Non-Point Water Pollution: Sources And Locations

Non-point water pollution is a type of pollution that does not come from a single source but from many sources. It is a leading threat to the health of rivers, lakes, wetlands, and marine water. Sources of non-point water pollution include agricultural and urban areas. In agricultural areas, it is caused by the leaching of nitrogen compounds from fertilized lands, and in urban areas, it is caused by contaminated stormwater runoff from parking lots, roads, and highways. Non-point water pollution can also be caused by atmospheric deposition, where air pollution is transported and deposited on the ground, and hydrological modifications such as rainfall and snowmelt.

Agricultural land

Non-point source (NPS) water pollution is a significant issue that arises from a variety of human activities, including agricultural practices. Agricultural land is a major contributor to NPS water pollution, as contaminants can be carried by rainwater or irrigation runoff into nearby water bodies without passing through a treatment facility.

Urban areas

Urbanization increases the variety and amount of pollutants carried into bodies of water. In urban areas, much of the land surface is covered by buildings, pavement, and compacted landscapes. These surfaces do not allow rain and snowmelt to soak into the ground, which increases stormwater runoff. This runoff can carry pollutants such as fertilizers, pesticides, and debris into nearby water bodies, harming fish and wildlife populations, killing native vegetation, fouling drinking water sources, and making recreational areas unsafe. This type of pollution, known as non-point source pollution, is challenging to regulate as it arises from various sources and everyday activities rather than a single identifiable source.

Urban runoff, or stormwater washed off parking lots, roads, and highways, is a significant contributor to non-point source pollution in urban areas. Unlike industrial discharges or sewage treatment plants, urban runoff pollution cannot be attributed to a specific activity or group of activities. Instead, it results from a combination of factors, including paved surfaces, construction sites, and the use of fertilizers and pesticides. These pollutants can enter water bodies through storm drain systems or directly, especially in developing and suburban areas.

Controlling non-point source pollution in urban settings requires improved management practices. This includes implementing low-impact development techniques, such as green infrastructure, to manage stormwater and protect water quality. The U.S. Environmental Protection Agency (EPA) provides guidance and resources to assist municipalities and environmental professionals in tracking and implementing best management practices (BMPs) for urban non-point source pollution control. The EPA also offers fact sheets and brochures to educate the public about urban runoff and stormwater pollution prevention.

In addition to runoff, other sources of non-point source pollution in urban areas include septic tank seepage and surface runoff in areas without reticulated sewerage systems. Sewerage systems and adequate street cleaning are crucial measures to mitigate this type of pollution. Furthermore, urban areas can contribute to air pollution, which can have indirect effects on water quality. For example, pollutants from smokestacks or car tailpipes can be transported over long distances and deposited into water bodies, becoming a non-point source of water pollution.

To address non-point source pollution in urban areas, various organizations provide resources and support. The Center for Watershed Protection, for instance, works with governmental agencies, consulting firms, and the public to offer scientifically sound information on protecting and restoring urban watersheds. The Stormwater Manager's Resource Center provides technical assistance to stormwater practitioners and local government officials dealing with stormwater management issues. These efforts aim to control and reduce the impact of non-point source pollution on water quality in urban environments.

Atmospheric deposition

The nitrogen emitted from these sources has significant environmental impacts. For example, the abundant growth of algae and aquatic plants in nutrient-rich waters can be unsightly and restrict recreational uses of lakes and slow-moving rivers. This eutrophication of surface waters is a major consequence of excessive nutrient inputs from atmospheric deposition.

Additionally, atmospheric deposition can contribute to non-point water pollution through the release of nitrogen from power plants and industries. While these are considered point sources, when the nitrogen they release reaches water bodies through precipitation, it becomes a non-point source of pollution. This highlights the complex nature of atmospheric deposition and its role in water pollution.

To address atmospheric deposition and its impact on non-point water pollution, efforts have been made to reduce nitrogen oxide emissions from point sources. However, with more than 3.2 million tons of nitrogen deposited in the United States each year, it is a significant challenge to mitigate the effects of this type of pollution on water quality.

Abandoned mining operations

The issue of abandoned mines is prevalent in many regions, including California, which has an estimated 47,000 abandoned mine sites spread across the state. These sites pose serious environmental and safety hazards, threatening the quality of surface water, groundwater, air, and soil. Similarly, in Colorado, abandoned mines have released arsenic, zinc, and copper, contaminating several streams. The mid-Atlantic and Appalachian regions of the United States have also experienced waterbody contamination due to AMD and other pollutants from abandoned mines.

The impact of abandoned mines on water quality can be long-lasting and devastating. The toxic heavy metals and acidic drainage can contaminate community water supplies, rivers, streams, and aquatic life. The Clean Water Act, enforced by the EPA and state agencies, regulates individual point sources of pollution and mandates mitigation measures. However, non-point sources, such as abandoned mines, have often been treated as part of the baseline rather than regulated sources, leading to slower improvement in reducing pollution from these sites.

Remediation of abandoned mines is crucial to mitigating their environmental impact. Efforts to address this issue include the Good Samaritan Initiative, which encourages volunteers and organizations to undertake cleanup projects without liability. Additionally, the EPA has supported market-based programs, such as water-quality trading, to reduce pollution in watersheds and streams affected by abandoned mines. State agencies, such as the SWRCB in California, also play a vital role in monitoring water quality and enforcing standards, utilizing funds from various sources, including the Cleanup and Abatement Account (CAA), to address water pollution issues caused by abandoned mines.

Residential areas

Non-point source water pollution is challenging to control because it arises from the everyday activities of numerous individuals. These activities include lawn fertilisation, pesticide application, road construction, and building construction. Non-point source pollution can be categorised into two main types: agricultural and urban.

• Urban runoff : In residential areas, contaminated stormwater from roads, parking lots, and highways can carry pollutants into nearby bodies of water. This is especially prevalent in developing and suburban areas where stormwater does not flow through storm drain systems but instead flows directly into water bodies. The pollutants in this stormwater, or urban runoff, can come from various sources, including industrial facilities, factories, and vehicular traffic.
• Lawn care : The use of chemicals for lawn care in suburban areas can contribute to non-point water pollution. These chemicals can be washed away by stormwater and enter the environment through storm drains, eventually making their way into water bodies.
• Residential renovation : Soil particles eroded from residential renovation sites can contribute to sediment pollution in nearby water bodies. Sediment turns the water cloudy or "turbid," impairing fish vision and breathing and damaging their gills. It also inhibits photosynthesis by clouding the water and covering aquatic plants.
• Failing septic systems : On-site septic systems that are not functioning properly can release bacteria and nutrients into the environment, which can then enter water bodies. These nutrients, primarily phosphorus and nitrogen, can cause excessive aquatic plant growth, leading to eutrophication. When these plants die, the decomposition process depletes the oxygen levels in the water.
• Pet waste : Improperly disposed-of pet waste can be a source of bacteria and nutrients, such as nitrogen and phosphorus, which contribute to nutrient pollution in water bodies.
• Insufficient streamside vegetation : Streamside trees play a crucial role in maintaining water quality by regulating water temperature, filtering out pollutants, and stabilising streambanks. However, residential areas with insufficient streamside vegetation can contribute to water pollution by failing to provide adequate filtration for runoff.

It is important to note that non-point water pollution is challenging to regulate because it arises from numerous sources and everyday activities. However, local agencies, tribes, and organisations often lead programs and initiatives to address and mitigate the impact of non-point source pollution in residential areas.

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