Marine biogenic emissions of benzene and toluene and their contribution to secondary organic aerosols over the polar oceans

Abstract

Reactive trace gas emissions from the polar oceans are poorly characterized, even though their effects on atmo-spheric chemistry and aerosol formation are crucial for assessing current and preindustrial aerosol forcing on climate. Here, we present seawater and atmospheric measurements of benzene and toluene, two gases typically associated with pollution, in the remote Southern Ocean and the Arctic marginal ice zone. Their distribution suggests a marine biogenic source. Calculated emission fluxes were 0.023 +/- 0.030 (benzene) and 0.039 +/- 0.036 (toluene) and 0.023 +/- 0.028 (benzene) and 0.034 +/- 0.041 (toluene) mu mol m-2 day-1 for the South-ern Ocean and the Arctic, respectively. Including these average emissions in a chemistry-climate model in-creased secondary organic aerosol mass concentrations only by 0.1% over the Arctic but by 7.7% over the Southern Ocean, with transient episodes of up to 77.3%. Climate models should consider the hitherto over-looked emissions of benzene and toluene from the polar oceans.