How Area Source Pollution Diffuses

Point source pollution and non-point source pollution are two types of pollution with distinct differences. Point source pollution, as defined by the US EPA, is any single identifiable source of pollution from which pollutants are discharged, such as a pipe, ditch, ship, or factory smokestack. On the other hand, non-point source pollution (NPS) comes from many diffuse sources and is caused by rainfall or snowmelt moving over and through the ground, carrying away natural and human-made pollutants and depositing them into bodies of water and groundwater. While point sources are regulated and require permits for discharging pollutants, non-point source pollution is more challenging to trace and regulate due to its diverse and widespread nature.

Point source pollution

Large farms that raise livestock, known as concentrated animal feeding operations (CAFOs), are another source of point source pollution if they do not treat their animal waste properly. Untreated animal waste from these farms can enter nearby water bodies, causing water pollution and unsafe drinking water. It can also lead to restrictions on activities like fishing and swimming due to health concerns.

In addition to water and air pollution, point source pollution can also contaminate groundwater reservoirs, posing a threat to human health and safety. Metal contamination, for example, has been an issue in Europe and North America, with releases from mining, smelting, refining, and other industrial activities. While metal releases have declined in these regions, they continue to increase in many developing countries.

Nonpoint source pollution

Nonpoint source (NPS) pollution is caused by rainfall or snowmelt moving over and through the ground. As the runoff moves, it picks up and carries away natural and human-made pollutants, depositing them into lakes, rivers, wetlands, coastal waters, and groundwater. NPS pollution generally results from land runoff, precipitation, atmospheric deposition, drainage, seepage, or hydrologic modification. Unlike pollution from industrial and sewage treatment plants, NPS pollution comes from many diffuse sources.

The major sources of NPS pollution in Illinois, for example, are agriculture, urban runoff, and habitat modification. Urban runoff flows through storm drains and the vast network of pipes below city streets. Water that flows into storm drains does not get treated; instead, it flows directly into lakes and streams. Habitat modification refers to the channelization of streams and the disturbance of riparian corridors (the area of land immediately adjacent to stream banks). The most common NPS pollutants in Illinois are nutrients and sediment. Nutrients come from fertilizers and animal waste. Sediment is soil that has eroded from farm fields, construction sites, and streambanks. When sediment reaches lakes and streams, it makes the water cloudy, impairing the ability of aquatic organisms to see and feed properly. Sediment can damage fish gills and the breathing of aquatic insects, cover fish spawning habitats, and reduce sunlight penetration, affecting plant growth. Sediments can also carry other pollutants such as metals and toxic chemicals.

Federal programs have been established to address nonpoint source pollution, and fact sheets have been published to provide information on the impact of nonpoint source pollution on coastal areas and the actions taken to address this issue. Other fact sheets address the impact of agricultural practices, forestry, and urban runoff on nonpoint source pollution and the steps that can be taken to reduce their impact.

To prevent stormwater runoff pollution, individuals can take simple steps such as keeping litter, pet waste, leaves, and debris out of street gutters and storm drains. It is also important to apply lawn and garden chemicals sparingly and according to directions and to dispose of used oil, antifreeze, paints, and other household chemicals properly, not in storm sewers or drains.

Stormwater pollution

Urbanization plays a significant role in stormwater pollution. As cities and towns develop, natural landscapes like forests and meadows are replaced with buildings and pavement. This transformation reduces the ability of the land to absorb rainwater, resulting in increased runoff. Urban and suburban areas, with their extensive paved surfaces, contribute significantly to stormwater runoff and the associated pollution.

The impact of stormwater pollution is widespread. Pollutants carried by stormwater can include nutrients such as nitrogen and phosphorus, which promote the growth of algae and weeds in water bodies. Bacteria and other contaminants can also enter water sources through stormwater runoff, leading to beach and shellfish bed closures due to unsafe conditions. Additionally, stormwater pollution can result in soil erosion and flooding, further exacerbating the environmental challenges.

To address stormwater pollution, various strategies can be implemented. Green infrastructure, also known as low-impact development, is one approach. This involves techniques such as rain gardens, pervious pavement, rain barrels, and green roofs. These methods slow down and disperse stormwater runoff, allowing plants to naturally filter out pollutants as the water infiltrates the ground. Implementing green infrastructure can help reduce the amount of polluted stormwater entering water bodies.

Another critical aspect of stormwater pollution prevention is public awareness and individual action. Homeowners and residents can play a significant role in reducing stormwater pollution by adopting simple practices. This includes properly disposing of litter, pet waste, leaves, and debris, ensuring they do not end up in street gutters and storm drains. Additionally, responsible usage and application of lawn and garden chemicals, as well as proper disposal of household chemicals, can help minimize the introduction of pollutants into stormwater.

Urban runoff

The sources of urban runoff pollution are varied and include atmospheric deposition, vehicular transportation-related activities, and metallic building envelopes. Atmospheric deposition refers to pollutants that are emitted into the atmosphere and then redeposited into watersheds, such as through rainfall or snowmelt. Vehicular transportation-related activities include pollutants from cars, trucks, and other vehicles that are then washed into stormwater systems. Metallic building envelopes are another source, as metals used in construction can be released into the environment over time.

In addition to these sources, urban runoff can also be contaminated by residential and commercial properties, construction sites, automotive facilities, and forestry operations. For example, litter, pet waste, leaves, and debris that are left in street gutters and storm drains can contribute to urban runoff, as these outlets drain directly into nearby water bodies. The improper disposal of household chemicals, such as used oil, antifreeze, and paints, can also pollute urban runoff.

The impact of urban runoff on waterway health can be significant. Pollutants carried by urban runoff can have harmful effects on drinking water supplies, recreation, fisheries, and wildlife. For example, high levels of pollutants in water can restrict activities like fishing and swimming and can have severe effects on fish populations. In some cases, urban runoff has been linked to the presence of perfluoroalkyl substances in water, sediment, and biota, further highlighting the diverse and detrimental effects of this type of pollution.

Agricultural pollution

Non-point source pollution is caused by rainfall or snowmelt moving over and through the ground, picking up and carrying away natural and human-made pollutants, and depositing them into lakes, rivers, wetlands, coastal waters, and groundwater. Agricultural operations can contribute to non-point source pollution through the use of pesticides, fertilizers, and animal manure, which can enter local streams, rivers, and groundwater. The National Water Quality Assessment in the US shows that agricultural runoff is the leading cause of water quality impacts on rivers and streams, the third-largest source for lakes, and the second-largest source of impairments to wetlands.

Point-source water pollution in agriculture can come from large farms that raise livestock, known as concentrated animal feeding operations (CAFOs). If these farms do not treat their animals' waste materials, they can enter nearby water bodies, causing water pollution and unsafe drinking water. Additionally, the widespread use of antibiotics in meat production contributes to the public health crisis of antibiotic resistance.

Mitigation of agricultural pollution is crucial for developing a sustainable food system. Management practices, such as nutrient management, manure storage, and drip irrigation, can help minimize water quality impacts. Implementing conservation practices through a systems approach can also control multiple pollutants simultaneously.

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