Spatial Dry Deposition of Reactive Gaseous Mercury in West Central Alberta
University of Alberta,
School of Public Health,
Edmonton, Alberta CAN
Four coal-fired power plants are situated about 60 km from Edmonton in west central Alberta. Collectively, these plants have the capacity to generate a total of 4,277 megawatts to Alberta’s electrical grid. A passive sampling approach developed by Frontier GeoSciences Inc. is being used to obtain weekly or bi-weekly measurements of reactive gaseous mercury (RGM) in an effort to understand the role of local mercury emissions and atmospheric deposition within the regional area. Cation-exchange membranes are deployed as surrogate surfaces for measurement of RGM deposition at six locations using the same schedule as the NADP Mercury Deposition Network. One of the locations is a Mercury Deposition Network site.
The sampling locations were selected based upon regional modeling of atmospheric mercury deposition in response to proposed expansions at two of the plants. Two sampling locations are within 5 to 10 km of the plants representing inferred high deposition loading. Another two locations are within 25 to 35 km of the plants representing inferred intermediate deposition loading. Finally, two sampling locations are within 20 to 35 km of the plants representing inferred low deposition loading.
The cation-exchange membranes are deployed on Frontier Geosciences Inc. specially-designed polyurethane aerodynamic sampling heads in a face down position. Mercury adsorbed to the membranes is extracted by Frontier GeoSciences Inc. using 100 mL of 10% 2N bromine monochloride and analyzed using US EPA Method 1631. Field sampling techniques and measured dry deposition rates for a nine-month period (April through December 2007) will be presented and discussed.