Grantee Research Project Results

Final Report: Monitoring Groundwater Contaminants

EPA Contract Number: EPD04039
Title: Monitoring Groundwater Contaminants
Investigators: Gonzalez-Martin, Anuncia
Small Business: Lynntech Inc.
EPA Contact: Richards, April
Phase: I
Project Period: March 1, 2004 through August 31, 2004
Project Amount: $70,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2004) RFA Text |  Recipients Lists
Research Category: Hazardous Waste/Remediation , SBIR - Waste , Small Business Innovation Research (SBIR)

Description:

Chlorinated hydrocarbons (CHCs) 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. The goal of this research project was to develop a reliable, compact, low-cost, in situ, long-term monitor of CHCs and benzene, toluene, ethylbenzene, and xylenes (BTEX) in groundwater. This goal was accomplished by the integration and field-testing of Lynntech, Inc.’s innovative array-based chemical sensor system with a dedicated sampling system. During Phase I, Lynntech developed and successfully tested a bench-scale miniature sensor capable of identifying CHCs and BTEX in water at the ppb level. The sensor combined an effective array-based chemical sensor with an efficient preconcentrator system. Operation of the monitor, sample collection, and data analysis was carried out by a computer.

Summary/Accomplishments (Outputs/Outcomes):

Efforts in Phase I focused on the following areas:

• Optimization of an array-based chemical sensor that utilizes thin-film, electrically conducting polymers as the array elements. An array of these sensing elements produces a reversible diagnostic pattern change upon exposure to different analytes (i.e., each analyte has a unique fingerprint). The advantage of this approach is that it can yield responses to a variety of different analytes.


• Fabrication of a miniaturized sensor chamber.


• Development of an effective preconcentrator system capable of retaining most of the CHCs and BTEX, while removing most of the water from the samples.


• Testing the system with water contaminated with CHCs and BTEX. Water samples contained single and multiple contaminants.


• Testing the system with groundwater contaminated with CHCs and BTEX.

Conclusions:

A laptop computer with a developed data acquisition system was used to run the monitoring system. It has an interface to an electronic system capable of resistance measurements, data acquisition, and analysis. The monitoring system used a circuit board with 16 channels to process the incoming signals from the sensor array (i.e., the 16-channel ohmmeter). This ohmmeter is capable of measuring variations of 0.25 Ω in 1M Ω. This type of array sensor is inexpensive and easy to fabricate and analyze. It uses a low-powered direct current resistance readout signal that converts chemical interactions into electrical signals. The output signals are readily integrated into a software-based neural network for the analysis of unknown samples.

Supplemental Keywords:

small business, SBIR, EPA, monitoring, groundwater, contaminants, chlorinated hydrocarbons, CHCs, benzene, toluene, ethylbenzene, xylene, BTEX, chemical sensor system, polymer, analyte, ohmmeter,, RESEARCH, RFA, Ecosystem Protection/Environmental Exposure & Risk, Scientific Discipline, Environmental Chemistry, Monitoring/Modeling, Environmental Engineering, Environmental Monitoring, Monitoring, aquatic ecosystem, chlorinated hydrocarbons, aqueous waste streams, continuous monitoring, groundwater monitoring