Dissolved and dispersed organic matter in natural waters. Progress by electroanalysis

Abstract

Organic matter in seawater is chemically complex, physically heterogeneous and variable in time and space. Electrochemical techniques provide the most direct method to study trace levels of organic material in concentrated electrolyte solutions such as seawater. We have identified a fraction of aquatic organic matter that was not amenable to analysis by conventional methods: fluid surface-active particles - droplets (d>0.5, urn). They are ubiquitous in productive surface waters, sea surface microlayer and mixing zones in estuaries (>109 particles/l). The electrochemical methodology allows direct characterization of size, fluidity and surface conductance of individual particles through single coalescence events at the electrode/seawater interface. The electrochemical characterization of organic matter at a natural fresh-water/seawater interface reveals a continuous transformation of biogenic dissolved organic matter into a highly hydrophobic surface-active material, both dissolved and dispersed, that forms a film. © 2013, Walter de Gruyter GmbH, Berlin/Boston. All rights reserved.