硅钙调控对酸矿水污染农田水稻镉含量的作用机制

Regulative Mechanism of Silicon and Calcium on the Cadmium Content of Rice in the Farmland Polluted by Acidic Mine Water

采用根际模拟和大田试验相结合的方法,探讨了硅钙调控对酸矿水污染农田水稻镉含量的作用机制,结果表明:(1)施硅明显提高了1～4mm主要根际微域及非根际pH值和有效硅含量,显著降低了根际和非根际有效镉含量,从而限制了镉在根际微域的迁移扩散;(2)在1mm根际范围,施硅处理的根际效应表现为酸化及降低有效硅含量,不施硅反而有提升pH和有效硅的根际效应;(3)持续酸矿水灌溉会增强重金属复合污染毒性,不利于水稻对镉的吸收,也会影响到硅钙介质调控提升pH、降低水稻镉含量的效果,但在持续清水灌溉条件下,硅钙介质调控能够有效降低水稻糙米Cd含量;(4)酸矿水复合污染农田pH和镉的根际活性以及镉生物有效性之间的反应并不完全一致,需要通过硅钙介质合理调控使得根际pH处于最适范围,才会抑制水稻对镉的吸收。

The mechanism of silicon and calcium on the cadmium content of rice in the field polluted by acidic mine water was studied by the method of rhizosphere simulation and field experiment, the results showed that： （1） Soil pH and available silicon were enhanced by silicon fertilization in the rhizosphere of 1～4 mm and in non-rhizosphere zone, thus the available cadmium decreased and cadmium migration limited in rhizosphere. （2） Without silicon application, soil pH and available silicon was enhanced evidently by the effect of rhizosphere within 1 mm zone, but soil available cadmium content not reduced properly because of cadmium diffusion in different distance of other rhizosphere zone. （3） Irrigated with acidic mine water continually, the acidification of soil made both the available cadmium and other exchangeable elements such as zinc, copper and manganese content increase, thus the toxicity of compound pollution from heavy metals was promoted. In this condi- tion, soil pH decreased but the biological validity of cadmium did not reduce properly. Irrigated with the clean water continually, the cadmium content of unpolished rice decreased evidently with silicon and calcium fertilization. （4）There were no unanimous effects among soil pH, the biological validity of cadmium and soil available cadmium content. The uptake of cadmium by rice could be controlled effectively only within the suitable range of soil pH regulated by silicon and calcium.