Source-receptor relationships for speciated atmospheric mercury at the remote Experimental Lakes Area, northwestern Ontario, Canada

摘要

Source-receptor relationships for speciated atmosphericmercury measured at the Experimental Lakes Area (ELA), northwestern Ontario,Canada were investigated using various receptor-based approaches. The dataused in this study include gaseous elemental mercury (GEM), mercury bound tofine airborne particles (<2.5 μm) (PHg), reactive gaseous mercury(RGM), major inorganic ions, sulphur dioxide, nitric acid gas, ozone, andmeteorological variables, all of which were measured between May 2005 andDecember 2006. The source origins identified were related to transport ofindustrial and combustion emissions (associated with elevated GEM),photochemical production of RGM (associated with elevated RGM), road-saltparticles with absorption of gaseous Hg (associated with elevated PHg andRGM), crustal/soil emissions, and background pollution. Back trajectorymodelling illustrated that a remote site, like ELA, is affected by distantHg point sources in Canada and the United States. The sources identifiedfrom correlation analysis, principal components analysis and K-means clusteranalysis were generally consistent. The discrepancies between the K-meansand Hierarchical cluster analysis were the clusters related to transport ofindustrial/combustion emissions, photochemical production of RGM, andcrustal/soil emissions. Although it was possible to assign the clusters tothese source origins, the trajectory plots for the Hierarchical clusterswere similar to some of the trajectories belonging to several K-meansclusters. This likely occurred because the variables indicative of transportof industrial/combustion emissions were elevated in at least two or more ofthe clusters, which means this Hg source was well-represented in the data.