酸性土壤活性锰与pH、Eh关系及其生物反应

Dynamic relationship between soil active Mn and pH, Eh in acid soils and its biological response

以灰潮土为对照研究了湖北省 3种有代表性的酸性土壤在盆栽条件下 ,不同酸化处理土壤pH、Eh与活性锰的动态变化关系。结果表明 ,供试的棕红壤和黄棕壤酸化后 ,在盆栽油菜生长的前 70d内 ,土壤交换性锰含量增加 ,土壤交换性锰与碳酸盐结合态锰呈一定负相关 ,且交换性锰含量增加明显滞后于碳酸盐结合态锰的增加 ;30～90d内 ,碳酸盐结合态锰与易还原性锰呈一定正相关。虽然土壤pH和Eh在作物生长季节不断变化 ,但其 pe +pH仍维持不变。土壤 pH、Eh与交换性锰的关系能较好地反映土壤锰的转化机制 ,在进一步酸化时 ,供试的棕红壤MnO2 Mn2 + 电对是该土壤锰化合物变化的主要形式 ,MnO2 是变化过程的电子受体。供试的黄棕壤则以MnOOH MnO电对为其锰化合物氧化还原的主要形式 ,土壤酸化对其锰电对电位的影响没有直接引起Mn2 + 的变化 ;Mn2 +的增加可能是MnO在该过程中进一步溶解所致。试验结果还表明 ,油菜体内的锰铁比随锰中毒程度的加强而急剧增加 ,这一趋势远高于土壤锰铁比的增加。

The dynamic changes of soil pH, Eh, active manganese and their relationship were studied in three acid soils(brown-red soil, yellow-brown soil and red soil)by contrast with a calcareous alluvial soil collected from Hubei Province in pot experiment of rape plant. The results showed that pH and Eh of the soils would decrease sharply within 80 d of the growth of rape. In the brown-red soil and yellow-brown soil with acidification treatment the contents of the exchangeable Mn (EXC-Mn) rose, and it was positively correlated with carbonate bond Mn (CARB-Mn) during the first 70d in the growth of rape. The increase of EXC-Mn was later than that of CARB-Mn. During the 30-90d, CARB-Mn concentrations were correlated with easily reducible oxide Mn (ERO-Mn). For every tested soil, the values of pe + pH remained stable with changes of pH and Eh. The models of soil pH, Eh and EXC-Mn could better reflect the relationship of the three factors in the acid soils with acidification except the red soil. Electrical pair MnO 2/Mn 2+ in the brown-red soil would be a better description to dynamic change of Mn oxides to Mn 2+ ion. And electrical pairs MnOOH/MnO would be main pattern in process of oxidation-reduction in the yellow-brown soil. The dissolution of MnO may be the reason of increase of Mn 2+ ion in this soil at the acidification condition. The experiment also showed that the radio of Mn/Fe of the plant increased significantly with enhancing of Mn toxicity in rape, this change would be more obvious than that of the radio of Mn/Fe in corresponding soil acidification.