Patterns of heavy metal concentration in core sediments, Wilgreen Lake, Madison County, Kentucky

Elevated levels of cadmium, copper, lead, and nickel were found within the waters of Wilgreen Lake during a preliminary survey in 2007. Accumulation of heavy metals in freshwater systems is a known problem. Heavy metals enter the lake in the dissolved phase or adsorbed onto sediment particles and may be linked to industries within the lake’s watershed. Under certain geochemical conditions such as anoxia, heavy metals may detach from sediment particles and diffuse into overlying lake waters, causing a renewed influx of heavy metals into the ecosystem. We hypothesize that heavy metals should decrease in concentration upcore as a result of improving industrial practices and strengthening of heavy-metal regulations over time. To test our hypothesis, we took 1-meter-long cores of lake sediment in each of the two major tributaries to see if metal concentrations changed with depth. We sub-sampled the core, freeze-dried the samples, and extracted metals from the sediments using hydrogen peroxide and trace-metal-grade nitric acid according to established Environmental Protection Agency (EPA) protocols. Samples were sent to Activation Laboratories and analyzed for a host of metals using ICP/OES. Most trace metals (Sb, As, Cd, Co, Ni, Se, Ag, Tl, Th) showed no patterns with core depth or between tributaries. However, lead increased markedly upcore at both sites, being more concentrated within Taylor Fork sediment by ~30%. We are investigating the possible effect of lithology on heavy metal concentration, in addition to identifying plausible heavy metal sources in each watershed

Patterns of heavy metal concentration in core sediments, Wilgreen Lake, Madison County

Accumulation of heavy metals in ecosystems is a known environmental problem, and several possible industry sources occur within the watershed of Wilgreen Lake, which is fed its two major tributaries, Taylor Fork and Old Town Branch. Elevated levels of cadmium, copper, lead, and nickel were found within the waters of Wilgreen Lake during a preliminary survey in 2007. A possible source of these contaminant occurrences is diffusion from lake sediments, which record past and present activities within their drainage basins. To obtain a history of anthropogenic practices within the drainage basin, we took 1-meter-long cores of lake sediment in each major tributary to see if metal concentrations changed with depth. The cores were taken from prominent levees that are relatively easy to sample and contain thick sediments with a good record of watershed history. We sub-sampled the core, freeze-dried the samples, and extracted metals from the sediments using hydrogen peroxide and trace-metal-grade nitric acid according to established U.S. Environmental Protection Agency (EPA) protocols. Samples were sent to Activation Laboratories and analyzed for a host of metals using ICP/OES. Most trace metals (Sb, As, Cd, Co, Se, Ag, Tl, Th) show no pattern with core depth or between the Taylor Fork and Old Town Branch coring sites. Moreover, there was no correlation between core lithology and heavy metal content for any of the measured metals. Antimony, cadmium, and thallium show concentrations at or just above the method blank (\u3c0.1 mg/L). Arsenic, cobalt, nickel, selenium, silver, thallium, and thorium show background concentrations of 5, 12, 17, 1.5, \u3c0.1, 1.5, and 6 mg/L, respectively. Chromium, copper, and nickel within the Taylor Fork core respectively increase 43%, 25% and 19% in the upper 10 to 30 cm of the core from deeper baseline values, perhaps due to diagenetic precipitation. Lead increases markedly downcore within Taylor Fork sediments peaking at ~ 53 mg/L, or about 40% above a background concentration of 23 mg/L observed at Old Town Branch. Copper increases slightly downcore with a higher background level at Taylor Fork (18 versus 12 mg/L). Taylor Fork sediments thus display more lead and copper, consistent with industrial sites existing within this tributary’s watershed. These elevated concentrations perhaps reflect industrial releases in the past

Patterns of Heavy Metal Concentration in Core Sediments, Wilgreen Lake, Madison County, Kentucky

Elevated levels of cadmium, copper, lead, and nickel were found within the waters of Wilgreen Lake during a preliminary survey in 20007. Accumulation of heavy metals in ecosystems is a known problem. Heavy metals enter the lake in the dissolved phase or adsorbed onto sediment particles and may be linked to industries within the lake watersheds. Under certain geochemical conditions such as anoxia, heavy metals may detach from sediment particles and diffuse into overlying lake waters, causing a renewed influx of heavy metals into the ecosystem. We hypothesize that heavy metals should decrease upcore as a result of improving industrial practices and strengthening of heavy-metal regulations over time. To test our hypothesis, we took 1-meter-long cores of lake sediment in each of the major tributaries to see if metal concentrations changed with depth. We sub-sampled the core, freeze-dried the samples, and extracted metals from the sediments using hydrogen peroxide and trace-metal-grade nitric acid according to established EPA protocols. Samples were sent to Activation Laboratories where they analyzed for a host of metals using ICP/OES. Most trace metals (Sb, As, Cd, Co, Ni, Se, Ag, Tl, Th) showed no patterns with core depth or between tributaries. However, lead increased markedly upcore at both sites with lead being more concentrated within Taylor Fork sediment by ~30%. We are investigating the possible effect of lithology on heavy metal concentration