Nutrient pollution
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Nutrient pollution, a form of
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.
Sources
Food types | Eutrophying emissions (g PO43-eq per 100g protein) |
---|---|
Beef | 365.3
|
Farmed fish | 235.1
|
Farmed crustaceans | 227.2
|
Cheese | 98.4
|
Lamb and mutton | 97.1
|
Pork | 76.4
|
Poultry | 48.7
|
Eggs
|
21.8
|
Groundnuts | 14.1
|
Peas
|
7.5
|
Tofu | 6.2
|
The principal source(s) of nutrient pollution in an individual watershed depend on the prevailing land uses. The sources may be point sources, nonpoint sources, or both:
- Agriculture: animal production or crops
- Urban/suburban: stormwater runoff from roads and parking lots; excessive fertilizer use on lawns; municipal sewage treatment plants; motor vehicle emissions
- Industrial: air pollution emissions (e.g. electric power plants), wastewater discharges from various industries.[9]
Nutrient pollution from some air pollution sources may occur independently of the local land uses, due to long-range transport of air pollutants from distant sources.[10]
In order to gauge how to best prevent eutrophication from occurring, specific sources that contribute to nutrient loading must be identified. There are two common sources of nutrients and organic matter: point and nonpoint sources.
Nitrogen
Use of
Phosphorus
Phosphorus pollution is caused by excessive use of fertilizers and manure, particularly when compounded by soil erosion. In the European Union, it is estimated that we may lose more than 100,000 tonnes of Phosphorus to water bodies and lakes due to water erosion.[13] Phosphorus is also discharged by municipal sewage treatment plants and some industries.[14]
Point sources
Nonpoint sources
Nonpoint source pollution (also known as 'diffuse' or 'runoff' pollution) is that which comes from ill-defined and diffuse sources. Nonpoint sources are difficult to regulate and usually vary spatially and temporally (with
It has been shown that nitrogen transport is correlated with various indices of human activity in watersheds,[17][18] including the amount of development.[19] Ploughing in agriculture and development are among activities that contribute most to nutrient loading.[9]
Soil retention
Nutrients from human activities tend to accumulate in
Runoff to surface water
Nutrients from human activities tend to travel from land to either surface or ground water. Nitrogen in particular is removed through
Atmospheric deposition
Nitrogen is released into the air because of
Impacts
Environmental and economic impacts
Excess nutrients have been summarized as potentially leading to:
- Excess growth of algae (harmful algal blooms);[26] and biodiversity loss;[27]
- Species composition shifts (dominant taxa);
- Food web changes, light limitation;
- Excess organic carbon (eutrophication); dissolved oxygen deficits (environmental hypoxia); toxin production;[10]
Nutrient pollution can have economic impacts due to increasing water treatment costs, commercial fishing and shellfish losses, recreational fishing losses, and reduced tourism income.[28]
Health impacts
Human health effects include excess nitrate in drinking water (blue baby syndrome) and disinfection by-products in drinking water. Swimming in water affected by a harmful algal bloom can cause skin rashes and respiratory problems.[29]
Reduction of discharges
Nutrient trading
Nutrient trading is a type of
A 2013
Nutrient source apportionment
Nutrient source apportionment is used to estimate the nutrient load from various sectors entering water bodies, following attenuation or treatment. Agriculture is typically the principal source of nitrogen in water bodies in Europe, whereas in many countries households and industries tend to be the dominant contributors of phosphorus.[32] Where water quality is impacted by excess nutrients, load source apportionment models can support the proportional and pragmatic management of water resources by identifying the pollution sources. There are two broad approaches to load apportionment modelling, (i) load-orientated approaches which apportion origin based on in-stream monitoring data[33][34] and (ii) source-orientated approaches where amounts of diffuse, or nonpoint source pollution, emissions are calculated using models typically based on export coefficients from catchments with similar characteristics.[35][36] For example, the Source Load Apportionment Model (SLAM) takes the latter approach, estimating the relative contribution of sources of nitrogen and phosphorus to surface waters in Irish catchments without in-stream monitoring data by integrating information on point discharges (urban wastewater, industry and septic tank systems), diffuse sources (pasture, arable, forestry, etc.), and catchment data, including hydrogeological characteristics.[37]
Country examples
United States
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
Development of nutrient policy
The basic requirements for states to develop nutrient criteria and standards were mandated in the 1972 Clean Water Act. Implementing this water quality program has been a major scientific, technical and resource-intensive challenge for both EPA and the states, and development is continuing well into the 21st century.
EPA published a wastewater management regulation in 1978 to begin to address the national nitrogen pollution problem, which had been increasing for decades.[40] In 1998, the agency published a National Nutrient Strategy with a focus on developing nutrient criteria.[41]
Between 2000 and 2010 EPA published federal-level nutrient criteria for rivers/streams, lakes/reservoirs, estuaries and wetlands; and related guidance. "Ecoregional" nutrient criteria for 14 ecoregions across the U.S. were included in these publications. While states may directly adopt the EPA-published criteria, in many cases the states need to modify the criteria to reflect site-specific conditions. In 2004, EPA stated its expectations for numeric criteria (as opposed to less-specific narrative criteria) for total nitrogen (TN), total phosphorus (TP), chlorophyll a(chl-a), and clarity, and established "mutually-agreed upon plans" for state criteria development. In 2007, the agency stated that progress among the states on developing nutrient criteria had been uneven. EPA reiterated its expectations for numeric criteria and promised its support for state efforts to develop their own criteria.[42]
After the EPA had introduced watershed-based
In 2008 EPA published a progress report on state efforts to develop nutrient standards. A majority of states had not developed numeric nutrient criteria for rivers and streams; lakes and reservoirs; wetlands and estuaries (for those states that have estuaries).[44] In the same year, EPA also established a Nutrient Innovations Task Group (NITG), composed of state and EPA experts, to monitor and evaluate the progress of reducing nutrient pollution.[45] In 2009 the NTIG issued a report, "An Urgent Call to Action", expressing concern that water quality continued to deteriorate nationwide due to increasing nutrient pollution, and recommending more vigorous development of nutrient standards by the states.[46]
In 2011 EPA reiterated the need for states to fully develop their nutrient standards, noting that drinking water violations for nitrates had doubled in eight years, that half of all streams nationwide had medium to high levels of nitrogen and phosphorus, and harmful algal blooms were increasing. The agency set out a framework for states to develop priorities and watershed-level goals for reductions of nutrients.[47]
Discharge permits
Many
Discharges from large livestock facilities (CAFO) are also regulated by NPDES permits.[51] Surface runoff from farm fields, the principal source of nutrients in many watersheds,[52] is classified as NPS pollution and is not regulated by NPDES permits.[39]
TMDL program
A
A TMDL can prescribe the minimum level of
EPA published a TMDL for the Chesapeake Bay in 2010, addressing nitrogen, phosphorus and sediment pollution for the entire watershed, covering an area of 64,000 square miles (170,000 km2). This regulatory plan covers both the estuary and its tributaries—the largest, most complex TMDL document that EPA had issued to date.[58][59]
In Long Island Sound, the TMDL development process enabled the Connecticut Department of Energy and Environmental Protection and the New York State Department of Environmental Conservation to incorporate a 58.5 percent nitrogen reduction target into a regulatory and legal framework.[54]
See also
References
- ISBN 978-1-63485-188-6.
- ^ "Reactive Nitrogen in the United States: An Analysis of Inputs, Flows, Consequences, and Management Options, A Report of the Science Advisory Board" (PDF). Washington, DC: US Environmental Protection Agency (EPA). EPA-SAB-11-013. Archived from the original (PDF) on February 19, 2013.
- .
- ^ "Fertilizer 101: The Big Three―Nitrogen, Phosphorus and Potassium". Arlington, VA: The Fertilizer Institute. 2014-05-07. Archived from the original on 2023-06-05. Retrieved 2021-08-21.
- ^ "The Sources and Solutions: Agriculture". Nutrient Pollution. EPA. 2021-11-04.
- .
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- ^ a b "Sources and Solutions". Nutrient Pollution. EPA. 2021-08-31.
- ^ a b "The Effects: Environment". Nutrient Pollution. EPA. 2021-03-01.
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- ^ "Phosphorus and Water". USGS Water Science School. Reston, VA: U.S. Geological Survey (USGS). 2018-03-13.
- ^ "Point Source; Pollution Tutorial". Silver Spring, MD: U.S. National Ocean Service. Retrieved 2022-06-10.
- ^ "Basic Information about Nonpoint Source Pollution". 15 September 2015.
- ISBN 0-387-98243-4.
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- ^ Sharpley AN, Daniel TC, Sims JT, Pote DH (1996). "Determining environmentally sound soil phosphorus levels". Journal of Soil and Water Conservation. 51: 160–166. Archived from the original on 2023-03-30. Retrieved 2021-02-12.
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- ^ "Critical Loads – Atmospheric Deposition". U.S. Forest Service. United States Department of Agriculture. Retrieved 2 April 2018.
- S2CID 17321339.[permanent dead link]
- ^ "Harmful Algal Blooms". Nutrient Pollution. EPA. 2020-11-30.
- ^ "National Nutrient Strategy". EPA. 2021-08-18.
- ^ "The Effects: Economy". Nutrient Pollution. EPA. 2022-04-19.
- ^ "The Effects: Human Health". Nutrient Pollution. EPA. 2022-04-19.
- ^ "Frequent Questions about Water Quality Trading". NPDES. EPA. 2022-02-25.
- ^ a b Genevieve Bennett; Nathaniel Carroll; Katherine Hamilton (2013). "Charting New Waters, State of Watershed Payments 2012" (PDF). Washington, DC: Forest Trends Association.
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- ^ a b National Nonpoint Source Program: A catalyst for water quality improvements (Report). EPA. October 2016. EPA 841-R-16-009.
- ^ a b "NPDES Permit Basics". EPA. 2021-09-28.
- ^ Kilian, Chris (2010). "Cracking down on Nutrient Pollution: CLF Fights to Bring New England's Coastal Waters Back to Life". Conservation Matters. 16 (2).
- ^ National Strategy for the Development of Regional Nutrient Criteria (Report). EPA. June 1998. EPA 822-R-98-002.
- ^ Grumbles, Benjamin (2007-05-25). "Nutrient Pollution and Numeric Water Quality Standards" (PDF). EPA. Memorandum to State and Tribal Water Program Directors.
- ^ "Permit Limits: Watershed-based Permitting". NPDES. EPA. 2021-10-11.
- ^ State Adoption of Numeric Nutrient Standards (1998–2008) (Report). EPA. December 2008. EPA 821-F-08-007.
- ^ "Programmatic Information on Numeric Nutrient Water Quality Criteria". EPA. 2017-05-16.
- ^ An Urgent Call to Action: Report of the State-EPA Nutrient Innovations Task Group (Report). EPA. August 2009. EPA 800-R-09-032.
- ^ Stoner, Nancy K. (2011-03-16). "Working in Partnership with States to Address Phosphorus and Nitrogen Pollution through Use of a Framework for State Nutrient Reductions" (PDF). EPA. Headquarters Memorandum to EPA Regional Administrators.
- ^ "Status of Nutrient Requirements for NPDES-Permitted Facilities". NPDES. EPA. 2021-09-28.
- ^ "Removing Nitrogen from Wastewater Protects our Waterways". Washington, D.C.: DC Water. Retrieved 2018-01-15.
- ^ "National Study of Nutrient Removal and Secondary Technologies". EPA. 2021-09-22.
- ^ "Animal Feeding Operations". NPDES. EPA. 2021-07-23.
- ^ "Agriculture". Learn the Issues. Annapolis, Maryland: Chesapeake Bay Program. Archived from the original on 2018-10-07. Retrieved 2018-10-06.
- ^ a b "Overview of Identifying and Restoring Impaired Waters under Section 303(d) of the CWA". Impaired Waters and TMDLs. EPA. 2021-09-20.
- ^ a b "TMDLs at Work: Long Island Sound". EPA. 2021-06-16.
- ^ Golen, Richard F. (2007). "Incorporating Shellfish Bed Restoration into a Nitrogen TMDL Implementation Plan" (PDF). Dartmouth, MA: University of Massachusetts, Dartmouth. Archived from the original (PDF) on 2016-11-16. Retrieved 2013-05-24.
- ^ "National Nutrient Strategy". EPA. 2007.
- ^ "Chapter 6. Water Quality-Based Effluent Limitations". NPDES Permit Writers' Manual (Report). EPA. September 2010. EPA-833-K-10-001.
- ^ "Chesapeake Bay Total Maximum Daily Load". EPA. 2022-04-20.
- ^ Chesapeake Bay TMDL Executive Summary (PDF) (Report). EPA. 2010-12-29.
- This article incorporates public domain material from Report for Congress: Agriculture: A Glossary of Terms, Programs, and Laws, 2005 Edition (PDF). Congressional Research Service.
- EPA. "Protecting Water Quality from Agricultural Runoff." March 2005. Document No. EPA 841-F-05-001. Fact sheet.