Non-point Source Pollution In Watershed Research Articles

Simulating the land use change effects on non-point source pollution in the Duliujian River Basin.

The uncertainty in the generation and formation of non-point source pollution makes it challenging to monitor and control this type of pollution. The SWAT model is frequently used to simulate non-point source pollution in watersheds and is mainly applied to natural watersheds that are less affected by human activities. This study focuses on the Duliujian River Basin (Xiqing section), which is characterized by a dense population and rapid urbanization. Based on the calibrated SWAT model, this study analyzed the effects of land use change on non-point source pollution both temporally and spatially. It was found that nitrogen and phosphorus non-point source pollution load losses were closely related to land use type, with agricultural land and high-density urban land (including rural settlements) being the main contributors to riverine nitrogen and phosphorus pollution. This indicates the necessity of analyzing the impact of land use changes on non-point source pollution loads by identifying critical source areas and altering the land use types that contribute heavily to pollution in these areas. The simulation results of land use type changes in these critical source areas showed that the reduction effect on non-point source pollution load is in the order of forest land > grassland > low-density residential area. To effectively curb surface source pollution in the study area, strategies such as modifying urban land use types, increasing vegetation cover and ground infiltration rate, and strictly controlling the discharge of domestic waste and sewage from urban areas can be implemented.

Characterization and prediction of soil hydraulic and solute transport parameters using a random forest model

AbstractTo effectively control nonpoint source pollution and predict its transport and load, understanding water and solute transport processes, patterns and mechanisms is essential. However, the measurement of water movement and solute transport parameters is usually a laborious and time‐consuming task. It is important to predict water movement and solute transport parameters from more readily available soil physical and chemical properties. In this study, a database of soil hydraulic and solute transport parameters containing information retrieved from 83 published studies on soil properties, land use, management measures, etc. was established to characterize and simulate soil water movement and solute transport processes. Our results showed that the soil particle composition was closely related to all soil hydraulic and solute transport parameters. As the soil texture changed from sand to clay, the soil residual water content (θr) obviously increased. The soil porosity was significantly positively correlated with θr, saturated water content (θs), van Genuchten parameter α, dispersity (λ) and retardation factor (R) and negatively correlated with van Genuchten parameter n (p < 0.01). The use of random forest models allowed the prediction of soil hydraulic and solute transport parameters by inputting common or even incomplete soil property parameters. The bulk density and particle composition jointly contributed 66% to the prediction of the soil hydraulic parameters and 44% to the prediction of the solute transport parameters. The pH exerted a notable impact on the solute transport parameters, especially dispersion coefficient (D), λ and R. The results may be useful in providing data support and facilitating the development of watershed nonpoint source pollution models.

Long-term control of non-point source pollution by adjusting human environmental behavior in watershed-a new perspective.

The control of non-point source pollution is a major scientific and technological problem faced by mankind. We proposed a new approach to eliminate non-point source pollution, focusing on adjusting human environmental behavior. The implementation procedures are as follows: (1) Investigate the intention of pollution discharge behavior through interviews and questionnaires. (2) Carry out targeted intervention within the framework of social psychology to transform it into an environmentally friendly mode. (3) Calculate the amounts of pollutants produced and discharged before and after the intervention, and then evaluate the effect of the intervention on reducing pollution. (4) Based on successful interventions, a scheme can be developed to curb non-point source pollution. Aiming to reduce fertilizer use, a case study was conducted in Hetao Irrigation District, one of the three major Irrigation districts in China. The results showed that the interventions indirectly affected intention through attitude, subjective norm, and perceived behavioral control. The structural equation model explained 76.0% of the total variance of farmers' intention to reduce fertilizer application (SMC = 0.760), indicating effective intervention. Subsequently, a program to curb non-point source pollution was developed. This study can provide a key scientific and applied reference for the long-term control of non-point source pollution in watershed.

An Overview of Non-Point Source Pollution Modeling: Current Status and Future Prospect

Non-point source (NPS) pollution control is an increasingly important topic in aquatic environment protection due to its significant adverse effect on water quality. Characterizing NPS pollution loads is crucial for preparing BMPs to improve water quality and protect the aquatic ecosystem. Modeling tools are commonly used for simulating NPS pollution in watersheds; however, the modeling process contains uncertainties and complications, which makes the prediction of NPS pollution loads challenging and complicated. To deal with this issue, significant progress has been made to address NPS pollution modeling problems in the past few decades. The current study reviews different approaches being used for NPS pollution modeling. In this context, the main methods in NPS modeling are described and classified into three categories. 1. Empirical models, 2. Physically based models, and 3. Simulation based optimization models. The present study contributes to fulfilling the gaps in the classification of NPS pollution modeling approaches and highlights the advantages and drawbacks of each approach in order to set a standard for choosing a proper simulation tool for estimating NPS pollution loads based on the limitations and requirements of the understudy circumstance

Quantification of multiscale links of key factors with watershed nitrogen and sediment exports based on a Bayesian modelling approach

The identification of key influencing factors of nonpoint source pollution is important to control such pollution in watersheds. The choice of spatial scale is vital in influencing factor analysis. However, many previous analyses were only carried out on a specific scale or evaluated different topics on different scales, which could not integrate various information of different scales. In this study, a multiscale approach based on Bayesian belief networks (BBNs), which can quantify the links between watershed nitrogen and sediment exports and their key factors, was developed. The main results indicated that influencing factors have relatively higher level of importance, i.e. higher degree of interpretation, at town scale or subcatchment scale compared with 1 km2 scale. Key factor set based on the nesting of town scale and subcatchment scale (i.e., town_sub scale) predict nitrogen and sediment exports better than those based on three separate scales (1 km2 scale, subcatchment scale and town scale), which implies that multiscale nesting reflects more comprehensive information about watershed processes. Moreover, different nitrogen and sediment reduction targets were achieved through land use changes and resulting economic benefits or losses were compared across three scales (subcatchment scale, town scale and town_sub scale). A relatively more appropriate scale with the lowest economic loss was determined. The decreased cultivated land and increased woodland and waterbody areas mostly contributed to the reductions in nitrogen and sediment exports and the economic loss of each reduction target. When achieving the same nitrogen and sediment reduction targets, the economic loss resulting from the land use changes at the subcatchment scale was lowest, followed by the town_sub and town scales. This multiscale approach attempted to determine how key factors with the highest level of importance at different scales and watershed nonpoint source pollution can be connected, which would better inform the management of watershed nonpoint source pollution.

Targeting the critical source areas of phosphorus based on hydrological sensitive area delineation to control nonpoint source pollution in watersheds

To pursue higher agricultural output, farmers have invested heavily in fertilizers, pesticides and other factors of production, which inevitably causes agricultural nonpoint source pollution (ANPSP) and seriously restricted the sustainable development of global agriculture. Accurate and efficient integrated prevention and control of ANPSP requires scientific identification of critical source areas and influencing factors of nonpoint source pollution, which is particularly important in geographic conditions where steep-slope agriculture dominates and landscape features are complex. In this study, a typical small watershed in the mountainous area of the Three Gorges Reservoir area was selected, and the risk of nonpoint source phosphorus loss in the watershed was assessed using the Phosphorus Index (PI) on the basis of Soil Topographic Index (STI) prediction of runoff production area in the watershed. Finally, the critical source areas (CSAs) for its loss were identified. The results showed that the area of hydrologically sensitive areas in the watershed was approximately 22.87% of the total study area, with an area of 37.05 hm2. The hydrology of variable source areas within hydrologically sensitive areas plays a dominant role and is more likely to produce runoff and increase the risk of agricultural nonpoint source phosphorus pollution. The results of PI analysis showed that the risk of phosphorus loss was low in most areas of the watershed (45.77%), the areas at high risk of phosphorus loss accounted for 29.33% of the entire watershed with an area of 47.52 hm2, and tea plantation was the most dominant land use type. The critical source area of nonpoint source phosphorus output accounts for 5.47% of the watershed area and is mainly distributed along the watershed system, 82.55% of which is tea plantation. Compared with the traditional phosphorus index evaluation system, this method is important for the accurate identification of critical source areas of nonpoint source pollutants, for strengthening the efficient prevention, control and management of ANPSP, and for improving the utilization rate of arable land as well as land management and sustainable development of watersheds.

Quantification of Effects of Natural Geographical Factors and Landscape Patterns on Non-point Source Pollution in Watershed Based on Geodetector: Burhatong River Basin, Northeast China as An Example

Quantification of Effects of Natural Geographical Factors and Landscape Patterns on Non-point Source Pollution in Watershed Based on Geodetector: Burhatong River Basin, Northeast China as An Example

基于“源-汇”景观的典型半城市化小流域非点源污染风险评价

PDF HTML阅读 XML下载 导出引用 引用提醒 基于“源-汇”景观的典型半城市化小流域非点源污染风险评价 DOI: 10.5846/stxb202109162610 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划课题（2016YFC0502902）；中国科学院战略性先导科技专项（A类）（XDA23030105） Risk assessment of non-point source pollution in a typical semi-urbanized small watershed based on source-sink landscape Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:小流域的水质恶化主要由点源污染和非点源污染引起，随着点源污染控制水平达到一定程度后，非点源污染已成为首要污染源。当前对非点源污染的管控仍存在难监测和难治理的问题，明晰非点源污染发生风险以及背后的原因是亟需解决的问题，因此开展非点源污染风险分析和评价具有重要意义。采用高分辨率影像解译了2010年、2015年和2020年三期厦门市后溪流域土地利用数据；基于"源-汇"景观格局方法计算研究区网格单元的网格污染指数（GPI）；结合土地利用变化数据分析非点源污染风险的时空变异，对风险区成因进行了分析。研究结果表明：当前，"汇"景观占流域面积的67.86%，非点源污染发生风险分布呈现北低南高；十年中，非点源污染风险呈现上升趋势，目前非点源污染发生风险处于低风险水平（GPI=0.27）。通过分析风险区的土地利用构成发现耕地面积的缩减（减少67.08%）和建设用地面积扩张（增加43.02%）是污染风险发生变动的主要原因。计算了风险区转移矩阵，发现非点源污染发生风险区呈现出中高风险区向低风险区和"汇"景观区域转移的趋势。基于"源-汇"景观格局理论计算的网格污染指数（GPI）可以有效地对流域非点源污染风险值进行表征，是评价和分析流域非点源污染发生风险的可用方法。 Abstract:The deterioration of water quality in small watershed is mainly caused by point source pollution and non-point source pollution. With the control level of point source pollution reaching a certain level, non-point source pollution has become the primary pollution source. At present, the control of non-point source pollution is still difficult to monitor and control. It is urgent to clarify the occurrence risk of non-point source pollution and the reasons behind it. Therefore, it is of great significance to conduct the risk analysis and evaluation of non-point source pollution. Land use data of Houxi Basin in Xiamen City in 2010, 2015 and 2020 were interpreted by high-resolution images. The grid pollution index (GPI) of grid units in the study area was calculated based on source-sink landscape pattern method. Combined with land use change data, the spatial and temporal variation of non-point source pollution risk was analyzed, and the causes of risk areas were analyzed. The results showed that sink landscape accounted for 67.86% of the Basin area, and the risk distribution of non-point source pollution was lower in the north and higher in the south. In the past decade, the risk of non-point source pollution showed an increasing trend, and the occurrence risk of non-point source pollution was at a low level (GPI=0.27). By analyzing the land use composition of the risk area, it was found that the decrease of the cultivated land area (67.08%) and the expansion of construction land area (43.02%) were the main reasons for the change of pollution risk. The risk area transfer matrix was calculated. It was found that the risk area of non-point source pollution presented a trend of transfer from the middle and high-risk area to the low-risk area and the sink landscape area. The grid pollution index (GPI) calculated based on the source-sink landscape pattern theory can effectively characterize the risk value of non-point source pollution in a watershed, and is a useful method to evaluate and analyze the occurrence risk of non-point source pollution in a watershed. 参考文献 相似文献 引证文献

Effects of irrigation-fertilization-tillage on nutrient loading and crop yield in Ulansuhai watershed based on improved SWAT model

不合理的灌溉、施肥和耕作是导致乌梁素海流域农业面源污染的主要根源，乌梁素海作为我国北方地区重要的生态安全屏障，多年来面临着湖泊水环境污染、水生态退化等问题，科学开展湖泊水环境综合治理首先要解决流域内农业面源污染问题. 研究通过修改土壤水平衡、溶质平衡、地下水平衡和作物生长等模块对SWAT 2012原始版本进行改进，并采用改进的SWAT模型构建了乌梁素海流域分布式水文模型，利用实测径流、硝态氮与总磷排放量、地下水埋深以及作物产量校正和验证模型. 基于现状情景，以玉米、葵花和小麦3种主要作物为研究对象，设置了削减灌水量、施肥量及调整耕作方式3种农田管理情景. 基于改进SWAT模型不同情景的模拟结果，计算分析各管理情景下的硝态氮与总磷负荷及对各作物产量的影响. 结果表明，改进SWAT模型具有良好的模拟效果. 不同作物削减5%夏灌水量增产最多达8.41%~10.32%，削减10%秋浇水量均明显减少硝态氮和总磷负荷. 不同作物营养物负荷均随着氮磷施肥削减比例的增大呈现逐渐降低的趋势，但下降曲线逐渐趋于平缓; 各作物产量随氮磷施肥削减比例的增加呈先增加后减少的趋势，其中玉米、小麦氮磷施肥削减比例达20%时产量开始下降，葵花氮磷施肥削减比例达25%时产量开始下降. 不同作物营养物负荷与小麦产量均随耕作方式混合深度与混合效率参数的增大逐渐减小，而玉米和葵花产量则随耕作参数增大逐渐增加. 综合分析，削减5%夏灌水量+削减20%氮磷施肥比例+模板犁耕作组合玉米产量增幅最大达36.5%;削减10%秋浇水量+削减25%氮磷施肥比例+模板犁耕作组合葵花硝态氮负荷降幅最大达42.1%;削减5%夏灌水量+削减20%氮磷施肥比例+免耕组合小麦产量增幅最大达29.1%;而削减5%秋浇水量+削减20%氮磷施肥比例+常规春耕组合小麦硝态氮负荷减少最大达27.2%，总磷负荷减少最大达18.5%. 本研究可为降低流域内面源污染、提高作物产量及减少乌梁素海营养物入湖负荷农业管理措施的实施提供理论依据.;Irrational irrigation, fertilization and farming are the main causes of agricultural non-point source pollution in Ulansuhai watershed. As an important ecological security barrier in northern China, Lake Ulansuhai has been facing problems, such as lake water environment pollution and water ecological degradation. To achieve the integrated management of lake water environment, agricultural non-point source pollution in the watershed must be controlled. The study improved the original version of SWAT 2012 by modifying the modules of soil water balance, solute balance, groundwater balance, and plant growth. A distributed hydrological model of Ulansuhai watershed was constructed with the improved SWAT model, which was calibrated and validated with measured runoff, nitrate nitrogen (NN), total phosphorus (TP) emissions, groundwater depth and crop yield. Three scenarios including reduced amount of irrigation, fertilization, and adjusted farming mode based on the current situation were applied on three main crops (corn, sunflower and wheat). NN and TP loadings and their effects on the crop yields under different management scenarios were simulated using the improved SWAT model. The results showed that the improved SWAT model has a good simulation fitting. For different crops, reducing the irrigation amount by 5% in summer can increase production by up to 8.41%-10.32%, and reducing 10% irrigation in autumn will significantly reduce the NN and TP loadings. The nutrient load of different crops showed a decreasing trend with an increasing reduction ratio of nitrogen and phosphorus fertilization (NPF), but the declining rate gradually became smaller. The yields of different crops increased first and then decreased with the ratio of NPF increase. When the ratio of NPF reduction reached 20%, the yield of corn and wheat began to decline, and when it reached 25% the yield of sunflower began to decline. The nutrient loads and wheat yield of different crops gradually decreased with an increase of the mixing depth and efficiency of the tillage mode, while the yield of corn and sunflower gradually increased with the tillage parameters. If combining cutting 5% of summer irrigation, reducing 20% NPF amount, and the template plowing combination, corn yield could increase by 36.5%. If cutting 10% of autumn watering, reducing 25% NPF, the template plowing combination, sunflower nitrate nitrogen load could reduce by 42.1%. If cutting 5% of summer irrigation, 20% reduction NPF, and no-tillage combination, wheat yield could increase by 29.1%. However, cutting 5% of autumn watering, 20% reduction NPF and conventional spring ploughing combination, NN loading of wheat farming could reduce by up to 27.2%, and TP loading could reduce by up to 18.5%. This research can provide a scientific basis for the implementation of agricultural management measures to reduce non-point source pollution, increase crop yields in Ulansuhai watershed and reduce the nutrients loads in Lake Ulansuhai.

Sub-Watershed Parameter Transplantation Method for Non-Point Source Pollution Estimation in Complex Underlying Surface Environment

The prevention and control of non-point source pollution is an important link in managing basin water quality and is an important factor governing the environmental protection of watershed water in China over the next few decades. The control of non-point source pollution relies on the recognition of the amount, location, and influencing factors. The watershed nonpoint source pollution mechanism model is an effective method to address the issue. However, due to the complexity and randomness of non-point source pollution, both the development and application of the watershed water environment model have always focused on the accuracy and rationality of model parameters. In this pursuit, the present study envisaged the temporal and spatial heterogeneity of non-point source pollution caused by the complex underlying surface conditions of the watershed, and the insufficient coverage of hydrological and water quality monitoring stations. A refined watershed non-point source pollution simulation method, combining the Monte Carlo analytic hierarchy process (MCAHP) and the sub-watershed parameter transplantation method (SWPT), was established on the basis of the migration and transformation theory of the non-point source pollution, considering the index selection, watershed division, sub-watershed simulation, and parameter migration. Taking the Erhai Lake, a typical plateau lake in China, as the representative research object, the MCAHP method effectively reduced the uncertainty of the weights of the watershed division indexes compared to the traditional AHP method. Furthermore, compared to the traditional all watershed parameter simulation (AWPS) approach, the simulation accuracy was improved by 40% using the SWPT method, which is important for the prevention and control of non-point source pollution in large-scale watersheds with significant differences in climatic and topographic conditions. Based on the simulation results, the key factors affecting the load of the non-point source pollution in the Erhai watershed were identified. The results showed that the agricultural land in Erhai Lake contributed a majority of the load for several reasons, including the application of nitro phosphor complex fertilizer. Among the different soil types, paddy soil was responsible for the largest pollution load of total nitrogen and total phosphorus discharge into the lake. The zones with slopes of 0–18° were found to be the appropriate area for farming. Our study presents technical methods for the assessment, prevention, and control of non-point source pollution load in complex watersheds.

Output Characteristics of Nitrogen and Phosphorus from Non-Point Source Pollution of Typical Land Use in A Micro-Watershed in Hilly Red Soil Region

Scientific identification of runoff output characteristics of different land use patterns is the premise of controlling non-point source pollution in watersheds. The hydrology and output process of non-point source pollutants of forest, planting, and construction land with different rainfall characteristics were observed using a micro-watershed in a low mountain and hilly region of Southern China. The results showed that land use affected the hydrological characteristics and water quality processes of runoff. The characteristics of runoff generation time and cumulative rainfall under typical rainfall conditions were as follows:construction land(9 min, 2.0 mm), planting land(35 min, 11.4 mm), and forest land(108 min, 24 mm). There were significant differences in the three land use types in the pollution output process characteristics, such as pollutant concentration of total suspended matter(TSS), total nitrogen(TN) and phosphorus(TP), their components, N/P ratio change, and output intensity. Under typical rainfall, different land use types had similar pollution output stages, the mass concentrations of TSS, TN, and TP in the initial runoff were high, and then gradually stabilized. In addition, the first 30 min of the flow generation process contributed to the TSS, TN, and TP loads within the 23%-43% range. At the annual scale, there were significant differences between the contribution rate of each land use type to TN and TP load and ratio per unit area; the highest contribution to total pollution load was planting land(57% and 45%), while the highest in pollution load per unit area was construction land(9.50-12.50). The results also showed that the distribution of key non-point source areas had different spatial and temporal dynamics, which was comprehensively determined by the land use types in catchment units, the characteristics of annual rainfall, among other factors. With the increase in rainfall, the main contribution non-point source pollution in the micro-watershed changed from construction land to planting land. Targeted ecological interception strategies should be implemented based on the distribution characteristics of key source areas and characteristics of underlying surface runoff production process.

Vegetation restoration and agricultural management to mitigate nitrogen pollution in the surface waters of the Dan River, China.

Non-point source pollution in rivers is an important factor affecting water quality. Quantifying the load of non-point source pollutants in the water and implementing improvement measures are critical for guaranteeing drinking water quality. In this study, the Dan River watershed, which is an important water source for Beijing, was investigated. Through a combination of water sampling and numerical simulations, the temporal and spatial distributions of nitrate nitrogen (NO3--N) and ammoniacal nitrogen (NH4+-N) loads in the watershed were determined, and the effects of vegetation restoration and agricultural management on reducing nitrogen pollution in the river were predicted. The NO3--N and NH4+-N loads in the watershed were higher during the wet season (July-September), accounting for more than 50% of the annual nitrogen output. The Soil and Water Assessment Tool (SWAT) was used to simulate the nitrogen load in the watershed. Pollution from nitrogen loading was serious in the lower reaches of the river; however, vegetation restoration can reduce the nitrogen output. Through scenario simulations, we found that an increase in forestland in the watershed would reduce the NO3--N and NH4+-N loads. The nitrate and NH4+-N loads in the watershed also decreased with reduced fertilizer use and reduced irrigation application in the watershed. Thus, reasonable land planning and agricultural management measures can effectively reduce nitrogen loss, which is an effective way to control non-point source pollution in watersheds and ensure river water quality.

Conservation management practices reduce non-point source pollution from grazed pastures

Producers in Northwest Arkansas and globally need alternative management practices to ensure long-term sustainable and economical use of poultry litter, which is an abundant source of valuable carbon (C), nitrogen (N) and phosphorus (P). Project objectives were to measure the efficacy of conservation management practices (i.e., pasture aeration and subsurface litter incorporation) to reduce nutrient runoff compared to poultry litter surface applications from small watersheds under rainfed and grazed conditions. Watersheds (0.23 ha each) were assigned a treatment [pasture aeration, subsurface litter incorporation, or surface application of litter (positive control)] on a Leadvale (fine-silty, siliceous, thermic Typic Fragiudult) silt loam. Poultry litter was applied annually to each watershed from 2007-2012. Over the 4-yr study period, runoff loads of NO3–N, total nitrogen (TN), soluble reactive phosphorus (SRP), and total phosphorus (TP) varied per conservation practice (P ≤ 0.05). Specifically, average annual loads of NO3–N, TN, SRP, and TP loads were reduced 49, 42, 28, and 35% following pasture aeration and by 78, 72, 55, and 59% from subsurface applying poultry litter, relative to surface applications, respectively. Greatest annual N loads and runoff corresponded with surface poultry litter applications, followed by pasture aeration, with subsurface incorporation of poultry litter resulting in lowest (P ≤ 0.05) TN and NO3–N loads. Overall, subsurface incorporation of poultry litter and pasture aeration are two promising conservation practices for reducing non-point source pollution in watersheds with nutrient imbalances. Further work needs to be done on factors influencing the efficacy of these conservation practices under rainfed conditions, as well as the economic feasibility of these conservation agricultural practices.

Management optimization of nonpoint source pollution considering the risk of exceeding criteria under uncertainty

Management of nonpoint source (NPS) pollution is highly important in watershed water environmental and ecological security. However, the many complexities and uncertainties that exist in the processes of export and management of NPS pollution exert substantial influences on the reliability of multiple management practices. This study developed an inexact multiobjective possibilistic mean-variance mixed-integer programming (IMPMMP) model for NPS pollution management through optimization of watershed land use pattern and livestock production structure. By coupling interval parameter programming, mixed-integer programming, multiobjective programming, and an export coefficient model within a general possibilistic mean-variance model framework, the IMPMMP model deals effectively with system uncertainties and complexities. Moreover, the risk of exceeding criteria (REC) in NPS pollution management systems can be considered. The proposed IMPMMP model was applied to a real-world case study in the Xinfengjiang Reservoir watershed in South China. Results showed that the preference of decision makers regarding land use adjustment plays a decisive role in determining model feasibility. The area provided for each land use type that could be adjusted has to reach a certain threshold to achieve the goals of reduced pollution load and REC control. The NPS pollution loads after optimization would be exported primarily from different land uses and the human population. Compared with NPS nitrogen pollution management, it is more difficult to reduce the NPS phosphorus load and to manage the corresponding REC through adjustment of the land use pattern and livestock production structure. Moreover, it is difficult to simultaneously reduce the NPS nitrogen and phosphorus pollution loads and REC in each subbasin. The model, which can provide policy makers with a series of schemes for optimization of land use pattern and livestock production structure, has satisfactory applicability and could be used for watershed NPS pollution management.

New insights into the role of lake sediments in understanding watershed non-point source phosphorus pollution

A deep understanding of the relationship between watershed non-point source (NPS) pollution and lake total phosphorus (TP) accumulation is the basis of watershed–lake environmental management and ecological reconstruction, in which the acquisition of long-term NPS P and lake TP data over corresponding temporal and spatial scales seems to be the key issue. In this study, three typical sub-basins within Hongze Lake were selected as study sites. The sediment TP concentrations were designated as the lake indicator to relate with the NPS P loads, and the role of sediment in representing watershed NPS pollution was quantitatively analyzed. The results showed that, first, a notable fluctuation tendency in NPS P loads, which was largely influenced by policy, was found for all three sub-basins. Second, the deposition rate for three sediment cores was approximately 0.40 cm per year, with 13 cm cores reflecting the period since 1990. Third, the sediment is a faithful recorder of watershed NPS P pollution and lake nutrient enrichment. The correlation coefficient (r) between watershed NPS P loads and lake sediment TP concentrations showed notable differences when each watershed was considered separately. In particular, an ideal relationship was found in Basins 1 and 2, especially in the bottom 7 and 8 cm of the sediment cores, in which r exceeded 0.8. This showed that sediment can be an effective indicator of NPS P pollution during certain periods, such as 1990 – 2002, and diverse roles can be attributed to land-use/cover change and lake resuspension conditions. In addition, the weakest relationship existed in the No. 3 watershed, largely due to higher rainfall amounts compared with other two watersheds. For all the watersheds, lake sediment is a suitable indicator of watershed NPS P pollution over certain temporal and spatial scales.

The Influence of Different Forest Characteristics on Non-point Source Pollution: A Case Study at Chaohu Basin, China.

Forestland is a key land use/land cover (LULC) type that affects nonpoint source (NPS) pollution, and has great impacts on the spatiotemporal features of watershed NPS pollution. In this study, the forestland characteristics of the Chaohu Basin, China, were quantitatively represented using forestland types (FLTs), watershed forest coverage (WFC) and forest distance from the river (DFR). To clarify the impact of forests on NPS pollution, the relationship between forestland characteristics and watershed nutrient outputs (TN and TP) was explored on a monthly scale using SWAT (Soil and Water Assessment Tool) and the period simulation was 2008–2016. The results showed that: (1) the TN and TP showed similar output characteristics and the rainy season was the peak period of nitrogen and phosphorus output. (2) Among the forestland characteristics of forestland types, watershed forest coverage and forest distance from the river, watershed forest coverage and forest distance from the river had greater effects than forestland types on the control of watershed nutrient outputs (TN and TP). (3) In different forestland types, the watershed nutrient outputs intensity remained at the lowest level when the FLTs was mixed forest, with a TN output of 1244.73kg/km2 and TP output of 341.39 kg/km2. (4) The watershed nutrient outputs and watershed forest coverage were negatively correlated, with the highest watershed forest coverage (over 75%) reducing the TN outputs by 56.69% and the TP outputs by 53.46% compared to the lowest watershed forest coverage (below 25%), it showed that in areas with high forest land coverage, the non-point source pollution load in the watershed is smaller than in other areas. (5) forest distance from the river had an uncertain effect on the TN and TP output of the basin, the forestland itself is a source of pollution, but it also has the function of intercepting pollution movement; the forest distance from the river in the range of 500–1000 m had the lowest NPS pollution. Considering the different forest characteristics and topographical factors, an optimal allocation mode of differentiated forest land was proposed, these suggestions will provide a scheme for surface source pollution prevention and control in the basin. This research gap is the basis of real forestland optimization. We may optimize the forestland layout for NPS pollution prevention and control by clarifying the internal mechanism.

An Integrated Approach for Targeting Critical Source Areas to Control Nonpoint Source Pollution in Watersheds

This study presents an integrated approach for targeting critical source areas (CSAs) to control nonpoint source pollution in watersheds. CSAs are the intersections between hydrologically sensitive areas (HSAs) and high pollution producing areas of watersheds. HSAs are the areas with high hydrological sensitivity and potential for generating runoff. They were based on a soil topographic index in consistence of a saturation excess runoff process. High pollution producing areas are the areas that have a high potential for generating pollutants. Such areas were based on simulated pollution loads to streams by the Soil and Water Assessment Tool. The integrated approach is applied to the Neshanic River watershed, a suburban watershed with mixed land uses in New Jersey in the U.S. Results show that several land uses result in water pollution: agricultural land causes sediment, nitrogen and phosphorus pollution; wetlands cause sediment and phosphorus pollution; and urban lands cause nitrogen and phosphorus pollution. The primary CSAs are agricultural lands for all three pollutants, urban lands for nitrogen and phosphorus, and wetlands for sediment and phosphorus. Some pollution producing areas were not classified into CSAs because they are not located in HSAs and the pollutants generated in those areas are less likely to be transported by runoff into streams. The integrated approach identifies CSAs at a very fine scale, which is useful for targeting the implementation of best management practices for water quality improvement, and can be applied broadly in different watersheds to improve the economic efficiency of controlling nonpoint source pollution.

Detection of the Sensitive Inflowing River Indicators Related to Non-Point Source Organic Pollution: A Case Study of Taihu Lake

Organic matter transport from watershed soil into an aquatic ecosystem plays a key role in the fate of contaminants and lake eutrophication. Special emphasis is needed to understand whether sensitive river indicators can reflect watershed non-point source organic carbon (OC) pollution, in which the accurate assessment of non-point source (NPS) pollution is crucial. This study selected a sub-basin within the Taihu basin, China, as the study site, a typical rural-urban fringe region undergoing rapid urbanization where soil organic carbon (SOC) loss would likely take place due to the integration of agriculture NPS and impervious surface NPS. The seasonal tendency of NPS soil organic carbon (SOC) loads were evaluated by using the integration of SEDD and PLOAD models, which consider the sediment adsorption fraction loads (Sed-OC) and runoff dissolved fraction loads (Dis-OC) together. And then the sensitive water indicators for OC loads were determined by measurements of inflowing river properties and stepwise regression analysis. The results showed that active dissolved carbon fraction loads were the dominant contributors to the total organic carbon loads (Tot-OC) and that Sed-OC loads have more spatial variation. With respect to sensitive river properties, the lignin owned the greatest correlation degree with different OC fraction loads, in which the correlation coefficient between particulate lignin and Sed-OC loads reached 0.782, which is the greatest among the different indicators. In addition, the colored dissolved organic matter (CDOM) was also correlated with Dis-OC loads. However, the particulate organic carbon (POC) was not well related to OC loads. The findings of this study are useful for better understanding the nutrient migration from watershed soil into aquatic ecosystem controlled by watershed NPS pollution.

Non-Point Source Pollution Control Effect Based on Comprehensive Management of Small Watershed

The urban surface runoff pollution is the most important type of urban non-point source pollution, random, wide area complex composition. The Beijing small watershed non-point source pollution comes mainly from the release of water, livestock and aquaculture, urban sewage waters, sediment release, aquatic organisms corruption farmland tail, rural solid waste and agricultural by-products pollution. Over the years these small watershed comprehensive management, significant effects of non-point source pollution control. It's mainly from non-point source pollution characteristics, hazards, main control practices begins to explain the effect of small watershed pollution in recent years, Beijing's governance, and governance prospects.

Covenants, cohesion, and community: The effects of neighborhood governance on lawn fertilization

Lawn fertilization is increasingly recognized as an important contributor to non-point source pollution in watersheds, but relatively little is known about how and why homeowners fertilize. Lawns are a social expression of citizenship and belonging in many American cities, for a well-maintained yard reflects a homeowner's work ethic as well as the pride in his home. There are also neighborhood influences, as homeowners conform to the dominant neighborhood standard of lawn esthetics. Homeowners associations (HOAs) are one way in which neighborhood lawn standards are maintained, as they use written rules and unwritten expectations backed by legal means of enforcement to ensure compliance with neighborhood guidelines. This paper examines household nitrogen fertilizer application rates in Baltimore, Maryland. We find that households which place a high importance on lawn care and occupy more valuable homes fertilize at higher rates compared with neighbors who place lower importance on lawn care, and live in less expensive homes. We also examine the effects of different neighborhood governance regimes, specifically homeowners associations and neighborhood associations. Households who belong to an HOA apply more fertilizer than those who do not, but households belonging to a neighborhood association do not fertilize more than their counterparts who are not so affiliated. HOA membership also mediates the effect of lawn care importance and home value and moderates the effect of social cohesion on fertilization application rates. HOAs shape household lawn behaviors: by obliging people to maintain a high esthetic standard, they encourage higher usage of chemicals to attain those standards.