A naturally occurring plant or other organism that is within its range and normal environment.
A salt of nitric acid; a common water pollutant.
Nutrient and pollution sources not discharged from a single point, e.g. runoff from agricultural fields, feedlots, residential lawns, septic leach fields, or urban streets, etc.
USDA Natural Resources Conservation Service
National Soil Erosion Research Laboratory (West Lafayette, Indiana)
Elements or compounds essential to growth and development of living things (e.g., nitrogen, potassium, phosphorus).