ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-12-1903-2012 Source-receptor relationships for speciated atmospheric mercury at the remote Experimental Lakes Area, northwestern Ontario, Canada Cheng I. 1 Zhang L. 2 Blanchard P. 2 Graydon J. A. 3 Louis V. L. St. 3 Independent researcher, 5785 Yonge St, Toronto, Ontario, M2M 4J2, Canada Air Quality Research Division, Science and Technology Branch, Environment Canada, 4905 Dufferin Street, Toronto, Ontario, M3H 5T4, Canada Department of Biological Sciences, University of Alberta, Edmonton, Alberta, T6G 2E9, Canada 17 02 2012 12 4 1903 1922 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/12/1903/2012/acp-12-1903-2012.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/12/1903/2012/acp-12-1903-2012.pdf

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.

 References % vor jede Referenz Abbott, M. L., Lin, C.-J., Martian, P., and Einerson, J. J.:. Atmospheric mercury near Salmon Falls Creek Reservoir in southern Idaho, Appl. Geochem., 23, 438–453, 2008. Amos, H. M., Jacob, D. J., Holmes, C. D., Fisher, J. A., Wang, Q., Yantosca, R. M., Corbitt, E. S., Galarneau, E., Rutter, A. P., Gustin, M. S., Steffen, A., Schauer, J. J., Graydon, J. A., Louis, V. L. St., Talbot, R. W., Edgerton, E. S., Zhang, Y., and Sunderland, E. M.: Gas-particle partitioning of atmospheric Hg(II) and its effect on global mercury deposition, Atmos. Chem. Phys., 12, 591–603, http://dx.doi.org/10.5194/acp-12-591-2012doi:10.5194/acp-12-591-2012, 2012. Arkian, F., Meshkatee, A.-H., and Bidokhti, A. A.: The effects of large-scale atmospheric flows on berylium-7 activity concentration in surface air, Environ. Monit. Assess., 168, 429–439, http://dx.doi.org/10.1007/s10661-009-1124-1doi:10.1007/s10661-009-1124-1, 2010. Baya, A. P. and Van Heyst, B.: Assessing the trends and effects of environmental parameters on the behaviour of mercury in the lower atmosphere over cropped land over four seasons, Atmos. Chem. Phys., 10, 8617–8628, http://dx.doi.org/10.5194/acp-10-8617-2010doi:10.5194/acp-10-8617-2010, 2010. Brooks, S., Luke, W., Cohen, M., Kelly, P., Lefer, B., and Rappenglu, B.,: Mercury species measured atop the Moody Tower TRAMP site, Houston, Texas, Atmos. Environ., 44, 4045–4055, 2010. Bullock, O. R.: Current methods and research strategies for modeling atmospheric mercury, Fuel Process. Technol., 65–66, 459–471, 2000. Bullock, O. R. and Brehme, K. A.: Atmospheric mercury simulation using the CMAQ model: Formulation description and analysis of wet deposition results, Atmos. Environ., 36, 2135–2146, 2002. Bullock, O. R., Atkinson, D., and Braverman, T.: The North American mercury model intercomparison study (NAMMIS): study description and model-to-model comparisons, J. Geophys. Res., 113, D17310, http://dx.doi.org/10.1029/2008JD009803doi:10.1029/2008JD009803, 2008. Canadian National Atmospheric Chemistry Particulate Matter Database for 2005–2006 (NatChem), Environment Canada, Science and Technology Branch, 4905 Dufferin Street, Toronto, Ontario, Canada M3H 5T4, 2010. Carpi, A.: Mercury from Combustion Sources: A Review of the Chemical Species Emitted and Their Transport in the Atmosphere, Water Air Soil Pollut., 98, 241–254, http://dx.doi.org/10.1023/A:1026429911010doi:10.1023/A:1026429911010, 1997. Cheng, I., Lu, J., and Song, X.: Studies of Potential Sources that Contributed to Atmospheric Mercury in Toronto, Canada, Atmos. Environ., 43, 6145–6158, 2009. Choi, H.-D., Holsen, T. M., and Hopke, P. K.: Atmospheric Mercury (Hg) in the Adirondacks: Concentrations and Sources, Environ. Sci. Technol., 42, 5644–5653, 2008. Christensen, J. H., Brandt, J., Frohn, L. M., and Skov, H.: Modelling of Mercury in the Arctic with the Danish Eulerian Hemispheric Model, Atmos. Chem. Phys., 4, 2251–2257, http://dx.doi.org/10.5194/acp-4-2251-2004doi:10.5194/acp-4-2251-2004, 2004. Cobbett, F. D. and Van Heyst, B. J.: Measurements of GEM fluxes and atmospheric mercury concentrations (GEM, RGM and Hgp) from an agricultural field amended with biosolids in Southern Ont., Canada (October 2004–November 2004), Atmos. Environ., 41, 2270–2282, 2007. Dastoor, A. P. and Larocque, Y.: Global circulation of atmospheric mercury: a modelling study, Atmos. Environ., 38, 147–161, 2004. Draxler, R. R. and Rolph, G. D.: HYSPLIT Model. Access via NOAA ARL READY Website. NOAA Air Resources Laboratory, Silver Spring, MD, available at: http://www.arl.noaa.gov/ready/hysplit4.html (last access: 20 February 2011), 2003. Du, S. and Rodenburg, L. A.: Source identification of atmospheric PCBs in Philadelphia/Camden using positive matrix factorization followed by the potential source contribution function, Atmos. Environ., 41, 8596–8608, 2007. Edgerton, E. and Jansen, J.: Operation of dual mercury speciation analyzers at a site in the southeastern U.S., 10th International Conference on Mercury as a Global Pollutant, 24–29 July 2011, Halifax, Nova Scotia, Canada, Abstract RS1-O3, 2011. Engle, M. A., Tate, M. T., Krabbenhoft, D. P., Kolker, A., Olson, M. L., Edgerton, E. S., DeWild, J. F., and McPherson, A. K.: Characterization and cycling of atmospheric mercury along the central US Gulf Coast, Appl. Geochem., 23, 419–437, http://dx.doi.org/10.1016/j.apgeochem.2007.12.024doi:10.1016/j.apgeochem.2007.12.024, 2008. Environment Canada: National Pollutant Release Inventory, available at: http://www.ec.gc.ca/inrp-npri/default.asp?lang=En&n=4A577BB9-1 (last access: 15 December 2010), 2010. Experimental Lakes Area (ELA): available at: http://www.experimentallakesarea.ca/ELA_Website.html (last access: 15 March 2011), 2010. Fiore, A., Jacob, D. J., Liu, H., Yantosca, R. M., Fairlie, T. D., and Li, Q.: Variability in surface ozone background over the United States: Implications for air quality policy, J. Geophys. Res., 108, 4787, http://dx.doi.org/10.1029/2003JD003855doi:10.1029/2003JD003855, 2003. Gabriel, M. C., Williamson, D. G., Brooks, S., and Lindberg, S.: Atmospheric speciation of mercury in two contrasting southeastern US airsheds, Atmos. Environ., 39, 4947–4958, 2005. Gbor, P. K., Wen, D., Meng, F., Yang, F., Zhang, B., and Sloan, J. J.: Improved model for mercury emission, transport and deposition, Atmos. Environ., 40, 973–983, 2006. Gustin, M. S. and Jaffe, D.: Reducing the uncertainty in measurement and understanding of mercury in the atmosphere, Environ. Sci. Technol., 44, 2222–2227, 2010. Hall, B. D., Olson, M. L., Rutter, A. P., Frontiera, R. R., Krabbenhoft, D. P., Gross, D. S., Yuen, M., Rudolph, T. M., and Schauer, J.J.: Atmospheric mercury speciation in Yellowstone National Park, Sci. Total. Environ., 367, 354–366, 2006. Han, Y.-J., Holsen, T. M., Hopke, P. K., and Yi, S.-M.: Comparison between Back-Trajectory Based Modeling and Lagrangian Backward Dispersion Modeling for Locating Sources of Reactive Gaseous Mercury, Environ. Sci. Technol., 39, 1715–1723, 2005. Han, Y.-J., Holsen, T. M., and Hopke, P. K.: Estimation of source locations of total gaseous mercury measured in New York State using trajectory-based models, Atmos. Environ., 41, 6033–6047, 2007. Holmes, C. D., Jacob, D. J., Mason, R. P., and Jaffe, D. A.: Sources and deposition of reactive gaseous mercury in the marine atmosphere, Atmos. Environ., 43, 2278–2285, 2009. Holmes, C. D., Jacob, D. J., Corbitt, E. S., Mao, J., Yang, X., Talbot, R., and Slemr, F.: Global atmospheric model for mercury including oxidation by bromine atoms, Atmos. Chem. Phys., 10, 12037–12057, http://dx.doi.org/10.5194/acp-10-12037-2010doi:10.5194/acp-10-12037-2010, 2010. Hopke, P. K.: Recent developments in receptor modeling. J. Chemom., 17, 255–265, 2003. Hopke, P. K. and Cohen, D. D.: Application of receptor modeling methods, Atmos. Pollut. Res., 2, 122–125, 2011. Huang, J., Choi, H.-D., Hopke, P. K., and Holsen, T. M.: Ambient Mercury Sources in Rochester, NY: Results from Principle Components Analysis (PCA) of Mercury Monitoring Network Data, Environ. Sci. Technol., 44, 8441–8445, 2010. Huang, J., Hopke, P. K., Choi, H.-D., Laing, J. R., Cui, H., Zananski, T. J., Chandrasekaran, S. R., Rattigan, O. V., and Holsen, T. M.: Mercury (Hg) emissions from domestic biomass combustion for space heating, Chemosphere, 84, 1694–1699, 2011. Kabashnikov, V. P., Chaikovsky, A. P., Kucsera, T. L., and Metelskaya, N. S.: Estimated accuracy of three common trajectory statistical methods, Atmos. Environ., 45, 5425–5430, 2011. Keeler, G. J., Landis, M. S., Norris, G. A., Christianson, E. M., and Dvonch, J.T.: Sources of mercury wet deposition in Eastern Ohio, USA, Environ. Sci. Technol., 40, 5874–5881, 2006. Keene, W. C., Khalil, M. A. K., Erickson III, D. J., McCulloch, A., Graedel, T. E., Lobert, J. M., Aucott, M. L., Gong, S. L., Harper, D. B., Kleiman, G., Midgley, P., Moore, R. M., Seuzaret, C., Sturges, W. T., Benkovitz, C. M., Koropalov, V., Barrie, L. A., and Li, Y. F.: Composite global emissions of reactive chlorine from natural and anthropogenic sources: Reactive Chlorine Emissions Inventory, J. Geophys. Res., 104, 8429–8440, 1999. Lee, J. H. and Hopke, P. K.:Apportioning sources of PM2.5 in St. Louis, MO using speciation trends network data, Atmos. Environ., 40, S360–S377, 2006. Lee, S. and Ashbaugh, L.: Comparison of multi-receptor and single-receptor trajectory source apportionment (TSA) methods using artificial sources, Atmos. Environ., 41, 1119–1127, 2007. Li, J., Sommar, J., Wängberg, I., Lindqvist, O., and Wei, S.-Q.: Short-time variation of mercury speciation in the urban of Göteborg during GÖTE-2005, Atmos. Environ., 42, 8382–8388, 2008. Lin, C.-J., Pan, L., Streets, D. G., Shetty, S. K., Jang, C., Feng, X., Chu, H.-W., and Ho, T. C.: Estimating mercury emission outflow from East Asia using CMAQ-Hg, Atmos. Chem. Phys., 10, 1853–1864, http://dx.doi.org/10.5194/acp-10-1853-2010doi:10.5194/acp-10-1853-2010, 2010. Lin, X. and Tao, Y.: A numerical modelling study on regional mercury budget for eastern North America, Atmos. Chem. Phys., 3, 535–548, http://dx.doi.org/10.5194/acp-3-535-2003doi:10.5194/acp-3-535-2003, 2003. Lindberg, S. E. and Stratton, W. J.: Atmospheric mercury speciation: concentrations and behavior of reactive gaseous mercury in ambient air, Enviro. Sci. Technol., 32, 49–57, 1998. Liu, B., Keeler, G. J., Dvonch, J. T., Barres, J. A., Lynam, M. M., Marsik, F. J., and Morgan, J. T.: Temporal variability of mercury speciation in urban air, Atmos. Environ., 41, 1911–1923, 2007. Liu, B., Keeler, G. J., Dvonch, J. T., Barres, J. A., Lynam, M. M., Marsik, F. J., and Morgan, J. T.: Urban-rural differences in atmospheric mercury speciation, Atmos. Environ., 44, 2013–2023, 2010. Logan, J. A.: Ozone in rural areas of the United States. J. Geophys. Res., 94, 8511–8532, 1989. Lohman, K., Seigneur, C., Gustin, M., and Lindberg, S.: Sensitivity of the global atmospheric cycle of mercury to emissions, Appl. Geochem., 23, 454–466, 2008. Lu, J. Y., Schroeder, W. H., Barrie, L. A., Steffen, A., Welch, H. E., Martin, K., Lockhart, L., Hunt, R. V., Boila, G., and Richter, A.: Magnification of atmospheric mercury deposition to polar regions in springtime: the link to tropospheric ozone depletion chemistry, Geophys. Res. Lett., 28, 3219–3222, 2001. Lynam, M. M. and Keeler, G. J.: Artifacts associated with the measurement of particulate mercury in an urban environment: The influence of elevated ozone concentrations, Atmos. Environ., 39, 3081–3088, 2005. Lynam, M. M. and Keeler, G. J.: Source–receptor relationships for atmospheric mercury in urban Detroit, Michigan. Atmos. Environ., 40, 3144–3155, 2006. Lyman, S. N. and Gustin, M. S.: Speciation of atmospheric mercury at two sites in northern Nevada, USA,~Atmos. Environ., 42, 927–939, 2008. Lyman, S. N., Jaffe, D. A., and Gustin, M. S.: Release of mercury halides from KCl denuders in the presence of ozone, Atmos. Chem. Phys., 10, 8197–8204, http://dx.doi.org/10.5194/acp-10-8197-2010doi:10.5194/acp-10-8197-2010, 2010. Malcolm, E. G. and Keeler, G. J.: Evidence for a sampling artifact for particulate-phase mercury in the marine atmosphere, Atmos. Environ., 41, 3352–3359, 2007. Malcolm, E. G., Ford, A. C., Redding, T. A., Richardson, M. C., Strain, B. M., and Tetzner, S. W.: Experimental investigation of the scavenging of gaseous mercury by sea salt aerosol, J. Atmos. Chem., 63, 221–234, http://dx.doi.org/10.1007/s10874-010-9165-ydoi:10.1007/s10874-010-9165-y, 2009. Manolopoulos, H., Schauer, J. J., Purcell, M. D., Rudolph, T. M., Olson, M. L., Rodger, B., and Krabbenhoft, D. P.: Local and regional factors affecting atmospheric mercury speciation at a remote location, J. Environ. Eng. Sci., 6, 491–501, 2007. Masiol, M., Rampazzo, G., Ceccato, D., Squizzato, S., and Pavoni, B.: Characterization of PM$_10$ sources in a coastal area near Venice (Italy): An application of factor-cluster analysis, Chemosphere 80, 771–778, 2010. Mouli, P. C., Mohan, S. V., and Reddy, S. J.: Rainwater chemistry at a regional representative urban site: influence of terrestrial sources on ionic composition, Atmos. Environ., 39, 999–1008, 2005. National Air Pollution Surveillance data for 2005–2006 (NAPS), Environment Canada, Science and Technology Branch, 4905 Dufferin Street, Toronto, Ontario, Canada M3H 5T4, 2011. Obrist, D., Tas, E., Peleg, M., Matveev, V., Faïn, X., Asaf, D., and Luria, M.: Bromine-induced oxidation of mercury in the mid-latitude atmosphere, Nat. Geosci., 4, 22–26, http://dx.doi.org/10.1038/ngeo1018doi:10.1038/ngeo1018, 2011. Ontario Climate Centre data for 2005–2006, Environment Canada, Ontario Climate Centre, 4905 Dufferin Street, Toronto, Ontario, Canada M3H 5T4, 2010. Pallant, J.: SPSS Survival Manual, second ed. Open University Press, Berkshire, UK (Chapter 15), 2005. Peleg, M., Matveev, V., Tas, E., Luria, M., Valente, R. J., and Obrist, D.: Mercury depletion events in the troposphere in mid-latitudes at the Dead Sea, Israel, Environ. Sci. Technol., 41, 7280–7285, http://dx.doi.org/10.1021/es070320jdoi:10.1021/es070320j, 2007. Pervez, S., Balakrishna, G., and Tiwari, S.: Source apportionment of mercury in dust fallout at urban residential area of Central India, Atmos. Chem. Phys. Discuss., 9, 21915–21940, http://dx.doi.org/10.5194/acpd-9-21915-2009doi:10.5194/acpd-9-21915-2009, 2009. Pirrone, N., Cinnirella, S., Feng, X., Finkelman, R. B., Friedli, H. R., Leaner, J., Mason, R., Mukherjee, A. B., Stracher, G. B., Streets, D. G., and Telmer, K.: Global mercury emissions to the atmosphere from anthropogenic and natural sources, Atmos. Chem. Phys., 10, 5951–5964, http://dx.doi.org/10.5194/acp-10-5951-2010doi:10.5194/acp-10-5951-2010, 2010. Poissant, L., Pilote, M., Xu, X., and Zhang, H.: Atmospheric mercury speciation and deposition in the Bay St. François wetlands, J. Geophys. Res., 109, D11301, http://dx.doi.org/10.1029/2003JD004364doi:10.1029/2003JD004364, 2004. Poissant, L., Pilote, M., Beauvais, C., Constant, P., and Zhang, H. H.: A year of continuous measurements of three atmospheric mercury species (GEM, RGM and Hgp) in southern Quebec, Canada, Atmos. Environ., 39, 1275–1287, 2005. Pongprueksa, P., Lin, C.-J., Lindberg, S. E., Jang, C., Braverman, T., Bullock, O. R., Ho, T. C., and Chu, H.-W.: Scientific uncertainties in atmospheric mercury models III: Boundary and initial conditions, model grid resolution, and Hg(II) reduction mechanism, Atmos. Environ., 42, 1828–1845, 2008. Prendes, P., Andrade, J. M., López-Mahía, P., and Prada, D.: Source apportionment of inorganic ions in airborne urban particles from Coruña city (N.W. of Spain) using positive matrix factorization, Talanta, 49, 165–178, 1999. Rolph, G. D.: Real-time Environmental Applications and Display System (READY), Website, NOAA Air Resources Laboratory, Silver Spring, MD, available at: http://www.arl.noaa.gov/ready/hysplit4.html (last access: 20 February 2011), 2003. Rothenberg, S. E., McKee, L., Gilbreath, A., Yee, D., Connor, M., and Fu, X.: Evidence for short-range transport of atmospheric mercury to a rural, inland site, Atmos. Environ., 44, 1263–1273, 2010. R\'ua, A., Hernández, E., de las Parras, J., Martín, I., Gimeno, L.: Sources of SO<sub>2</sub>, SO$_4^2-$, NO<sub>x</sub>, and NO<sub>3</sub> in the air of four Spanish remote stations, J. Air Waste Manage., 48, 838–845, 1998. Rutter, A. P., Snyder, D. C., Stone, E. A., Schauer, J. J., Gonzalez-Abraham, R., Molina, L. T., Márquez, C., Cárdenas, B., and de Foy, B.: In situ measurements of speciated atmospheric mercury and the identification of source regions in the Mexico City Metropolitan Area, Atmos. Chem. Phys., 9, 207–220, http://dx.doi.org/10.5194/acp-9-207-2009doi:10.5194/acp-9-207-2009, 2009. Ryaboshapko, A., Bullock Jr., O. R., Christensen, J., Cohen, M., Dastoor, A., Ilyin, I., Petersen, G., Syrakov, D., Artz, R. S., Davignon, D., Draxler, R. R., and Munthe, J.: Intercomparison study of atmospheric mercury models: 1. Comparison of models with short-term measurements, Sci. Total. Environ., 376, 228–240, 2007. Scheifinger, H. and Kaiser, A.: Validation of trajectory statistical methods, Atmos. Environ., 41, 8846–8856, 2007. Schroeder, W. H. and Munthe, J.: Atmospheric mercury – an overview, Atmos. Environ., 32, 809–822, 1998. Seigneur, C. and Lohman, K.: Effect of bromine chemistry on the atmospheric mercury cycle, J. Geophys. Res., 113, D23309, http://dx.doi.org/10.1029/2008JD010262doi:10.1029/2008JD010262, 2008. Selin, N. E., Jacob, D. J., Park, R. J., Yantosca, R. M., Strode, S., Jaeglé, L., and Jaffe, D.: Chemical cycling and deposition of atmospheric mercury: Global constraints from observations, J. Geophys. Res., 112, D02308, http://dx.doi.org/10.1029/2006JD007450doi:10.1029/2006JD007450, 2007. Sigler, J. M., Mao, H., and Talbot, R.: Gaseous elemental and reactive mercury in Southern New Hampshire, Atmos. Chem. Phys., 9, 1929–1942, http://dx.doi.org/10.5194/acp-9-1929-2009doi:10.5194/acp-9-1929-2009, 2009. Sillman, S., Marsik, F. J., Al-Wali, K. I., Keeler, G. J., and Landis, M. S.: Reactive mercury in the troposphere: model formation and results for Florida, the northeastern United States, and the Atlantic Ocean, J. Geophys. Res., 112, D23305, http://dx.doi.org/10.1029/2006JD008227doi:10.1029/2006JD008227, 2007. Song, X., Cheng, I., and Lu, J.: Annual atmospheric mercury species in downtown Toronto, Canada, J. Environ. Monit., 11, 660–669, 2009. Sprovieri, F., Hedgecock, I. M., and Pirrone, N.: An investigation of the origins of reactive gaseous mercury in the Mediterranean marine boundary layer, Atmos. Chem. Phys., 10, 3985–3997, http://dx.doi.org/10.5194/acp-10-3985-2010doi:10.5194/acp-10-3985-2010, 2010a. Sprovieri, F., Pirrone, N., Ebinghaus, R., Kock, H., and Dommergue, A.: A review of worldwide atmospheric mercury measurements, Atmos. Chem. Phys., 10, 8245–8265, http://dx.doi.org/10.5194/acp-10-8245-2010doi:10.5194/acp-10-8245-2010, 2010b. StatSoft, Inc.: Electronic Statistics Textbook. Tulsa, OK, available at: http://www.statsoft.com/textbook/ (last access: 15 March 2011), 2011, (Printed Version): Hill, T. and Lewicki, P.: STATISTICS: Methods and Applications, StatSoft, Tulsa, OK, 2007. Steffen, A., Douglas, T., Amyot, M., Ariya, P., Aspmo, K., Berg, T., Bottenheim, J., Brooks, S., Cobbett, F., Dastoor, A., Dommergue, A., Ebinghaus, R., Ferrari, C., Gardfeldt, K., Goodsite, M. E., Lean, D., Poulain, A. J., Scherz, C., Skov, H., Sommar, J., and Temme, C.: A synthesis of atmospheric mercury depletion event chemistry in the atmosphere and snow, Atmos. Chem. Phys., 8, 1445–1482, http://dx.doi.org/10.5194/acp-8-1445-2008doi:10.5194/acp-8-1445-2008, 2008. Stohl, A.: Computation, accuracy and applications of trajectories – a review and bibliography, Atmos. Environ., 32, 947–966, 1998. Stohl, A., Eckhardt, S., Forster, C., James, P., Spichtinger, N., and Seibert, P.: A replacement for simple back trajectory calculations in the interpretation of atmospheric trace substance measurements, Atmos. Environ., 36, 4635–4648, 2002. Swartzendruber, P. C., Jaffe, D. A., Prestbo, E. M., Weiss-Penzias, P., Selin, N. E., Park, R., Jacob, D., Strode, S., and Jaeglé, L.: Observations of reactive gaseous mercury in the free-troposphere at the Mt. Bachelor observatory, J. Geophys. Res., 111, D24301, http://dx.doi.org/10.1029/2006JD007415doi:10.1029/2006JD007415, 2006. Talbot, R., Mao, H., Feddersen, D., Smith, M., Kim, S. Y., Sive, B., Haase, K., Ambrose, J., Zhou, Y., and Russo, R.: Comparison of Particulate Mercury Measured with Manual and Automated Methods, Atmosphere 2, 1–20, http://dx.doi.org/10.3390/atmos2010001doi:10.3390/atmos2010001, 2011. USEPA: Toxics Release Inventory Explorer, available at: http://www.epa.gov/triexplorer/facility.htm (last access: 15 December 2010), 2011. Valente, R. J., Shea, C., Humes, K. L., and Tanner, R. L.: Atmospheric mercury in the Great Smoky Mountains compared to regional and global levels, Atmos. Environ., 41, 1861–1873, 2007. Viana, M., Kuhlbusch, T. A. J., Querol, X., Alastuey, A., Harrison, R. M., Hopke, P. K., Winiwarter, W., Vallius, M., Szida, S., Prévôt, A. S. H., Hueglin, C., Bloemen, H., Wåhlin, P., Vecchi, R., Miranda, A. I., Kasper-Giebl, A., Maenhaut, W., and Hitzenberge, R.: Source apportionment of particulate matter in Europe: A review of methods and results, J. Aerosol Sci., 39, 827–849, 2008. Vijayaraghavan, K., Karamchandani, P., Seigneur, C., Balmori, R., and Chen, S.-Y.: Plume-in-grid modeling of atmospheric mercury, J. Geophys. Res., 113, D24305, http://dx.doi.org/10.1029/2008JD010580doi:10.1029/2008JD010580, 2008. Wang, H. and Shooter, D.: Water soluble ions of atmospheric aerosols in three New Zealand cities: seasonal changes and sources, Atmos. Environ., 35, 6031–6040, 2001. Wang, Y. Q., Zhang, X. Y., and Arimoto, R.: The contribution from distant dust sources to the atmospheric particulate matter loadings at XiAn, China during spring, Sci. Total. Environ., 368, 875–883, 2006. Watson, J. G., Chen, L. W. A., Chow, J. C., Doraiswamy, P., and Lowenthal, D. H.: Source Apportionment: Findings from the U.S. Supersites Program, J. Air Waste Manag. Assoc., 58, 265–288, http://dx.doi.org/10.3155/1047-3289.58.2.265doi:10.3155/1047-3289.58.2.265, 2008. Weiss-Penzias, P., Gustin, M. S., and Lyman, S. N.: Observations of speciated atmospheric mercury at three sites in Nevada: Evidence for a free tropospheric source of reactive gaseous mercury, J. Geophys. Res., 114, D14302, http://dx.doi.org/10.1029/2008JD011607doi:10.1029/2008JD011607, 2009. Xu, X. and Akhtar, U. S.: Identification of potential regional sources of atmospheric total gaseous mercury in Windsor, Ontario, Canada using hybrid receptor modeling, Atmos. Chem. Phys., 10, 7073–7083, http://dx.doi.org/10.5194/acp-10-7073-2010doi:10.5194/acp-10-7073-2010, 2010. Xu, X., Yang, X., Miller, D. R., Helble, J. J., and Carley, R. J.: A regional scale modeling study of atmospheric transport and transformation of mercury. I. Model development and evaluation, Atmos. Environ., 34, 4933–4944, 2000. Yatavelli, R. L. N., Fahrni, J. K., Kim, M., Crist, K. C., Vickers, C. D., Winter, S. E., and Connell, D. P.: Mercury, PM2.5 and gaseous co-pollutants in the Ohio River Valley region: Preliminary results from the Athens supersite, Atmos. Environ., 40, 6650–6665, 2006. Yoshimori, M.: Atmospheric Transport Inferred from Seasonal Variations in Cosmogenic Be-7 Concentrations, Proceedings of the 30th International Cosmic Ray Conference, Merida, Mexico, 3–11 July 2007, 224, 2007. Zhang, L., Vet, R., Wiebe, A., Mihele, C., Sukloff, B., Chan, E., Moran, M. D., and Iqbal, S.: Characterization of the size-segregated water-soluble inorganic ions at eight Canadian rural sites, Atmos. Chem. Phys., 8, 7133–7151, http://dx.doi.org/10.5194/acp-8-7133-2008doi:10.5194/acp-8-7133-2008, 2008. Zhang, L., Blanchard, P., Johnson, D., Dastoor, A., Ryzhkov, A., Lin, C.-J., Vijayaraghavan, K., Gay, D., Holsen, T. M., Huang, J., Graydon, J. A., St. Louis, V. L., Castro, M. S., Miller, E. K., Marsik, F., Lu, J., Poissant, L., Pilote, M., and Zhang, K. M.: Assessment of modelled mercury deposition over the Great Lakes region, Environ. Pollut., 161, 272–283, 2012.