Study On Chemical Behavior Of Extraneous Lead Under The Rhizosphere Of Red Soil And Yellow Cinnamon Soil

This paper investigated the extraneous source lead adsorption characteristics, transformation and its rhizosphere effect in wheat rhizosphere, using rhizobox technique and the chemical analysis method. Red soil (variable charge soil) and yellow cinnamon soil (permanent charge soil) were used as the material, heavy metal lead as the instructing ion, explored the heavy metal chemical behavior in the rhizosphere environment. The results indicated that:1. After planting wheat, the pH, organic matter content for rhizosphere of red soil and yellow cinnamon soil, have changed by root exudates and root surface physical-chemical processes.2. The adsorption characteristic of lead by red soil and yellow cinnamon soil rhizosphere could be described by the Langmiur equation. The results demonstrated that, the adsorption capacity of Pb²⁺ by yellow cinnamon soil rhizosphere was greater than that of red soil rhizosphere, the adsorption capacity of Pb²⁺ in rhizosphere was greater than that of corresponding non-rhizosphere. The rhizosphere effect had the tendency to increase with the initial concentrations of Pb²⁺ increased.3. At the low concentration of Pb (50 mg/kg), different species Pb in red soil rhizosphere were Fe-Mn oxides bound＞Exchangeable＞Carbonates bound＞Organic matter＞Residual, and in the non- rhizosphere it was also the same. Exchangeable Pb in rhizosphere was far bigger than in non-rhizosphere; different species Pb in yellow cinnamon soil rhizosphere were Exchangeable＞Fe-Mn oxides＞Carbonates＞Organic matter＞Residual, and in the non-rhizosphere, Fe-Mn oxides was the highest, then was Exchangeable. Exchangeable Pb in rhizosphere was far bigger than in non-rhizosphere. At the high level (300mg/kg), different species Pb in red soil rhizosphere were Exchangeable＞Fe-Mn oxides＞Residual＞Carbonates＞Organic matter, but in the non-rhizosphere Fe-Mn oxides was the highest, then was Exchangeable, Carbonates, Residual and Organic matter, exchangeable lead in rhizosphere was significantly higher than non-rhizosphere. Different species Pb in yellow cinnamon soil rhizosphere were Carbonates＞Fe-Mn oxides＞Exchangeable＞Residual＞Organic matter, but in the non-rhizosphere the order was Fe-Mn oxides, Carbonates, Exchangeable, Organic matter and Residual. Carbonates combined Pb of rhizosphere was far bigger than non-rhizosphere.4. Exchangeable, Fe-Mn oxides, and carbonates Pb were the predominant species in both the rhizosphere and non- rhizosphere, and not because the increasing pollution of lead to change its basic form under the test conditions, the ratio of effectively Pb increaseed and the activation was further enhanced with the increasing pollution of lead.