镉污染池塘底泥的Fe-KMnO4-BC钝化修复机制及其农用的生态环境效应

Using as fertilizers for plantation is one of the main disposal approach for pond sediments. However, cadmium (Cd) accumulation caused by intensive cultivation has raised great risks to human health and agricultural ecology which restricted sediments recycling. Recently, modified biochar becomes a hot issue in remediation of Cd-polluted sediments, while the researches on its mechanisms, influencing factors and effectiveness evaluations are rare reported. Therefore, biochar (Fe-KMnO4-BC) modified through magnetization and oxidation is intended to apply for the immobilization of Cd in sediments, aiming to (1) reveal the mechanisms of Fe-KMnO4-BC on Cd2+ adsorption, with observation of its surface characteristics and adsorption properties variations, by using the techniques of Nano-FTIR,XRD and XPS et.al; (2) explore the influencing mechanisms of Fe-KMnO4-BC dosage and moisture condition on the long-term field immobilization effectiveness, through measuring the speciation distribution and leaching concentration of Cd in sediments, based on XANES, XRF and TCLP technologies; and (3) evaluate the environmental effects of the treated sediments applying for plantation, via determining cadmium's total amount and δ114/110 Cd value in farmland water, soils and rice grains, by applying the to be built soil-water-crop quality assessment and isotopic tracing methods. The expected results could provide the theoretical and practical basis for the development of site remediation technology as well as the harmless utilization of Cd-polluted sediments.

集约化养殖引起的池塘底泥镉累积因对人类健康、生态环境有重要影响，制约了底泥的还田农用。近年来，改性生物炭用于镉污染底泥的处置颇具成效，但其钝化机理、影响机制和效果评价鲜有报道。本项目以负磁、氧化手段制备改性生物炭(Fe-KMnO4-BC)，开展镉污染底泥的钝化及还田农用的生态环境效应研究，旨在：(1)通过Nano-FTIR、XRD和XPS等手段，观测改性生物炭的表征变化和吸附特性，揭示其吸附Cd2+的作用机理；(2)采用XANES、XRF、TCLP技术，测定底泥中镉的形态分布和浸出浓度，探讨场地修复中改性生物炭用量与水分条件影响长期钝化效果的机制；(3)以农田水、土壤、稻粒的全镉含量和δ114/110 Cd值为主要指标，利用构建的水土-农产品综合质量指数法和同位素示踪技术，对钝化底泥还田的环境效应作出评价。研究成果可为镉污染底泥场地钝化技术的形成及无害化农用提供理论和实践依据。

为修复镉(Cd)、铅(Pb)污染河湖底泥，加速其资源化农用，本研究采取裂解参数优化、硝酸-高锰酸钾联合改性手段制备试验用改性椰壳炭，通过理化性质表征、动力学特性分析揭示其吸附Cd2+、Pb2+的机制，并进一步通过种植试验评估其场地修复的长期效果，研究结果如下：（1）低温 (400~500℃)、短时 (1~2h)条件下制备的椰壳炭理化性质较优，改性后其比表面积、总孔容积、表面微孔和酸性含氧官能团数量进一步提高，重金属吸附性能显著提升；（2）改性椰壳炭对Pb2+、Cd2+的吸附均符合Langmuir和Freundlich模型，吸附反应易于发生且以化学吸附为主，其吸附动力特征符合准二级动力学模型，颗粒内扩散并非控制吸附过程的唯一限速步骤；（3）改性椰壳炭钝化底泥Cd、Pb的长期稳定化效果理想，15~18周后浓度均低于《农用地土壤环境质量标准》中规定的安全限值，二次释放风险较小，且底泥还田后，土壤和蔬菜中的Cd、Pb有效含量均可达到相关安全标准。相关研究结果为底泥无害化处理和资源化农用提供了理论和实践依据。

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