Mercury Measurement Inter-comparison Study
ARL scientists participated in a mercury dry deposition measurement inter- comparison study from August 4-13 near Ann Arbor, Michigan. The study was hosted by the University of Michigan with funds from the Great Lakes Air Deposition (GLAD) program. The study involved an inter-comparison of various techniques to measure mercury compounds in ambient air and dry deposition. ARL used a technique it pioneered called a modified Bowen ratio micro-meteorological measurement method of gaseous elemental and reactive gaseous mercury. This technique measures the mercury flux to a real ecosystem. Other participants in the study included scientists from Environment Canada, U.S. EPA, University of Michigan, Clarkson University, and the University of Nevada, Reno. With the exception of ARL and Environment Canada, the participants used surrogate surface techniques, which measure the mercury flux to an artificial surface. The outcome of this inter-comparison study will assist the GLAD with its atmospheric deposition monitoring program priority.
Scientists have a good handle on quantifying mercury in rainfall, but measuring dry deposition (particles and gases which deposit without the assistance of precipitation) remains a challenge. Methods to measure mercury in air and dry deposition are actively under development. Yet, little is known regarding the uncertainty and comparability of various measurement approaches. Through a competitive research initiative, the GLAD program works with leading scientists to better understand the sources of toxic pollutants, their transport in the environment, their deposition to the Great Lakes basin and the resulting impacts on human health and the Great Lakes ecosystem.
The greatest input of mercury to aquatic and terrestrial ecosystems is atmospheric deposition from mercury emissions. While surrogate surfaces potentially offer a less expensive and simpler technique to estimate mercury fluxes, the relationship between mercury collected by an artificial surface and a real ecosystem flux is uncertain. ARL, as a recognized leader in the field of mercury measurement research, is providing critical information of mercury fluxes to a real ecosystem.
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