Reconciling the Fugitive Dust Emission Inventory with the Fine Sediment Deposition Budget for Lake Tahoe

摘要

Lake Tahoe is losing its famed clarity due to excess loading of nutrients that stimulate algae production and excess loading of fine sediments. As a result a comprehensive research and restoration planning effort was initiated in 2001 that included developing a pollutant deposition budget for the lake. These multi-year research efforts indicate that atmospheric sources of fine sediment (i.e., primarily inert fugitive dust) contribute about 935 tons of fine sediment depositing into the lake each year. CARB's 2005 annual PM emission inventory for the Lake Tahoe air basin indicates that fugitive dust emissions are estimated to be about 2,100 tons/year. However, CARB's emission inventory is flawed in that it contains questionable sources and underestimates the emissions for major sources of fugitive dust, such that the actual annual fugitive dust emission estimate is closer to 5,300 tons/year. This paper describes the steps taken to improve CARB's fugitive dust emission estimates as well as the steps used to reconcile the revised fugitive dust emission inventory for the Lake Tahoe air basin with the fine sediment deposition budget developed for Lake Tahoe. One of these steps involved developing a conceptual model to account for deposition losses of particles during transport between their source and the lake surface. This conceptual model utilizes both estimates of airborne PM deposition losses measured by CARB and USEPA's estimates of the 'transportable fraction' for fugitive dust.