| The harm and control of cadmium(Cd) pollution have always been one of the focuses environmental scientists concerned, for Cd is a typical pollutant drastically dangerous to environment. Now, people have acquainted with many important aspects about Cd pollution such as source, enrichment and harm etc, and put forward some controlling measures based on the laws of Cd's transfer and transformation in soil-plant system. But most of these controlling measures cannot be applied widely because of high cost or long-time spending, and the relatively economic and effective method to handle with the severe Cd pollution problem is still agricultural measure which use chemical inhibitorThere have been many studies on inhibitor selection and many effective inhibitors have been obtained. However, the studied object is so complexity and the condition of experiment is so different that the researchers often draw quite different even opposite conclusion about inhibitors'function controlling Cd's bioavailability. So, available methods in some places cannot be adopted directly. Furthermore, in the past studies, there were short of systematic compare among the different types, dose and their cooperation in controlling effects and mechanisms under the same condition. Therefore, as to some specific soil condition, what the most effective and rational method is still lacks scientific basis. With the purpose of better understanding some weak links in this subject, we comprehensively and systematically compared the effects of some typical inhibitors and their different combined ways in inhibiting Cd bioavailability in purple soil, further studied the laws and affecting factors of Cd's transfer and transformation in soil-plant system, revealed the mechanisms inhibitors function, and explored the practicable inhibitor prescriptions and their usage. The results are expected to provide reliable techniques for controlling Cd pollution of agricultural soils in Chongqing and it is also significant to ameliorate soils polluted by other kinds of heavy metals.Comprehensive methods including pot experiment, laboratory culture experiment, kinetic and thermodynamic adsorption-desorption experiment were adopted in this study, and the acidified purple soil was chosen to test, considering that Cd is highly active in this soil. The tested inhibitors are listed as follows: alkali matter including lime, silicon-containing fertilizer and coal ash; organic matter including plant compost, pig manure and humic acid(HA); ion inhibitor such as ZnSO4 Pot experiment, in which lettuce(Lacruca sativa var.augustana Irish) was chosen as the tested plant, involved 27 treatments, 4 replications each. Biomass and Cd concentration in different parts of plants was observed to study the effects of different treatments. Laboratory culture experiment with the same treatments as pot experiment but without plant was carried out synchronously under constant temperature(25眑 癈) and 20% soil moisture. To study the influence of inhibitors on the dynamic process of transformation and variation of availability of Cd in soil, laboratory cultured soil was sampled in certain interval during the 128-day cultured period for the analysis of Cd availability and speciation. In adsorption-desorption experiment, the tested soil had fistly beencultured under constant temperature (25 1 ) and 20% soil moisture for two months after the treatment according to the designed plan, then isothermal adsorption-desorption experiment was proceeded when the reaction between inhibitor and soil tended to be stable. The purpose of this experiment is to study the relationship between the bioavailability and the characteristics of soil to adsorption-desorption kinetics and dynamics under the effects of inhibitors.The results showed that using inhibitor could significantly affect lettuce biomass. The ratio of the maximum of biomass (treated by pig manure) to the minimum (treated by ZnSO4) was 2.38. It also showed that the biomass would decrease when added Cd but dramatically increase when added...
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