Abstract

The atmospheric deposition and regional dispersion pattern of the elements As, Cd, Cu, Hg, Pb and Zn, emitted from Pb-Zn smelters at Trail, British Columbia, Canada, were studied for a period of two years using the passive collection moss-monitoring method. Concentrations of these elements in moss bags, exposed to atmospheric deposition for three months, were first corrected for geogenic input and then site-specific local background level to produce common background elemental concentrations for all monitoring stations. The results of this study indicate that the deposition of these elements is greatest in proximity to the smelter and decreases with an increase in distance. The regional dispersion pattern generally varies seasonally, with the magnitude of variation being dependent on the element under study and the location of the monitoring station. Overall, the deposition of these elements (as registered by moss-monitoring stations) appears to be a complex phenomenon involving various factors such as meteorological conditions (prevailing wind direction and precipitation), physiography (topography, valley shape and orientation) and in-process activities at the smelters (production level, emission control efficiency and the geochemistry of feed). However, the results of this study indicate that, on an annual basis, in-process activities, particularly production levels of Pb and Zn and the quantity of emissions from the stack, are more directly related to the observed deposition of the elements than any of the other factors.