A MULTIPLE APPROACH TO THE DETERMINATION OF RADON FLUXES FROM SEDIMENTS

Determination of sedimentary fluxes of Rn-222 via diffusion was requir ed as an input for a mass balance model of radon in a freshwater lake. We obtained these fluxes by: (1) direct measurement in the laboratory using a simulated sediment bed and water column; (2) a ''sediment equ ilibration'' technique; and (3) porewater modeling. The first method, analogous to an in situ benthic chamber approach, uses direct observat ion of the increasing Rn-222 activity in water overlying a sediment be d packed in plastic columns. This allows one to directly measure the f luxes and determine the effective wet bulk sediment diffusion coeffici ent (D-s). Radon flux estimates using these three techniques agreed to within approximately 10-15%.