PLUTONIUM IN THE GREAT LAKES 661 



1955 



1960 



1965 

 YEAR OF INPUT 



1970 



1975 



Fig. 2 Estimates of the annual deposition of 2 3 9,2 4op^j ^^^ ^j^jj ^^^ ^^^j. Lake 

 Michigan on the basis of monitoring ^°Sr in rainwater at Aigonne, III., and Green Bay, 

 Wis., the average rainfall, and the monitoring of 2 3 9,2 4npjj ^J^ atmospheric fallout at 

 Argonne. 



TABLE 1 Inventory of Plutonium 

 in the Great Lakes as of 1977 



*The amount stored in the sediments is greater than that 

 deposited on the lake surface because of the ^"Pu exported 

 from Lake Erie down the Niagara River. 



The purpose of this chapter is to describe mainly the biogeochemical and physical 

 processes that appear to determine the behavior of plutonium and other transuranic 

 elements in the Great Lakes. The roles of recent atmospheric and watershed erosion 

 inputs, sedimentation and resuspension, and export by outflow as controls of the longer 

 term availability of plutonium are discussed. Rapid sedimentation from the epilimnion by 

 association with autochthonous particulate material is shown to account for the seasonal 

 cycling of plutonium in Lake Michigan. The methods for measuring the transuranic 

 elements in the lakes have been adequately described elsewhere (Golchert and Sedlet, 

 1972; Nelson etal., 1974; Wahlgren et al.. 1976). 



