Journal Article

Sulfur isotope homogeneity of oceanic DMSP and DMS

Amrani, Alon, Shaked, Yeala, Kiene, Ronald P., Said-Ahmad, Ward

2013

Overview

Oceanic emissions of volatile dimethyl sulfide (DMS) represent the largest natural source of biogenic sulfur to the global atmosphere, where it mediates aerosol dynamics. To constrain the contribution of oceanic DMS to aerosols we established the sulfur isotope ratios (34S/32S ratio, δ34S) of DMS and its precursor, dimethylsulfoniopropionate (DMSP), in a range of marine environments. In view of the low oceanic concentrations of DMS/P, we applied a unique method for the analysis of δ34S at the picomole level in individual compounds. Surface water DMSP collected from six different ocean provinces revealed a remarkable consistency in δ34S values ranging between +18.9 and +20.3‰. Sulfur isotope composition of DMS analyzed in freshly collected seawater was similar to δ34S of DMSP, showing that the in situ fractionation between these species is small (<+1‰). Based on volatilization experiments, emission of DMS to the atmosphere results in a relatively small fractionation (-0.5 ± 0.2‰) compared with the seawater DMS pool. Because δ34S values of oceanic DMS closely reflect that of DMSP, we conclude that the homogenous δ34S of DMSP at the ocean surface represents the δ34S of DMS emitted to the atmosphere, within +1‰. The δ34S of oceanic DMS flux to the atmosphere is thus relatively constant and distinct from anthropogenic sources of atmospheric sulfate, thereby enabling estimation of the DMS contribution to aerosols.

• Publisher: NATIONAL ACADEMY OF SCIENCES,National Acad Sciences,National Academy of Sciences
• Subject: Aerosols / Air pollution / anthropogenic activities / Anthropogenic factors / Atmosphere / Atmospheric aerosols / Chemical analysis / Chemical composition and interactions. Ionic interactions and processes / Chromatography, Gas / dimethyl sulfide / dimethylsulfoniopropionate / Earth, ocean, space / Emissions / Exact sciences and technology / External geophysics / Fractionation / Isotopes / Marine environment / Mass Spectrometry / Meteorology / Oceans / Oceans and Seas / Physical and chemical properties of sea water / Physical Sciences / Physics of the oceans / Phytoplankton / Sea water / Seas / Seawater / Seawater - chemistry / stable isotopes / Sulfates / Sulfides - analysis / Sulfonium Compounds - analysis / Sulfur / Sulfur isotopes / Sulfur Isotopes - analysis / Surface water / volatilization / Water analysis