Keeping Tahoe Blue: Quantifying Atmospheric Nitrogen Oxides Upwind and in the Lake Tahoe Basin Final rept

摘要

Observations of No (sub 2), total peroxy nitrates, total alkyl nitrates, and HNO (sub 3) along with a variety of correlative measurements over the full annual cycle (March 2003-February 2004) were collected at Big Hill CA. During winter, total reactive nitrate nitrogen is lower, net flow at the surface is downhill and the urban plume rarely reaches the Basin. Individual episodes of high NO (sub 2) inorganic nitrates associated with small-scale burning events along the western slope may generate HNO (sub 3) that can reach Tahoe. During summer, the Sacramento plume is the dominant source of reactive nitrogen in the region of the western slope of the Sierra Nevada, but this plume rarely reaches as far as the Tahoe Basin. HNO (sub3) deposition is sufficiently fast that very little remains in the plume by the time it reaches high elevation sites near the Lake Tahoe Basin. At Big Hill, similar concentrations of HNO (sub 3) are found in air masses coming from Sacramento (west) and Tahoe (east), demonstrating that urban areas to the west of Tahoe cannot be identified as a net source of nitric acid to the Tahoe Basin. Organic nitrates are significantly elevated in the plume compared to background conditions but their contribution to nitrogen deposition remains poorly understood.