210Pb_Lake_sedimentation - 210 Pb 137 Cs and Metal Analysis...

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Two sediment cores have been extracted from southern Lake Michigan and have been analyze by radioisotopes and metals. 210 Pb and 137 Cs were used to radio date the sediments core sections for the last ~200 years and these sections were subsequently analyzed for 12 standard metals. The core and the deduced sedimentation rate are consistent with primarily aerosol deposition, with some non­ aerosol contribution evident on one core. The historical profile clearly shows the onset of industrialization around the southern Lake Michigan basin, with the dramatic increase in the concentration of anthropogenic metals. There is an obvious change in the metal deposition rate after air pollution regulations were enacted in the 1970’s. The presence of coincident layers of manganese and arsenic near the surface of the sediment suggests an active zone for manganese diagenesis. 210 Pb, 137 Cs, and Metal Analysis of Two Lake Michigan Sediment Cores Carolina Contreras 1 , Christopher W. Avery 1 , Paul A DeYoung 2 , Natalie L. Hoogeveen 1 , Utsab Khadka 2 , Graham F. Peaslee 1 , Richard R. Rediske 3 1 Chemistry Department and 2 Physics Department, Hope College, Holland, MI 49424 3 Annis Water Resources Institute, Grand Valley State University, Muskegon, MI 49441
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Lake and oceans sediments have often been used to reconstruct a historical profile of the anthropogenic pollutants. The Great Lakes have been a subject of many sediment studies over the past 35 years because their size allows for the significant capture of atmospheric pollutants, which then become part of the sedimentary record. The southern Lake Michigan basin is no exception, and the industrialization of the Chicago/Gary area has been observed and even quantified using historical profile of lake sediment cores several times. 210 Pb­dating is a particular useful tool in this endeavor because its half­life of 22.3 years permits dating over the period of peak human industrial activity around the Great Lakes if the sediment core displays five or more 210 Pb half­lives.
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210Pb_Lake_sedimentation - 210 Pb 137 Cs and Metal Analysis...

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