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Lake Michigan sediment lead storage and history of loads
Citation:
Rossmann, R., E. Pfeiffer, AND J. Filkins. Lake Michigan sediment lead storage and history of loads. JOURNAL OF GREAT LAKES RESEARCH. International Association for Great Lakes Research, Ann Arbor, MI, 40:851-858, (2014).
Impact/Purpose:
Lead is known to have neural effects on both children and adults. In response to this, the use of leaded gasoline was phased out beginning in the 1970s. Where historic measurements are lacking, lead-210 dated sediment cores is one way to document changes in lead loads to the environment and associate those changes with economic, political, and regulatory changes. Sediment box cores from 52 stations in Lake Michigan were dated at NOAA in Ann Arbor, MI and analyzed for lead at USEPA in Grosse Ile, MI. Careful interpretation of the cores has resulted in an estimate of lead storage in the lake’s sediment and description of the changes of lead loads to the lake with time. Between 1850 and 1995, storage of anthropogenic and total lead in the lakes sediments were 143,000 and 171,000 metric tons, respectively. Prior to 1850, loads were at pre-settlement values (219 metric tons/year). After 1850, lead loads associated with anthropogenic sources began to increase. Loads peaked between 1959 and 1962 at 2,440 metric tons/year and declined to 1,170 metric tons during the 1994 to 1995 period of sample collection. Largest lead loads were to southeastern Lake Michigan in a region downwind of Chicago, illustrating the impact of large populated areas utilizing coal and gasoline on lead loads to the lake. Loading trends were impacted by coal consumption, gasoline consumption, increased industrial activity during World War II, the Clean Air Act of 1970, and the phase out of leaded gasoline.
Description:
Dated sediment box cores collected in 1994-1996 from 52 locations in Lake Michigan were analyzed for to access storage, trends, and loading history of lead. The results of this study provide information of historic lead loads to the lake for a time period for which no other information exists. The information can be utilized by those wishing to model lead and to access lead loading trends. Anthropogenic lead storage in the lake’s sediments totaled 143,000 metric tons as of 1994. Storage of acid-extractable total (anthropogenic + background) lead totaled 171,000 metric tons between 1850 and 1994. The date of 1850 is the time at which lead fluxes increased above background loads (219 metric tons/y) to the lake. Anthropogenic loads peaked between 1959 and 1962 at 2,440 metric tons/y and were 1,170 metric tons/y between 1994 and 1995, illustrating that at the time of collection in 1994, loads were decreasing from previous highs. The load in 1994 to 1995 was equivalent to the load during the time frame of 1922 to 1925. Largest lead loads were to southeastern Lake Michigan in a region downwind of Chicago, illustrating the impact of large populated areas utilizing coal and gasoline on lead loads to the lake. Loading trends were impacted by coal consumption, gasoline consumption, increased industrial activity during World War II, the Clean Air Act of 1970, and the phase out of leaded gasoline.
