What natural and human factors affect nutrient occurrence and transport to streams and groundwater?
Nutrients released into the environment as diffuse nonpoint sources (for example, fertilizers, manure) or as point sources (for example, municipal and industrial discharges) enter streams along with runoff from precipitation, irrigation, or through drainage ditches and subsurface-tile drain systems; are transported to groundwater by infiltrating rainfall or irrigation; and, are transported to the atmosphere by volatilization either directly from a source or from a contaminated surface-water body. Within each of the hydrologic compartments, nutrient concentrations are affected by physical features, such as soils and slope of the land, as well as biological and geochemical processes that can change the chemical form of the nutrient (for example, denitrification and (or) transfer it from the water to a solid phase (attachment to sediment or uptake by plants) or the atmosphere. The chemical, physical, and biological processes that influence nutrient transport vary in intensity among differ
