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Study sites on the River Wandle, a tributary of the Thames, UK. The blue dot is the outfall location of the WWTP effluent to the river. Red dots are the upstream site (U0.2) and the downstream site (D3.0). The black triangle denotes Beddington WWTP
Source publication
River ecosystem metabolism (REM) is a measure of ecological function which integrates gross primary production (GPP) and ecosystem respiration (ER). Urban rivers often receive effluents from wastewater treatment plants (WWTP) which frequently alter nutrient concentrations and modify temperature regimes of receiving water bodies. To investigate how...
Citations
... These challenges have been documented in the United States (Rakhimbekova et al. 2021;Herren et al. 2021), Canada (Robertson et al. 2021;Digaletos et al. 2023), Spain (Pérez-Ruzafa et al. 2019), Ethiopia (Menberu et al. 2021), China (Wang et al. 2019), France (Louis et al. 2023), and other countries (Oliver et al. 2018). Elevated nitrogen inputs from anthropogenic sources have been found to negatively affect river ecosystem functioning (Zhang and Chadwick 2022) and can endanger public health by increasing the risk of methemoglobinemia from consumption of elevated nitrate in drinking water (Raju and Singh 2017). These studies suggest that agriculture, wastewater (centralized and/ or decentralized), and/or stormwater can be major sources of nitrogen to water resources. ...
Septic systems are potentially significant sources of nitrogen to groundwater and surface water. In-stream practices, such as in-stream bioreactors (IBRs), that promote or enhance nitrogen treatment are promising solutions to reduce nitrogen loads to nutrient-sensitive water. More work is needed to evaluate the efficiency of IBRs in new applications, such as residential sub-watersheds with a high-density of septic systems. The goal of this study was to quantify nitrogen treatment by an in-stream bioreactor (IBR) during baseflow conditions. The IBR was constructed in March 2017 when approximately 1 m of streambed sediment was excavated and backfilled with 0.75 m of woodchips capped by 0.2 m of rotary-kiln, expanded slate and boulder-sized riprap. Samples were collected monthly from July 2017 – March 2019 including IBR inflow, monitoring ports within the IBR, groundwater seeps draining to the IBR, and IBR outflow. Water samples were analyzed for total dissolved nitrogen (TDN), nitrate, ammonium, dissolved organic carbon, chloride, and nitrate isotopic fractionation. The IBR reduced the median concentration of TDN and nitrate by 40% and 77%, respectively. The median mass removal of TDN and nitrate was 26 and 5.2 g day− 1, respectively. Nitrogen-chloride ratios and isotopic fractionation data suggest that denitrification was likely a predominant nitrogen reduction mechanism. In addition to nitrogen treatment, the IBR provided other benefits by improving erosion control, streambank stabilization, and increased bank-full storage from 6 m³ to 19.2 m³. Results indicated that the IBR improved water quality and other residential sub-watersheds with septic systems would benefit from similar practices.
... Text on the graphs shows the Pearson correlation coefficients (r) and p-value of the longitudinal trends with downstream distance Rhine River. We contend that these inflows likely contributed to elevated nutrients and labile organic carbon concentrations, which fueled in-situ N 2 O and CH 4 production processes or directly added externally sourced dissolved N 2 O and CH 4 , similar to what was found in other studies (Brown et al. 2023;Mwanake et al. 2023a;Zhang and Chadwick 2022). The comparison of both lotic ecosystems showed that divergent drivers controlled longitudinal heterogeneities in the GHG fluxes. ...
Lotic ecosystems are sources of greenhouse gases (GHGs) to the atmosphere, but their emissions are uncertain due to longitudinal GHG heterogeneities associated with point source pollution from anthropogenic activities. In this study, we quantified summer concentrations and fluxes of carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and dinitrogen (N2), as well as several water quality parameters along the Rhine River and the Mittelland Canal, two critical inland waterways in Germany. Our main objectives were to compare GHG concentrations and fluxes along the two ecosystems and to determine the main driving factors responsible for their longitudinal GHG heterogeneities. The results indicated that the two ecosystems were sources of GHG fluxes to the atmosphere, with the Mittelland Canal being a hotspot for CH4 and N2O fluxes. We also found significant longitudinal GHG flux discontinuities along the mainstems of both ecosystems, which were mainly driven by divergent drivers. Along the Mittelland Canal, peak CO2 and CH4 fluxes coincided with point pollution sources such as a joining river tributary or the presence of harbors, while harbors and in-situ biogeochemical processes such as methanogenesis and respiration mainly explained CH4 and CO2 hotspots along the Rhine River. In contrast to CO2 and CH4 fluxes, N2O longitudinal trends along the two lotic ecosystems were better predicted by in-situ parameters such as chlorophyll-a concentrations and N2 fluxes. Based on a positive relationship with N2 fluxes, we hypothesized that in-situ denitrification was driving N2O hotspots in the Canal, while a negative relationship with N2 in the Rhine River suggested that coupled biological N2 fixation and nitrification accounted for N2O hotspots. These findings stress the need to include N2 flux estimates in GHG studies, as it can potentially improve our understanding of whether nitrogen is fixed through N2 fixation or lost through denitrification.
... Owing to the influences of global climate change and human activities, small-to-medium river ecosystems in northern China (hereinafter referred to as the target river systems) have been confronted with escalating thermal stress challenges [1,2]. These rivers, besides playing critical roles in water resource provision, biodiversity, and local communities, hold pivotal significance in maintaining regional ecological balance [3][4][5]. ...
... A major state road also used for transport of hazardous and heavy cargo, passes through the catchment area and represents an additional pollution risk. All of these, in conjunction with climate change and water temperature increase, may lead to algal blooms and eutrophication trough promoted metabolic rate (Zhang and Chadwick 2022). The vulnerability of the system to climate and anthropogenic factors is more than obvious. ...
As closed systems, lakes are extremely vulnerable to climate change. Understanding the response to climate change is crucial for effective management and conservation of the lakes and their associated ecosystems. This study focuses on Lake Kozjak, Croatia, a small lake belonging to the Plitvice Lakes system. This system represents a unique hydrogeological karstic phenomenon, closely dependent on a delicate biochemical balance necessary for tufa formation. We apply a simple one-dimensional model, SIMO v.1.0, to predict future water temperature in Lake Kozjak under three scenarios (RCP2.6, RCP4.5 and RCP8.5) from 2006 to 2100. The model was calibrated using measured water temperature profiles and meteorological data from a nearby station. In addition to analyzing the average temperatures of the epilimnion, hypolimnion and the whole lake, we also studied the surface and bottom layer temperatures and their relation to specific forcing parameters. The Schmidt stability index was used as a quantitative indicator to assess lake stability. The simulation results indicate average lake water temperature increase of 0.51, 1.41 and 4.51 °C (100 y)⁻¹ for RCP2.6, RCP4.5 and RCP8.5, respectively. This increase in the water temperature is not accompanied by a substantial strengthening of stratification under RCP2.6 and RCP4.5 scenarios due to the temperature raise being present both in the epilimnion and hypolimnion. However, significant lengthening of the stratification period is observed even for the most stringent scenario, 16, 28 and 47 d (100 y)⁻¹ for RCP2.6, RCP4.5 and RCP8.5, respectively. The predicted water temperature increase and prolonged stratification period may carry serious ecological and environmental implications.
Highlights
• Mean lake water temperature is projected to increase by 0.51 to 4.51 °C (100 y)⁻¹.
• Baseline scenario surface temperature increase of 5.2 °C (100 y)⁻¹ is predicted.
• Stratification period is predicted to lengthen by 16 (RCP2.6) to 47 days (RCP8.5).
• Substantial stratification strengthening is expected only under RCP8.5.
Plastic products are widely used globally, leading to their extensive presence in various wastewaters, water resources, and the environment, which poses environmental risks. Wastewater treatment plants are a significant source of the entry and release of microplastics (MPs) into the environment. So, this study aims to investigate the abundance, shape, size, color, type of polymer, and risk of microplastic hazards in a hospital wastewater treatment plant. The method of analysis included physical separation by filtration using a stainless metal sieve, chemical digestion and counting/characterization by optical methods. The study utilized FESEM and FTIR analysis to examine the surface morphology and identify the polymer type of the MPs. A semi-quantitative risk assessment model was used to calculate the production risk of polymers present in the wastewater. The study found that the most common shape of microplastic particles in hospital wastewater treatment plants was fiber, and the predominant polymer identified was polypropylene. The hazard risk associated with certain polymers, such as polyethylene terephthalate, polyamide, and polyethylene, was found to be higher than the standard rate obtained from other studies. These findings highlight the need for further assessment and investigation of the environmental risks and impacts associated with MPs entering the environment through wastewater treatment plants. In order to further reduce and control these substances, solutions such as establishing environmental laws, reducing consumption and, if possible, replacing them with other materials should be implemented.
Aerobic respiration of organic matter is a key metabolic process influencing carbon (C) biogeochemistry in aquatic ecosystems. Anthropogenic and environmental perturbations to stream ecosystem metabolism can have deleterious effects on downstream water quality. Various environmental features of rivers also influence stream metabolism, including physical (e.g., discharge, light, flow regimes) and chemical factors (nutrients, organic matter) and watershed characteristics (e.g., stream size or drainage area, land use). The relative proportion of surface water contact with benthic sediments has been considered the primary driver of ecosystem processes, including ecosystem respiration (ER). While aquatic ecosystem respiration occurs in the water column (ERwc) and in benthic sediments—including surficial and subsurface sediments (ERsed)—ERsed has long been assumed to be the primary contributor to whole-river ecosystem respiration (ERtot). Recent studies show, however, that somewhere along the river continuum (e.g., 5th–9th order), rivers transition from being dominated by benthic processes to being dominated by water column processes. Yet few metabolism studies have parsed contributions from the water column (ERwc) to ERtot, making it difficult to evaluate the relative magnitude and importance of ERwc across the river continuum and across biomes. In this study, we used the Yakima River basin, Washington, USA, to increase our understanding of basin-scale variation in ERwc. We collected ERwc data and water chemistry samples in triplicate at 47 sites in the Yakima River basin distributed across Strahler stream orders 2–7 and different hydrological and biophysical settings during summer baseflow conditions in 2021. We found that observed ERwc rates were consistently slow throughout the basin during baseflow conditions, ranging from −0.11–0.03 mg O2 L⁻1 d⁻1, and were generally at the very slow end of the range of published ERwc literature values. When compared to reach-scale ERtot rates predicted for rivers across the conterminous United States (CONUS), the very slow ERwc rates we observed throughout the Yakima River basin indicate that ERwc is likely a small component of ERtot in this basin. Despite these slow rates, ERwc nonetheless shows spatial variation across the Yakima River basin that was well explained by watershed characteristics and water chemistry. Multiple linear regression model results show that nitrate (NO3-N), dissolved organic carbon (DOC), and temperature together explained 41.5 % of the spatial variation in ERwc. Supporting the findings of other studies, we found that ERwc increased linearly with increasing NO3-N, increasing DOC, and increasing temperature. We hypothesize that low concentrations of nutrients, DOC, and low temperatures in the water column, coupled with low TSS concentrations, likely contribute to the slow ERwc rates observed throughout the Yakima River basin. Because ERtot measurements integrate contributions from water column respiration and sediment-associated respiration (ERsed), estimating ERtot in cold, clear, low nutrient rivers like those in the Yakima River basin with very slow ERwc will essentially measure contributions from ERsed.
