Soil dust as a potential bridge from biogenic volatile organic compounds to secondary organic aerosol in a rural environment

The role of coarse particles has recently been proven to be underestimated in the atmosphere and can strongly influence clouds, ecosystems and climate. However, previous studies on atmospheric chemistry of volatile organic compounds (VOCs) have mostly focused on the products in fine particles, it remains less understood how coarse particles promote secondary organic aerosol (SOA) formation. In this study, we investigated water-soluble compounds of size-segregated aerosol samples (0.056 to >18 mu m) collected at a coastal rural site in southern China during late summer and found that oxygenated organic matter was abundant in the coarse mode. Comprehensive source apportionment based on mass spectrum and C-14 analysis indicated that different from fossil fuel SOA, biogenic SOA existed more in the coarse mode than in the fine mode. The SOA in the coarse mode showed a unique correlation with biogenic VOCs. C-13 and elemental composition strongly suggested a pathway of heterogeneous reactions on coarse particles, which had an abundant low-acidic aqueous environment with soil dust to possibly initiate iron-catalytic oxidation reactions to form SOA. This potential pathway might complement understanding of both formation of biogenic SOA and sink of biogenic VOCs in global biogeochemical cycles, warrantying future relevant studies.

Automated summary

The role of coarse particles in the atmosphere has been underestimated, but recent studies have shown that they can strongly influence clouds, ecosystems, and climate. This study focused on the formation of secondary organic aerosol (SOA) and found that oxygenated organic matter was abundant in the coarse mode. The source apportionment analysis indicated that biogenic SOA existed more in the coarse mode than in the fine mode, and the SOA in the coarse mode showed a unique correlation with biogenic volatile organic compounds (VOCs). This suggests a potential pathway of heterogeneous reactions on coarse particles that contribute to the formation of biogenic SOA and the sink of biogenic VOCs in global biogeochemical cycles.