Big Hill, California
Fall 2002-Spring 2004 El Dorado National Forest, CA
Visibility in the water of Lake Tahoe has decreased more than 30% over the last 35 years. Atmospheric deposition of nitrogen to the Lake Tahoe basin is suspected to be a significant cause of the decline in lake clarity. To investigate the sources of atmospheric nitrogen in the Lake Tahoe basin, we will use thermal dissociation laser-induced fluorescence (TD-LIF) to measure NO2, HNO3, and two classes of organic nitrates, peroxynitrates and alkylnitrates, at Big Hill. Big Hill is located 20 miles west of Lake Tahoe, in the foothills of the Sierra Nevada range. The location of this site will allow us to determine the global background of atmospheric nitrogen in the Tahoe basin, as well as the fraction that is local or regional (transported from sources in the San Francisco Bay area and the Central Valley).
J.G. Murphy and R.C. Cohen, Chemistry and Transport of Nitrogen Oxides on the Western Slopes of the Sierra Nevada Mountains: Implications for Lake Tahoe, CARB Interim Review of the Effects of Atmospheric Nitrogen Deposition on Lake Tahoe, submitted January 2004, revised June 2004.