Since the 1970's, when the first in situ measurements of oxygen in the oceans were reported, the development of electrochemical methods for the analysis of trace element biogeochemistry in the environment has significantly improved. From conductimetry to measure salinity, to amperometric and potentiometric sensors that can measure a single analyte, to voltammetric sensors that can measure several species during the same scan, a variety of electrochemical techniques have been utilized to better understand biogeochemical processes in the environment. These techniques have been integrated into a variety of devices for laboratory experimentation and in situ deployment (or online measurements). The development of microsensors has significantly contributed to the application of these techniques in sediments, biofilms, and microbial mats, where data can now be collected at the micrometer scale. Electrochemical techniques have also been adapted to measure the chemical speciation of trace elements in natural environments following physical and chemical separations. Finally, the complexation properties of most naturally occurring ligands have been determined by electrochemical measurements performed on synthetic and natural samples. This first chapter is intended to familiarize the reader with the electrochemical terminology, techniques, current applications, and future directions in environmental chemistry and biogeochemistry research.
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