Investigating Source Contributions of Size‐Aggregated Aerosols Collected in Southern Ocean and Baring Head, New Zealand Using Sulfur Isotopes

Abstract

Abstract Marine sulfate aerosols in the Southern Ocean are critical to the global radiation balance, yet the sources of sulfate and their seasonal variations are unclear. We separately sampled marine and ambient aerosols at Baring Head, New Zealand for 1 year using two collectors and evaluated the sources of sulfate in coarse (1–10 μm) and fine (0.05–1 μm) aerosols using sulfur isotopes (δ 34 S). In both collectors, sea‐salt sulfate (SO 4 2− SS ) mainly existed in coarse aerosols and nonsea‐salt sulfate (SO 4 2− NSS ) dominated the sulfate in fine aerosols, although some summer SO 4 2− NSS appeared in coarse particles due to aerosol coagulation. SO 4 2− NSS in the marine aerosols was mainly (88–100%) from marine biogenic dimethylsulfide (DMS) emission, while the SO 4 2− NSS in the ambient aerosols was a combination of DMS (73–79%) and SO 2 emissions from shipping activities (~21–27%). The seasonal variations of SO 4 2− NSS concentrations inferred from the δ 34 S values in both collectors were mainly controlled by the DMS flux.