Seasonal changes in TC and WSOC and their 13C isotope ratios in Northeast Asian aerosols: land surface–biosphere–atmosphere interactions

Abstract

In order to understand the relative importance of anthropogenic and biological sources of carbonaceous aerosols in Northeast Asia, we measured total carbon (TC) and water-soluble organic carbon (WSOC) and their stable carbon isotope ratios (δ13C) in total suspended particulates collected from Sapporo, northern Japan (43.07°N, 141.36°E) over a 1-year period (during 2 September 2009 and 5 October 2010). Temporal variations of TC showed a gradual decrease from mid-autumn to winter followed by a gradual increase to growing season with a peak in early summer. Both δ13CTC and δ13CWSOC showed very similar temporal trends with a gradual enrichment of 13C from mid-autumn to winter followed by a depletion in the 13C to early summer and thereafter it remained stable, except for few cases. Based on the results obtained together with the air mass trajectories, we found that biogenic emissions including biological particles (e.g., pollen) and secondary organic aerosol formation from biogenic volatile organic compounds are the important sources of carbonaceous aerosols in spring/summer whereas fungal spores from soil and biomass burning and enhanced fossil fuel combustion contribute significantly in autumn/winter and in winter, respectively, in Northeast Asia.