Temporal variability of atmospheric total gaseous mercury in Windsor, ON, Canada

Abstract

Atmospheric Total Gaseous Mercury (TGM) concentrations were monitored in Windsor, Ontario, Canada, during 2007 to 2011, to investigate the temporal variability of TGM. Over five years, the average concentration was 2.0 ± 1.3 ng/m3. A gradual decrease in annual TGM concentrations from 2.0 ng/m3 in year 2007 to 1.7 ng/m3 in 2009 was observed. The seasonal means show the highest TGM concentrations during the summer months (2.4 ± 2.0 ng/m3), followed by winter (1.9 ± 1.4 ng/m3), fall (1.8 ± 0.81 ng/m3), and spring (1.7 ± 0.73 ng/m3). Diurnal patterns in summer, fall, and winter were similar. A different diurnal pattern was observed in spring with an early depletion in the morning. The TGM concentrations were lower on weekends (1.8 ± 0.77 ng/m3) than on weekdays (2.0 ± 1.5 ng/m3), suggesting 10% of TGM in Windsor was attributable to emissions from industrial sectors in the region. Directional TGM concentrations also indicated southwesterly air masses were TGM enriched due to emissions from coal-fired power plants and industrial facilities. Correlation and principal component analysis identified that combustion of fossil fuel, ambient temperature, wind speed, synoptic systems, and O3 concentrations influenced TGM concentrations significantly. Overall, inter-annual, seasonal, day-of-week, and diurnal variability was observed in Windsor. The temporal patterns were affected by anthropogenic and surface emissions, as well as atmospheric mixing and chemistry. © 2014 by the authors.