Concentrations, isotopic compositions, and sources of size‐resolved, particulate organic carbon and oxalate in near‐surface marine air at Bermuda during spring

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Abstract
During spring 1998, concentrations and stable isotopic compositions of organic carbon and oxalate were measured in size‐segregated aerosols at Bermuda to characterize sources and chemical processing. Marine‐derived organic carbon in super‐μm‐radius aerosol was enriched by an average of 724 ± 91 times relative to surface seawater. Carbon isotopic compositions indicated that, on average, marine‐derived carbon accounted for approximately 38% of carbon in both the super‐ and sub‐μm size fractions. Oxalate was present and significantly correlated with marine derived carbon in all size fractions. Most oxalate in super‐μm radius aerosol (>1 μm) originated from in situ production involving marine‐derived organic precursors, whereas oxalate in smaller size fractions originated primarily from condensation of oxalic acid vapor produced from the oxidation of gaseous marine precursors. The average dry‐deposition fluxes of marine organic carbon, continental organic carbon, and oxalate was 3.6, 7.3, and 0.15 μmol C m−2 day−1, respectively. Super‐μm aerosol dominated the dry‐deposition fluxes of marine (93%) and continental (96%) particulate carbon and oxalate (93%).

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