黔西南高砷煤矿区污染农田土壤钝化剂修复过程与原理

The agricultural soils in some districts in southwest Guizhou were long-term contaminated by their neighbouring arsenic-coal mines. It is of great risks to engage in agricultural production activities in these areas. Chemical amendments have been considered as economical and effective methods for remediating As-contaminated soils. In this study, one type of iron oxides (ferrihydrite) and an industry by-product (phosphogypsum) are amended into the soils as amendments. The effects of amendments on As immobilization and the main influence factors are investigated by using soil incubation experiments. The rhizo-box experiments are also conducted to explore the interaction of the amendments and arsenic on the root-soil interface. The long term effectiveness of the amendments are evaluated by continuous cropping using pot experiments. Besides, some advanced analytical techniques, such as X-ray diffraction (XRD), transmission electron microscopy (TEM), synchrotron based X-ray fluorescence (μXRF), and high-throughput sequencing, are introduced to study the stabilization mechanisms of As by amendments. The microbial community structure in soils after amendments addition will be determined and its mechanisms among amendments-microorganism-As will be probed into. The possible sub-cellular mechanisms of amendments-inhibited As uptake by crops will be uncovered. This study is of great guiding significance in promoting safety utilization of As-contaminated agricultural soils around high-As coal mining area in southwestern Guizhou, ensuring quality and safety of agricultural products, as well as protecting agricultural ecological environment.

贵州省黔西南高砷煤矿区周围的农田土壤受到不同程度的砷污染，并且这些农田大多尚在种植，进行农产品安全生产的风险较高。利用化学钝化剂来修复砷污染农田土壤已被认为是一种有效且经济的措施。本项目拟采用一种铁氧化物（水铁矿）和一种工业副产品（磷石膏）作为钝化剂材料，对矿区周围砷污染旱作农田土壤进行修复。利用土壤培养试验，明确钝化剂对土壤砷的固定效果及影响因素；利用根箱试验，探讨根-土界面上钝化剂与砷的相互作用；利用盆栽试验，研究钝化剂的长效性。结合XRD、TEM、μXRF、高通量测序等分析技术，探明钝化剂固定砷的机制，从分子生物学水平揭示添加钝化剂后土壤微生物群落结构变化及钝化剂-微生物-砷之间的作用机制，从亚细胞水平揭示钝化剂阻控作物吸收砷的可能机理。研究结果对促进黔西南高砷煤矿区周边砷污染农田安全利用、保障农业生态环境和农产品质量安全等，均具有十分重要的指导作用。

我国是受砷污染影响较严重的国家，据2014年发布的《全国土壤污染状况调查公报》，全国土壤中砷的点位超标率为2.7%，其中，96.3%为中度以下污染。贵州省高砷煤矿区周围的耕地受到不同程度的污染，土壤砷含量在5.25-234.14 mg/kg之间，且这些农田种植作物，农产品安全生产风险巨大。利用化学钝化剂来修复或调控砷污染农田土壤已被认为是一种有效且经济的措施。贵州省高砷煤矿区周围的耕地受到不同程度的污染，农产品安全生产风险巨大。项目初步掌握了黔西南高砷煤矿周边农田土壤砷及其他重金属的含量分布概况；评价了调查区域内土壤和农作物的污染程度和健康风险；选择对土壤砷具有固定能力的铁氧化物（水铁矿）和工业副产品（磷石膏）为钝化剂材料，确定了钝化剂对土壤砷的固定效果，明确了钝化剂促使土壤砷从非稳态向稳定态转化以降低砷移动性的固定机制；钝化剂可增强作物对砷的抗性，促使作物根尖细胞将砷集中在根表皮细胞、细胞壁及液泡中，以调节地上部分对砷的吸收积累；钝化剂可改变作物根际微生物群落结构，以钝化剂-作物根系-微生物协同互作，调控作物吸收砷，促进作物健康生长。