The National Atmospheric Deposition Program (NADP) is a long-term monitoring program in support of research on the effects of atmospheric chemical deposition. Organized in 1977, today the NADP operates three networks that monitor precipitation chemistry at more than 300 sites. It is a cooperative program receiving support from federal, state, and local government agencies; Native American organizations; State Agricultural Experiment Stations; universities; and non-governmental organizations. The NADP Program Office and Central Analytical Laboratory are housed at the Illinois State Water Survey. The NADP Mercury Analytical Laboratory is located at Frontier Geosciences, Inc.
Go to: NADP home

National Trends Network
The National Trends Network (NTN) is the only network providing a long-term record of precipitation chemistry across the United States. It began in 1978 with 22 sites and now has more than 250 sites. The purpose of the NTN is to provide data on the amounts, trends, and geographic distributions of the atmospheric deposition of acids, nutrients, and base cations. Precipitation samples are collected weekly according to standard operating procedures. The NADP Central Analytical Laboratory (CAL) analyzes NTN samples for acidity (as pH), sulfate, nitrate, ammonium, chloride, calcium, magnesium, potassium and sodium.
Go to: NTN home – Data retrieval – Maps

Atmospheric Integrated Research Monitoring Network
The Atmospheric Integrated Research Monitoring Network (AIRMoN) joined the NADP in 1992. Located in the eastern United States, the 8 AIRMoN sites collect samples daily to provide data for studying atmospheric processes and for developing and testing models that simulate these processes. AIRMoN samples are kept refrigerated after collection and are analyzed at the NADP CAL for the same constituents as NTN samples.
Go to: AIRMoN home – Data retrieval

Mercury Deposition Network
The Mercury Deposition Network (MDN), currently with over 90 sites, joined the NADP in 1996. MDN sites collect samples according to strict clean-handling procedures. The NADP Mercury Analytical Laboratory analyzes all samples for total mercury and offers methyl mercury measurements as an option. The objective of the MDN is to provide data on the geographic distributions and trends of mercury deposition, information that may help scientists better understand the possible link between mercury deposition and mercury-contaminated fish.
Go to: MDN Home – Data retrieval – Maps