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	NADP History and Overview
	The National Atmospheric Deposition Program/National Trends Network (NADP/NTN) is a nationwide network of precipitation monitoring sites. 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. For a full list of contributors, see the collaborating agencies page. The NADP/NTN has grown from 22 stations at the end of 1978, our first year, to over 250 sites spanning the continental United States, Alaska, and Puerto Rico, and the Virgin Islands. 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. It is then sent to the Central Analytical Laboratory where it is analyzed for hydrogen (acidity as pH), sulfate, nitrate, ammonium, chloride, and base cations (such as calcium, magnesium, potassium and sodium). Our excellent quality assurance programs ensure that the data remain accurate and precise. The National Atmospheric Deposition Program has also expanded its sampling to two additional networks. The Mercury Deposition Network (MDN), currently with over 90 sites, was formed in 1995 to collect weekly samples of precipitation which are analyzed by Frontier Geosciences for total mercury. The objective of the MDN is to monitor the amount of mercury in precipitation on a regional basis; information crucial for researchers to understand what is happening to the nation's lakes and streams. Another network, the Atmospheric Integrated Research Monitoring Network (AIRMoN), was formed for the purpose of studying precipitation chemistry trends with greater temporal resolution. Precipitation samples are collected daily from a network of seven sites and analyzed for the same constituents as the NADP/NTN samples. Through this web site, one can access NADP data products, which include: Weekly and daily precipitation chemistry data Monthly, seasonal, and annual precipitation-weighted mean concentrations Annual and seasonal wet deposition totals Mercury deposition data Daily precipitation totals Color isopleth maps of precipitation concentrations and wet deposition Site photos, maps, and information Quality Assurance data and information Comments and Suggestions | Use Conditions Return to :[NADP Home] [AIRMoN] [MDN] [Search]