TH-228 RADIOACTIVE RA-228 RADIOACTIVE DISEQUILIBRIUM IN THE NEW-YORK BIGHT AND ITS IMPLICATIONS FOR COASTAL POLLUTION
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abstract
In the summer of 1975, the half removal time of 228Th by settling particles, tc, was about 11 4, 29 8 and 70 10 days in the shelf surface water, the shelf winter water and the slope surface water of the New York Bight, respectively. In the fall of 1974, tc was about 17 1 to 28 2 days from the inner shelf to the outer shelf surface waters and about 70 10 days in the slope surface water. A simple box model of the shelf water in the Middle Atlantic Bight shows that (1) the exchange rate between the shelf and the slope waters is about 2500 800 km3/yr, (2) the mean residence time of the shelf water is only about 132 36 days, and (3) the average 226Ra and 228Ra fluxes per unit area of the coastal sediments are about 0.05 dpm 226Ra/cm2 yr and 0.37 dpm 228Ra/cm2 yr. These rates are consistent with previously reported results. The implication of these rates to pollutants in the coastal environment is discussed. 1979.
