[Aging characteristics of copper and zinc added to typical soils of China].
The aging processes of copper and zinc in single and combined metal-contaminated typical soils of China, red soil, paddy soil and cinnamon soil, were studied. The results showed that available copper and zinc (metals extracted by 0.01 mol x L(-1) CaCl2 ) decreased rapidly at initial stages, and then reduced slowly, where the turning point occurred at about 90 d. The difference in aging of copper and zinc was insignificant whether in single metal-contaminated soils or in combined metal-contaminated soils, suggested there were similar chemical behaviors between copper and zinc. The aging processes of copper and zinc in red soil, paddy soil and cinnamon soil fitted best a second-order equation (R2 = 0.9940-0.9999, p < 0.0001), whereas parabolic diffusion equation has less goodness of fit. It indicated that the transformation from availability to unavailability of metals, i.e. aging, was not completely controlled by diffusion, but controlled by the interactions from surface nucleation/precipitation, occlusion by organic matter, and diffusion, etc. The aging of copper and zinc in soils was significantly affected by pH. In soils with low pH such as red soil, the ratio of available metals was higher and the aging rate was slower [constant of rate, k2 4.36x10(-3)-7.05x10(-3) kg x (mg x d)(-1)]; whereas in soils with high pH, for example in cinnamon soil, the ratio of available metals was lower and the aging rate was faster [k2 1.095x10(-2)-1.377x10(-2) kg x (mg x d)(-1)]. That is, the aging rate of metals in soils increased obviously with increasing pH.
Xu
Ming-Gang
MG
Key Laboratory of Plant Nutrition and Nutrition Cycling, Ministry of Agriculture, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China. mgxu@caas.ac.cn
Wang
Bao-Qi
BQ
Zhou
Shi-Wei
SW
Li
Shu-Qin
SQ
Chen
Miao-Miao
MM
Duan
Gai-Lian
GL
D002681:China; D003300:Copper / Q000032:analysis / Q000737:chemistry*; D004784:Environmental Monitoring; D006863:Hydrogen-Ion Concentration; D012987:Soil / Q000032:analysis*; D012989:Soil Pollutants / Q000032:analysis / Q000737:chemistry*; D015032:Zinc / Q000032:analysis / Q000737:chemistry*
D012987:Soil; D012989:Soil Pollutants; D003300:Copper; D015032:Zinc