User:Garner Kohrell/sandbox

= Agricultural pollution = From Wikipedia, the free encyclopedia Jump to navigationJump to search Agricultural pollution refers to biotic and abiotic byproducts of farming practices that result in contamination or degradation of the environment and surrounding ecosystems, and/or cause injury to humans and their economic interests. It may originate from a variety of sources, ranging from point source water pollution (from a single discharge point) to more diffuse, landscape-level causes, also known as non-point source pollution. Management practices play a crucial role in the amount and impact of these pollutants. Management techniques range from animal management and housing to the spread of pesticides and fertilizers in global agricultural practices. Water pollution due to dairy farming in the Wairarapa area of New Zealand (photographed in 2003).

Contents

 * 1Abiotic sources
 * 1.1Pesticides
 * 1.1.1Pesticide leaching
 * 1.2Fertilizers
 * 1.2.1Leaching, runoff, and eutrophication
 * 1.2.2Organic contaminants
 * 1.3Heavy metals
 * 1.4Land management
 * 1.4.1Tillage and nitrous oxide emissions
 * 1.4.2Soil erosion and sedimentation
 * 2Biotic sources
 * 2.1Greenhouse gases from fecal waste
 * 2.2Biopesticides
 * 2.3Introduced species
 * 2.3.1Invasive species
 * 2.3.2Biological control
 * 2.4Genetically modified organisms (GMO)
 * 2.4.1Genetic contamination and ecological effects
 * 2.4.2GMO as a tool of pollution reduction
 * 2.5Animal management
 * 2.5.1Manure management
 * 2.5.2Manure treatment
 * 2.5.2.1Composting
 * 2.5.2.2Solid-liquid separation
 * 2.5.2.3Anaerobic digestion and lagoons
 * 3See also
 * 4References

Fertilizers[ edit]
'''Fertilizers are used to provide crops with additional sources of nutrients, such as Nitrogen, Phosphorus, and Potassium, that promote plant growth and increase crop yields. While they are beneficial for plant growth, they can also disrupt natural nutrient and mineral biogeochemical cycles and pose risks to human and ecological health.'''

Nitrogen
'''Nitrogen fertilizers supply plants with forms of nitrogen that are biologically available for plant uptake; namely NO3- (nitrate) and NH4+ (ammonium). This increases crop yield and agricultural productivity, but it also negatively affects groundwater and surface waters, pollutes the atmosphere, and degrades soil health. Not all of the fertilizer that is applied are taken up by the crops, and the remainder accumulates in the soil or is lost as runoff. Nitrate fertilizers are much more likely to be lost to the soil profile through runoff because of its high solubility and like charges between the molecule and negatively charged clay particles'''. High application rates of nitrogen-containing fertilizers combined with the high water-solubility of nitrate leads to increased runoff into surface water as well as leaching into groundwater, thereby causing groundwater pollution. Nitrate levels above 10 mg/L (10 ppm) in groundwater can cause "blue baby syndrome" (acquired methemoglobinemia) in infants and possibly thyroid disease and various types of cancer '''. Nitrogen fixation, which coverts atmospheric nitrogen (N2) to more biologically available forms, and denitrification, which converts biologically available nitrogen compounds to N2 and N2O, are two of the most important metabolic processes involved in the nitrogen cycle because they are the largest inputs and outputs of nitrogen to ecosystems. They allow nitrogen to flow between the atmosphere, which is around 78% nitrogen) and the biosphere. Other significant processes in the nitrogen cycle are nitrification and ammonification which covert ammonium to nitrate or nitrite and organic matter to ammonia respectively. Because these processes keep nitrogen concentrations relatively stable in most ecosystems, a large influx of nitrogen from agricultural runoff can cause serious disruption . A common result of this in aquatic ecosystems is eutrophication which in turn creates hypoxic and anoxic conditions - both of which are deadly and/or damaging to many species. Nitrogen fertilization can also release NH3 gases into the atmosphere which can then be converted into NOx compounds. A greater amount of NOx compounds in the atmosphere can result in the acidification of aquatic ecosystems and cause various respiratory issues in humans. Fertilization can also release N2O which is a greenhouse gas and can facilitate the destruction of ozone (O3) in the stratosphere'''. '''Soils that receive nitrogen fertilizers can also be damaged. An increase in plant available nitrogen will increase a crop's net primary production, and eventually, soil microbial activity will increase as a result of the larger inputs of nitrogen from fertilizers and carbon compounds through decomposed biomass. Because of the increase in decomposition in the soil, its organic matter content will be depleted which results in lower overall soil health'''.

Phosphorus
The most common form of phosphorus fertilizer used in agricultural practices is phosphate (PO43-), and it is applied in synthetic compounds that incorporate PO43- or in organic forms such as manure and compost '''. Phosphorus is an essential nutrient in all organisms because of the roles it plays in cell and metabolic functions such as nucleic acid production and metabolic energy transfers. However, most organisms, including agricultural crops, only require a small amount phosphorous because they have evolved in ecosystems with relatively low amounts of it . Microbial populations in soils are able to convert organic forms of phosphorus to soluble plant available forms such as phosphate. This step is generally bypassed with inorganic fertilizers because it is applied as phosphate or other plant available forms. Any phosphorus that is not taken up by plants is adsorped to soil particles which helps it remain in place. Because of this, it typically enters surface waters when the soil particles it is attached to are eroded as a result of precipitation or stormwater runoff. The amount that enters surface waters is relatively low in comparison to the amount that is applied as fertilizer, but because it acts as a limiting nutrient in most environments, even a small amount can disrupt an ecosystem's natural phosphorus biogeochemical cycles . Although nitrogen plays a role in harmful algae and cyanobacteria blooms that cause eutrophication, excess phosphorus is considered the largest contributing factor due to the fact that phosphorus is often the most limiting nutrient, especially in freshwaters . In addition to depleting oxygen levels in surface waters, algae and cyanobacteria blooms can produce cyanotoxins which are harmful to human and animal health as well as many aquatic organisms'''.

Metals[ edit]
'''The major inputs of heavy metals (e.g. lead, cadmium, arsenic, mercury) into agricultural systems are fertilizers, organic wastes such as manures, and industrial byproduct wastes. Inorganic fertilizers especially represent an important pathway for heavy metals to enter soils. Some farming techniques, such as irrigation, can lead to accumulation of selenium (Se) that occurs naturally in the soil, which can result in downstream water reservoirs containing concentrations of selenium that are toxic to wildlife, livestock, and humans. This process is known as the “Kesterson Effect,” eponymously named after the Kesterson Reservoir in the San Joaquin Valley (California, USA), which was declared a toxic waste dump in 1987. Heavy metals present in the environment can be taken up by plants, which can pose health risks to humans in the event of consuming affected plants. Some metals are essential to plant growth, however an abundance can have adverse effects on plant health.'''