RECORDS OF TRACE METAL DEPOSITION DURING THE 19TH AND 20TH CENTURIES IN THREE LAKES IN EASTERN NY STATE

Downcore profiles of exchangeable metals in lake sediments can record local and regional sources of anthropogenic pollutants. We chose three lakes in eastern NY State that are in different geographic settings to differentiate among local and regional sources. Collins Pond is an ox-bow lake on the Mohawk River floodplain near the industrial center of Schenectady, NY. Ballston Lake is a long and narrow lake that occupies a portion of an avulsed channel of the Mohawk River, and is surrounded by numerous houses and roads. In contrast, Long Pond is the most remote of the three lakes and has been the least impacted by recent human activities. Eight sediment cores were obtained from the deepest basin of each of the lakes. The cores were sampled every 2-4 cm. Samples were dried and crushed, and 10 ml of high purity HNO3 acid was added to 100 mg of dry sample. Samples were analyzed using ICP-mass spectrometry for the elements: Cu, Cr, Cd, V, Fe, Ni, Co, Zn, Pd, Sr, Ba, Mn, U, and Al. We determined organic carbon content by coulometry. In all cores, trends in Cd, Pb, Co, Zn and Cr illustrate similar patterns. From the base of cores upward, an initial rise in these elements is followed by a subsequent decline, however the initial rise in these metals occurs at different depths in each of the lakes. The initial increase in Pb, for example, occurs at a depth of 20 cm in Long Pond, 100 cm in Ballston Lake, and 150 cm in Collins Pond. Rates of metal accumulation in Ballston Lake and Collins Pond are 4-7 times higher than those at Long Pond. Twentieth century trends in organic carbon content are not consistent among the three lake basins. Whereas Collins Pond reveals increasing organic C concentrations, Long Pond demonstrates declining levels and Ballston Lake shows no trend through the 20th century. This inconsistency likely reflects the competing influence of lake eutrophication and landscape erosion on sediment carbon levels.