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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. The pollution may come from a variety of sources, ranging from point source 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 ...view middle of the document...
Soil contamination can occur when pesticides persist and accumulate in soils, which can alter microbial processes, increase plant uptake of the chemical, and also cause toxicity to soil organisms. The extent to which the pesticides and herbicides persist depends on the compoundâ€™s unique chemistry, which affects sorption dynamics and resulting fate and transport in the soil environment. Pesticides can also accumulate in animals that eat contaminated pests and soil organisms. In addition, pesticides can be more harmful to beneficial insects, such as pollinators, and to natural enemies of pests (i.e. insects that prey on or parasitize pests) than they are to the target pests themselves.
Pesticide leaching occurs when pesticides mix with water and move through the soil, ultimately contaminating groundwater. The amount of leaching is correlated with particular soil and pesticide characteristics and the degree of rainfall and irrigation. Leaching is most likely to happen if using a water-soluble pesticide, when the soil tends to be sandy in texture, if excessive watering occurs just after pesticide application, or if the adsorption ability of the pesticide to the soil is low. Leaching may not only originate from treated fields, but also from pesticide mixing areas, pesticide application machinery washing sites, or disposal areas.
Leaching, runoff, and eutrophication
Eutrophication of the Potomac River.
The nitrogen (N) and phosphorus (P) applied to agricultural land (via synthetic fertilizers, composts, manures, biosolids, etc.) can provide valuable plant nutrients. However, if not managed correctly, excess N and P can have negative environmental consequences. Excess N supplied by both synthetic fertilizers (as highly soluble nitrate) and organic sources such as manures (whose organic N is mineralized to nitrate by soil microorganisms) can lead to groundwater contamination of nitrate. Nitrate-contaminated drinking water can cause blue baby syndrome. Together with excess P from these same fertilizer sources, eutrophication can occur downstream due to excess nutrient supply, leading to anoxic areas called dead zones.
Manures and biosolids contain many nutrients consumed by animals and humans in the form of food. The practice of returning such waste products to agricultural land presents an opportunity to recycle soil nutrients. The challenge is that manures and biosolids contain not only nutrients such as carbon, nitrogen, and phosphorus, but they may also contain contaminants, including pharmaceuticals and personal care products (PPCPs). There a wide variety and vast quantity of PPCPs consumed by both humans and animals, and each has unique chemistry in terrestrial and aquatic environments. As such, not all have been assessed for their effects on soil, water, and air quality. The US EPA has surveyed sewage sludge from wastewater treatment plants across the US to assess...