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Soil and groundwater chemistry have traditionally been characterized via laboratory analysis of "grabbed" samples ? either samples of the soil itself or gas samples, and groundwater. In situ sensors that monitor chemical parameters, including nutrients in either soil or groundwater, are subject to numerous limitations, in particular for continuous monitoring: a requirement for consumables (mainly for nutrient monitoring), significant maintenance, bulky instrumentation, and cost. There is a clear need for a single monitoring system capable of collecting data for a range of biochemical parameters of interest, at a reasonable cost and with low maintenance.<
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Intelligent Optical Systems, Inc. (IOS) has demonstrated the feasibility of developing a compact multiparameter monitor that collects real-time information on key geochemical parameters in groundwater and soil. We have demonstrated a compact multiparameter monitor (OPTOSES ? Optical Sensors for Subsurface) incorporating sensor for nitrate, dissolved oxygen, pH and temperature, with all of the elements integrated in a 25 mm x 35 mm cylindrical sensor head, connected with a single, hand-held size readout unit. Sensor contamination is prevented in the sensor head by a passive antibiofouling element (no moving parts and no consumables) that will reduce sensor maintenance, a key innovation of the OPTOSES technology.<
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Current instrumentation for nitrate monitoring is bulky, expensive, and presents significant challenges for integration in multiparameter probes. In Phase I we demonstrated novel sensor materials for nitrate monitoring with excellent reversibility and sensitivity. These sensor coatings are small and inexpensive, and are based on the same technology used in luminescent dissolved oxygen (LDO) sensors, which makes integration of multiparameter probes much simpler. All of the chemical sensors are based on a common technology so they can share a single multi-channel detection unit, reducing complexity and cost. The sensor elements consist of a specific luminescent chemistry immobilized in a polymeric film, and can be produced in quantity at low cost.<
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