Atmospheric deposition is often one of the major sources of nitrogen.
For instance, it has been identified as a primary source in the Chesapeake Bay. The network is a cooperative effort between many different groups, including the State Agricultural Experiment Stations, U.S. Geological Survey, U.S. Department of Agriculture, and numerous other governmental and private entities. The purpose of the network is to collect data on the chemistry of precipitation for monitoring of geographical and temporal long-term trends. The precipitation at each station is collected weekly according to strict clean-handling procedures. There are approximately 200 sites with atmospheric deposition estimates, measured in kilograms per hectare per year.