Application of stable sulfur isotopes to differentiate sources of size‐resolved Particulate sulfate in polluted marine air at Bermuda during spring

Abstract

Stable sulfur isotopic compositions of size‐segregated aerosols were measured at Bermuda during spring 1998 to differentiate contributions of marine biogenic and pollution sources of non‐sea‐salt SO42− (NSS). Marine biogenic sources contributed an average 0.41±0.33 nmol m−3 (15±7%) of supermicron NSS and 2.55±0.45 nmol m−3 (11±2%) of submicron NSS. Calculated concentrations of submicron NSS from marine biogenic sources are within the range of reported values for the remote southeastern Pacific. The average molar ratio of marine biogenic NSS/CH3SO3− for aerosol with geometric mean radius (GMR) of 0.6 µm (10.1±1.9) was significantly greater than that for aerosols with GMR 0.34 µm (3.9±1.4), suggesting differential atmospheric processing. Supermicron radius aerosol accounted for 75% of the NSS dry‐deposition flux.