Water Pollutants: Nonpoint Sources And Their Impact

Nonpoint source (NPS) pollution is the leading cause of water quality issues, according to reports from various states. NPS pollution is challenging to manage because it originates from numerous sources and locations, including land runoff, precipitation, drainage, and atmospheric deposition. As rainwater or snowmelt flows over various surfaces, it collects contaminants such as oil, pet waste, pesticides, fertilizers, road salt, and bacteria, eventually depositing them into water bodies. This form of pollution affects aquatic habitats, drinking water supplies, and recreational activities, with potential economic repercussions for coastal communities. While the concentration of pollutants from NPS pollution may be lower compared to point source pollution, the cumulative effect from multiple sources can result in a higher total amount of pollutants. Understanding and addressing NPS pollution is crucial for maintaining water quality and minimizing its impact on the environment and human well-being.

Oil and oil-based chemicals

Nonpoint source (NPS) pollution is defined as any source of water pollution that does not meet the legal definition of "point source" in the Clean Water Act. Point sources are specific and identifiable, such as pipes or ditches, whereas nonpoint sources are diffuse and challenging to control as they come from multiple sources and locations. NPS pollution is primarily caused by rainfall or snowmelt moving over and through the ground, absorbing and carrying pollutants, which are eventually deposited into bodies of water.

One significant nonpoint source pollutant is oil and oil-based chemicals. Oil pollution is a pressing issue, with consumers contributing the most oil pollution in our seas, including oil and gasoline dripping from cars and trucks. Land-based sources, such as factories, farms, and cities, are responsible for nearly half of the estimated 1 million tons of oil that enters marine environments annually. Oil spills, both land-based and maritime, are a prominent form of oil pollution, with maritime spills receiving more attention due to their rapid spread and severe consequences.

Oil spills occur when liquid petroleum hydrocarbons are released into the environment, particularly the marine ecosystem, due to human activity. They can result from tanker releases, offshore platforms, drilling rigs, wells, or refined petroleum products like gasoline and diesel fuel. These spills have detrimental environmental, economic, and social impacts, affecting the health of both humans and wildlife. Oil penetrates the plumage of birds and the fur of mammals, reducing their insulating ability and making them more susceptible to temperature changes and less buoyant in the water.

In addition to large-scale oil spills, oil and oil-based chemicals also enter water bodies through urban runoff. Motor oil and oil-based chemicals on roads and parking lots are picked up by rainwater and eventually flow into streams, rivers, lakes, or oceans. This form of nonpoint source pollution is identifiable by the characteristic rainbow-colored sheen on the water's surface.

The impact of oil and oil-based chemicals as nonpoint source pollutants extends beyond the immediate contamination of water sources. Oil spills, for instance, can lead to air pollution during the cleanup and recovery process, generating air pollutants like nitric oxides and ozone. Furthermore, oil pollution in water can have far-reaching consequences for coastal communities, affecting their economies and social conditions. Water-based activities like shipping, boating, tourism, and fishing contribute significantly to the economy, and oil pollution can deter these activities, driving down property values and causing financial losses.

E. coli

Escherichia coli (E. coli) is a common bacterium found in the digestive tract of all warm-blooded animals, including humans. While E. coli is not always harmful to humans, it is often found in conjunction with bacteria that are harmful, and is therefore used as an indicator of water pollution by animal or human waste.

The detection of E. coli in water systems is a priority to understand the potential health risks and mitigate the source of pollution. Human sources of E. coli can contain harmful pathogens such as Salmonella, Shigella, and hepatitis A, while agricultural animals can carry pathogens including Cryptosporidium parvum and E. coli 0157:H7.

The genetic diversity of E. coli strains found in urban rivers and beach water has been studied, and it was found that river water contained strains from many diffuse sources of nonpoint source pollution. Urban stormwater, in particular, is recognised as a major source of E. coli, carrying the bacterium from numerous host animals.

Overall, E. coli is a significant water pollutant that can have harmful effects on both ecosystems and the economy, impacting activities such as tourism and recreational fishing.

Sediment

Land Runoff

Land runoff is a significant contributor to sediment pollution in water bodies. When rainfall or snowmelt occurs, water moves across the landscape, picking up and carrying away pollutants, including sediment, from the ground. This polluted runoff then flows into nearby water bodies, depositing the sediment.

Precipitation

Precipitation, in the form of rainfall or snowmelt, directly causes nonpoint source pollution by moving through the ground and picking up pollutants. As the water seeps into the ground, it can carry away natural and human-made pollutants, including sediment, and transport them into water bodies through hydrologic modification.

Construction Activities

Improperly managed construction sites are significant sources of sediment pollution. Construction activities that disturb large areas of land increase the risk of sediment runoff into nearby waterways. Indiana has implemented rules to limit the amount of sediment permitted to leave construction sites, recognizing the impact of this nonpoint source.

Agricultural Practices

Agricultural practices, such as tilling fields, contribute to sediment pollution in water bodies. Tilled fields in agricultural watersheds are a major source of sediment, which is then carried by erosion and runoff into nearby streams and lakes. Additionally, improper livestock management can lead to overgrazing and pasture erosion, further increasing sediment runoff.

It is important to note that while sediment is a significant pollutant, it often carries other nutrients and contaminants into water bodies, exacerbating the impact on aquatic ecosystems. Addressing nonpoint source pollution, including sediment, is crucial for maintaining water quality, protecting ecosystems, and ensuring the well-being of communities that depend on these water sources.

Thermal pollution

Causes of Thermal Pollution

• Industrial Cooling: The most common cause of thermal pollution is the use of water as a coolant by power plants and industrial manufacturers. Power plants, particularly those generating power from fossil fuels, biomass, or nuclear energy, use water to cool down their machinery, and this heated water is then returned to natural bodies of water, raising their overall temperature. In the United States, about 75-80% of thermal pollution is generated by power plants.
• Urban Runoff: During warm weather, urban runoff can significantly impact small streams. As stormwater passes over hot surfaces like rooftops, roads, and parking lots, it absorbs heat, raising the temperature of the water it eventually empties into.
• Deforestation: Deforestation contributes to thermal pollution by removing trees and shrubs from riverbanks and lakeshores, exposing the water to more sunlight and causing it to heat up.
• Natural Events: While less common, natural events such as wildfires, volcanoes, underwater thermal vents, and lightning strikes can also cause sudden spikes in water temperature.

Effects of Thermal Pollution

• Decreased Dissolved Oxygen: Warmer water has a reduced capacity to carry dissolved oxygen, leading to stress and potential harm to fish and other aquatic organisms.
• Altered Metabolic Rates: Increased water temperature can raise the metabolic rates of aquatic animals, causing them to consume more food in a shorter time, potentially leading to resource competition and altered food chains.
• Biodiversity Loss: Thermal pollution can directly harm or kill aquatic plants, insects, and amphibians, as they are sensitive to changes in temperature. This can lead to a decrease in biodiversity.
• Ecosystem Disruption: The sudden change in water temperature can throw the entire ecosystem into disarray, altering water chemistry and harming both plant and animal life.

Mitigation Strategies

To mitigate the impacts of thermal pollution, several strategies can be employed:

• Closed-Loop Systems: Converting facilities from once-through cooling to closed-loop systems can help decrease thermal pollution. These systems release water at temperatures closer to the natural environment.
• Reservoir Design: Dams can be designed to release warmer surface water instead of colder water from the bottom, reducing the thermal impact on receiving water bodies.
• Cooling Ponds and Towers: Implementing cooling ponds and towers can help transfer waste heat to the atmosphere through evaporation and/or heat transfer, reducing the thermal impact on water sources.
• Cogeneration: Recycling waste heat for domestic and/or industrial heating purposes can also help reduce thermal pollution.

Acid rain

Nonpoint source (NPS) pollution is defined as any source of water pollution that does not meet the legal definition of "point source" as outlined in the Clean Water Act. Point sources refer to confined conveyances from which pollutants are discharged, such as pipes, ditches, tunnels, and containers. NPS pollution, on the other hand, arises from various diffuse sources and is challenging to control. It primarily occurs due to land runoff, precipitation, atmospheric deposition, drainage, seepage, or hydrologic modification.

The acidic particles and gases then fall to the earth through wet and dry deposition. Wet deposition, commonly associated with acid rain, occurs when the sulfuric and nitric acids mix with precipitation, such as rain, snow, fog, or hail, before reaching the ground. Dry deposition, on the other hand, involves the deposition of acidic particles and gases directly onto surfaces, including water bodies, vegetation, and buildings.

The impact of acid rain extends to soil, forests, streams, and lakes. When acid deposition is washed into lakes and streams, it can turn the water acidic, harming aquatic ecosystems. Acid rain also affects soil chemistry, vegetation, and wildlife, including insects and fish. The accumulation of acids on surfaces can be washed off by rainfall, leading to acidic water flowing over and through the ground, further exacerbating its environmental impact.

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