A Study of Metal Accumulation Trends in Sediment Cores from the Turkey Lakes (Algoma, Ontario)
Temporal (vertical) and spatial trends in sediment accumulations of nonresidual aluminum, manganese, lead, zinc, copper, and nickel were investigated in 18 core samples collected from four of the Turkey Lakes in 1980–81. Accumulation rates of nonresidual Al differed among sampling sites, both within and among lakes, but was assumed to have been temporally constant at each location. Concentrations of dry matter and all other metals were expressed as mass per unit mass of Al. Cumulative Al was used as an index of time. Since Mn enrichments near the sediment surface may reflect an oxidation zone, they were not interpreted as increased Mn inputs. Other metal enrichments were considered anthropogenic. Little Pb occurred at the bottom of sediment cores, but Pb accumulation rates increased greatly towards the sediment surface. Major Pb enrichments were assumed to have begun at 1940. Zn accumulation rates had also progressively increased through most of the previous four decades. During the same period, there was a modest rise in Cu and Ni accumulation rates. Metal accumulation rates differed considerably among lakes, and among sites within lakes, but these differences primarily reflected variations in dry matter sedimentation rates.