GCS-CEAS: a novel tool for exposure assessment during disaster response

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BRI will develop and demonstrate a Gas Chromatography Selector (GCS) that front-ends a Cavity Enhanced Absorption Spectrometer (CEAS) for the fast, accurate, selective, sensitive (0.025 ppbv, or better, using pre- concentration) measurement of a wide spectrum of volatile organic hydrocarbons (VOHs) that are beyond current CEAS technology. BRI will develop and demonstrate an inexpensive, reusable Pre-concentration Sample Module (PSM) to collect samples for later analysis. Thus GCS-CEAS significantly extends industry- leading CEAS technology capabilities for air quality monitoring opening many new applications. GCS-CEAS will be suitable for mobile applications with a time response comparable to or better than other gas analyzers (1-2 minutes). Extreme weather events are increasing instances of cascading technological disasters, e.g., hurricanes damage infrastructure, causing chemical releases, and thus, exposure. GCS-CEAS addresses the resulting VOHs released and can be expanded to include any gas that can be measured by gas chromatography. Thus, GCS-CEAS supports disaster response as a reliable, accurate sensor that detects an extensive range of toxic gases for exposure assessment for first responders and the community. The GCS-CEAS uses fast (0.1-2 s time response) analysis by the CEAS of CH4 to guide GCS-CEAS data collection or PSM collection for later analysis. GCS-CEAS can be adapted easily to other VOHs of interest. Envisioned mobile applications are for cars, a 4WD vehicles, or small ATVs. There are direct health applications: exposure, breath analysis, diagnostics, or monitoring exhaled anesthetic. GCS-CEAS will be commercially accessible, requiring minimal technical expertise, maintenance, and calibration. Fusion of mobile real-time, focused speciation by GCS-CEAS with archival full speciation will transform source monitoring. GCS-CEAS enables in-plume sample collection that stationary monitors can easily miss or misinterpret to estimate exposure. Mobile data are snapshot data that removes the large uncertainty in stationary datasets wherein transport processes and emission unsteadiness become confounded. We demonstrate field application of GCS-CEAS using remote PSM sample collection downwind of the Carson Refinery for complete analysis by the bench top system. Tasks involve developing and validating optimization modules to meet target time response, accuracy, selectivity, and detection limits and accounting for H2 balance effects on CEAS calibration. Target GCS-CEAS accuracy is 5%. PSM target detection limits are sub-25 ppt at 1-3 minute time response for BTEX and alkanes, similar to fluorescence analyzer time-scales, which only measure (selectively) one (not large molecule) gas per analyzer and cannot be re-tasked for other gases, unlike the GCS-CEAS.