Nutrient and Metal Contents Recored In Griffy Lake, Bloomimngton, In

Nutrient and metal concentrations in the sediments of Griffy Lake, Bloomington, IN are of interest for the lake used for recreation and as part of the Indiana University Research and Teaching Preserve. Sediment cores and grab samples were collected in early spring and late summer from the lake, wetland and three feeder creeks. Weight percents of total C_org and P_org, and total N were determined by elemental analysis and Pb, Zn and Cu contents were determined by X-ray fluorescence. Sedimentation rates, determined by Cs-137 and Pb-210, are greatest near the inflow into the lake at 7.95mm/yr and decreases to 3.75mm/yr near the dam. The data show C_org represents the bulk of the total C in the system with values ranging from 0.2 -3% in the lake cores and .06-6% in stream grab samples. The N values ranged from 0.05-0.25% in the cores and 0.05-.45% in grab samples and P_org from 325 to 490μg/L. Metals in the watershed are derived from remnants of industrial spoils piles. Concentrations of Pb in the sediments correlate well with the C_org, while the Zn and Cu correlate well with the clay content in the sediments. Overall, the data suggest that the rate of sediment and nutrient loading into Griffy Reservoir sediments has remained fairly constant over the past 80 years and the streams and wetlands above the lake provide an adequate metals filter in all but the most extreme sediment flooding events that bypass the wetland.