The distribution and transformation of added and native Ni in purple soils were investigated with both sequential extraction procedure and isotopic tracer technique.The distribution of added and native Ni was greatly ...The distribution and transformation of added and native Ni in purple soils were investigated with both sequential extraction procedure and isotopic tracer technique.The distribution of added and native Ni was greatly dependent on soil properties.Low soil PH was favorable for soluble plus exchangeable (EX) Fraction,while Fe/Mn oxides and clay for Fe/Mn oxide bound (OX) and residual (RES) fractions. The added Ni,however,has not yet reached the distribution equilibrium up to the 150th day after incubation.This was reflected in the fact that the proportion of EX fraction from added Ni was 150%-600% as much as that of native Ni, while that of RES fraction was only about 80%.Once entering soil, the applied soluble Ni was rapidly transformed into Other fractions, but the organic complexed (OM) fraction of added Ni was relatively stable during incubation.The carbonate bound(CAB) fraction showed a progressive increase and attained a peak value after 0-14 d of incubation and thereafter decreased gradually. The occurrence time of this peak advanced as initial soil PH increased, but the peak would disappear when initial soil pH was higher than 7.5(or containing free CaCO3). The transformation processes of the EX,OX and RES fractions could be described by Elovich and two-constant rate equstions,and the rates were positively correlated with soil pH,CEC and clay.These findings could explain why there are differences in ecological and environmental effects of Ni in different soils and at various intervals.展开更多
Co, Ni, Cr and V in 25 typical soils of China were fractionated into exchangeable, carbonate bound (calcareous soils), Mn oxide bound, organically bound, amorphous Fe oxide bound, crystalline Fe oxide bound and residu...Co, Ni, Cr and V in 25 typical soils of China were fractionated into exchangeable, carbonate bound (calcareous soils), Mn oxide bound, organically bound, amorphous Fe oxide bound, crystalline Fe oxide bound and residual forms using a seven-step sequential extraction procedure, so as to study the distribution of chemical forms of these metals as well as the effects of soil properties on the distribution. The results showed that most of soil Co, Ni, Cr and V were present in residual forms, and the distribution ratio averaged 48.2% for Co, 53.0% for Ni, 81.5% for Cr and 68.7% for V. The speciation of heavy metals was greatly influenced by soil physico-chemical properties and the chemistry of elements. The results also indicated that the recovery of metal elements by the sequential extraction procedure was satisfactory, with the relative difference between the sum of seven forms and the total content in soils averaging 9.5% for Co, 12.8% for Ni, 6.6% for Cr and 7.2% for V.展开更多
文摘The distribution and transformation of added and native Ni in purple soils were investigated with both sequential extraction procedure and isotopic tracer technique.The distribution of added and native Ni was greatly dependent on soil properties.Low soil PH was favorable for soluble plus exchangeable (EX) Fraction,while Fe/Mn oxides and clay for Fe/Mn oxide bound (OX) and residual (RES) fractions. The added Ni,however,has not yet reached the distribution equilibrium up to the 150th day after incubation.This was reflected in the fact that the proportion of EX fraction from added Ni was 150%-600% as much as that of native Ni, while that of RES fraction was only about 80%.Once entering soil, the applied soluble Ni was rapidly transformed into Other fractions, but the organic complexed (OM) fraction of added Ni was relatively stable during incubation.The carbonate bound(CAB) fraction showed a progressive increase and attained a peak value after 0-14 d of incubation and thereafter decreased gradually. The occurrence time of this peak advanced as initial soil PH increased, but the peak would disappear when initial soil pH was higher than 7.5(or containing free CaCO3). The transformation processes of the EX,OX and RES fractions could be described by Elovich and two-constant rate equstions,and the rates were positively correlated with soil pH,CEC and clay.These findings could explain why there are differences in ecological and environmental effects of Ni in different soils and at various intervals.
文摘Co, Ni, Cr and V in 25 typical soils of China were fractionated into exchangeable, carbonate bound (calcareous soils), Mn oxide bound, organically bound, amorphous Fe oxide bound, crystalline Fe oxide bound and residual forms using a seven-step sequential extraction procedure, so as to study the distribution of chemical forms of these metals as well as the effects of soil properties on the distribution. The results showed that most of soil Co, Ni, Cr and V were present in residual forms, and the distribution ratio averaged 48.2% for Co, 53.0% for Ni, 81.5% for Cr and 68.7% for V. The speciation of heavy metals was greatly influenced by soil physico-chemical properties and the chemistry of elements. The results also indicated that the recovery of metal elements by the sequential extraction procedure was satisfactory, with the relative difference between the sum of seven forms and the total content in soils averaging 9.5% for Co, 12.8% for Ni, 6.6% for Cr and 7.2% for V.