This project is part of the exposure assessment task group initiated by the Consortium for Risk Evaluation with Stakeholder Participation (CRESP) sponsored by the US DOE. Our project will develop and evaluate a unique real-time site monitoring system based on Remote Optical Sensing of Emissions (ROSE) coupled with Computed Tomography (CT). A ROSE system detects contaminant emissions in situ by measuring the absorbance of infrared light along multiple downwind beam paths of several hundred meters. This real-time downwind concentration data is coupled with simultaneous real-time wind turbulence data to compute the emission rates of contaminants from a non-homogeneous source. With suitable instrumentation ROSE monitoring can both identify a wide range of gaseous contaminants and quantify the contamination of each chemical in a beam path.
Existing optical sensing technology, usually only gives concentration data averaged over the length of the beam path. In contrast the CT-ROSE approach would provide spatially resolved data on contaminant emission rates (e.g. source fluxs). The proposed CT-ROSE instrument would rapidly scan the fenceline surrounding the site with a series of beam paths and reconstruct a 2-dimensional map of source emission rates. When deployed near an active remediation site this would create a continuous monitoring network completely surrounding the area, with the capability to identify and locate potential fugitive emissions.
This CT-ROSE system will fulfill several needs at DOE sites. A primary application would be for worker exposure monitoring during remediation activities, such as excavation, filling, or transfer of mixed waste. CT-ROSE could provide real-time data about the air concentration, the chemical species, and the location of any contaminants released during work activities. This information would insure that air concentrations remained within acceptable limits or could warn workers in the event an out of control situation developed. A second application comes in the larger context of risk assessment at DOE sites. Little is known about the actual volitization of organic contaminants at waste sites during remedaiation of material or as a fence line warning system for surrounding communities.
The specific aims of this project are:
(1) to assess the technical feasibility of CT-ROSE monitoring;
(2) develop and evaluate hardware and software needed for the system;
(3) validate and field test the CT-ROSE measuring system in pilot-scale experiments.
Significance to CRESP and DOE:
The Department of Energy faces a challenging problem at facilities now targeted for remediation because many sites have a wide variety of unknown volatile pollutants. Assessing potential airborne emissions from handling and clean-up of this mixed waste will require extensive on-site air sampling. Using conventional sampling methods, the subsequent analysis of these samples will require considerable personnel and laboratory expense. Further, this approach produces a significant time delay for sample analysis before any useful data becomes available to apply to the active work site. This makes it difficult to judge what emissions (if any) resulted from particular activities on the site, and affords little warning to workers or neighboring communities in the event that a significant release occurs.
CT-ROSE monitoring as described here would use real-time instruments to continuously monitor for emissions at an active remediation site, thus providing rapid feedback to workers, a fence line warning system for any potential fugitive releases, and documentation of clean-up performance. Since CT-ROSE monitoring can furnish spatially resolved data, this would allow personnel on-site to locate and identify pollutant sources and take appropriate immediate action to control the emissions. Two applications stand out for a CT-ROSE instrument: (1) for monitoring potential emissions at mixed waste storage facilities; and (2) for monitoring sites during active handling, transfer, or processing of waste streams at DOE facilities These monitoring applications would provide immediate benefit to workers and to surrounding communities.