根瘤菌对土壤铜、锌和镉形态分配的影响

以湖南郴州红壤和河北巩义褐土为供试土壤。制备Cu、Zn、Cd污染土壤。接种大豆根瘤菌(Rhi-zobium fredii)HN01，用连续提取法浸提土壤中不同形态的重金属．结果表明。褐土接种根瘤菌后固相结合态Zn总量降低10％。专性吸附态、氧化锰结合态和有机结合态Zn减少达9％～26％．红壤中结合态Zn的总量变化不显著，但专性吸附态和氧化锰结合态Zn含量显著减少。交换态Zn含量显著增加．褐土中接种根瘤菌抑制了Cu向土壤溶液的释放，固相结合态Cu总量增加18％，可交换态、专性吸附态、氧化锰结合态和有机结合态的Cu增加20％～54％．接种根瘤菌对土壤中Cd的溶解没有明显的抑制或促进作用，但改变了红壤中各形态Cd的含量高低顺序．Cd污染红壤中可交换态和有机结合态Cd含量分别增加22％和11％，专性吸附态和氧化锰结合态Cd分别减少14％和29％．根瘤菌对不同类型重金属及不同土壤中重金属形态影响的差异主要与土壤pH降低有关．

Effects of rhizobia on morphological distribution of Cu, Zn and Cd in soil

Red soil from Chenzhou of Hunan and brown soil from Gongyi of Henan were collected and treated with Cu (NO3)2, Zn(NO3)2 or Cd(NO3)2, respectively for 2 weeks, and Rhizobium fredii strain HN01 was inoculated. Sequential extraction method was employed to investigate the forms of Cu, Zn and Cd in the examined soils with the absence and presence of rhizobia. The results showed that after inoculation, the total amount of solid-bound Zn decreased 10%, and the amount of Zn associated with carbonate, Mn oxides, and organic matter fraction decreased 9-26%. No significant change was observed for the total amount of Zn combined with the solid phase of red soil in the presence of rhizobia. However, the amount of specifically adsorbed and Mn oxides bound Zn decreased, while the amount of exchangeable Zn increased. Inoculation of rhizobia depressed the release of Cu to the soil solution, and increased the total amount of Cu associated with the solid phase of brown soil. The increase of the amount of exchangeable Cu and of the Cu in fractions of carbonate, Mn oxides and organic matter ranged from 20% to 54%. There was no significant change for the level of Cd in the solution in both soils after rhizobia inoculation. The amount of exchangeable and organic Cd increased 22% and 11%, while the specifically adsorbed, and Mn oxides bound Mn decreased 14% and 29%, respectively. The different influence of rhizobia on the morphological distribution of test heavy metals in two soils was mainly ascribed to the soil pH changes.