铁基硅盐对土壤环境镉砷赋存形态及转化影响

为探明铁基硅盐对土壤镉砷赋存形态影响及各形态间转化规律,采用室内长期淹水培养吸附实验,研究不同比例铁硅材料对土壤离子态镉砷活性影响;筛选适宜铁基硅盐(FS)配比同时添加腐殖酸(FSC)和金属氧化物(FSCa),明确复配处理土壤中镉砷分级形态转化程度.结果显示,铁:硅比值增加10%,土壤pH值平均降低0.35;F₂-S₈处理土壤离子态镉降幅71%;F₁₀-S₀处理土壤离子态砷降低59.9%,离子态镉砷含量与硅酸盐-铁盐施用量互呈反比;处理F₄-S₆和F₆-S₄之间镉、砷钝化率产生交点,约为25%~30%.土壤中镉主要以可溶态为主,占比58%;砷主要以铁铝氧化态和钙结合态为主,占比40%和23%.铁硅比例为5:5或5.5:4.5左右复配能有效将铝结合态砷和铁铝氧化态砷转变为钙结合态砷和残渣态砷,可溶态镉转化为碳酸盐结合态镉以及铁锰氧化态镉,同步降低土壤中镉砷的活性.

Effects of Iron-based silicon salts on fractions and transformation of cadmium and arsenic in soil environment

To explore the effects of iron-based silicon on the bioavailability and transformation of cadmium (Cd) and arsenic (As) in soil, laboratory long-term flooding cultivation culture adsorption experiment were carried out with Cd/As mild co-contaminated soil. Different proportions of Fe-Si materials and various iron-silicon salt (FS) components in combination with humic acid (FSC) and metal oxide (FSCa) were studied in the Cd-As soil. The morphological changes of Cd and As in the soil treated with the above complex agents were evaluated. The results showed that the ratio of iron to silicon was increased by 10%, the soil pH value was decreased by 0.35. Under F₂-S₈ treatment, ionized Cd in the soil was decreased by 71%. F₁₀-S₀ treatment reduced As ion state by 59.9%, and the content of ionized Cd and As were inversely proportional to the application ratios of iron salts and silicates. The intersection of Cd and As passivation rates between F₄-S₆ and F₆-S₄ was found to be between 25%~30%. Soluble Cd was the main compound of total Cd in soil, representing approximately 58%; As was mainly present in Fe-Al oxidation state and Ca binding state, accounting for 40% and 23% of total As, respectively. The ratios of iron to silicon from about 5.0:5.0 or 5.5:4.5 could effectively convert Al-bound As and Fe-Al oxide-bound As to Ca-bound As and residue state As. Meanwhile, soluble Cd can be converted into carbonate state Cd and Fe-Mn oxides state Cd. In conclusion, the bioavailability of Cd and As in soil can be simultaneously reduced by iron-based silicon compounds.