ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-4-275-2004 New insights in the global cycle of acetonitrile: release from theocean and dry deposition in the tropical savanna of Venezuela Sanhueza E. 1 2 Holzinger R. 1 3 Kleiss B. 1 Donoso L. 2 Crutzen P. J. 1 MPI für Chemie, Luftchemie, Postfach 3060, 55020 Mainz, Germany IVIC, Atmospheric Chemistry Laboratory, Apartado 21827, Caracas 1020A, Venezuela now at Univ. Calif. Berkeley, Div Environm Sci, Dept. Ecosyst. Sci. Policy & Management, Berkeley, CA 94720, USA 09 02 2004 4 1 275 280 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/4/275/2004/acp-4-275-2004.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/4/275/2004/acp-4-275-2004.pdf

Using the proton transfer reaction mass spectrometry (PTR-MS) technique, acetonitrile was measured during the wet season in a Venezuelan woodland savanna. The site was located downwind of the Caribbean Sea and no biomass burning events were observed in the region. High boundary layer concentrations of 211&plusmn;36pmol/mol (median, &plusmn;standard deviation) were observed during daytime in the well mixed boundary layer, which is about 60pmol/mol above background concentrations recently measured over the Mediterranean Sea and the Pacific Ocean. Most likely acetonitrile is released from the warm waters of the Caribbean Sea thereby enhancing mixing ratios over Venezuela. Acetonitrile concentrations will probably still be much higher in biomass burning plumes, however, the general suitability of acetonitrile 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 <IMG WIDTH="15" HEIGHT="15" ALIGN="BOTTOM" BORDER="0" src="acp-4-275-img2.gif" ALT="${sim}$">0.14cm/s when a nocturnal boundary layer height of 100m is assumed.