Solid-water partitioning of elements in Czech freshwaters

Partitioning of 41 elements between solids and water was studied by filtration and dialysis in situ in Czech freshwaters. Field-based distribution (partition) coefficients, K-D, between suspended particulate matter (SPM) and filtrate ('dissolved' fraction) differed by 4 orders of magnitude. The highest K-D values (log K-D > 2.0 l/g) were exhibited by Zr, Al, Ce, Pb, La, Ti, Fe, Sm, Th and Cr which are extremely insoluble in near-neutral water or generally poorly soluble (Zr,Ti). The K(D)s decrease with element and DOC loading due to the relative increase of the element in the low molecular fraction. Log K-D mostly increased linearly with pH within a range from 3.5 to 9. K-D(U) decreased at pH >6 due to carbonate complexation. The colloidal fraction (> 1 kDa < 0.4 <mu>m) in a reservoir with a pH of 6.8 was mainly preferred by Fe, Pb, Be, Nb, Y, Al, Ni, U and Zr. When the colloidal fraction is not differentiated from true solution, then incorrect information about partitioning may be obtained and the highest K-D may decrease. (C) 2001 Elsevier Science Ltd. All rights reserved.