CHLORINE ISOTOPIC COMPOSITION OF MARINE AEROSOLS - IMPLICATIONS FOR THE RELEASE OF REACTIVE CHLORINE AND HCL CYCLING RATES

We have determined the elemental and the stable chlorine isotopic comp osition of size-segregated aerosols collected in the marine boundary l ayer. All size fractions have chlorine deficiencies. Mid-size aerosols are isotopically enriched in delta(37)Cl and contain significant quan tities of non-sea-salt-SO42- and NO3-. This is consistent with the aci d displacement of HCl from the aerosols. Coarse aerosols tend to be is otopically depleted and have Cl deficiencies that are not charge balan ced by MSA(-), SO42- and NO3- with Cl volatilization by a different me chanism. The isotope systematics imply a fractionation factor, alpha, of 1.00306+/-0.0005 if the volatilization mechanism is first order wit h respect to Cl or 1.00280+/-0.0005 if the volatilization mechanism is zeroth order with respect to Cl. Our data are consistent with the eff icient recycling of aerosol Cl through the gas phase.