Nonpoint source pollution
Types of nonpoint source water pollution include sediment, nutrients, toxic contaminants and chemicals and pathogens.
[3] Nutrient runoff in storm water from "sheet flow" over an agricultural field or a forest are also examples of non-point source pollution.
[5] Sediment creates turbidity (cloudiness) in water bodies, reducing the amount of light reaching lower depths, which can inhibit growth of submerged aquatic plants and consequently affect species which are dependent on them, such as fish and shellfish.
[6] With an increased sediment load into a body of water, the oxygen can also be depleted or reduced to a level that is harmful to the species living in that area.
It is a main ingredient in many fertilizers used for agriculture as well as on residential and commercial properties and may become a limiting nutrient in freshwater systems and some estuaries.
Excess amounts of phosphorus in aquatic systems (particularly freshwater lakes, reservoirs, and ponds) leads to proliferation of microscopic algae called phytoplankton.
Bacterial decomposition of algal blooms consumes dissolved oxygen in the water, generating hypoxia with detrimental consequences for fish and aquatic invertebrates.
Similar to phosphorus in fresh-waters, excess amounts of bioavailable nitrogen in marine systems lead to eutrophication and algae blooms.
Hypoxia is an increasingly common result of eutrophication in marine systems and can impact large areas of estuaries, bays, and near shore coastal waters.
During recent summers, the aerial extent of this "dead zone" is comparable to the area of New Jersey and has major detrimental consequences for fisheries in the region.
[10] Other toxic contaminants include organic compounds such as polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs), fire retardants, and many agrochemicals like DDT, other pesticides, and fertilizers.
These compounds can have severe effects to the ecosystem and water-bodies and can threaten the health of both humans and aquatic species while being resistant to environmental breakdown, thus allowing them to persist in the environment.
[10] Acids and salts mainly are inorganic pollutants from irrigated lands, mining operations, urban runoff, industrial sites and landfills.
[17] Contaminated stormwater washed off parking lots, roads and highways, and lawns (often containing fertilizers and pesticides) is called urban runoff.
Some people may also consider it a point source because many times it is channeled into municipal storm drain systems and discharged through pipes to nearby surface waters.
[19][20] Nutrients (nitrogen and phosphorus) are typically applied to farmland as commercial fertilizer, animal manure, or spraying of municipal or industrial wastewater (effluent) or sludge.
2–9 Nutrient pollution such as nitrates can harm the aquatic environments by degrading water quality by lowering levels of oxygen, which can inturn induce algal blooms and eutrophication.
Pesticides such as DDT or atrazine can travel through waterways or stay suspended in air and carried by wind in a process known as "spray drift".
The effects of vehicular traffic on the wet and dry deposition that occurs on or near highways, roadways, and parking areas creates uncertainties in the magnitudes of various atmospheric sources in runoff.
Nutrient and bacteria levels are increased by poorly maintained sanitary waste receptacles on the boat and pump-out stations.
Buffer strips provide a barrier of grass in between impervious paving material like parking lots and roads, and the closest body of water.
[37] At least two shellfish protection districts in south Puget Sound have instituted septic system operation and maintenance requirements with program fees tied directly to property taxes.
[17] Nutrients are typically applied to farmland as commercial fertilizer; animal manure; or spraying of municipal or industrial wastewater (effluent) or sludge.
[17] Installing shut off valves on fuel pumps at a marina dock can help reduce the amount of spillover into the water.
Additionally, pump-out stations that are easily accessible to boaters in a marina can provide a clean place in which to dispose of sanitary waste without dumping it directly into the water.
[44]: 15 [21] The definition of a nonpoint source is addressed under the U.S. Clean Water Act as interpreted by the U.S. Environmental Protection Agency (EPA).
For example, many states have taken the steps to implement their own management programs for places such as their coastlines, all of which have to be approved by the National Oceanic and Atmospheric Administration and the EPA.
[45] The goals of these programs and those alike are to create foundations that encourage statewide pollution reduction by growing and improving systems that already exist.
[46] Programs within these state and local governments look to best management practices (BMPs) in order to accomplish their goals of finding the least costly method to reduce the greatest amount of pollution.
Federal agencies, including EPA and the Natural Resources Conservation Service, have approved and provided a list of commonly used BMPs for the many different categories of nonpoint source pollution.
