Remote optical sensing instrument monitoring to demonstrate compliance with short-term exposure action limits during cleanup operations at uncontrolled hazardous waste sites

Remote optical sensing (ROS) is an emerging analytical technique. ROS provides the capability to remotely monitor and measure trace atmospheric gases by transmitting a beam of radiation across a parcel of air several hundred meters in length (e.g., open-path Fourier transform infrared spectroscopy). The information gained from these measurements can be used to calculate emission rates from sources, which can be modeled to determine downwind air quality impacts. Traditionally, two monitoring methods were available to estimate air quality impacts: receptor measurements and source measurements. Receptor measurements are air monitoring or sampling methods that directly determine concentrations at downwind locations of concern (e.g., absorbent tubes collected at a school). Source measurements are air monitoring or sampling at or immediately downwind of a source to determine an emission rate (e.g., stack sampling at a facility). This emission rate is then used for estimating concentrations at downwind locations of concern. The path-integrated approach has been utilized at Superfund sites to examine source emission impacts during full-scale remediation operations and during pilot-scale studies. The emission rates for the various compounds were modeled to determine if health-based action levels for the targeted compounds were exceeded at designated distances downwind of the monitoring. Utilization of ROS during these types of operations provided near real-time data to demonstrate compliance with short-term exposure action limits. The data were also used to determine the overall daily average fence line concentration and compare it with longer-term, exposure-based action limits.