Atmospheric transport of speciated mercury across southern Lake Michigan: Influence from emission sources in the Chicago/Gary urban area

Quantifying the local and regional impacts of speciated mercury (Hg) emissions from major urban and industrial areas is critical for understanding Hg transport and cycling in the environment. The Chicago/Gary urban area is one location where Hg emissions from industrial sources are significant and t...

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Bibliographic Details
Published in:The Science of the total environment 2013-03, Vol.448, p.84-95
Main Authors: Gratz, Lynne E., Keeler, Gerald J., Marsik, Frank J., Barres, James A., Dvonch, J. Timothy
Format: Article
Language:English
Subjects:
Air Movements
Air Pollutants - analysis
Air Pollutants - chemistry
Atmosphere - chemistry
case studies
Chicago - epidemiology
Chicago/Gary
Cluster Analysis
Dispersion modeling
Dispersions
emissions
Environmental Monitoring
Geography
Holland
Illinois
Lake Michigan
Lakes - chemistry
Local source emissions
Mercury
Mercury (metal)
Mercury - analysis
Mercury - chemistry
Michigan
oxidation
Oxidation-Reduction
Pollution sources
Position (location)
Regional transport
Speciation
Transport
Urban areas
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Summary:Quantifying the local and regional impacts of speciated mercury (Hg) emissions from major urban and industrial areas is critical for understanding Hg transport and cycling in the environment. The Chicago/Gary urban area is one location where Hg emissions from industrial sources are significant and the regional transport of emissions may contribute to elevated ambient Hg concentrations at downwind locations. From July to November 2007, we collected semi-continuous measurements of gaseous elemental Hg (Hg0), fine particulate bound Hg (Hgp), and divalent reactive gaseous Hg (RGM) in Chicago, IL and Holland, MI to characterize the impact of Chicago/Gary source emissions on Hg concentrations in southwest Michigan and to improve our overall understanding of speciated Hg transport and deposition. The mean (and median) concentrations of Hg0, Hgp, and RGM in Chicago were 2.5ng/m3 (1.9ng/m3), 9pg/m3 (5pg/m3), and 17pg/m3 (6pg/m3), respectively. In Holland the mean (and median) concentrations were 1.3ng/m3 (1.3ng/m3), 6pg/m3 (6pg/m3), and 8pg/m3 (2pg/m3), respectively. Cluster analysis of 24-hour HYSPLIT back-trajectories associated with the semi-continuous Hg measurements indicated that southwest transport from Chicago/Gary to Holland occurred during approximately 27% of the study. In Holland, under this transport regime, we observed a five-fold increase in RGM relative to the median concentration of the other transport clusters. We applied the HYSPLIT dispersion model to two case study periods to further quantify the impact of Chicago/Gary sources on southeast Michigan and investigate the role of direct transport and dispersion of speciated Hg emissions. Results suggested that more than 50% of the maximum RGM concentrations observed in Holland during the selected periods could be attributed to direct transport of primary RGM emissions from Chicago/Gary. The remaining RGM fractions are believed to be associated with Hg0 oxidation during transport over Lake Michigan. ► We measured speciated atmospheric Hg in Chicago, IL and Holland, MI in summer 2007. ► Transport from Chicago/Gary resulted in elevated Hg concentrations in Holland. ► Primary RGM emissions and Hg0 oxidation both influenced elevated RGM in Holland. ► Chicago/Gary source emissions significantly impact receptors along Lake Michigan.
ISSN:0048-9697
1879-1026
DOI:10.1016/j.scitotenv.2012.08.076