Source Apportionment of Inorganic Aerosols in Europe and Role of Biogenic VOC Emissions

Abstract

In this study, we investigated the contribution of various source categories and regions to the secondary inorganic aerosol (SIA) in Europe with CAMx and its source apportionment tool PSAT during two measurement periods, representing cold and warm seasons. The results suggested that the main source for particulate nitrate was road transport, whereas energy industries were the most important contributor to sulfate particles. Emissions from international shipping were also found to be very important for both nitrate and sulfate particle formation. We found a large increase in secondary organic aerosol (SOA) concentrations when we doubled the biogenic volatile organic compound (BVOC) emissions during the warm season, as expected. We also found, however, a decrease in particulate inorganic nitrate and sulfate concentrations by about −35% and −12%, respectively, at different locations. The negative correlation between BVOCs and SIA indicates the importance of precursor gases and biogenic emission types. The results of further tests suggested that terpene reactions with nitrate radicals at night led to a decline in inorganic nitrate formation. Sulfate concentrations, on the other hand, decreased due to the reactions of BVOCs with OH radicals.