BAI ZHANGUO;WAN GUOJIANG;WANG CHANGSHENG;WAN XI;HUANG RONGGUI

erosion trace;geochemical speciation;radionuclides;soils

A brunisolic soil collected from an erosive forest land (HF-1-1) and a yellow soil from an accumulative shallow basin (HF-6-1) in the watershed of Lake Hongfeng (HF) were used for activity measurements of ~7Be, ~(137)Cs, ~(226)Ra and ~(228)Ra in different geochemical speciation. More than 85% of ~7Be, ~(137)Cs, ~(226)Ra and ~(228)Ra in the soils were bound to organic, Fe-Mn oxy-hydroxide and residual fractions. They could move with soil particles and be used as tracers for the erosion and/or accumulation of soil particles. ~7Be geochemical speciation in the soils agreed with its trace for seasonal particle transport. ~(137)Cs geochemical speciation was suitable for tracing soil particle accumulation and for sediment dating. ~(226)Ra and ~(228)Ra were combined in crystalline skeleton of clay minerals and mainly remained as residues in the soils and little was bound to the soluble, exchangeable and carbonate fractions. The differentiation of ~(226)Ra/~(228)Ra activity ratios in different geochemical fractions in the soils could be used as a parameter to trace accumulation and /or erosion of soil particles.