Point and Nonpoint Pollution Sources
Point-source pollutants in surface water and groundwater are usually found in a plume that has the highest concentrations of the pollutant nearest the source (such as the end of a pipe or an underground injection system) and diminishing concentrations farther away from the source. The various types of point-source pollutants found in waters are as varied as the types of business, industry, agricultural, and urban sources that produce them. Commercial and industrial businesses use hazardous materials in manufacturing or maintenance, and then discharge various wastes from their operations. The raw materials and wastes may include pollutants such as solvents, petroleum products (such as oil and gasoline), or heavy metals . Point sources of pollution from agriculture may include animal feeding operations, animal waste treatment lagoons, or storage, handling, mixing, and cleaning areas for pesticides, fertilizers, and petroleum. Municipal point sources might include wastewater treatment plants, landfills, utility stations, motor pools, and fleet maintenance facilities. For all of these activities, hazardous materials may be included in the raw materials used in the process as well as in the waste stream for the facility. If the facility or operator does not handle, store, and dispose of the raw materials and wastes properly, these pollutants could end up in the water supply. This may occur through discharges at the end of a pipe to surface water, discharges on the ground that move through the ground with infiltrating rainwater, or direct discharges beneath the ground surface. Groundwater.
Some of the most persistent point-source pollutants in groundwater are volatile organic compounds , which include manufactured and refined toxic substances such as solvents, oils, paint, and fuel products. In general, it takes only a small amount of these chemicals to raise health concerns. For example, approximately 4 liters (about one gallon) of pure trichloroethylene, a common solvent, will contaminate over 1 billion liters (300 million gallons) of water. Once groundwater is contaminated, it is difficult, costly, and sometimes even impossible to clean up. Surface Water.
The most common point-source pollutants in surface water are: •
Microorganisms (such as bacteria, viruses, and Giardia ); and •
Nutrients (such as nitrogen and phosphorus).
Temperature increases and nutrients can result in excessive plant growth and subsequent decaying organic matter in water that depletes dissolved oxygen levels and consequently stressing or killing vulnerable aquatic life. Microorganisms can be hazardous to both human health and aquatic life. Pesticides and other toxic substances can also be hazardous to both human health and aquatic life, but are less commonly found in surface water because of high dilution rates. Point source water pollution happens when harmful substances are put directly into water. An example is garbage dumping by factories.
Nonpoint-source pollution occurs as water moves across the land or through the ground and picks up natural and human-made pollutants, which can then be deposited in lakes, rivers, wetlands, coastal waters, and even groundwater. The water that carries nonpoint-source pollution may originate from natural processes such as rainfall or snowmelt, or from human activities such as crop irrigation or lawn maintenance. Nonpoint-source pollution is usually found spread out throughout a large area. It is often difficult to trace the exact origin of these pollutants because they result from a wide variety of human activities on the land as well as natural characteristics of the soil, climate, and topography . The most common nonpoint-source pollutants are sediment , nutrients, microorganisms and toxics. Sediment can degrade water quality by contaminating drinking water supplies or silting in spawning grounds for...
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