The Chemistry of Near-Surface Seawater
The top few hundred micrometres of the sea (often called the surface microlayer) is a difficult part of the oceans to study. The depth of the region is almost impossible to define in a meaningful way, and microlayer thicknesses are by default specified in terms of what the various sampling devices appear to collect. The organic composition of the microlayer is poorly characterized and its study suffers from similar problems to analogous work in bulk seawater. Some dissolved constituents in the microlayer appear to show small enrichments in concentration over subsurface waters, although such enrichments now seem smaller than was previously thought to be the case. Particulate material, on the other hand, does show significant microlayer enrichments.
What is clear is that processes in the water close to the sea surface are important not only for the chemistry of the underlying water but also for the marine atmosphere. Such processes include air-sea exchange of stable gases and particles, as well as free radicals and other unstable species. Furthermore, biological and photochemical activity near the ocean surface leads to the production of gases and to speciation changes for ionic forms. Photoreduction of multivalent elements in the presence of organic matter appears to be a particularly important sea surface mechanism for redox reactions.
KeywordsSurface Microlayer Marine Atmosphere Underlying Water Dimethyl Sulphide Layer Enrichment
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