Superfund Research Program
Low-Cost Electronic Nose for Groundwater Contaminants
Project Leader: Sanjay V. Patel
Grant Number: R44ES016941
Funding Period: Phase II: May 2011 – May 2013
Several US agencies and regulators require low-cost chemical sensors for detecting and monitoring environmental clean-up, remediation, and decommissioning processes where groundwater may be contaminated. The sensors must be capable of detecting contaminants in the sub-surface groundwater and must be compatible with use in a range of environments. Most significantly, these customers require a low cost alternative to current expensive and labor intensive methods, namely using mobile laboratories. Seacoast Science, Inc., is developing an innovative use of low cost sensor systems that will be capable of detecting and monitoring for dense non-aqueous phase liquids in the subsurface and groundwater, unattended, and in real-time from within a push-probe, using a chemicapacitor array and miniature preconcentrator.
Patel is providing agencies with a method to map and track subsurface contamination plumes in real-time without requiring an operator. In Phase I, Seacoast successfully demonstrated the feasibility of using a microsensor array with a proprietary trap-and-purge preconcentrator to detect chlorinated solvents, specifically TCE and TCA, at levels low enough to meet EPA mandated levels for drinking water. In Phase II Seacoast is improving the selectivity and sensitivity of the system to better meet the needs identified in Phase I. The systems have MEMS microcapacitor sensor arrays that can monitor for leaks of toxic chemicals, contaminants from wastes, and changes in groundwater streams. A preconcentrator traps the contaminants and releases them to a microsensor array. These sensor arrays are filled with several chemoselective polymers whose dielectric permittivity changes when exposed to different vapors, creating a fingerprint response for each chemical.
In Phase II Seacoast is specifically developing new materials to improve the sensor array selectivity:
- by using impedance spectroscopy to study the mechanisms by which the polymer-based sensors sorb the target chemicals,
- by implementing pattern recognition algorithms to identify chemicals for the sensor responses, and
- by designing new preconcentrator materials that can bind these chemicals more strongly.
The most important application to public health and safety is unattended monitoring of drinking water, water treatment processes, and water sources. Potential markets include building chemical process monitoring and control, toxic vapor leak detection, industrial process control, and industrial health and safety. Transitioning the developed prototype to other markets such as worker and public health, environmental health and regulatory compliance are being investigated to reduce the financial risks and broaden the acceptance of the technology.