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A method for estimation of historic contaminant loads using dated sediment cores
Citation:
Rossmann, R., E. Pfeiffer, J. Filkins, AND R. Kreis. A method for estimation of historic contaminant loads using dated sediment cores. IAGLR Conference, Burlington, VT, May 25 - 29, 2015.
Impact/Purpose:
not applicable
Description:
Dated sediment cores were used to assess the history of contaminant loads. The contaminant selected must be one that is not significantly remobilized by post depositional processes such as diagenesis. In addition, the core must be from an area with a high deposition rate and little sediment reworking by biota or wave action to provide a highly resolved profile. Finally there must be an independent estimate of the load to the lake that can be used to calibrate the profile. These criteria were met for Lake Michigan during the 1994 to 1996 Lake Michigan Mass Balance Project. Box cores from 54 stations collected between 1994 and 1996 were used to estimate both historic lead and mercury loads to Lake Michigan. 186 and 143,000 t of anthropogenic mercury and lead are stored in the lake's sediments, respectively. A core was calibrated to represent the entire load of each metal to the lake. The annual load for each dated interval of the core was then calculated. Anthropogenic mercury and lead loads for 1994 were 973 kg/y and 1170 t/y, respectively. Mercury and lead loads were last this low in 1892 and 1920, respectively. Anthropogenic loads for mercury and lead first appeared in 1858 and 1852 and peaked in 1946 and 1960, respectively.