Pedosphere 6(2): 183--192, 1996
ISSN 1002-0160/CN 32-1315/P
©1996 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Distribution and transformation of native and added Ni fractions in purple soils from Sichuan Province |
| TU Cong |
| College of Resources and Environment, Southwest Agricultural University, Chonyqiny 630716 (China) |
| ABSTRACT |
| 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 equations, 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. |
| Key Words: distribution, Ni fraction, purple soil, tracer technique, transformation |
| Citation: Tu, C. 1996. Distribution and transformation of native and added Ni fractions in purple soils from Sichuan Province. Pedosphere. 6(2): 183-192. |
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