The National Atmospheric Deposition Program (NADP) monitors precipitation chemistry.
The program is a cooperative effort between many different groups, including
federal, state, tribal and local governmental agencies, educational institutions, private companies, and non-governmental agencies.
In 1977, U.S. State Agricultural Experiment Stations (SAES) organized a project,
later titled the National Atmospheric Deposition Program (NADP), to measure atmospheric deposition and study its effects on the environment.
Sites in the NADP precipitation chemistry network began operations in 1978 with the goal of
providing data on the amounts, trends, and geographic distributions of acids, nutrients,
and base cations in precipitation. The network grew rapidly in the early 1980s. Much of this
expansion was funded by the National Acid Precipitation Assessment Program (NAPAP), established
in 1981 to improve understanding of the causes and effects of acidic precipitation. Reflecting
the federal NAPAP role in the NADP, the network name was changed to NADP National Trends Network (NTN). Today, the NADP
is SAES National Research Support Project - 3. The NTN network currently has 263 sites.
A second network, the Atmospheric Integrated Research Monitoring Network (AIRMoN) joined the NADP in 1992, and currently has six sites.
Although measuring the same chemicals as NTN, AIRMoN sampling is daily rather than weekly.
These higher resolution samples enhance researchers’ ability to evaluate how emissions
affect precipitation chemistry using computer simulations of atmospheric transport and
pollutant removal. This network also evaluates alternative sample collection and
A third network, the Mercury Deposition Network (MDN) joined the NADP in 1996, and currently has about 100 sites in the United States and Canada. All MDN samples are analyzed
for total mercury, and some for the more toxic methyl mercury. Fish consumption advisories for mercury exist in almost every state in the country
warning people to limit consumption of fish, and a few states also have wildlife consumption advisories for mercury. Researchers use MDN data to evaluate
the role of precipitation as a source of mercury in these water bodies.
The Atmospheric Mercury Network (AMNet), joined NADP in 2009. This network measures atmospheric mercury fractions which
contribute to dry and total mercury deposition. At AMNet's 28 sites, automated continuous measuring systems collect concentrations of atmospheric mercury species,
concentrations of total mercury in precipitation, and meteorological measurements. Data is collected with standardized methods, with quality assured data archived in an online data base.
The Ammonia Monitoring Network (AMoN) joined NADP in 2010. It began as a special study in 2007, and now comprises about 100 monitoring locations. The AMoN is the only network providing a consistent, long-term record of ammonia gas concentrations across the United States.
For more information about NADP's early history, please see Thirty Years Down and a Century to Go, from a presentation by Ellis Cowling. A listing of past officers and meeting locations is also available.