复合钝化剂对砷污染土壤钝化修复及微生物群落结构的影响

Effect of Composite Passivator on Arsenic Contaminated Soil Passivation Remediation and Microbial Community Structure

将羟基磷灰石(HAP)和水热炭(HTC)混合制备新型复合钝化剂HAP−C,采用扫描电子显微镜和能谱分析、X射线衍射、傅立叶红外光谱等测试方法表征HAP−C的形貌特征、晶体结构和官能团;以As污染土壤为研究对象,探究添加质量分数为1%,3%,5%的HAP−C对土壤理化性质、砷形态及酶活性的影响,采用高通量测序技术分析土壤微生物群落组成的变化特征。结果表明:HAP−C含有HAP和HTC的主要特征元素(碳、氧、磷和钙)、晶体结构与主要官能团(P—O,—OH,C=O,—CH2—);HAP−C的添加可降低土壤中可被生物利用的吸附态砷含量(22.20%~40.26%,质量分数,下同),3%HAP−C的钝化效果最显著;HAP−C对土壤砷的钝化机理主要包括表面络合、化学沉淀和离子交换,HAP−C的添加可提高土壤的pH(19.56%~21.51%)和电导率(205.99%~290.91%)及增加土壤的有机质(23.12%~32.16%)、有效磷(104.29%~176.54%)和硝态氮含量(203.33%~250.19%),同时提高土壤酶活性及微生物物种的丰富度和多样性;砷污染土壤中产黄杆菌属(Rhodanobacter)和鞘脂单胞菌属(Sphingomonas)相对丰度较高,3%HAP−C处理组中产黄杆菌属(Rhodanobacter)和芽单胞菌属(Gemmatimonas)的相对丰度与对照组相比分别增加了10.30%~29.06%,34.94%~48.12%。HAP−C的添加不仅可提高土壤As的钝化效果,还可改善土壤环境健康状态,其在As污染土壤修复工程中具有一定的应用潜力。

A novel composite passivator HAP−C was prepared by mixing hydroxyapatite(HAP)and hydrothermal carbon(HTC).The morphological characteristics,crystal structure,and functional groups of the prepared composite passivator were characterized using scanning electron microscopy and energy spectrum analysis,X ray diffraction,and Fourier transform infrared spectroscopy.Taking As-contaminated soil as the research object,the effects of adding HAP−C with mass fraction of 1%,3%,and 5%on the physicochemical properties of the soil,arsenic speciation,and enzyme activity were investigated.High-throughput sequencing technology was used to analyze the changes in the composition of the soil microbial community.The results show that the prepared HAP−C contains the main characteristic elements of HAP and HTC(carbon,oxygen and calcium),along with theircrystal structures and main functional groups(P-O,-OH,C=O,-CH_(2)-).The addition of HAP−C can reduce the content of bioavailable adsorbed arsenic in the soil(22.20%−40.26%,mass fraction,the same below),with 3%HAP−C showing the most significant immobilization effect.The mechanisms by which HAP−C immobilizes arsenic in soil mainly include surface complexation chemical precipitation,and ion exchange.Adding HAP−C can increase soil pH(19.56%–21.51%),electrical conductivity(205.99%–290.91%),and enhance soil organic matter(23.12%–32.16%),available phosphorus(104.29%–176.54%)and nitrate nitrogen content(203.33%–250.19%).It also improves soil enzyme activity and richness and diversity of the microbial species.The relative abundances of Rhodanobacter and Sphingomonas in arsenic contaminated soil are relatively high.The relative abundances of Rhodanobacter and Gemmatimonas in 3% HAP−C treatment group are 10.30%–29.06% and 34.94%–48.12%,respectively,compared with the control group.The addition of HAP−C can not only enhance the passivation effect of As but also improve the health status of soilt,indicating potential application in As-contaminated soil remediation projects.