This book involves inter-disciplinary research in electrical, environmental, and chemical engineering. It describes methodologies and techniques of environmental monitoring for the detection of hazardous materials by using microelectronic sensors. Design considerations focus on improving key areas such as: (1) sampling methodology; (2) context awareness; and (3) sensor placement. Moreover, design techniques using wireless sensor networks (WSN) are applied to the detection of methylmercury (MeHg) and environmental parameters affecting its formation (methylation) and deformation (demethylation).