Characterization and sources of water-soluble organic species in PM_2.5 in a remote mountain environment in Southeastern China

A comprehensive campaign was conducted in 2014–2015 to characterize and identify potential sources of water-soluble organic matter (WSOM) in a remote mountain area in Southeastern China. Weekly measurements of PM_2.5 and its dominant chemical components, including organic carbon (OC), elemental carbon (EC), water-soluble inorganic ions (WSIIs), water-soluble organic carbon (WSOC), Humic-like Substances (HULIS), water-soluble organic species (sugar alcohols, anhydrosugars, primary sugars, and carboxylic acids), and trace elements were conducted. PM₁₀, PM_2.5, NO₂, O₃, and meteorological parameters were also routinely measured at the same site. WSOM was dominated by HULIS (49%), carboxylic acids (12%), and saccharides (3%, a sum of sugar alcohols, anhydrosugars, and primary sugars). Carboxylic acids exhibited a flat seasonal variation, while high mass concentrations of sugar alcohols and anhydrosugars were observed in summer and winter, respectively. The converting factor from WSOC to WSOM was estimated to be 2.1 for this mountain site. Six major source factors were identified for WSOM using positive matrix factorization (PMF) analysis, which include aqueous processes, biogenic secondary organic aerosols (SOAs), biomass burning, mixed urban aerosols, soil dust, and secondary nitrate. These factors contributed 34 ± 22%, 20 ± 24%, 18 ± 18%, 14 ± 8%, 10 ± 13%, and 5 ± 10%, respectively, to annual WSOM mass concentration. Results of this study suggest that aqueous chemical reactions of gaseous pollutants during the transport process, the transport of biomass burning, urban aerosols and dust storm, and local formation of biogenic SOAs contributed to WSOM in the remote area of Southeastern China.