Chemical Characteristics and Source Analysis of Aerosol Composition over the Bohai Sea and the Yellow Sea in Spring and Autumn

Abstract

he total suspended particulate (TSP) samples over the Bohai Sea and the Yellow Sea were collected during two cruises in spring and autumn in 2012. Concentrations of water-soluble ions {Na+, K+, NH4+, Mg2+, Ca2+, Cl?, NO3 ?, SO42?, and CH3SO3 ? [methanesulfonic acid (MSA)]} and trace metals (Al, Pb, Zn, Cd, Cu, and V) were measured. Mass concentrations of TSP samples ranged from 65.2 to 136 ?g m?3 in spring and from 15.9 to 70.3 ?g m?3 in autumn, with average values of 100 ± 22.4 and 40.2 ± 17.8 ?g m?3, respectively. The aerosol was acidic throughout the sampling periods according to calculation of equivalent concentrations of the cations (NH4+, nss-Ca2+, and nss-K+) and anions (nss-SO42? and NO3 ?). Correlation analysis and enrichment factors revealed that the aerosol composition in the coastal marine atmosphere had a feature of a mixture of air masses: that is, crustal, marine, and anthropogenic emissions. Trace metals were enriched by a wide range of 1?103, and enrichment factors for crustal source (EFc) were relatively higher in spring. Species like Cd, Zn, and Pb had an overwhelming contribution from anthropogenic sources. In addition, the concentrations of MSA varied from 0.0075 to 0.17 and from 0.0019 to 0.018 ?g m?3 during the spring and autumn cruises, respectively, with means of 0.061 and 0.012 ?g m?3, respectively. Based on the observed MSA and nss-SO42? concentrations in spring and autumn, the relative biogenic sulfur contributions to nss-SO42? were estimated to be 8.0% and 3.5% on average, respectively, implying that anthropogenic sources had a dominant contribution to the sulfur budget over the observational area.