South-hemispheric marine aerosol Hg and S isotope compositions reveal different oxidation pathways

Abstract

Particle-bound mercury (PBM) records the oxidation of elemental mercury, of which the main oxidation pathways (Brž/Clž/OHž/O3) remain unclear, especially in the Southern-Hemisphere. Here, we present latitudinal covariations of Hg and S-isotopic anomalies in cross-hemispheric marine aerosols that evidence an equator-to-poleward transition of Hg oxidants from OHž/O3 in tropics to Brž/Clž in polar regions highlighting thus the presence of distinct oxidation processes producing PBM. The correlations between Hg, S and O-isotopic compositions measured in PBM, sulfates and nitrates respectively within the aerosols highlight the implication of common oxidants in their formations at different latitudes. Our results open a new window to better quantify the present-day atmospheric Hg, S and N budgets and to evaluate the influences of aerosols on climate and ecosystems once the isotopic fractionations associated to each process have been determined.