Document Type

Article

Department/Program

Virginia Institute of Marine Science

Publication Date

1986

Journal

JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS

Volume

91

First Page

896

Last Page

908

Abstract

The atmospheric flux of cosmogenic Be-7 (53.3-day half-life) and the mode of ?Be deposition in river- estuarine and coastal environments have been examined. The atmospheric flux of ?Be commonly sup- ports inventories ranging from 1.0 to 2.0 pCi/cm 2 (1 pCi = 0.037 Bq). Beryllium 7 concentrations in water phase samples, collected across salinity gradients in several estuaries along the eastern coastline of the United States, range from 0.03 to 0.53 pCi/L and primarily reflect variations in Be-7supply and sorption kinetics. The major process controlling the concentration of Be-7 on estuarine suspended particles appears to be the length of time that these particles remain in the water column. Field particle-to- water distribution coefficients for Be-7have a median value of about 4 x 10 '• but range over an order of magnitude reflecting short-term variations in 7Be input, particle dynamics, and particulate iron content rather than equilibrium sorption-desorption responses to changes in water salinity or particle type. Residence times of 7Be in the water column range from a few days in estuarine areas of rapid fine-particle deposition, to several weeks in high-energy environments where pronounced sediment resuspension reintroduces deposited 7Be back into the water column. Inventories of ?Be in sediments range-from nondetectable to 3.3 pCi/cm 2, with the highest inventories in areas where fine particles are accumulating rapidly. Such sites are also major repositories for other particle-reactive substances. A ?Be budget for the James estuary indicates that less than 5% of the expected ?Be input is in the water column and that the short-term estuarine trapping efficiency for atmospherically derived ?Be is somewhere between 50 and 100%.

DOI

10.1029/JC091iC01p00896

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