Development of a Multipass Raman Cell and Instrument for Vapor Analysis of Subsurface Chemical Contaminants

Past Department of Energy (DOE) operations at its weapons complex facilities involve the use of organic solvents that were then not properly disposed and released into the environment resulting in the contamination of soils and groundwater. DOE faces monumental remediation challenges in restoring these sites to their pristine conditions. Contaminated site restoration involved several steps, which include characterization, evaluation, selection, implantation of containment or restoration measures, and performance monitoring during and after remediation. Current monitoring methods are costly and time-intensive and mainly involve grab sampling of headspace gases from monitoring wells installed around the perimeter of these contaminated sites and then remotely analyzed at a laboratory by gas chromatograph technique. The integrity of the grab sampling protocol can be compromised during sample collection, transport and storage. Also, current requirements for surrounding aquifer contamination requires a more frequent sampling intervals that will be hard to be met by current methods because of cost and sampling time. A novel portable Raman instrument is proposed with a power buildup cavity sampling gas cell that can be used for quantitative vapor phase monitoring of soil gases for onsite use. This in situ monitoring instrument will allow direct analyses of monitoring well gases without the necessity of sampling and laboratory analysis. This will have an advantage of faster analysis time and a more cost effective sampling protocols. Commercial applications and other benefits: The principal market for the instrument will be the environmental monitoring field, mainly in the area of soil and groundwater monitoring where field-sampling instruments are needed to track leaks or migration of environmental contaminants underground. Other environmental markets where the Raman Gas Cell would find use is in air pollutants monitoring where the instrument could be used for monitoring the release of hazardous gases from industrial sites for regulatory purposes. Also, the instrument could find use in furnace atmosphere control monitoring where control and monitoring of effluents such as hydrocarbons gases are required.