Point and nonpoint sources of water pollution pdf

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point and nonpoint sources of water pollution pdf

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Point sources release pollutants from discrete conveyances, such as a discharge pipe, and are regulated by federal and state agencies.

Sediment fences such as this one are used in urban and suburban areas and construction sites to control erosion, trap large materials, filter sediment from rainwater, and slow runoff. While research, monitoring, and assessment look at the larger environmental effects of nonpoint source pollution, taking measures to stop pollution before it begins is also essential for controlling the problem. This is especially true in coastal communities where more than half of the U.

Basic Information about Nonpoint Source (NPS) Pollution

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Surface water is the main source of irrigation and drinking water for rural communities by the Hulan River basin, an important grain-producing region in northeastern China. Understanding the spatial and temporal distribution of water quality and its driving forces is critical for sustainable development and the protection of water resources in the basin. Following sample collection and testing, the spatial distribution and driving forces of water quality were investigated using cluster analysis, hydrochemical feature partitioning, and Gibbs diagrams.

The results demonstrated that the surface waters of the Hulan River Basin tend to be medium—weakly alkaline with a low degree of mineralization and water-rock interaction.

Changes in topography and land use, confluence, application of pesticides and fertilizers, and the development of tourism were found to be important driving forces affecting the water quality of the basin. Non-point source pollution load fluxes of nitrogen N and phosphorus P were simulated using the Soil Water and Assessment Tool. The simulation demonstrated that the non-point source pollution loading is low upstream and increases downstream.

The distributions of N and P loading varied throughout the basin. The findings of this study provide information regarding the spatial distribution of water quality in the region and present a scientific basis for future pollution control. Rivers are an important component of the global water cycle, connecting the two major ecosystems of land and sea and providing a critical link in the biogeochemical cycle. The spatial distribution of water quality is indicative of the environment in which a river flows.

River chemical composition is influenced by natural factors such as climate, lithology, soil, vegetation, and anthropogenic activities. Hence, studies on river water chemical characteristics can provide important information on geochemical behavior, rock weathering, and human activities in a basin 1 , 2 , 3.

Over the last 50 years, scholars have studied the water chemistry of major rivers in all continents and have explored the main forces affecting water chemistry in river basins 4 , 5. For instance, the main driving forces affecting river water chemistry include land use and land cover changes 6 , 7 , 8 , 9 , 10 , rainfall intensity, pollution build-up levels, wastewater discharges, and anthropogenic influences 11 , 12 , Pollution inputs to surface water result in the evolution and deterioration of river water quality.

Pollutants can be classified as point source and non-point source. Point source pollution is relatively easy to adjust and control because it is easy to monitor their concentration and flux Conversely, non-point sources often come from extensive areas of land and can be transported overland, underground, or even through the atmosphere to receiving water bodies 15 , making them difficult to measure and control.

Non-point source pollution, mainly nitrogen N and phosphorus P , has led to excessive nutrient inputs and surface water quality decline.

In China, human activities have resulted in widespread water quality deterioration, directly impacting the overall ecological environment and socioeconomic development. Agriculture and urban life are the main sources of N and P in aquatic ecosystems. Atmospheric deposition is also an important source of N. Non-point source inputs of these pollutants are difficult to measure and adjust because these elements come from various human activities that are distributed over a large area.

Temporal changes due to the influence of weather also contribute to this difficulty. In aquatic ecosystems, N and P can cause the proliferation of toxic algae, anoxia, fish deaths, biodiversity loss, and the loss of aquatic plant beds and coral reefs. Eutrophication severely impacts aquatic ecosystems and threatens water use for drinking, industry, agriculture, and recreation 17 , In recent decades, the basin hydrological model has developed rapidly, and models considering hydrological and sediment transport processes in complex basins have emerged.

The SWAT model is widely used in the assessment of hydrological sediment and pollutant migration processes at the basin scale. It employs a number of factors, including meteorological data, underlying surfaces, and human management measures, to effectively simulate surface runoff, groundwater, sediment transport, and non-point source pollution 20 , 21 , The SWAT model can be used to simulate changes in hydrological sediment and non-point source pollution in a variety of vegetation cover and land use types including forest cover 23 , biodiversity-rich areas 24 , and highly developed agricultural regions At the same time, the SWAT model can simulate the impact of climate change on the water environment processes of the basin.

More importantly, the SWAT model can effectively simulate the melting of snow and the process of glacial snowmelt The model has been successfully applied to rainfall 27 , 28 and snowmelt events Therefore, using the SWAT model to simulate hydrological, soil erosion, and pollutant migration processes in mid to high latitude freeze-thaw areas can produce good results, and play an important role in the study of water and soil resources and environmental effects evaluation.

The Hulan River is a tributary of the Songhua River. The Hulan River basin is a productive agricultural area and is an important commodity grain base in the fertile Heilongjiang Province. The Hulan River is the main source of farmland irrigation in the region; hence, river water quality impacts food quality and community health. For this reason, our study has two objectives: 1 to analyze the spatial distribution characteristics of surface water quality and its driving factors in the basin and 2 to simulate the non-point source pollution load flux of the main pollutants nitrogen and phosphorus in the basin.

The study of watershed chemical characteristics and simulations of non-point source pollution load flux will provide a scientific basis for the effective control of non-point source pollution, water pollution, improvement of the water environment, and for the comprehensive planning of Hulan River basin water conservation. The terrain of the Hulan River Basin is fan-shaped.

The terrain slopes from the northeast to southwest, as shown in Fig. Owing to mountain airflow uplift, precipitation decreases from east to west. The average annual basin runoff is The geological structures in the study area are formed through the processes of fault depression, depression and shrinkage. The Mesozoic is dominated by fault depression, forming a basement. The Mesozoic and Cenozoic are dominated by sedimentation and depression, forming a caprock. Generally, the strata of the study area are divided into Cretaceous, Paleogene, Neogene and Quaternary.

The Hulan River meets with the Tongken River, which flows from the north to the south in Tongjiang, Wangkui County, then turns to the south. Water sampling point in main stream and tributaries of the Hulan River basin Symbolizing each river by capital letters A to H from upper reaches to lower reaches, the same below.

Based on existing survey data and according to the distribution of the water system and land use in the survey area, field sampling of the Hulan River Basin was conducted during June and October Sampling points were distributed in the upper, middle, and lower reaches of the river, both upstream and downstream of confluences and cities.

The spatial distribution of sampling points is shown in Fig. An HQ40d Hach water quality monitor was used to test water temperature, total dissolved solids TDS , conductivity, dissolved oxygen, and redox potential. The statistical analysis of water quality indicators was conducted using SPSS. A cluster analysis and principal component dimensionality reduction were used to determine the spatial difference and similarity of water quality.

Water chemistry type was determined according to the Shukalev classification 30 , and pollutant sources were analyzed using the end element map 1 and Gibbs diagrams 4. The SWAT model is used for basin wide simulations of surface source pollution; water resources assessment and management; soil and water conservation; prediction of the influence of climate change; and land management measures on hydrology, sediment and nutrient production, and migration in complex watersheds.

The SWAT model is divided into four modules; hydrological, soil erosion and sediment transport, nutrient transport, and plant growth and management. The migration and transformation of N, particularly NO 3 contained in runoff, lateral flow, and infiltration, are calculated by the volume of water and the average degree of aggregation.

Effects of filtration are considered for underground infiltration and lateral runoff. Nitrogen can be divided into dissolved N and adsorbed N, where dissolved nitrogen is mainly nitrate N. Before calculating the total amount of nitrate N, it is necessary to calculate the concentration of nitrate N in mobile water, and then multiply the concentration by the amount of water to obtain the total amount of nitrate N. The calculation of free water nitrate N concentration is as follows:.

Adsorbed N is mainly organic N and is determined using the model developed by McElroy et al. The expression is:. Phosphorus is also divided into dissolved P and adsorbed P. The migration of dissolved P in the soil is mainly achieved by diffusion. Since dissolved P is not very active, the surface layer of P in dissolved form is rarely removed from surface runoff. Dissolved P transported by surface runoff is calculated by:. Adsorbed P is mainly divided into organic P and mineral P, which are usually adsorbed on soil particles and migrate with runoff.

The calculation expression is:. The cluster analysis and principal component dimensionality reduction analysis were used to classify rivers in Hulan basin based on the spatial distribution of pollutants. Average values of water quality indicators for the seven tributaries flowing into the main stream of the Hulan River Basin were clustered using squared Euclidean distance as the clustering index and results are shown in Fig.

Sampling points 39 and 41 downstream of the Keyin River are not in this grouping due to the influx of other tributaries, which impact water quality. The water quality samples in the blue region are relatively similar and represent the sampling points of the remaining tributaries, corresponding well to the results of the cluster analysis.

Water chemistry determined using the Shukalev classification method are shown in the Piper three-line diagram Fig. The TDS of surface water in the basin is generally low, increasing gradually downstream except for in the Keyin River following the injection of the Numin River. The ion types of the rivers in the basin are gradually enriched downstream.

It is apparent that ion concentrations in Group A are lower as compared to Group B, while the ion concentrations of the main stream are between these two groups. Ion concentrations generally increase downstream. Comprehensive environmental indicators characterize the overall salinity of the water body, including total hardness and conductivity. Total hardness and conductivity generally show an increasing trend downstream and Group B values are much higher as compared to Group A and the mainstream.

The pH values of surface waters are between 7. The pH of the main stream increases gradually downstream, while Group A and B pH decreases gradually. It is apparent that samples generally fall in the rock weathering control area, indicating that the water chemistry of the basin is mainly controlled by rock weathering 4 , 32 , According to land use remote sensing data Figs.

Forest land is concentrated in the upper reaches of the basin and the middle reaches are mainly cultivated. Following the confluence of tributaries in the lower reaches, residential land intensifies. Due to the number of parameters in the SWAT model, individual calibration of parameters is difficult. Therefore, the sensitivity analysis method is generally used to determine the sensitivity of model parameters. The hydrological cycle forms the basis of the hydrological model; however, rainfall and runoff are the driving forces of non-point source pollution.

Therefore, the calibration and verification sequence of SWAT model parameters are runoff, sediment, and water quality. The model was calibrated spatially from the upper to lower reaches at Tieli, Sifang, and Qinjia stations.

The accuracy of the model simulation results can directly reflect the applicability of the model in a study area.

Point Source and Nonpoint Sources of Pollution

Individual participation of pollutants in the pollution load should be estimated even if roughly for the appropriate environmental management of a river basin. It is difficult to identify the sources and to quantify the load, especially in modeling nonpoint source. In this study a revised model was established by integrating point and nonpoint sources into one-dimensional Streeter-Phelps S-P model on the basis of real-time hydrologic data and surface water quality monitoring data in the Jilin Reach of the Songhua River Basin. Point source pollution was stronger than nonpoint source pollution in the study area at present. The water quality of upstream was better than that of downstream of the rivers and cities.


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Controlling Nonpoint Source Pollution

Waste filled water is dumped into a river, polluting it for the people and animals who use it as a source for eating and drinking. This lists the logos of programs or partners of NG Education which have provided or contributed the content on this page. Powered by. Almost everything humans do, from growing food to manufacturing products to generating electricity, has the potential to release pollution into the environment.

Nonpoint Source Pollution

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COMMENT 3

  • NPS pollution generally results from land runoff, precipitation, atmospheric deposition, drainage, seepage or hydrologic modification. Rammanoharm - 17.03.2021 at 02:20
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