Assessment of Particulate Mercury Measured with the Tekran System

Robert Talbot1, Huiting Mao1, Kevan Carpenter1, Dara Feddersen1,2, Melissa Smith3, Su Youn Kim1, Barkley Sive1, Karl Haase1,2, Jesse Ambrose1, Yong Zhou1 and Rachel Russo1

A seasonal study was conducted to ascertain cycling of speciated atmospheric mercury in the marine and continental atmospheric boundary layers. A component of this work focused on assessing the accuracy of the automated Tekran system for measuring HgP. Our results suggest that the filter-based HgP has minimal positive artifact from uptake of RGM during sampling. In coastal New Hampshire, where RGM is at its highest mixing ratios in springtime, periodic artifact from RGM uptake could occur. However, comparison of the Tekran and filter HgP values during a period of elevated RGM showed no difference in the measured mixing ratios suggesting that the artifact is essentially immeasurable. The largest discrepancy in measured mixing ratios of filter and Tekran HgP always were associated with the highest levels of filter HgP. Peaks in filter HgP occurred in all seasons and there was corresponding enhancements in selected hydrocarbons, halocarbons, and oxygenated compounds. Most of these cases also had enrichments in HCN and CH3CN, indicative of a biomass burning contribution. Since there were no reported wildfires in the backward trajectory determined source regions, we concluded that in winter this must include contributions from regional wood stove and fireplace emissions. In other seasons a variety of anthropogenic sources may be involved, including vehicle emissions, coal combustion, and other combustion types. Almost every peak in filter HgP showed a potential biomass contribution as indicated by tracer compounds. In comparison, the Tekran exhibited little response to these events. Furthermore, we found no consistent disparity in the two methods caused by aerosol size distribution factors. In summer and winter the Tekran yielded minimal correlation with the filter measurements. In springtime they tracked each other much more closely, with the Tekran still providing lower mixing ratios. We conclude that until the discrepancies are understood better between the filter and Tekran methodologies, the filterbase HgP may provide more accurate measurement of HgP for research applications in chemical cycling studies.

1Climate Change Research Center, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, New Hampshire 03824
2Department of Chemistry, University of New Hampshire, Durham, New Hampshire 03824
3Department of Earth Science, University of New Hampshire, Durham, New Hampshire 03824
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