湖北大冶农田土壤重金属的形态分析及其污染的化学钝化修复

发布时间：2018-11-08 06:42

【摘要】：矿产资源开发带来的土壤重金属污染问题已经成为全球面临的重大环境问题,当农田土壤受到重金属污染,有效态的重金属会富集到农作物上,并通过食物链危害人类健康。本研究以矿冶城市大冶为研究区域,展开了农田土壤重金属污染状况的调查,并选用矿物材料通过室内钝化试验和室外田间试验对重金属污染土壤进行低成本的防治研究,主要研究结果如下:(1)分析了大冶市10个区域农田土壤的重金属含量,Cu、Zn、Pb、Cd的平均含量均高于湖北省土壤背景值,分别是背景值的4.14、1.25、2.63、15.29倍。以湖北省土壤背景值为评价标准,内梅罗综合污染指数法的评价结果显示,所有采样点和区域均为重污染,Cd和Cu污染贡献最大,其次是Pb和Zn。潜在生态危害指数法的评价结果显示,大部分采样点和区域为强风险,Cd是风险最高的污染物,Cu次之。10个区域中,污染最重且风险最高的3个区域依次是铜绿山、柯湾、大箕铺。(2)分析了大冶市主要作物油菜和小麦的重金属含量,籽粒的Cu、Zn、Pb含量都有不同程度的超标。籽粒对重金属的富集能力为ZnCuPb,二者相比,油菜籽粒更易吸收Zn,小麦籽粒更易吸收Cu。采用改进BCR法对作物土壤中Cu、Zn、Pb的形态进行分级,除油菜土壤的Pb以外,其余的重金属形态主要集中在残渣态,酸溶态的含量最低,平均比例不超过15%。作物籽粒的Cu含量与土壤非残渣态Cu含量呈极显著正相关,与酸溶态Cu含量的相关性最强。(3)通过室内钝化试验研究了白云石、石灰石、硅灰石和磷矿粉对土壤Cu、Zn、Pb的钝化作用,4种矿物都能在提升土壤p H的同时钝化土壤重金属,高添加量的效果优于低添加量,p H4.79和p H5.13的土壤中酸溶态的降低幅度和残渣态的升高幅度大于p H6.70和p H7.27的土壤。多数情况下,白云石和石灰石对Cu的效果较好,石灰石和硅灰石对Zn的效果较好,磷矿粉和硅灰石对Pb的效果较好。(4)通过室外田间试验研究了白云石和硅灰石对土壤重金属的实际修复效果,将矿物添加量设置为1%、2%、4%(W/W),两种矿物有效地降低了土壤重金属的活性,并减少玉米对重金属的吸收。白云石对Cu和Zn的效果较好,土壤酸溶态较对照组降低37.54%~51.52%和17.90%~25.58%,玉米籽粒的Cu和Zn含量分别降低29.86%~39.06%和19.71%~24.05%。硅灰石对Pb的效果较好,处理后土壤残渣态Pb是对照组的2.18~3.00倍,玉米籽粒的Pb含量降低30.25%~33.46%。两种矿物还能促进玉米生长,株高和产量随矿物添加量的增加呈现先升后降的趋势,在2%(W/W)添加量时达到最大值,白云石对提升株高效果较好,硅灰石对增加产量效果较好。
[Abstract]:The pollution of heavy metals in soil caused by the exploitation of mineral resources has become a major environmental problem all over the world. When farmland soils are polluted by heavy metals, the available heavy metals will be enriched into crops and endanger human health through the food chain. In this study, the investigation of heavy metal pollution in farmland soil was carried out in Daye, a mining and metallurgical city, and the low cost control of heavy metal contaminated soil was studied by means of indoor passivation test and outdoor field experiment. The main results are as follows: (1) the contents of heavy metals in farmland soil of 10 regions of Daye City were analyzed. The average content of Cu,Zn,Pb,Cd was higher than the background value of Hubei Province, which was 4.14 ~ 1.25 ~ 2.63 ~ 15.29 times of background value respectively. Using the soil background value of Hubei Province as the evaluation criterion, the evaluation results of Nemero comprehensive pollution index method show that all sampling sites and regions are heavily polluted, Cd and Cu contribute the most, followed by Pb and Zn.. The results of the potential ecological hazard index method showed that most of the sampling sites and regions were at strong risk, Cd was the most risky pollutant, and Cu was the second. Among the 10 regions, the three regions with the most serious pollution and the highest risk were Tonglushan and Kewan, respectively. (2) the heavy metal contents of rape and wheat in Daye City were analyzed, and the Cu,Zn,Pb content of grain exceeded the standard to some extent. The enrichment ability of grain to heavy metal is ZnCuPb, rapeseed grain is easier to absorb Zn, than rapeseed grain, wheat grain is easier to absorb Cu.. The improved BCR method was used to classify the forms of Cu,Zn,Pb in crop soil. Except for the Pb of rape soil, the other heavy metals were mainly concentrated in residue, the content of acid soluble state was the lowest, the average proportion was not more than 15%. The Cu content of crop grain was significantly positively correlated with soil non-residual Cu content, and the correlation with acid-soluble Cu content was the strongest. (3) the effect of dolomite, limestone, wollastonite and apatite powder on soil Cu,Zn, was studied by laboratory passivation test. The passivation effect of Pb, all four minerals can passivate heavy metals in soil, and the effect of high addition is better than that of low addition. The decrease of acid soluble state and the increase of residual state in pH 4.79 and pH 5.13 soils were larger than those in pH 6.70 and pH 7.27 soils. In most cases, dolomite and limestone have better effect on Cu, limestone and wollastonite have better effect on Zn. The effect of phosphate and wollastonite on Pb was better. (4) the effect of dolomite and wollastonite on the remediation of heavy metals in soil was studied through outdoor field experiments. The mineral addition was set to 1 / 2% (W / W). The two minerals effectively reduced the activity of heavy metals in soil and the absorption of heavy metals by maize. The effect of dolomite on Cu and Zn was better. The acid soluble state of soil decreased by 37.54% and 17.90% and 25.58, and the contents of Cu and Zn in corn grain decreased 29.86% and 19.71%, respectively. The effect of wollastonite on Pb was better. After treatment, the Pb of residual soil was 2.18 ~ 3.00 times of that of the control, and the content of Pb in corn grain was 30.25 ~ 33.46 times lower than that of the control. The plant height and yield increased first and then decreased with the increase of mineral addition, and reached the maximum at 2% (W / W), and dolomite had better effect on plant height. Wollastonite has a good effect on increasing yield.
【学位授予单位】：华中农业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X53

【参考文献】