Seasonal variations of stable carbon isotopic composition of bulk aerosol carbon from Gosan site, Jeju Island in the East China Sea

This study explores the usefulness of stable isotopic composition (delta C-13) along with other chemical tracers and air mass trajectory to identify the primary and secondary sources of carbonaceous aerosols. Aerosol samples (n = 84) were collected continuously from April 2003 to April 2004 at Gosan site in Jeju Island, South Korea. The concentrations of total carbon (TC), HCl fumed carbonate-free total carbon (fumed-TC) and their delta C-13 were measured online using elemental analyzer interfaced to isotope ratio mass spectrometer (EA-IRMS). Similar concentrations of TC and fumed-TC and their similar delta C-13 values suggest the insignificant contribution of inorganic carbon to Gosan aerosols. The monthly averaged delta C-13(TC) showed the lowest in April/May (-24.2 to 24.4 parts per thousand), which is related with the highest concentrations of oxalic acid (a secondary tracer). The result indicates an enhanced contribution of TC from secondary sources. The monthly averaged delta C-13(TC) in July/August (-23.0 to 22.5 parts per thousand) were similar to those in January/February (-23.1 parts per thousand to 22.7 parts per thousand). However, chemical tracers and air mass transport pattern suggest that the pollution source regions in January/February are completely different from those in July/August Higher delta C-13 values in July/August are aligned with higher concentration ratios of marine tracers (azelaic acid/TC and methanesulfonate/TC), suggesting an enhanced contribution of marine organic matter to the aerosol loading. Higher delta C-13 values in January/February are associated with higher concentrations of phthalic acid and K+/TC, indicating more contributions of carbonaceous aerosols from fossil fuel and C-4-plant biomass combustion. This study demonstrates that delta C-13(TG) along with other chemical tracers and air mass trajectory, can be used as a tracer to understand the importance of primary versus secondary pollution sources of carbonaceous aerosols in the atmosphere. (C) 2014 Elsevier Ltd. All rights reserved.