Marine and Environment: Geochemical Sensing

Scholar: Zachary Wilhelm

Home Institution: University of Utah

PROJECT

We propose to construct a modified electrode array to perform continuous, long-term in situ voltammetric observations. Our array will have eight vertical pads each with three electrodes (i.e. triplicate redundancy) and the electrodes will be made from Au. Our array will be inexpensive to manufacture and easy to reproduce. The electrodes can be operated with or without the Hg amalgam, depending on the analytes of interest. This design will eliminate the requirement of polishing each electrode, allow for faster data acquisition, and enable long-term, continuous observations from a fixed position in sediments. Unlike our current electrode, we will physically insert the electrode array into the sediment before taking any readings and the electrode will remain at a fixed-position for the duration of the monitoring experiment. This will allow for us to take both dissolved O2 measurements in the overlying water, while also allowing measurement of reduced anaerobic metabolites within the sediments. A series of voltammetric experiments will be conducted at each of the eight pads in succession. The measurements will ultimately generate an eight-point depth profile. While this is of much coarser vertical resolution than that produced by the microprofiling technique, it should be possible to resolve the relative depths of aerobic, metal, and sulfate respiration. These processes provide information regarding the rates of organic carbon degradation, sediment oxygen consumption and overlying water column hypoxia, the potential for nutrient release from sediments and eutrophication of the water column, and the generation of “toxic” sulfide which may adversely affect burrowing organisms and plant health.

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