METAL POLLUTION IN LAKE SEDIMENT IN SOUTHWEST OHIO

Metal pollution impacts global ecosystems and potentially human health through fish and water fowl consumption as well as atmospheric exposure. Ohio has high concentrations of pollution coming from industrial and agricultural activities. This investigation is the first detailed survey of metal pollution in lakes of southwest Ohio utilizing inductively coupled plasma- mass spectroscopy (ICP-MS), electron microscopy and X-ray diffraction. A total of 46 samples from the upper 2 cm of sediments from 12 lakes were investigated. Samples are dominated by a mineralogy of illite, chlorite, quartz and calcite. The chemical index of alteration values indicate moderate weathering. Combined the bulk major element chemistry and mineralogy suggest a typical geologic source for the sediment.

For the majority of samples concentrations of Cu, Zn, V, Sn, Co, Sb, and As were higher than that of the geological background. Some correlations between metals such as Cu and Zn, Co and Sn, Cr and Sn were observed suggesting multiple sources of pollution. The electron microscopy indicates coal combustion particulate pollution such as micrometer-scale spherules and barite occur in some samples. Nickel rich-particles were also observed. Limited scanning transmission electron microscopy – energy dispersive spectroscopy mapping at the nanoscale indicates that nickel is dispersed on illite particles. The absence of abundant particulate suggests that the pollutants are adsorbed by the mineral fraction and very dispersed throughout the clay surface.

No correlation is observed between pollutant metal concentrations and land use designated as agricultural, forested and urban or carbon, nitrogen and phosphorous and sedimentation rate parameters. This suggests that the rate of the atmospheric deposition of pollution is much greater than the pollution coming from urban particulate in overland flow for these lakes. The major source of pollution is interpreted to be from atmospheric sources such as traffic emissions and coal combustion. Coupling electron microscopy and bulk chemical analysis enables source interpretation. This investigation illustrates unrecognized complexity in metal pollution in southwest Ohio and demonstrates the fate and transport of atmospheric metal pollution into lake systems.