Abstract
Abstract. Source-receptor relationships for speciated atmospheric mercury measured at the Experimental Lakes Area (ELA), northwestern Ontario, Canada were investigated using various receptor-based approaches. The data used in this study include gaseous elemental mercury (GEM), mercury bound to fine airborne particles (<2.5 μm) (PHg), reactive gaseous mercury (RGM), major inorganic ions, sulphur dioxide, nitric acid gas, ozone, and meteorological variables, all of which were measured between May 2005 and December 2006. The source origins identified were related to transport of industrial and combustion emissions (associated with elevated GEM), photochemical production of RGM (associated with elevated RGM), road-salt particles with absorption of gaseous Hg (associated with elevated PHg and RGM), crustal/soil emissions, and background pollution. Back trajectory modelling illustrated that a remote site, like ELA, is affected by distant Hg point sources in Canada and the United States. The sources identified from correlation analysis, principal components analysis and K-means cluster analysis were generally consistent. The discrepancies between the K-means and Hierarchical cluster analysis were the clusters related to transport of industrial/combustion emissions, photochemical production of RGM, and crustal/soil emissions. Although it was possible to assign the clusters to these source origins, the trajectory plots for the Hierarchical clusters were similar to some of the trajectories belonging to several K-means clusters. This likely occurred because the variables indicative of transport of industrial/combustion emissions were elevated in at least two or more of the clusters, which means this Hg source was well-represented in the data.
Highlights
The finding that the measurements at the Experimental Lakes Area (ELA) site were in line with other remote sites not affected by anthropogenic Hg sources gives an idea about the precision of the Tekran speciated atmospheric Hg data
A data set consisting of major ions and trace gases in particulate matter, ground-level ozone concentrations and meteorological variables were analyzed to explain seasonal and diurnal variations in speciated atmospheric Hg concentrations and to identify potential sources affecting speciated atmospheric Hg concentrations at the remote Experimental Lakes Area site
Analysis of seasonal variability revealed that the season with highest gaseous elemental mercury (GEM) and reactive gaseous mercury (RGM) concentrations coincided with highest O3 concentrations
Summary
Many studies using source-based methods have been conducted for Hg during the past decade (e.g., Xu et al, 2000; Bullock and Brehme, 2002; Lin and Tao, 2003; Dastoor and Larocque, 2004; Christensen et al, 2004; Gbor et al, 2006; Ryaboshapko et al, 2007; Selin et al, 2007; Sillman et al, 2007; Bullock et al, 2008; Vijayaraghaven et al, 2008; Lin et al, 2010). The studies conducted sensitivity analyzes, model intercomparisons, and improved on the atmospheric Hg chemistry component of the model to better simulate RGM and PHg concentrations.
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