Nutrient pollution
Nutrient pollution, a form of water pollution, refers to contamination by excessive inputs of nutrients. It is a primary cause of eutrophication of surface waters (lakes, rivers and coastal waters), in which excess nutrients, usually nitrogen or phosphorus, stimulate algal growth.[1] Sources of nutrient pollution include surface runoff from farm fields and pastures, discharges from septic tanks and feedlots, and emissions from combustion. Raw sewage is a large contributor to cultural eutrophication since sewage is high in nutrients. Releasing raw sewage into a large water body is referred to as sewage dumping, and still occurs all over the world. Excess reactive nitrogen compounds in the environment are associated with many large-scale environmental concerns. These include eutrophication of surface waters, harmful algal blooms, hypoxia, acid rain, nitrogen saturation in forests, and climate change.[2]
This article is about a type of pollution. For one of the effects of this type of pollution on water bodies, see eutrophication.
Since the agricultural boom in the 1910s and again in the 1940s to match the increase in food demand, agricultural production relies heavily on the use of fertilizers.[3] Fertilizer is a natural or chemically modified substance that helps soil become more fertile. These fertilizers contain high amounts of phosphorus and nitrogen, which results in excess amounts of nutrients entering the soil. Nitrogen, phosphorus and potassium are the "Big 3" primary nutrients in commercial fertilizers, each of these fundamental nutrients play a key role in plant nutrition.[4] When nitrogen and phosphorus are not fully utilized by the growing plants, they can be lost from the farm fields and negatively impact air and downstream water quality.[5] These nutrients can eventually end up in aquatic ecosystems and are a contributor to increased eutrophication.[6] When farmers spread their fertilizer, whether it is organic or synthetically made, some of it will leave as runoff and can collect downstream generating cultural eutrophication.[7]
Mitigation approaches to reduce nutrient pollutant discharges include nutrient remediation, nutrient trading and nutrient source apportionment.
Country examples[edit]
United States[edit]
Agricultural nonpoint source (NPS) pollution is the largest source of water quality impairments throughout the U.S., based on surveys by state environmental agencies.[38]: 10 NPS pollution is not subject to discharge permits under the federal Clean Water Act (CWA).[39] EPA and states have used grants, partnerships and demonstration projects to create incentives for farmers to adjust their practices and reduce surface runoff.[38]: 10–11