Collaborative Research: Refining and Testing Methods for Identifying and Quantifying Gaseous Oxidized Mercury in Air

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Atmospheric mercury (Hg) occurs in many forms some of which are more toxic than others. The largest component of Hg, gaseous elemental mercury (GEM) is relatively inert but it oxidizes to gaseous oxidized mercury (GOM) or converts to particle bound mercury (PBM) that are reactive and toxic. Therefore, it is critical to monitor these distinct forms of mercury accurately. The investigators' past work sponsored by NSF has shown that the commercial Tekran systems, which are used widely to monitor reactive mercury and accepted as the standard, are prone to large errors and systematic biases. Specifically, Tekran based reactive GOM and RGM show a persistent low bias and call into question our current understanding of mercury toxicity and exposure. The project will deploy a new suite of instruments globally to provide robust and well-calibrated measurements of reactive mercury globally to improve our predictive knowledge of mercury and its health risks for humans.The project will develop and deploy a suite of new stable and sensitive instruments for calibrated speciated reactive mercury measurements at a network field sites where conventional Tekran systems have been operating. It builds on preliminary promising results that were supported by NSF. The instruments include a new active GOM system developed by the team that collects GOM on cation exchange and nylon membranes and then analyzes them for reactive mercury. The two-distinct collection and analysis methods will confirm the absence of potential biases from speciation or atmospheric sampling conditions (e.g. high humidity or ozone). This method has been shown to be highly selective with no interference from GEM that is present in much larger amounts. Furthermore, the investigators will deploy an automated GOP and GEM calibrator for routine field verification. Finally, a gas chromatography/mass spectrometry system to separate and identify various oxidized mercury compounds will be co-deployed at multiple sites. The 10 core sites will span the globe and cover a wide range of atmospheric conditions and emission cases. The harmonized bias-free chemically rich global mercury data on mercury will be analyzed to lay a solid observational foundation for the mercury modeling and assessment research community. The systems developed here will be commercialized and made available to the wider community for reliable speciated mercury measurements.