The Mercury Deposition Network (MDN) has been a part of NADP since 1996. Glacier National Park joined the MDN in October of 2002. Site operators collect weekly precipitation samples which are sent to Frontier GeoScience, Inc. of Seattle, Washington. Samples are analyzed for total mercury.

The MDN is a nationwide (with 10 Canadian sites) effort to understand and quantify wet deposition as a pathway for mercury into terrestrial and aquatic ecosystems.

The Mercury Deposition Network (MDN) is developing a national database of weekly concentrations of total mercury in precipitation.

About half of atmospheric mercury comes from natural sources such as volcanoes, soil, and oceans. The remainder occurs as a result of human activity such as coal burning for electricity. After remaining in the atmosphere for up to two years, mercury falls out as wet or dry deposition to the earth's surface.

Although mercury is not usually a health concern in soil and vegetation, when fire occurs, it will be released from trees into the atmosphere where it may be transported to other locations. This methylmercury may settle out into bodies of water where it is taken into organisms through he food chain. the highest levels of mercury occur in large predator fish and in the birds and mammals which consume those fish. The ingestion of fish in the primary human health risk.