Trace metals in Florida lake sediments

Despite substantial research on metals in the environment, there remain uncertainties concerning trace metal pollution and associated human health concerns. Although metal pollution is found world-wide, impacts are often site-specific. I investigated the input, fate and transport of trace metals in north Florida lake sediments.;To accurately quantify anthropogenic impacts on trace metal inputs to lakes, it is necessary to estimate background or pre-anthropogenic inputs. Sediment cores from Florida Lakes Sheelar, Pebble, and Little Johnson were dated using 210Pb and analyzed for trace metals. Metals V, Cr, Ni, Cu, Zn, Sn, Sb, Bi, and Pb show up-core enrichment beginning ∼1900, coinciding with the onset of population growth and development in Florida. Trace metal concentrations measured in these lake sediments provide a baseline (reference) record of pre-anthropogenic metal accumulation and a record of modern, anthropogenically influenced metal deposition this area.;Lake sediments are typically sinks for trace metals, if the deposits remain undisturbed and permanently buried. Future climate change scenarios suggest increased duration and frequency of dry events, which may cause stage declines in shallow Florida lakes and lead to physical and/or chemical redistribution of legacy metal pollution. I examined the impact of low water levels on metal transport in lake sediments by measuring metal concentrations along transects of lake sediment exposed following extreme lake level declines in 2012. From the historic lake shore to the center of the lake trace metal concentrations increased up to 3 times. The main mechanism for metal dispersal during low lake levels was focusing of fine-grain material and organic matter toward the lake center. The main source of Pb in these exposed lake sediments was anthropogenic, largely from automobile gas additives, and was associated with a relatively mobile sediment fraction. Finally, I assessed the preservation of trace metal stratigraphy in lake sediments after dry periods. Using metal concentrations and Pb isotope ratios from repeat cores in two shallow lakes, taken before and after low water levels, I determined that the record of metal accumulation is preserved stratigraphically.;Metal concentrations in Florida lake sediments have increased over the last century. Climate change scenarios predict more intense rainy periods, alternating with more severe droughts. The combined effects of changing hydrology and relic metal pollution may create future management concerns, including legacy metal pollution in sediments and water, as well as the potential for increased metal-laden dust.