Mapping the geospatial distribution of atmospheric BTEX compounds using portable mass spectrometry and adaptive whole air sampling

Abstract

Atmospheric environmental monitoring with mobile laboratories is becoming more common as instrumentation evolves and the benefits of taking the lab-to-sample are realized. One of the benefits of this approach is the ability to screen a geographic area for compounds of interest and to use ‘real-time’ data to inform adaptive sampling. We report on the use of a membrane introduction mass spectrometer (MIMS) for continuous monitoring of atmospheric volatile organic compounds (VOCs) associated with hydrocarbon upgrading and refining facilities in northern Alberta, Canada. Field campaigns involved continuous ambient-air sampling from a moving vehicle (collected at ~ 1Hz). Real-time MIMS data were used to monitor chemical concentrations of benzene, toluene, and ethylbenzene/xylene/s (BTEX) and to prompt collection whole air sample (WAS) canisters for laboratory-based, trace-level VOC speciation and quantitation. The MIMS data showed a high degree of spatiotemporal variability, which allowed for near real-time feedback to guide otherwise subjective or random collection of whole air samples. Laboratory based comparisons using lab constructed air samples showed the percent difference in quantitation between MIMS and WAS to be within 20% across targeted analytes in the low ppbv concentration range.