施硅降低碱性土壤铅生物有效性的机制研究

Preliminary study on the mechanism by which silicon application reduces lead bioavailability in alkaline soil

为明确硅降低碱性土壤铅生物有效性的机制,在中和硅酸钠碱性和消除钠离子影响的基础上,采取吸附-解吸试验、红外分析和盆栽试验相结合的方式,研究了硅对碱性土壤液相、固相和固液界面铅行为以及水稻产量与稻米铅含量的影响。结果表明,加硅降低了碱性土壤吸附铅的容量和强度,增强了铅吸附-解吸过程中的滞后效应;应用红外光谱表征溶液中硅铅反应产物,发现Si-O弯曲振动吸收峰和Si-O-Si反对称伸缩振动特征峰均出现了红移,暗示硅酸或聚硅酸与铅发生了配位反应,生成了水溶性复合物;施硅使土壤酸可提取态和可还原态铅含量分别降低了11.18%、18.54%;可氧化态和残渣态铅分别提高了42.56%、7.84%;与对照相比,铅胁迫下水稻产量降低了64.5%(P<0.01),糙米铅含量明显升高(P<0.01),达到了0.31 mg·kg-1;与铅胁迫处理相比,施硅使水稻产量提高了152.3%(P<0.01),明显降低糙米铅的含量(P<0.01),并符合国家标准的安全要求。综上,在碱性土壤中,促进土壤液相、固相铅向无效态转化,抑制固相铅解吸是施硅降低铅生物有效性的土壤化学机制。

In order to clarify the mechanism of silicon reduces the bioavailability of lead in alkaline soils, by neutralizing the effects of sodium silicate alkalinity and eliminating sodium ions, the effects of silicon affected the behavior of lead, liquid, solid-liquid, and solid-liquid interfaces in alkaline soils, rice yields and lead content in rice were studied. Testing included adsorption-desorption testing, infrared analyses and pot experiments. The results showed that silicon addition reduced the capacity and strength of lead adsorption in alkaline soils, while enhancing the lag effect in lead adsorption-desorption processes. The reaction products of silicon-lead in solution were characterized by infrared spectroscopy, and it was found that both the bending vibration absorption peak of Si-O, and the anti-symmetric stretching vibration characteristic peak of Si-O-Si appeared to red shift, suggesting that the coordination reactions of either silicic acid or polysilicic acid with lead resulted in the formation of water-soluble complexes. Silicon addition reduced the contents of acid extractable and reducible lead by11.18% and 18.54% respectively. Oxidizable lead and residual lead were observed to increase by 42.56% and 7.84% respectively, while compared with the control, rice yield decreased by 64.5%(P<0.01), and the lead content of brown rice increased significantly(P<0.01),reaching 0.31 mg·kg-1. Compared with lead stress treatment, silicon addition increased rice yield by 152.3%(P<0.01), while the lead content in brown rice decreased significantly, to the extent that the content of lead in brown rice(P<0.01)met the safety requirements specified in the applicable national standard. In conclusion, the experiments showed that silicon addition promoted the transformation of soil liquid and solid lead to an ineffective state and inhibited desorption of solid lead, thus demonstrating the chemical mechanism which reduced the bioavailability of lead in alkaline soils.