Studies of plutonium cycling and sedimentation in Lake Michigan
Estimates of cumulative deposition, together with the results of extensive lakewide sampling in 1972, yielded estimates of mean halftimes for removal from the water column of Lake Michigan of 1.0 +- 0.3 yr for $sup 239$ $sup 240$Pu, and 1.4 +- 0.3 yr for $sup 137$Cs. However, data from 1971, 1972 and 1973 water samples indicate that the recent half-time is much greater than the 1963-1972 average, presently being on the order of 3 to 4 yrs for both $sup 239$Pu and $sup 137$Cs. The longer turnover time is consistent with the $sup 137$Cs turnover time in the water column deduced from analysis of preserved Lake Michigan alewives. Water filtration experiments have demonstrated that greater than or equal to 75 percent of the plutonium is nonfilterable and is present as colloid or sub-colloidal sized fractions. At an offshore station near Grand Haven, Michigan, the concentration of $sup 137$Cs in the epilimnion underwent a slight but significant decline from June to November, whereas $sup 239$Pu was reduced to a small fraction of its spring value. In net plankton samples dominated by phytoplankton a much lower mean $sup 137$Cs:$sup 239$Pu ratio is observed than in water samples, indicating a preferential sorption of $sup 239$Pu over $sup 137$Cs by phytoplankton. The results of these experiments suggest that sorption by phytoplankton (and the subsequent rapid settling from the epilimnion of phytodetritus and/or zooplankton fecal pellets) is responsible for the rapid removal of $sup 239$Pu from the epilimnion. (auth)
- Research Organization:
- Argonne National Lab., IL
- NSA Number:
- NSA-33-025979
- OSTI ID:
- 4025748
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
*LAKE MICHIGAN-- RADIATION MONITORING
*PLUTONIUM 239-- DIFFUSION
*PLUTONIUM 240-- DIFFUSION
520300* --Environmental Sciences
Aquatic--Radioactive Materials Monitoring & Transport
ENVIRONMENT
FISHES
N44300* --Environmental & Earth Sciences--Radioactivity Monitoring & Transport
PLANKTON
RADIOACTIVITY
RADIOECOLOGICAL CONCENTRATION
RADIONUCLIDE KINETICS
RADIONUCLIDE MIGRATION
SAMPLING
SEDIMENTS
SURFACE WATERS
TIME DEPENDENCE