Organic trace gases of oceanic origin observed at South Pole during ISCAT 2000

• Main Authors: Swanson, AL, Davis, DD, Arimoto, R, Roberts, P, Atlas, EL, Flocke, F, Meinardi, S, Sherwood Rowland, F, Blake, DR
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: eScholarship, University of California 2004
• Subjects: oceanic emissions; DMS; South Pole; methyl iodide; bromoform; alkyl nitrates; photochemistry; Environmental Engineering; Atmospheric Sciences; Statistics; Meteorology & Atmospheric Sciences; Antarctic; Austral; Southern Ocean; The Antarctic; Antarc*; South pole
• Online Access: https://escholarship.org/uc/item/1r6661nv

Volatile organic compounds (VOCs) were measured at the South Pole (SP) from late Austral spring to mid-summer 2000 as part of the Investigation of Sulfur Chemistry in the Antarctic Troposphere Program (ISCAT-2000). This paper focuses on VOCs that are directly emitted from the ocean, specifically dimethyl sulfide (DMS), methyl nitrate (CH3ONO2), methyl iodide (CH 3I) and bromoform (CHBr3). A partial seasonal cycle of these gases was also recorded during the year following ISCAT-2000. During the summer, the SP periodically receives relatively fresh marine air containing short-lived oceanic trace gases, such as DMS (τ≈1 day). However, DMS was not detected at the SP until January even though DMS emissions from the Southern Ocean typically start peaking in November and elevated levels of other ocean-derived VOCs, including CH3ONO2 and CHBr 3, were observed in mid-November. We speculate that in November and December most of the DMS is oxidized before it reaches the SP: a strong correlation between CH3ONO2 and methane sulfonate (MSA), an oxidation product of DMS, supports this hypothesis. Based on a limited number of samples taken over the course of one year, CH3ONO2 apparently accumulates to a quasi-steady-state level over the SP in winter, most likely due to continuing emissions of the compound coupled with a lower rate of photochemical destruction. Oceanic emissions were concluded to be the dominant source of alkyl nitrates at the SP; this is in sharp contrast to northern high latitudes where total alkyl nitrate mixing ratios are dominated by urban sources. © 2004 Elsevier Ltd. All rights reserved.