This Small Business Innovation Research (SBIR) Phase II project involves the development of a novel array-based chemical microsensor and a dedicated sampling system for the monitoring of organic contaminants in the subsurface. Chlorinated hydrocarbons represent the most prevalent contaminants in the subsurface, threatening the quality of groundwater at aquifers. Existing technologies for monitoring these contaminants require expensive, labor-intensive, methods of sample collection and analysis. In the proposed sensor, the chemical and electrical properties of the individual elements of the array will be controlled so that a unique fingerprint will identify each pollutant. The output signals will be integrated into a software-based neural network for analyte identification. The simple design, cost, fabrication, and operation requirements of the proposed sensor will overcome the limitations of other existing array sensors. The development of a low-cost, reliable sampling and monitoring system would reduce the costs associated with sampling and contaminant monitoring. Also, it would offer the possibility for automated and unattended monitoring of the migration of contaminant plumes. A lab-scale version of the proposed sensor was successfully tested in the Phase I project, where it was incorporated into a hand-held unit. During the Phase II project, a field deployable prototype instrument will be developed and demonstrated in a field test.<br/> The increasing emphasis on environmental issues, waste reduction, and improved efficiency for industrial processes has underlined the importance of the development of new chemical sensors for field or in-plant use. Specifically, sensors are needed to gauge the effectiveness of remediation efforts, to effect waste minimization, and to detect the presence of toxic, hazardous, or otherwise regulated chemicals in waste effluents, drinking water, and other environmental systems. In addition, this proposed sensor will find wide application in the food, beverage and perfume industries for the determination of odors and aromas, as well as in the clinical (e.g., breath monitor) and agronomic industries (e.g., detection of pesticides).