Showing papers on "Nonpoint source pollution published in 2022"

Research on the Non-Point Source Pollution Characteristics of Important Drinking Water Sources

Abstract: In recent years, freshwater resource contamination by non-point source pollution has become particularly prominent in China. To control non-point source (NPS) pollution, it is important to estimate NPS pollution exports, identify sources of pollution, and analyze the pollution characteristics. As such, in this study, we established the modified export coefficient model based on rainfall and terrain to investigate the pollution sources and characteristics of non-point source total nitrogen (TN) and total phosphorus (TP) throughout the Huangqian Reservoir watershed—which serves as an important potable water source for the main tributary of the lower Yellow River. The results showed that: (1) In 2018, the non-point source total nitrogen (TN) and total phosphorus (TP) loads in the Huangqian Reservoir basin were 707.09 t and 114.42 t, respectively. The contribution ratios to TN export were, from high to low, rural life (33.58%), farmland (32.68%), other land use types (20.08%), and livestock and poultry breeding (13.67%). The contribution ratios to TP export were, from high to low, rural life (61.19%), livestock and poultry breeding (21.65%), farmland (12.79%), and other land use types (4.38%). The non-point source pollution primarily originated from the rural life of the water source protection zone. (2) Non-point source TN and TP pollution loads and load intensities showed significantly different spatial distribution patterns throughout the water source protection area. Specifically, their load intensities and loads were the largest in the second-class protected zone, which is the key source area of non-point source pollution. (3) When considering whether to invest in agricultural land fertilizer control or rural domestic sewage, waste, and livestock manure pollution control, the latter is demonstrably more effective. Thus, in addition to putting low-grade control on agricultural fertilizer loss, to rapidly and effectively improve potable water quality, non-point source pollution should, to a larger extent, also be controlled through measures such as establishing household biogas digesters, introducing village sewage treatment plants, and improving the recovery rate of rural domestic garbage. The research results discussed herein provide a theoretical basis for formulating a reasonable and effective protection plan for the Huangqian Reservoir water source and can potentially be used to do the same for other similar freshwater resources.

Assessing effects of non-point source pollution emission control schemes on Beijing's sub-center with a water environment model

Abstract: A high-quality water environment is a strategic demand for constructing Beijing's Sub-center. Controlling non-point source (NPS) pollution is the key to water environment management in Beijing's Sub-center. We developed a water environment model of Beijing's Sub-center using MIKE 11. Ammonia-Nitrogen and Total Phosphorus concentrations and Chemical Oxygen Demand were used as pollution indicators. Water quality response to the control of agricultural and urban NPS pollution under different scenarios was predicted. The effects of different scenarios were evaluated. Results show that water quality in Beijing's Sub-center can be considerably improved by controlling emissions of NPS pollution. Reducing agricultural NPS pollution is the key to reducing Ammonia-Nitrogen and Total Phosphorus concentrations and improving water quality. Results also demonstrate that water quality response varies with land use type. This study aims to provide reliable and practical information to support water pollution control in Beijing's Sub-center, especially NPS pollution. This water environment model fills the gap in the NPS pollution simulation in rivers in Beijing's Sub-center and promotes the application of the water environment model in water pollution management.

New framework for nonpoint source pollution management based on downscaling priority management areas

Abstract: • A new framework for NPS pollution management based on scale transformation was constructed. • The uncertainty of the framework was quantified. • After the re-downscaling the PMAs, the area and the pollution load intensity of the top priority management area increased by 34.41% and 29.66%. • The framework reduced the area of non-point source management. • Hydrological period, water quality target and assessment points were the main factors affecting framework uncertainty. Scale transformation is a problem in many fields, especially in geoscience. But there is less report on the use of scale transformation to control non-point source (NPS) pollution. This study constructs a new framework for NPS pollution management by re-downscaling pollution source area and exploring the effects of Best Management Practices (BMPs) on water quality improvement at large scale after treatment of small-scale subwatersheds. Combined with Soil and Water Assessment Tool (SWAT), the advantage and uncertainty of the framework were explored though a case study in the Three Gorges Reservoir Region, China. Based on the results, the framework improved the efficiency of priority management areas (PMAs) identification. After the re-downscaling the PMAs, the total phosphorus (TP) load intensity increased from 59.3 kg/km 2 to 84.3 kg/km 2 for those high-ranking PMAs, while the area of PMAs with the maximum intensity increased by 4.44%. The framework has the most obvious advantages when the TP reduction target is set as 38.00%. The NPS management area after re-downscaling would reduce by 2.46% compare to primary PMAs. Water quality target, assessment points and hydrological periods are identified as the uncertain factors. The selection of proper water quality target and the assessment point would account for 19.03% and 10.61% reduction of NPS control area. From dry to wet years, the NPS control area increased by 647 km 2 which accounts for 26.71% of the watershed, while the maximum intensity changed from 27.6 kg/km 2 to 59.3 kg/km 2 . The new framework can be extended to other watersheds for the NPS management at watershed scale.

First Flush Stormwater Runoff in Urban Catchments: A Bibliometric and Comprehensive Review

Abstract: First flush is a phenomenon in stormwater runoff that has been considered a topic of great interest in the field of nonpoint source pollution. Despite several attempts to define the first flush quantitively, the specified characteristics of the phenomenon vary among sources. To address these uncertainties, a bibliometric and comprehensive review on published articles related to first flush was conducted. A corpus of 403 research articles was obtained from the Scopus database, which was then parsed using the CorText Manager for the bibliometric analysis. The study examined quantitative definitions of first flush from various sources; climate and topographic characteristics of monitoring and experimental sites where the studies on first flush were performed; the sample collection methods applied; the first flush values obtained on the studies and how it influenced the nonpoint source pollution in urban watersheds. A network map, two contingency matrices, and a Sankey diagram were created to visualize the relationship of significant keywords related to first flush, as well as their co-occurrences with journals, countries, and years. It was found that the strength of the first flush effect could vary depending on the geographical location of the site, climatic conditions, and the pollutants being analyzed. Therefore, initial rainfall monitoring, runoff sampling, and water quality testing were seen as critical steps in characterizing the first flush in urban catchments. Furthermore, the characterization of first flush was found to be significant to the selection of best management practices and design of low-impact development (LID) technologies for stormwater runoff management and nonpoint source pollution control.

Major point and nonpoint sources of nutrient pollution to surface water have declined throughout the Chesapeake Bay watershed

Abstract: Understanding drivers of water quality in local watersheds is the first step for implementing targeted restoration practices. Nutrient inventories can inform water quality management decisions by identifying shifts in nitrogen (N) and phosphorus (P) balances over space and time while also keeping track of the likely urban and agricultural point and nonpoint sources of pollution. The Chesapeake Bay Program’s Chesapeake Assessment Scenario Tool (CAST) provides N and P balance data for counties throughout the Chesapeake Bay watershed, and these data were leveraged to create a detailed nutrient inventory for all the counties in the watershed from 1985–2019. This study focuses on three primary watershed nutrient balance components—agricultural surplus, atmospheric deposition, and point source loads—which are thought to be the leading anthropogenic drivers of nutrient loading trends across the watershed. All inputs, outputs, and derived metrics (n=53) like agricultural surplus and nutrient use efficiency, were subjected to short- and long-term trend analyses to discern how sources of pollution to surface water have changed over time. Across the watershed from 1985–2019, downward trends in atmospheric deposition were ubiquitous. Though there are varying effects, long-term declines in agricultural surplus were observed, likely because nutrients are being managed more efficiently. Multiple counties’ point source loads declined, primarily associated with upgrades at major cities that discharge treated wastewater directly to tidal waters. Despite all of these positive developments, recent increases in agricultural surpluses from 2009–2019 highlight that water quality gains may soon be reversed in many agricultural areas of the basin. Besides tracking progress and jurisdictional influence on pollution sources, the nutrient inventory can be used for retrospective water quality analysis to highlight drivers of past improvement/degradation of water quality trends and for decision makers to develop and track their near- and long-term watershed restoration strategies.

Analysis of *Policy Alternatives in the Implementation of a Coastal Nonpoint Pollution Control Program for Agriculture.

Abstract: Agriculture has been singled out as one of the major nonpoint sources of water pollution. To identify alternative policy tools for the implementation of a non-regulatory approach to comply with the Coastal Nonpoint Pollution Control Program (CNPCP) required by The Coastal Zone Act Reauthorization Amendments of 1990, policy makers need to determine factors that may influence producers' willingness to adopt proposed Best Management Practices (BMPs). Neoclassical economic concepts of utility maximization on the part of agricultural producers constitutes the theoretical background in this study, but it is enhanced with the incorporation of a well proved set of theoretical tools based on psychological constructs that account for the measurement of attitudes as complementary causes of behavior. Policy analysis and implementation are studied in terms of (1) achievement of environmentally desirable goals and (2) the aim of keeping agriculture as an economically viable activity. A set of multivariate probit models are tested using primary data collected through a mail survey of Louisiana's sugarcane producers. Results indicate that contemporaneous correlation of the error terms exists among management practices within management measures, and between management measures. It indicates that policy tools must be developed in an integrated manner. The decision to adopt BMPs is significantly influenced by the number of times producers have met with extension service personnel and the number of grower meetings that the producer has attended in the previous year. Participation in cost-sharing has also had a very significant effect on adoption of best management practices, even if no cost sharing programs exist for all practices. Risk of yield loss is not a factor in the adoption of the BMPs included in the study. Farmers' belief that agriculture reduces the quality of water coming off farmland is significant for most management measures. Debt is also a significant variable for most management measures, with a positive sign. As compliance requirements become more stringent, tenure becomes a factor in the adoption of best management practices. Policy makers should consider these results as new strategies are developed to promote adoption of BMPs that reduce nonpoint source water pollution from agricultural sources.

The Nonpoint Sources and Transport of Baseflow Nitrogen Loading Across a Developed Rural‐Urban Gradient

Abstract: Nonpoint source urban nutrient loading into streams and receiving water bodies is widely recognized as a major environmental management challenge. A dominant research and management paradigm assumes that loading primarily derives from elevated stormwater. However, baseflow can account for a large portion of total loading, especially for low development intensity watersheds which comprise the largest urban areas. We investigated the sources and drivers of nonpoint source baseflow nitrogen loading across 27 headwater catchments in the urbanized Piedmont region of North Carolina, USA. Nitrate isotopes, predictors of concentration-discharge (CQ) slopes, and predictors of mean annual total dissolved nitrogen (TDN) loading suggest that wastewater was a major baseflow nonpoint source of nitrogen across developed catchments likely contributing 61% of nitrate loading from septic served catchments and 49% from sewer served catchments. Our findings suggest that subsurface TDN was abundant, loading was largely transport limited, and the hydrogeomorphic position of sanitary infrastructure strongly influences transport. We developed an empirical model showing catchment loading increased with the topographic wetness index of sanitary sewer location, convergent sloping land area, parcel density, and residual agricultural landcover (R2 = 0.78). We extended this model to the study region's 1,436 developed small (0.3–20.8 sq km) catchments. We estimated up to 92.7% of nonpoint source baseflow TDN loading comes from low and medium development intensity catchments, and sanitary infrastructure in wet areas of the landscape accounts for 39% of regional baseflow loading. Our research indicates that managing baseflow loading will require addressing lower development intensity catchments and sanitary infrastructure.

Assessment of BMPs by Estimating Hydrologic and Water Quality Outputs Using SWAT in Yazoo River Watershed

Abstract: Water quality is a global concern; it is due to point and non-point source pollution. Non-point sources for pollution are mainly runoff from Agricultural and forest. To decrease nutrient inputs, management practices are implemented. Using Soil and Water Assessment Tool, water quality parameters can be quantified. Yazoo River Watershed is the largest watershed in Mississippi, which have impact on surface water quality due to large scale agriculture and forest lands. Model has been calibrated and validated for streamflow, sediment, Total Nitrogen (TN), Total Phosphorus (TP) for the USGS gauge stations in the watershed. Model efficiency was assessed with Coefficient of Determination (R2) and Nash-Sutcliffe Efficiency index (NSE). Best Management Practices (BMPs) were implemented throughout the watershed to simulate the impact of BMPs on streamflow, sediment, and nutrient yields. Vegetative Filter Strips (VFS), Riparian Buffer, combination of VFS and Riparian buffer and Cover Crops (CC) were tested for assessing the effective BMP in improving water quality. VFS, Riparian buffer and both (VFS + riparian) have no effect on streamflow, but they were able to decrease sediment, TN, and TP yields. Scenario with both VFS and Riparian buffer had the highest reduction capability as per varying width (5, 10, 15, and 20 m). For CC, Rye grass, Winter Barley and Winter Wheat (WW) were used, of which Rye grass had highest, 5.3% reduction in streamflow. WW has the highest Total Nitrogen reduction that is of 25.4%. CC also has significant reduction ranged between 10% to 11% for TP. This research would assist the Agricultural community to apply appropriate Management practices to improve water quality.

Connecting sources, fractions and algal availability of sediment phosphorus in shallow lakes: An approach to the criteria for sediment phosphorus concentrations.

Abstract: Although point and nonpoint sources contribute roughly equal nutrient loads to lakes, their relative role in supporting algae growth has not been clarified. In this research, we have established a quantitative relationship between algae-available phosphorus (P) and P chemical fractions in sediments; the latter indicates the relative contribution of point versus nonpoint sources. Surface sediments from three large shallow lakes in eastern China, namely, the Chaohu, Taihu and Hongzehu Lakes, were sampled to assess their algae-available P and chemically extracted P fractions. The algae-available P primarily comes from iron/aluminium (hydr)oxide-bound P (Fe/Al-bound P), 45% of which is algae-available P. The ratio of Fe/Al-bound P to calcium compound-bound P (Ca-bound P) indicated the relative contribution of point to nonpoint sources, with the point sources contributing the majority of increased Fe/Al-bound P in sediments. Therefore, the reduction of point sources from urbanized areas, rather than nonpoint sources from agricultural areas that primarily contribute to the Ca-bound P fraction, should be prioritized to alleviate cyanobacterial algal blooms (CyanoHABs) in shallow lakes with sediment P as a potential source to support algae growth. With these important results, we proposed a conceptual model for "P-pumping suction" from sediments to algae to aid in the development of the criteria for sediment P concentrations in shallow lakes.

Reclaimed water for landscape water replenishment: Threshold nitrogen and phosphorus concentrations values for bloom control

Abstract: Considering the high risk of algal blooms caused by nitrogen and phosphorus in reclaimed water during the utilization of reclaimed water in the landscape, an association model for the nitrogen and phosphorus concentrations in reclaimed water for algal blooms control was derived, which considers the local climatic conditions (temperature and light intensity), hydraulic retention time (HRT), and non-point source pollution. Based on the association model, the effects of different non-point source pollution and HRT on the threshold nitrogen and phosphorus concentration values for bloom control were studied by conducting some numerical simulations for three single species and one mixed algae. At HRT = 30 d, the threshold nitrogen and phosphorus concentrations were obtained for different non-point resource pollution coefficients. The numerical results for different non-point source pollution loads show that, with an increase in non-point source pollution, the control curve of nitrogen and phosphorus concentrations gradually approached the coordinate axis, indicating that the threshold nitrogen and phosphorus concentration values in reclaimed water also be gradually reduced. There have been similar conclusions regarding the effect of HRT on the threshold values of nitrogen and phosphorus concentrations in reclaimed water. This study provides a theoretical scientific basis for determining reasonable water quality control levels in the replenishment of landscape water with reclaimed water.

Identification of priority management areas for non-point source pollution based on critical source areas in an agricultural watershed of Northeast China.

Abstract: Identification of critical source areas (CSAs) for non-point source (NPS) pollution is of great significance for environment governance and prevention. However, the CSAs are generally characterized as great spatial dispersion, and spatially heterogeneous precipitation has a great influence on the spatial distribution of nutrient yields. Therefore, we identify the CSAs for nutrient yields in an agricultural watershed of Northeast China at hydrological response units (HRUs) scale based on the Soil and Water Assessment Tool (SWAT), assess the impacts of spatially heterogeneity of precipitation on the identification of the CSAs, analyze the sensitivity of nutrient yields to precipitation by scenarios analysis method, and further identify priority management areas (PMAs) that have poor ability to retain nutrients. The results showed that the CSAs for nutrient yields identified by uniform precipitation showed greater fluctuation range and coverage area than actual precipitation; the major prevention areas of total nitrogen (TN) yield were mainly distributed in regions nearby main stem of lower reaches, while that of total phosphorus (TP) yield were mostly located in urban area nearby outlet of the watershed; the identification of the PMAs significantly decreased the CSAs for TN yield, whereas that for TP yield was no significant difference with the CSAs. This study could provide scientific guidance for the NPS pollution governance and prevention.