Anthropogenic Zinc and Cadmium Burdens in Sediments of Selected Southern Ontario Lakes
The concentrations of Cd and Zn were measured in the sediments of 10 softwater lakes in southern Ontario. Elevated Cd and Zn levels were present in the recently deposited sediments of all the lakes, despite the absence of local point-source inputs. Whole-lake anthropogenic Zn and Cd burdens, calculated by prorating site-specific burdens according to the ratio of the site-specific Pb burden to the whole-lake Pb burden, range between 322 and 617 mg.m-2for Zn and between 6.2 and 11.3 mg.m-2for Cd. There were no significant differences in anthropogenic Zn or Cd burdens between lakes. The lack of a relationship between Zn or Cd burdens and the ratio of watershed area to lake area or the water replenishment time of the lakes indicates that deposition from the atmosphere directly onto the lakes' surfaces is an important input of these metals to the lakes.