Determination of Diffusion Coefficients in Sandy Sediments Using Resistivity Techniques

Diffusion coefficients at the sediment-water interface are essential for prediction of flux rates across the interface. For calculating bulk sediments diffusion coefficients from free solution diffusion coefficients, Formation factor, F, can be estimated from Phi, porosity of sediments. To determine formation factor, resistivity of pore water and sandy sediments with different diameter, originated from Qingdao´s seashore, were measured by using a modified Miller Soil Box, then the exponent, m, of Archie formula was obtained through curve fit. The results indicate that using the empirical m (for Phi les 0.7, m = 2) given by Ullman and Aller to calculate bulk diffusion coefficient may introduce 40%~50% error; the relationship between F and Phi can be expressed as F = Phi^-1.52 for nearshore sandy sediments; substitution of m = 1.52 into D_s = D₀ldrPhi^m-1 is verified to be suited for calculating bulk diffusion coefficient in sandy sediments.