New insights in the global cycle of acetonitrile: release from theocean and dry deposition in the tropical savanna of Venezuela
[摘要] Using the proton transfer reaction mass spectrometry (PTR-MS) technique,acetonitrile was measured during the wet season in a Venezuelan woodlandsavanna. The site was located downwind of the Caribbean Sea and no biomassburning events were observed in the region. High boundary layerconcentrations of 211±36pmol/mol (median, ±standard deviation)were observed during daytime in the well mixed boundary layer, which isabout 60pmol/mol above background concentrations recently measured over theMediterranean Sea and the Pacific Ocean. Most likely acetonitrile isreleased from the warm waters of the Caribbean Sea thereby enhancing mixingratios over Venezuela. Acetonitrile concentrations will probably still bemuch higher in biomass burning plumes, however, the general suitability ofacetonitrile as a biomass burning marker should be treated with care.During nights, acetonitrile dropped to levels typically around 120pmol/mol,which is consistent with a dry deposition velocity of
0.14cm/s whena nocturnal boundary layer height of 100m is assumed.
