How do nutrients get into the environment?
Nutrients occur naturally in the environment. However, concentrations above naturally occurring levels result from human activities. Human-related sources of nutrients can be classified as either point or nonpoint contamination. Point sources, such as from municipal and industrial discharge and concentrated animal feeding operations, are regulated by laws that place limits on the types and amounts of contaminants released to water (Clean Water Act, 1972). Nonpoint sources include applications of commercial fertilizers on agricultural and residential lands, cultivation of nitrogen-fixing crops, and nutrients from livestock and pet wastes and from septic systems. Atmospheric deposition also is a nonpoint source of nitrogen contamination, which is derived either naturally from chemical reactions (such as through lightning) or from the combustion of fossil fuels, such as in coal fired power plants, or volatilization of ammonia from fertilizer and manure.
