The Interactions of Biogenic and Anthropogenic Gaseous Emissions with Respect to Aerosol Formation in the United States

Fine particulate matter less than 2.5 microns in diameter (PM2.5) is composed of primary and secondary aerosols and are harmful to human health. Both anthropogenic and biogenic sources contribute to PM2.5. Recent studies of aerosol formation in the southeast U.S. have investigated the interactions between precursor gases emitted from the aforementioned sources with respect to the formation of biogenic secondary organic aerosol (SOA). However, little work has been done on the reverse influence to understand how inorganic aerosol formation is affected by biogenic precursors. In this two-part study, model results from the U.S EPA Community Multi-scale Air Quality (CMAQ) Model are used to evaluate current understanding of aerosol formation and the change in dry deposition over the continental U.S. Although biogenic emissions contribute to PM2.5 via SOA, sensitivity simulations using CMAQ for July 2007 predict that the contribution of biogenic gases to total PM2.5 is surprisingly negative. By “zeroing out ” biogenic emissions, total PM2.5 increases by approximately 10 % due to large increases in both particulate sulfate and particulate nitrate