Biogenic halocarbons from the Peruvian upwelling region as tropospheric halogen source

Hepach, Helmke, Quack, Birgit, Tegtmeier, Susann, Engel, Anja, Bracher, Astrid, Fuhlbrügge, Steffen, Galgani, Luisa, Atlas, Elliot, Lampel, Johannes, Frieß, Udo and Krüger, Kirstin (2016) Biogenic halocarbons from the Peruvian upwelling region as tropospheric halogen source Atmospheric Chemistry and Physics, 16 . pp. 12219-12237. DOI 10.5194/acp-16-12219-2016.

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Halocarbons are produced naturally in the oceans by biological and chemical processes. They are emitted from surface seawater into the atmosphere, where they take part in numerous chemical processes such as ozone destruction and the oxidation of mercury and dimethyl sulfide. Here we present oceanic and atmospheric halocarbon data for the Peruvian upwelling zone obtained during the M91 cruise onboard the research vessel METEOR in December 2012. Surface waters during the cruise were characterized by moderate concentrations of bromoform (CHBr3) and dibromomethane (CH2Br2) correlating with diatom biomass derived from marker pigment concentrations, which suggests this phytoplankton group is a likely source. Concentrations measured for the iodinated compounds methyl iodide (CH3I) of up to 35.4 pmol L−1, chloroiodomethane (CH2ClI) of up to 58.1 pmol L−1 and diiodomethane (CH2I2) of up to 32.4 pmol L−1 in water samples were much higher than previously reported for the tropical Atlantic upwelling systems. Iodocarbons also correlated with the diatom biomass and even more significantly with dissolved organic matter (DOM) components measured in the surface water. Our results suggest a biological source of these compounds as a significant driving factor for the observed large iodocarbon concentrations. Elevated atmospheric mixing ratios of CH3I (up to 3.2 ppt), CH2ClI (up to 2.5 ppt) and CH2I2 (3.3 ppt) above the upwelling were correlated with seawater concentrations and high sea-to-air fluxes. During the first part of the cruise, the enhanced iodocarbon production in the Peruvian upwelling contributed significantly to tropospheric iodine levels, while this contribution was considerably smaller during the second part.

Document Type: Article
Keywords: Gases; Field Measurements; Troposphere; Chemistry (chemical composition and reactions); Biosphere Interactions
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-BI Biological Oceanography
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-CH Chemical Oceanography
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-ME Maritime Meteorology
Refereed: Yes
DOI etc.: 10.5194/acp-16-12219-2016
ISSN: 1680-7316
Projects: SOPRAN, Phytoscope
Date Deposited: 18 Mar 2016 10:05
Last Modified: 19 Dec 2017 12:46

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