土壤中重金属矿物细或超细颗粒的胶体促使运移行为及水文化学因素研究

It is believed that colloid-facilitated transport of heavy metals is an important diffuse route for heavy metals in soil and groundwater, which may cause a wider diffusion of pollutants in the soil and groundwater. Now many researches focus on the colloid-facilitated transport of dissolved heavy metals in soils, while few studies have been carried on the colloid-facilitated transport of insoluble fine and ultrafine mineral particulates of heavy metals in dust and fly ash from the industry of mining, chemical industry and metallurgies. Therefore, the present study will be carried out. Firstly, the interaction between heavy metal mineral particles and soil colloids will be investigated by the combination of instrumental analysis such as transmission electron microscopy, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy and chemical analysis such as titration analysis. Secondly, the colloid-facilitated transport of dissolved heavy metals and insoluble fine and ultrafine mineral particulates of heavy metals in quartz-sand column will be compared and the role of ionic strength, flow rate, pH, and soluble organic matter also be investigated. Thirdly, the colloid-facilitated transport of dissolved heavy metals and insoluble fine and ultrafine mineral particulates of heavy metals in soil column will be investigated and the role of ionic strength, flow rate, pH, and soluble organic matter also be compared. Finally, the mathematical model of the colloid-facilitated transport of insoluble fine and ultrafine mineral particulates of heavy metals in soil will be established. The present study aims to clarify the colloid-facilitated transport of insoluble fine and ultrafine mineral particulates of heavy metals in soil and the role of ionic strength, flow rate, pH, and soluble organic matter. The present study will reveal the diffusion and retention of insoluble fine and ultra-fine mineral particles of heavy metals from the industry of mining, chemical industry and metallurgies in soil and groundwater. It improves the scientific understanding for the remediation of soil contaminated with heavy metals.

重金属的胶体促使运移行为促进了重金属在更大范围土壤-地下水污染扩散。目前溶解态重金属的胶体促使运移研究受到关注，而来源于采矿、冶金等工业生产的粉尘扬尘中难溶态重金属矿物细或超细颗粒的胶体促使运移研究则缺乏。本课题首先利用扫描电镜、X射线衍射和X射线光电子能谱等仪器分析和滴定等化学分析方法系统研究胶体与难溶重金属矿物颗粒相互作用；然后研究重金属矿物细或超细颗粒在石英砂均质介质中的胶体促使运移规律以及pH、溶解性有机质、流速和离子强度等对运移的影响机制；进而研究难溶重金属矿物细或超细颗粒在土壤中的胶体促使运移规律及关键要素；最终建立土壤中难溶重金属矿物细或超细颗粒的胶体促使运移数学模型。该研究阐明土壤中难溶重金属矿物细或超细颗粒的胶体促使运移规律和关键影响因素，揭示来源于冶金化工、采矿尾矿等释放重金属矿物颗粒在土壤及地下水扩散行为和机理，为重金属污染的防治提供科学参考。

本课题研究溶解态金属、重金属矿物细/超细颗粒和土壤胶体的相互作用、重金属离子和重金属矿物细或超细颗粒在饱和/非饱和土壤/非均砂柱中的运移及数值模拟分析。获得如下主要研究成果：（1）静态实验中重金属离子/矿物颗粒与土壤胶体相互作用。静态实验中，pH值、离子强度和腐殖酸是影响离子吸附的重要因素。重金属离子相对均匀地吸附于土壤胶体表面；重金属矿物细颗粒则分布不均匀，由此将影响其动态运移。（2）饱和条件下均质柱重金属离子/矿物颗粒与土壤胶体共运移。50mg·L-1黑土和红壤细颗粒对Pb(II)运移起到促进作用。离子强度对Pb(II)运移的影响受土壤胶体存在的干扰。低pH值（pH4）明显促进Pb(II)运移，而pH6-8范围内PbO运移变化较小。鉴于低pH下金属的可能的溶解作用，pH是两者运移中的重要因子。高岭土胶体对Pb(II)和PbO运移的影响与其浓度有关。红壤胶体对CuO的运移的影响与其粒径有关。10mg·L-1腐殖酸对Pb(II)影响较小，但明显增加PbO的运移。流速增大有效提高两者的运移。运移实验数值可以用两点动力学描述。（3）重金属离子/矿物颗粒在土壤中的运移与溶出行为。短时间内Pb(II)与PbO在土柱难以穿透，发生梯度滞留。表层Zn(II)及ZnO可以穿透土柱发生运移。外源Pb(II)、Zn(II)在土壤中的溶出随时间延长保持稳定的水平；其矿物细颗粒则具有较缓慢的溶出动力学，但溶出运移风险不可忽略。（4）重金属离子/矿物颗粒在饱和/不饱和非均质柱的运移行为。黑土、红壤细颗粒的存在使Pb(II)和PbO的穿透通量增加。模拟竖直孔隙非均质加快了Pb(II)和PbO的穿透；层状结构导致Pb(II)及PbO的垂向分布差异变小；其他条件的强化将削弱介质构成差异的影响；运移实验数值可以用两区模型描述。非饱和条件抑制Pb(II)和PbO与土壤细颗粒的共运移。流速增加明显增加不饱和条件下的共运移。土壤细颗粒浓度的增加促进运移，但影响较小。高离子强度促进Pb(II)运移，降低PbO运移。鉴于低pH下金属的可能的溶解作用，pH是影响共运移的重要因素。