Calcium Content of the Western Basin of Lake Erie

Water samples from the western basin of Lake Erie were filtered to restrain suspended particles larger than 4 /xm and were analyzed for copper, iron, zinc, manganese, magnesium, and calcium by atomic absorption spectrophotometry. Samples were collected at weekly intervals during July-August and with less frequency in September, October and November (1970). Mean seasonal and range of concentrations for elements considered did not vary with depth. Mean seasonal and range of concentrations for soluble elements from 4.5 m depth were (/xg/ml): copper, 0.091 (0.04-0.20); iron, 0.284 (0.06-0.050); zinc, 0.087 (0.000.11); manganese, 0.039 (0.025-0.003); magnesium, 10.38 (6.54-13.54); and calcium, 35.78 (30.30-43.60). Solvent extracted elements from suspended particulates were present in mean seasonal and range of concentrations (/ug/ml) for copper, 0.014 (0.003-0.038); iron, 0.550 (0.30-1.00); and zinc, 0.050 (0.020-0.150). Manganese content was below detectable limits, while magnesium and calcium were non-extractable. Except for calcium, the mean seasonal concentration varied for elements considered from those reported previously for either Lake Erie or for the western basin. A close association existed between the levels of soluble and particulate copper, iron and zinc. Concentrations of copper, iron, zinc, manganese, magnesium and calcium were measured by atomic absorption spectrophotometry in water samples removed and filtered (0.45 fim pore size) from an area in the western basin of Lake Erie. The area was located between Rattlesnake, Middle, and South Bass islands (approximately 83°50 W; 41°40 N). Element content was determined on water samples taken from 0, 4.5, and 9.0 m depths. Values for calcium concentrations of Lake Erie date back to 1854 (Ayers 1962) and for calcium and magnesium concentrations to 1906-1907 (Beeton 1965). The conclusions reached by Beeton (1965) from available data spanning the years 1906 to 1959 were that calcium increased in concentration from 31 to 39 fig/ml with eutrophication while magnesium was unaffected (9.0 fig/ml). The only values observed in the literature on trace metals copper, manganese and zinc concentrations of Lake Erie were those of Weiler and Chawla (1968). However, this latter work was concerned with water taken from a single depth and assayed for elements without any distinction between soluble and particulates suspended in it. It was our contention that suspended particulates would contribute to increased or decreased values of trace elements in Lake Erie. Hence, eutrophication would be associated with increases in particulates which, in turn, would influence the concentrations of trace metals at the time of analysis.