In Virginia and most other states, rain and snow collection stations have been used to determine the concentration of mercury in precipitation. These mercury measurements are distributed by the National Atmospheric Deposition Program through the Illinois State Water Survey (http://nadp.sws.uiuc.edu). Mercury deposition data has been gathered for over a decade and may be compared to the on-line data currently reported from collection sites. Coal-burning power plants are thought to contribute most of the atmospheric mercury, and it was thought that the precipitation collections would prove this hypothesis. In Virginia, this hypothesis is supported. It has been found that the atmospheric content of mercury increases during prolonged intervals without precipitation. In this study, it was found that the atmospheric content of mercury was exceptionally low following an unusually prolonged precipitation event.
Metcalf, James and Mose, Douglas G.
"Monitoring Sources of Mercury in the Atmosphere,"
Proceedings of the Annual International Conference on Soils, Sediments, Water and Energy: Vol. 17
, Article 4.
Available at: http://scholarworks.umass.edu/soilsproceedings/vol17/iss1/4