A review of the moss-monitoring survey around the Trail smelter, British Columbia

The distribution of aerially deposited metals, As, Cd, Cu, Hg, Pb and Zn, was studied using passive collection moss monitoring in the vicinity of the smelter in Trail, British Columbia, Canada. The concentrations of metals/metalloids were measured in moss bags exposed to atmospheric deposition for periods of three months. The results show the greatest deposition of metals proximal to the smelter, and a decrease in deposition with increasing distance from the smelter. The pattern of deposition varies with the season, the element under study, and the location of the monitoring station. The depositional pattern around the Trail smelter is controlled mainly by the physiography of the region as related to shape and orientation of the Columbia river valley and direction of the prevailing wind. The results show that the annual aerial deposition of metals is directly related to the quantity of stack-emitted metals and Pb-Zn production levels. The distribution of Pb, Zn and Cd in surface soils around the Trail smelter shows a similar pattern to their deposition at moss-monitoring stations. These soils are characterized by an elevated concentration of metals in the proximity of the smelter, indicating the effect of airborne materials on the geochemistry of the soils in the study area. Such similarity was not found for Hg, Cu and As, indicating that the variation of these elements in soil samples is more likely related to soil chemistry rather than to atmospheric deposition.