Figure 3 - uploaded by Alexandre Albinet
Content may be subject to copyright.
Spring–summer SOC (green) and POC (grey) contributions to PM2.5 OC estimated using the EC tracer method for all the monitored sites from 2006 to 2016. Results are presented in increasing order of OC concentration levels (µgC m−3). In black, urban sites; in blue, suburban sites; in red, rural sites and in green, remote sites.
Source publication
Secondary organic aerosol (SOA) is known to account for a major fraction of airborne particulate matter, with significant impacts on air quality and climate at the global scale. Despite the substantial amount of research studies achieved during these last decades, the source apportionment of the SOA fraction remains difficult due to the complexity...
Similar publications
To accurately apportion the sources of aerosols, a combined method of positive matrix factorization (PMF) and the Bayesian mixing model was applied in this study. The PMF model was conducted to identify the sources of PM2.5 in Guangzhou. The secondary inorganic aerosol source was one of the seven main sources in Guangzhou. Based on stable isotopes...
Citations
... Additionally, primary coal combustion and biomass burning have higher OC/EC ratios (Chen et al., 2005;Han et al., 2010), thus perhaps leading to an overestimate of SOC. Thus, it is important that the key of the EC tracer method is to find a proper primary OC/EC ratio (Srivastava et al., 2018). The main uncertainty in determining (OC/EC) pri is the lack of a definitive criterion for selecting a percentile that accurately represents (OC/EC) pri , which can vary spatially and temporally Kaskaoutis et al., 2020). ...
Brown carbon (BrC) is an important light-absorbing component of organic carbon (OC), causing large uncertainty in aerosol radiative forcing evaluation and being related to health issues as well. Knowledge of BrC in an atmospheric background station is beneficial to understand its role in a changing climate. A year-long sampling campaign was conducted at Nanling background station to get a comprehensive knowledge of WS-BrC, a total of seventy-two PM2.5 samples throughout a year were used. Light absorption and fluorescence spectra of WSOC were analyzed synchronously using a fluorescence spectrophotometer. The low levels of PM2.5, OC, and elemental carbon (EC) conferred a background site. The optical properties of WS-BrC were characterized using excitation-emission matrix (EEM) fluorescence spectroscopy. The WS-BrC made a significant contribution (365 nm, 18% ± 10%) to total carbonaceous aerosol absorption. The mass absorption efficiency (MAE) of WS-BrC is 0.81 ± 0.34 m² gC–1, and varies among seasons due to the different sources or atmospheric processing. Three EEM fluorescent components were identified by parallel factor (PAFAFAC) analysis, including two humic-like substances (HULIS, C1, C2), and one phenolic-like component. The HULIS components accounted for approximately 70% of the total fluorescence intensities. Primary combustion emissions showed enhanced activity during the winter and spring seasons, but there were no significant influences on WS-BrC in spring. Secondary sources contributed significantly to WS-BrC during winter, summer, and autumn (all exceeding 50%), except for spring. Photooxidation is a significant process in the formation of secondary WS-BrC in winter and autumn, but there may be another formation pathway in summer, i.e., the ammonia pathway. This study contributes to our understanding of BrC in the background atmosphere.
... This source also emits large amounts of volatile and semi-volatile organic compounds (VOCs and SVOCs) (Akherati et al., 2020;Bruns et al., 2016;Ahern et al., 2019;Hartikainen et al., 2018;Růžičková et al., 2022;Hatch et al., 2015Hatch et al., , 2017Hatch et al., , 2018Baudic et al., 2016) that can undergo (photo-) chemical oxidation processes involving atmospheric oxidants, such as ozone (O3), hydroxyl (OH) or nitrate (NO3) radicals, resulting in the formation of Secondary Organic Aerosols (SOA) (Kroll and Seinfeld, 2008;Hallquist et al., 2009;Jimenez et al., 2009;Ziemann and Atkinson, 2012;Carlton 45 et al., 2009;Heald and Kroll, 2020). OA constitute a significant fraction of fine PM (Bressi et al., 2021;Zhang et al., 2007Zhang et al., , 2011, and SOA account for a large proportion of OA (up to 90%, depending on the location) (Zhang et al., 2007Srivastava et al., 2018a;Kroll and Seinfeld, 2008). Identifying the major SOA precursors and investigating the physicochemical properties, formation yields, and chemical composition of SOA are crucial to implement efficient air quality policies. ...
Secondary organic aerosols (SOA) formed by oxidation of typical precursors largely emitted by biomass burning, such as PAHs and furans, are still poorly characterized in terms of formation yields, physical and light absorption properties, particularly those generated at night following reaction with nitrate radicals (NO3). In the present study, we evaluated and compared the formation yields, effective density (ρeff), absorption Ångström exponent (α), and mass absorption coefficient (MAC) of laboratory-generated SOA from three furan compounds (furan, 2-methylfuran, and 2,5-dimethylfuran) and four PAHs (naphthalene, acenaphthylene, fluorene, and phenanthrene). SOA were generated in an oxidation flow reactor from the reaction between hydroxyl radicals (OH; 0.1 - 20 equivalent aging days) or NO3 radicals (0.05 - 6 equivalent aging nights of 14 h) with single furan or PAH. The ρeff, formation yields, α, and MAC of the generated SOA varied depending on the precursor and oxidant considered. The ρeff of SOA formed with OH and NO3 tended to increase with particle size before reaching a “plateau”. This was particularly evident for the nighttime chemistry experiments with NO3 radicals (1.2 to 1.6 on average for particles > 100 nm). Such results highlighted potential differences in the chemical composition of the SOA, as well as probably in their morphology, according to the particle size. Three times lower SOA formation yields were obtained with NO3 compared to OH. The yields of PAH SOA (18 to 76 %) were 5 to 6 times higher than those obtained for furans (3-12 %). While furan SOA showed low or negligible light absorption properties, PAH SOA was found to have a significant impact in the UV-Visible region, implying a significant contribution to atmospheric brown carbon (BrC). No increase in the MAC values was observed from OH to NO3 oxidation processes, probably due to a low formation of nitrogen-containing chromophores through homogeneous gas phase oxidation processes with NO3 only (without NOx). Overall, the results obtained in this work demonstrated that PAHs are significant precursors of SOA emitted by biomass burning, through both, day- and nighttime processes, and have a substantial impact on the aerosol light absorption properties and so probably on climate.
... A minimum R-square (MRS) method was applied to estimate light absorption by secondary BrC versus primary BrC. Similar to the EC-tracer method for estimating Secondary Organic Carbon (Srivastava et al., 2018), this method presumed that the total light-absorption of BrC was from primary emissions and secondary formation and eBC only formed from combustion processes. Meanwhile, it was assumed that primary BrC originated from the same sources as eBC. ...
Understanding the evolution of brown carbon (BrC) in the atmosphere is essential for investigating its climate effects. This study deployed a novel in‐situ BrC continuous observation system to firstly measure water‐soluble BrC absorption (AbsWS‐BrC) in an offshore island over the Bohai Sea in the winter of 2020. The AbsWS‐BrC abundance before the cold wave (BCW) was more than twice higher than that after the cold wave (ACW). This was mainly ascribed to the substantially suppressed formation of secondary WS‐BrC (WS‐BrCsec). Diurnal patterns of AbsWS‐BrC exhibited nighttime peaks, which derived from enhanced primary emissions and strong aqueous‐phase processes. Photochemical processes bleached daytime WS‐BrC during BCW, while daytime peaks of WS‐BrCsec emerged during ACW due to the weakened photobleaching effect. Statistical analysis indicated ambient temperature and relative humidity as well as total oxidized nitrogen (NO2 + NO3⁻) and reduced nitrogen (NH4⁺ + NH3) were the dominant factors promoting WS‐BrCsec. Moderate aerosol pH (>2.5) also facilitated the formation of WS‐BrCsec while no obvious dependences of WS‐BrCsec on gas‐particle partitioning of ammonia, O3, and sulfur precursors were found. At the molecular level, BrC chromophores with the identified compositions, carbon oxidation state, O/C, H/C, and absorption spectra were compared between the two periods. Characteristics of water‐soluble CHO‐ and CHON‐BrC were more of secondary origin during BCW, while primary emissions contributed significantly to BrC chromophores during ACW. This study highlights the advantage of high resolution BrC measurement in probing its dynamic evolution and influencing factors.
... 28−34 Overall, the SOA-tracer method tends to underestimate the SOC concentrations when compared to others, and CMB and EC-tracer methods are prone to giving higher estimation of SOC, notably during wintertime, than the PMF results. 35 Bayesian inference (BI) has been introduced in atmospheric sciences for data assimilation in CTMs 36−40 and source apportionment of EC and NO x using isotope analysis. 41−44 In this paper, we describe a novel BI approach for the differentiation of POC and SOC that relies on only major species measurement data, as detailed in Section 2.4. ...
The determination of primary organic carbon (POC) and secondary organic carbon (SOC) in fine particulate matter using ambient measurements is essential in atmospheric chemistry. A novel Bayesian inference (BI) approach is proposed to achieve such quantification using only major component measurement data and tested in two case studies. One case study composes of filter-based daily compositional data made in the Pearl River Delta region, China, during 2012, while the other uses online measurement data recorded at the Dianshan Lake monitoring site in Shanghai in wintertime 2019. Source-specific organic trace measurement data are available in both the cases so that positive matrix factorization (PMF) analysis is performed, where PMF-resolved POC and SOC are used as the best available reference values for model evaluation. Meanwhile, traditional techniques, i.e., minimum ratio value, minimum R squared, and multiple linear regression, are also employed and evaluated. For both the cases, the BI models have shown significant advantages in accurately estimating POC and SOC amounts over conventional methods. Further analysis suggests that using sulfate as the SOC tracer in BI model gives the best model performance. This methodological advance provides an improved and practical tool to derive POC and SOC levels for addressing PM-related environmental impacts.
... The OC/EC ratio is commonly used for qualitative assessment of carbonaceous-aerosol sources and SOC estimation (Pio et al., 2011;Srivastava et al., 2018). The mean winter OC/EC ratio in Ioannina (range: 5.4-19.6; ...
This study examines the concentrations and characteristics of carbonaceous aerosols (including saccharides) and inorganic species measured by PM2.5 filter sampling and a multi-wavelength Aethalometer during two campaigns in a mountainous, medium-sized, Greek city (Ioannina). The first campaign was conducted in summer and used as a baseline of low concentrations, while the second took place in winter under intensive residential wood burning (RWB) emissions. Very high winter-mean OC concentrations (26.0 μg m⁻³) were observed, associated with an OC/EC ratio of 9.9, and mean BCwb and PM2.5 levels of 4.5 μg m⁻³ and 57.5 μg m⁻³, respectively. Simultaneously, record-high levoglucosan (Lev) concentrations (mean: 6.0 μg m⁻³; max: 15.9 μg m⁻³) were measured, revealing a severely biomass burning (BB)-laden environment. The water-soluble OC component (WSOC) accounted for 56 ± 9% of OC in winter, exhibiting high correlations (R² = 0.93–0.97) with BB tracers (nss-K⁺, BCwb, Lev), nitrate and light absorption, potentially indicating the formation of water-soluble brown carbon (BrC) from fast oxidation processes. The examination of diagnostic ratios involving BB tracers indicated the prevalence of hardwood burning, while the mean Lev/OC ratio (22%) was remarkably higher than literature values. Applying a mono-tracer method based on levoglucosan, we estimated very high BB contributions to OC (∼92%), EC (∼64%) and WSOC (∼87%) during winter. On the contrary, low levels were registered during summer for all carbonaceous components, with winter/summer ratios of 4–5 for PM2.5 and BC, 10 for OC, 30 for BCwb and ∼1100 for levoglucosan. The absence of local BB sources in summer, combined with the photochemical processing and aging of regional organic aerosols, resulted in higher WSOC/OC fractions (64 ± 13%). The results indicate highly soluble fine carbonaceous aerosol fraction year-round, which when considered alongside the extreme concentration levels in winter can have important implications for short- and long-term health effects.
... 2OH (Peng et al. 2015). Ozone could also be reacted with other pollutants that are not related to human activities like biogenic volatile organic compounds (BVOC) or volatile organic compounds (VOC) and sulfur dioxide (SO 2 ), leading to the formation of secondary organic aerosols (SOA) or secondary inorganic aerosols (SIA) which represents a significant fraction of PM (Abis et al. 2021;Srivastava et al. 2018). This could explain the increase in PM or the small decrease found in comparison with other pollutants, according to results of several studies (Sbai et al. 2021b;Chauhan and Singh 2020;Dantas et al. 2020). ...
Climate and air quality change due to COVID-19 lockdown (LCD) are extremely concerned subjects of several research recently. The contribution of meteorological factors and emission reduction to air pollution change over the north of Morocco has been investigated in this study using the framework generalized additive models, that have been proved to be a robust technique for the environmental data sets, focusing on main atmospheric pollutants in the region including ozone
(O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), particulate matter (PM2.5 and PM10), secondary inorganic aerosols (SIA), nom-methane volatile organic compounds and carbon monoxide (CO) from the regional air pollution dataset of the Copernicus Atmosphere Monitoring Service. Our results, indicate that secondary air pollutants (PM2.5, PM10 and O3) are more influenced by metrological factors and the other air pollutants reported by this study (NO2 and SO2). We show a negative effect for PBHL, total precipitation and NW10M on PM (PM2.5 and PM10), this meteorological parameters contribute to decrease in PM2.5 by 9, 2 and 9% respectively, before LCD and 8, 1 and 5% respectively during LCD. However, a positive marginal effect was found for SAT, Irradiance and RH that contribute to increase PM2.5 by 9, 12 and 18% respectively, before LCD and 17, 54 and 34% respectively during LCD. We found also that meteorological factors
contribute to O3, PM2.5, PM10 and SIA average mass concentration by 22, 5, 3 and 34% before LCD and by 28, 19, 5 and 42% during LCD respectively. The increase in meteorological factors marginal effect during LCD shows the contribution of photochemical oxidation to air pollution due to increase in atmospheric oxidant (O3 and OH radical) during LCD, which can explain the response of PM to emission reduction. This study indicates that PM (PM2.5, PM10) has more controlled by SO2 due to the formation of sulfate particles especially under high oxidants level. The positive correlation between
westward wind at 10 m (WW10M), Northward Wind at 10 m (NW10M) and PM indicates the implication of sea salt particles transported from Mediterranean Sea and Atlantic Ocean. The Ozone mass concentration shows a positive trend with Irradiance, Total and SAT during LCD; because temperature and irradiance enhance tropospheric ozone formation via photochemical reaction.This study shows the contribution of atmospheric oxidation capacity to air pollution change.
... Several molecular markers from specific sources (or SOA precursors) have been reported in the literature and are used for source apportionment purposes (Hopke et al., 2020;Karagulian et al., 2015;Kleindienst et al., 2007;Lanzafame et al., 2021;Schauer et al., 1996;Srivastava et al., 2019Srivastava et al., , 2018bSrivastava et al., , 2018cSrivastava et al., , 2018aSrivastava et al., , 2021. For instance, levoglucosan is commonly used as a primary marker for biomass burning emissions (Bhattarai et al., 2019;Simoneit et al., 1999) and constant ratios between the wood burning organic matter (OM wb ) and particulate phase levoglucosan, estimated by measurement data, are often used to evaluate the contribution of wood-burning aerosol to organic aerosol (Herich et al., 2014;Puxbaum et al., 2007;Schmidl et al., 2008). ...
... However, it has also been observed as a degradation product of phthalates emitted by plastic materials (Hankett et al., 2013) and it might be directly emitted by vehicular engines (Kawamura and Kaplan, 1987). Although all the PM source apportionment marker-based methods assume that these compounds are stable in the atmosphere and mainly associated to the particulate phase, they can be degraded in atmosphere by sunlight and by reaction with atmospheric radicals (Nozière et al., 2015;Srivastava et al., 2018b). In addition, evidences of their semi-volatile behavior have been provided by different authors (Al Naiema and Stone, 2017;Bannan et al., 2017;Booth et al., 2012;Lanzafame et al., 2021;Xie et al., 2014;Yee et al., 2013). ...
We developed and implemented in the 3D air quality model CHIMERE the formation of several key anthropogenic aerosol markers including one primary anthropogenic marker (levoglucosan) and 4 secondary anthropogenic markers (nitrophenols, nitroguaiacols, methylnitrocatechols and phthalic acid). Modelled concentrations have been compared to measurements performed at 12 locations in France for levoglucosan in winter 2014–15, and at a sub-urban station in the Paris region over the whole year 2015 for secondary molecular markers. While a good estimation of levoglucosan concentrations by the model has been obtained for a few sites, a strong underestimation was simulated for most of the stations especially for western locations due to a probable underestimation of residential wood burning emissions. The simulated ratio between wood burning organic matter and particulate phase levoglucosan is constant only at high OM values (>10 μg m⁻³) indicating that using marker contribution ratio may be valid only under certain conditions. Concentrations of secondary markers were well reproduced by the model for nitrophenols and nitroguaiacols but were underestimated for methylnitrocatechols and phthalic acid highlighting missing formation pathways and/or precursor emissions. By comparing modelled to measured Gas/Particle Partitioning (GPP) of markers, the simulated partitioning of Semi-Volatile Organic Compounds (SVOCs) was evaluated. Except for nitroguaiacols and nitrophenols when ideality was assumed, the GPP for all the markers was underestimated and mainly driven by the hydrophilic partitioning. SVOCs GPP, and more generally of all SVOC contributing to the formation of SOA, could therefore be significantly underestimated by air quality models, especially when only the partitioning on the organic phase is considered. Our results show that marker modelling can give insights on some processes (such as precursor emissions or missing mechanisms) involved in SOA formation and could prove especially useful to evaluate the GPP in 3D air quality models.
... In contrast, SOC contributed 53-70% of OC at the seven sites. A literature review by Srivastava et al. (2018) suggested that SOC accounted for 5-98% of PM 2.5 OC across the U.S., and if only urban locations were considered, 5-61%. The SOC contributions to OC at Canadian urban locations presented in this study were within the range of those reported in the U.S., although at upper-end values. ...
Chemically resolved data for fine particulate matter (PM2.5) have been collected across Canada since 2003 through the National Air Pollution Surveillance (NAPS) network. Seven urban sites that have 10–17 years (2003–2019) of PM2.5 organic carbon (OC) and elemental carbon (EC) data were selected for analysis of decadal trends of OC, EC, and OC/EC ratio using the Ensemble Empirical Mode Decomposition method. Results showed that OC and EC decreased by 0.009–0.072 μg m⁻³ yr⁻¹ and 0.028–0.049 μg m⁻³ yr⁻¹, or 0.77–3.1 % yr⁻¹ and 3.2–6.7 % yr⁻¹, respectively, depending on the location. The more rapid decrease in EC than OC resulted in an increasing trend in the OC/EC ratio of 0.03–0.19 yr⁻¹ across the sites. Macro-tracer approach was used to estimate source attributions of OC and EC from wood burning, fossil fuel combustion, and secondary aerosol formation. Using this approach, it was identified that the significant decrease in EC during the past decade was predominately caused by reduced on-road emissions. The decreased emissions from wood burning and transportation dominated the decline of OC, but such a decline was largely offset by the enhanced secondary organic aerosol (SOA) formation, resulting in much weaker decline of OC than EC. The enhanced SOA formation was due to the increased biogenic emissions fully offsetting the decreased anthropogenic emissions for volatile organic compounds. These findings highlight the need for quantifying biogenic sources of VOCs and other oxidants that are involved in OC formation at the national scale.
... A minimum R-squared (MRS) method was developed to separate light absorption by BrCsec (b abs BrCsec(λ)) versus primary BrC. The BC tracer method for calculating SOC was applied in this approach (Srivastava et al., 2018). Aerosol light absorption is due to carbonaceous particles from both primary and secondary sources. ...
Absorbing carbonaceous aerosols, i.e. black and brown carbon (BC and BrC), affected heavily on climate change, regional air quality and human health. The nationwide lockdown measures in 2020 were performed to against the COVID-19 outbreak, which could provide an important opportunity to understand their variations on light absorption, concentrations, sources and formation mechanism of carbonaceous aerosols. The BC concentration in Wuhan megacity (WH) was 1.9 μg m⁻³ during lockdown, which was 24% lower than those in the medium-sized cities and 26% higher than those in small city; in addition, 39% and 16-23% reductions occurred compared with the same periods in 2019 in WH and other cities, respectively. Fossil fuels from vehicles and industries were the major contributors to BC; and compared with other periods, minimum contribution (64-86%) mainly from fossil fuel to BC occurred during the lockdown in all cities. Secondary BrC (BrCsec) played a major role in the BrC light absorption, accounting for 65-77% in WH during different periods. BrCsec was promoted under high humidity, and decreased through the photobleaching of chromophores under higher Ox. Generally, the lockdown measures reduced the BC concentrations significantly; however, the variation of BrCsec was slight.
... Fine organic carbon (OC) aerosol plays a major role in environmental impacts and health risks derived from air pollution exposure [1][2][3]. As part of the urban air pollution by PM 2.5 (fine particles with aerodynamic diameters less than 2.5 µm), the levels of OC have become a central issue in decision making in improving air quality in urban areas [4,5]. Fine OC is frequently the major fraction of the ambient PM 2.5 mass in urban environments [6,7]. ...
... Thus, the use of organic markers has been helpful in distinguishing types of source emissions in source apportionment studies around the world (e.g., [17]). In particular, the use of organic markers to construct source profiles and their application to source attribution using a chemical mass balance approach has proven fruitful [4]. ...
... The EC analysis was conducted using temperature profiles with a withhold time of 45 s and a final holding time of 120 s at 870 • C in an oxidizing atmosphere (He:O 2 90:10 v/v). EC was oxidized from the filter into the oxidation oven, converted into CO 2 , reduced to CH 4 , and detected by FID as CH 4 . During this stage, a pyrolysis correction was made. ...
Source attribution of airborne particulate matter (PM) relies on a host of different chemical species. Organic molecular markers are a set of particularly useful marker compounds for estimating source contributions to the fine PM fraction (i.e., PM2.5). Although there are many source apportionment studies based on organic markers, these studies heavily rely on the few studies that report region-specific emission profiles. Source attribution efforts, particularly those conducted in countries with emerging economies, benefit from ad hoc information to conduct the corresponding
analyses. In this study, we report organic molecular marker source profiles for PM2.5 emitted from
12 major sources types from five general source categories (meat cooking operations, vehicle exhausts,
industries, biomass and trash burning, and urban background) for the Monterrey Metropolitan Area (Mexico). Source emission samples were obtained from a ground-based source-dominated sampling approach. Filter-based instruments were utilized, and the loaded filters were chemically characterized for organic markers by GC-MS. Levoglucosan and cholesterol dominate charbroiled-cooking operation sources while methoxyphenols, PAHs and hopanes dominate open-waste burning, vehicle exhaust and industrial emissions, respectively. A statistical analysis showed values of the Pearson
distance < 0.4 and the similarity identity distance > 0.8 in all cases, indicating dissimilar source profiles. This was supported by the coefficient of divergence average values that ranged from 0.62 to 0.72. These profiles could further be utilized in receptor models to conduct source apportionment in regions with similar characteristics and can also be used to develop air pollution abatement strategies.
