8 different soils amended with one wood ash. Plant availability was assessed by measuring the biomass and P concentration of corn (Zea mays) L.) plants grown in the greenhouse for 28 d in soil amended with either CaCO3 (control), wood ash to supply 200 mg kg–1 total P, or monocalcium phosphate (MCP) to supply 200 mg kg–1 total P and CaCO3. Both corn growth and P uptake were highest in the MCP treatments, intermediate in the wood ash treatments, and lowest in the controls for all soil types. The soil property which seemed to have the greatest influence on P availability was pH buffer capacity. The soils with the greatest capacity to buffer OH additions also tended to exhibit the greatest absolute P uptake from wood ash-amended soils and the greatest P uptake relative to that from MCP-amended soils. The ability of soil test extractants to predict uptake of P in the three soil treatments was examined. A buffered ammonium acetate extradant overestimated P availability in the ash-amended soils relative to the MCP-amended soils. An unbuffered, acid, fluoride-containing extract provided a measure of P levels that was consistent with P uptake from all soil treatments. In this study the predictive relationship was as follows: P uptake = 0.017 (Bray P, mg kg–1) + 1.19; r = 0.81.
PCB congener concentrations in air, water, fish, and snow were determined in the lake Tahoe basin and in the water and fish of an adjacent but more remote rural comparison lake, Marlette lake, to examine whether atmospheric transport and deposition are primary sources of contamination to this alpine region of the Sierra Nevada Mountains. Profiles of 97 congeners analyzed by capillary GC-ECD from surface waters of Lake Tahoe and Marlette Lake were closely matched, with total dissolved PCB (t-PCB) concentrations of 0.37 ng/L in Lake Tahoe and 0.67 ng/L in Marlette Lake. Gas-phase t-PCB concentrations measured in air samples from the Lake Tahoe basin averaged 72 pg/m(3), and t-PCB (dissolved and particulate) concentrations in snow were 4.8-5.1 ng/L. Rainbow trout from Marlette Lake and lake trout from Lake Tahoe had similar distributions of congeners, with t-PCB tissue levels varying from 3 to 14 ng/g wet weight. The finding of PCBs in all sampled compartments, particularly snow and air, and the similar pattern of congeners in surface waters and in fish from Lake Tahoe and Marlette Lake indicate an atmospheric source of contamination.
Emissions rates of ammonia (NH3) are reported for a fleet of 39 in-use light-duty gasoline-fueled vehicles. The fleet consisted of both light-duty passenger vehicles and light-duty trucks with various levels of emission control technologies, ranging from non-catalyst vehicles to those that were certified at the ULEV standard for California. NH3 measurements were performed using Fourier transform infrared spectroscopy and the federal test procedure (FTP) driving cycle. The FTP NH3 emission rate for this fleet of vehicles averaged 54 mg mi−1 with a range from <4 to 177 mg mi−1. For this fleet of vehicles, NH3 emissions did not decline as significantly as the regulated pollutants with improvements in emission control technology. A subset of 5 vehicles was tested over the US06, the New York City Cycle (NYCC), and a high-speed freeway cycle for comparison with the FTP cycle. NH3 emissions showed a strong cycle dependence, with increased emissions under more aggressive driving conditions. These results show that NH3 emissions formed during more aggressive driving conditions should be considered in the development of NH3 emission factors. The onset of NH3 emissions typically occurred after catalyst light-off, near when the catalyst reached its equilibrium temperature. Initial studies showed that NH3 emissions increased as the sulfur content in the fuel was decreased.
A comprehensive trajectory model, Atmospheric Chemistry and Deposition model (ACDEP), has been developed to calculate the nitrogen deposition to the Danish sea waters. The model is constructed with the ability of taking into account spatially detailed emissions and land use data for Denmark and on a more coarse grid for the rest of Europe. In the ACDEP-model a one-dimensional column is advected along 96 h back-trajectories. The chemical mechanism in the model is a slightly extended version of the Carbon-Bond Mechanism IV (CBM-IV). The model describes the dry deposition processes with special emphasis on the conditions at sea. For the wet deposition processes both in-cloud and below-cloud scavenging are taken into account. The model results are tested versus one years measurements from six Danish and one Swedish monitoring station. Additional tests are performed for six selected stations from the European Monitoring and Evaluation Programme (EMEP) networks. The model is capable of reproducing both air concentrations and wet depositions of the nitrogen compounds in land and sea areas.
The annular denuder method (ADM), consisting of a denuder-filter pack assembly, has been developed to measure several gaseous and aerosol species without sampling artifacts. Its application to the determination of gaseous acids and ammonia in the atmosphere indicates that this aim is achieved, even though the ratio of analytes in the gas phase and particulate matter is extremely low. The procedure is particularly suitable for the measurement of trace levels (0.1 μg m−3) of HNO3 and SO2 (even in the presence of high levels of sulfate and nitrate) as well as of HNO2 (by making correction for the positive interference of NO2 and PAN).The ADM sampling and analysis precision for the examined gases does not exceed ±10% in the 0.1–10 μg m−3 range. By sampling at an air flow rate of 151 min−1, the minimum detectable atmospheric concentrations is ∼0.1 μgm−3 for each species over a 3 h interval.
Although organic nitrogen (ON) has been found to be a ubiquitous and significant component in wet and dry deposition, almost nothing is known about its concentration or composition in fog waters. To address this gap, we have investigated the concentration and composition of ON in fog waters collected in Davis, in California's Central Valley. Significant quantities of dissolved organic nitrogen (DON) were found in these samples, with a median concentration of 303 μM N (range=120–1630 μM N). DON typically represented approximately 16% of the total dissolved nitrogen (inorganic+organic) in Davis fog waters. The median concentration of nitrogen in free amino acids and alkyl amines was 16 μM N (range=3.8–120 μM N), which accounted for 3.4% of the DON in Davis fogs. Thus, although the absolute concentrations of free amino compounds were significant, they were only a minor component of the DON pool. Combined amino nitrogen (e.g., proteins and peptides) was present at higher concentrations and accounted for 6.1–29% (median=16%) of DON. Overall, free and combined amino compounds typically accounted for a median value of 22% of DON in the fog waters.
A large body of information on emissions from the various types of
biomass burning has been accumulated over the past decade, to a large
extent as a result of International Geosphere-Biosphere
Programme/International Global Atmospheric Chemistry research
activities. Yet this information has not been readily accessible to the
atmospheric chemistry community because it was scattered over a large
number of publications and reported in numerous different units and
reference systems. We have critically evaluated the presently available
data and integrated these into a consistent format. On the basis of this
analysis we present a set of emission factors for a large variety of
species emitted from biomass fires. Where data were not available, we
have proposed estimates based on appropriate extrapolation techniques.
We have derived global estimates of pyrogenic emissions for important
species emitted by the various types of biomass burning and compared our
estimates with results from inverse modeling studies.
Organic compound emission rates for volatile organic compounds (VOC), gas-phase semivolatile organic compounds, and particle-phase organic compounds are measured from residential fireplace combustion of wood. Firewood from a conifer tree (pine) and from two deciduous trees (oak and eucalyptus) is burned to determine organic compound emissions profiles for each wood type including the distribution of the alkanes, alkenes, aromatics, polycyclic aromatic hydrocarbons (PAH), phenol and substituted phenols, guaiacol and substituted guaiacol, syringol and substituted syringols, carbonyls, alkanoic acids, resin acids, and levoglucosan. Levoglucosan is the major constituent in the fine particulate emissions from all three wood types, contributing 18-30% of the fine particulate organic compound emissions. Guaiacol (2-methoxyphenol), and guaiacols with additional substituents at position 4 on the molecule, and resin acids are emitted in significant quantities from pine wood combustion. Syringol (2,6-dimethoxyphenol) and syringols with additional substituents at position 4 on the molecule are emitted in large amounts from oak and eucalyptus firewood combustion, but these compounds are not detected in the emissions from pine wood combustion. Syringol and most of the substituted syringols are found to be semivolatile compounds that are present in both the gas and particle phases, but two substituted syringols that have not been previously quantified in wood smoke emissions, propionylsyringol and butyrylsyringol, are found exclusively in the particle phase and can be used to help trace hardwood smoke particles in the atmosphere. Benzene, ethene, and acetylene are often used as tracers for motor vehicle exhaust in the urban atmosphere. The contribution of wood smoke to the ambient concentrations of benzene, ethene, and acetylene could lead to an overestimate of the contribution of motor vehicle tailpipe exhaust to atmospheric VOC concentrations.
Over the past 50 years, Lake Tahoe, an alpine lake located in the Sierra Nevada mountains on the border between California and Nevada, has seen a decline in water clarity. With significant urbanization within its borders and major urban areas 130 km upwind of the prevailing synoptic airflow, it is believed the Lake Tahoe Basin is receiving substantial nitrogen (N) input via atmospheric deposition during summer and fall. We present preliminary inferential flux estimates to both lake surface and forest canopy based on empirical measurements of ambient nitric acid (HNO3), ammonia (NH3), and ammonium nitrate (NH4NO3) concentrations, in an effort to identify the major contributors to and ranges of atmospheric dry N deposition to the Lake Tahoe Basin. Total flux from dry deposition ranges from 1.2 to 8.6 kg N ha-1 for the summer and fall dry season and is significantly higher than wet deposition, which ranges from 1.7 to 2.9 kg N ha-1 year-1. These preliminary results suggest that dry deposition of HNO3 is the major source of atmospheric N deposition for the Lake Tahoe Basin, and that overall N deposition is similar in magnitude to deposition reported for sites exposed to moderate N pollution in the southern California mountains.
Biomass burning is widespread, especially in the tropics. It serves to clear land for shifting cultivation, to convert forests to agricultural and pastoral lands, and to remove dry vegetation in order to promote agricultural productivity and the growth of higher yield grasses. Furthermore, much agricultural waste and fuel wood is being combusted, particularly in developing countries. Biomass containing 2 to 5 petagrams of carbon is burned annually (1 petagram = 10(15) grams), producing large amounts of trace gases and aerosol particles that play important roles in atmospheric chemistry and climate. Emissions of carbon monoxide and methane by biomass burning affect the oxidation efficiency of the atmosphere by reacting with hydroxyl radicals, and emissions of nitric oxide and hydrocarbons lead to high ozone concentrations in the tropics during the dry season. Large quantities of smoke particles are produced as well, and these can serve as cloud condensation nuclei. These particles may thus substantially influence cloud microphysical and optical properties, an effect that could have repercussions for the radiation budget and the hydrological cycle in the tropics. Widespread burning may also disturb biogeochemical cycles, especially that of nitrogen. About 50 percent of the nitrogen in the biomass fuel can be released as molecular nitrogen. This pyrdenitrification process causes a sizable loss of fixed nitrogen in tropical ecosystems, in the range of 10 to 20 teragrams per year (1 teragram = 10(12) grams).
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