Chemical Characterization of Volatile Organic Emissions from Complex Environmental Mixtures

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ABSTRACT Complex environmental substances pose risks to human, animal, and environmental welfare in the event of natural or manmade disasters. No two disasters are alike: contaminants vary in composition and source, and disaster sites vary in location, rate of spreading, weathering, climate, and ecosystem. Such factors contribute to the complexity of environmental pollutants, yielding intricate mixtures of unpredictable composition. Mitigation of hazards posed by these complex mixtures is therefore of the utmost importance, as the health of afflicted communities and first responders is dependent upon characterization of environmental hazards through analytical techniques. Extensive recent research identified polycyclic aromatic compounds (PAC) to be representative environmental contaminants. PAC can be used as a proxy for complex mixtures because they are ubiquitously persistent, can be characterized by traditional analytical instrumentation, and are structurally similar compounds. Analytical fingerprinting techniques (GC-MS variants, GC-FID, FT-ICR MS, etc.) and computational practices have considerably advanced our understanding of environmental pollutants, including PAC; still, a substantial fraction of these compounds and detailed molecular identification of constituents remain challenging to decipher. Therefore, this overall project is focused on the development of an analytical-to-in vitro approach to comprehensively characterize PAC in environmental samples collected from disaster scenarios. The aims to accomplish this are three-fold: first, we will conduct untargeted chemical analysis of several hundred environmental samples using rapid, untargeted ion mobility spectrometry-mass spectrometry (IMS-MS), focusing on the PAC fraction as a basis to comprehensively identify individual molecular constituents. Second, the effect of environmental weathering on the chemical composition and bioactivity of complex mixtures over time will be evaluated by a case study modeling a complex chemical spill in the environment. Finally, we will test the relevance and reliability of various scaled-down passive dosing methods to enable both in vitro toxicity testing of complex substances and complete characterization of the bioactive fraction. To supplement this research, we propose an externship at Los Alamos National Laboratory (LANL) to explore additional analytical characterization of the airborne fraction of PAC in complex mixtures. Longwave-infrared (LWIR) imaging, a technique that has been pioneered at LANL, enables visualization of gaseous emissions from concentrated sources, including city- wide emissions, field plumes, and most relevant to this research, volatile, airborne chemicals that may be released during disaster events. With this analytical approach, individual volatile organic compounds (VOCs) identified thus far have been collected into a spectral library of approximately 700 constituents. By collaboration with LANL, we aim to characterize the VOC fraction of environmental mixtures using LWIR imaging by targeting PAC. We hypothesize that chemically characterizing the VOC fraction of representative complex mixtures will ultimately improve exposure assessment to inform hazard mitigation strategies for disaster scenarios.