Development of an In-situ Dissolved Oxygen Sensing Network to Map the Temporal Dynamics of the Oxic/Anoxic Interface in Ecosystems

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Environmental sensor networks are an emerging tool in earth science research that will enable scientists to study the effects of climate on a complete ecosystem. The sensor network must be capable of making measurements that cover rapid fluctuations spanning minutes or hours as well as seasonal and annual processes. What is needed is instrumentation that can provide in-situ data from an entire ecosystem 24 hours/day, 365 days/year. Dissolved oxygen concentration is a key variable in the environment that influences the habitability of ecosystems, carbon cycling and sequestration, along with the basic bio-chemical reactions in both terrestrial and aquatic systems. Scientists need to track the boundary between the oxic (oxygen containing) and anoxic (depleted of oxygen) regions in water. How this boundary evolves in time can reflect global or local environmental changes including unusual events such as formation of dead zones in the Gulf of Mexico or Lake Erie, leaching of toxic metals from bioremediation sites or the transport of volatile organic compounds in drinking water supply wells. Current technologies for monitoring oxygen concentration do not have the capability to provide the required data over extended periods at the ecosystem level. This project will develop a new oxygen sensor system capable of autonomous, remote monitoring of the oxic/anoxic interface. In addition to instrumentation development, the project will establish a community resource for local stakeholders concerned about water quality. The objective is to provide information on available technologies in a manner that is accessible to the general public. The project scientists will work with the Michigan Lakes and Streams Association, whose members include watershed/water resource management communities and lake associations. These interactions will lead to the creation of a website, tentatively titled ?MyMIwater?, on water quality monitoring methods accessible to the citizen environmentalist.The intellectual merit of this project lies in the synthesis of nano-scale metal-halide cluster photophysics, chemical measurement techniques, optical and electronic device design and fiber optic engineering to develop a real-time oxygen sensing system. The unique photochemistry of the phosphorescent MoCl luminophores developed at Michigan State University enables in-situ oxygen monitoring for months to years with the same device in both aquatic systems and partially saturated porous sediment. Vertically resolved fiber optic oxygen probes, with mm scale resolution, will be deployed 24/7 without need for recalibration despite the presence of common contaminants. With current technologies such a system could only be deployed at prohibitive monetary cost while requiring significant labor to operate; this new optical oxygen sensor probe will circumvents the limitations of these existing techniques.