地下水系统铬赋存形态与长效稳定机制研究

Chromium contamination in groundwater system has drawn great attention due to its environmental safety and ecological risks. Based on the key scientific problems of the chromium morphology and long-term stability, the research is carried out on the morthodology and mobility, driving forces of transformation, and biological effectiveness of chromium in groundwater system, which identify the environmental behavior, migration and transformation on composite interface, morphological structure and stability characteristics of chromium in the groundwater system. By the research on micro combined form between chromium and medium, revealing control factors of chrome stability and micro migration process, establishing the relationship between morphology and stability of chromium. The relationship between chromium stability and volume conversion was established by analyzing the interface transfer and transformation of the chromium. Through analyzing the relationship between chromium occurrence, morphology, stability and quantity transformation in groundwater system, the mechanism of influence of chromium stability will be revealed in complex media of groundwater system. With the development of the stability materials, the long-term stability of chromium is established and strengthened. The research results will provide a theoretical basis for the long-term control of chromium pollution，the ecological and environmental safety in groundwater system.

地下水系统铬污染所引起的环境安全和生态风险问题受到高度关注。课题针对地下水系统铬形态与长效稳定性关键科学问题，围绕地下水系统铬的赋存状态与移动性、迁移转化驱动力与形态转变、生物有效性等开展深层次研究，识别地下水系统铬的环境行为、复合界面的迁移转化、形态结构与稳定性特征；通过铬与介质之间的微观结合形态研究，揭示地下水系统铬稳定性控制因素和迁移转化微观过程，创建地下水系统铬形态与稳定性关系模式；解析铬界面输移、转化微观过程，建立铬稳定性与物量转化关系；分析地下水系统中铬赋存、形态、稳定和物量转化关系，揭示复杂体系铬稳定性的影响机制；利用稳定性材料的研发，创建铬长效稳定性靶向调控机制，强化铬的长效稳定性。研究成果为地下水系统铬污染长效控制和生态环境安全提供理论基础。

土壤铬具有多价态、高移动性、生物利用性和毒性，其污染所引起的环境安全和生态风险问题受到高度关注。由于土壤组分构成复杂，显著增加铬赋存形态与稳定性识别的难度，为此，需研究土壤铬转化与稳定机制。基于我国典型铬渣场地土壤污染特征。基于分析土壤铬微观结合形态，发现土壤非可溶性Cr(VI)占总Cr(VI)的30%~82%，以吸附态或酸溶态CaCrO4存在于层状双氢氧化物或方解石中，成为非可溶性Cr(VI)的主要赋存形态，对于土壤铬稳定性产生重要影响。.通过土壤铬稳定因素和形态转化的微观过程研究表明，方解石中酸溶态CaCrO4和水铝钙石酸解，以及吸附态CrO42-的阴离子交换是非可溶性Cr(VI)释放的主因，SO42-和H+对土壤非可溶Cr(VI)再释放的贡献比重分别为1%~22%和7%~27%。研究发现被氧化的Cr(III)最大理论值不足Cr(III)总量的1%，说明Cr(III)再氧化在短期内不会影响铬稳定性，但铬-锰重分布为Cr(III)再氧化提供条件（R2=0.73~0.91，P<0.001），需关注Cr(III)再氧化对于铬稳定性的长期影响。.基于土壤铬赋存形态与释放条件，研制出含酚羟基团的炭基硫—铁负载型铬稳定化材料（SFB300），具有正电性、耐氧化、耐碱性能，通过降低土壤pH和SO42-的交换作用，促进CaCrO4酸解和吸附态Cr(VI)等非可溶Cr(VI)转化为强结合态的FeCr2O4，使残渣态铬增加1.42~1.74倍，较对照稳定化材料对土壤总Cr(VI)、非可溶性Cr(VI)及可迁移态铬的去除率分别提高了近25%、18%和42%。.基于土壤铬稳定老化与浸出试验，发现SFB300通过表面酚羟基等基团的还原性和螯合作用，使Cr(VI)在老化中以被还原为主（50.41%~81%），进一步强化铬稳定性。吸附态Cr(VI)的解吸是土壤Cr(VI)长期老化中再释放的关键机理，而SFB300可针对性促进吸附态Cr(VI)稳定，效果较FeSO4提高64.34%，显示其具有维持铬稳定的优势性。针对Pb-Cu-Zn-Ni复合重金属污染，研发了铁锰系磷基、磷基和硅氧基三种生物炭修复材料，均可通过络合作用和沉淀作用实现土壤重金属由活跃态向稳定态的转变，增加了土壤重金属的环境稳定度。研究成果为土壤铬污染及复合重金属污染的精准修复，提升重金属的长效稳定化提供理论与技术支撑。