西安污灌区土壤的调查与修复

发布时间：2018-08-05 15:06

【摘要】：本研究主要通过对西安北郊西查寨村污灌区农耕地中土壤及其对应的三种农作物菜花、萝卜、小白菜进行研究,选取同一区域采用地下水灌溉的苹果园区域土壤做背景,通过测定污灌土壤颗粒组成、pH、氮、磷、有机质、过氧化氢酶活性和相对应三种作物株高和叶片面积来分别评价土壤的质量和农作物的受损状况,再分别测定农田土壤重金属全量及其对应的三种农作物不同部位的重金属含量,最后对重金属的赋存形态采用Tessier定义提取并进行综合评估。实验结果表明研究区土壤的重金属含量显著超标,不同元素在土壤中累积强度明显不同,其顺序为CdZnPbCu;污灌区土壤四种重金属含量与非污灌区存在显著性差异(P0.01),萝卜(Raphanus sativus)和菜花(Ottelia acuminata)分别对于Cd和Cu具有很好的富集累积作用;三种农作物对于西安污灌区土壤的修复作用为萝卜菜花小白菜(Brassica chinensis),不同农作物组织对于重金属的积累分布部位为根茎、叶果实。4种土壤重金属可交换态比例明显不同,分别为萝卜菜花小白菜苹果,表明萝卜和菜花较易吸收土壤重金属。通过室外田间修复试验结果表明,石灰石通过钝化作用来影响土壤的理化性质和降低重金属元素在土壤中的生物有效性,从而达到理想的修复效果。一定质量分数的石灰石对植物生长有促进作用,超过植物的最大耐受性,则起到抑制作用。在石灰石质量分数较小时候,对植物的株高、叶面积有比较明显的促进作用;较高质量分数的浓度不利于植物生长。低浓度石灰石质量分数对小白菜的过氧化氢酶活性、超氧化物歧化酶活性、游离脯氨酸含量及丙二醛含量影响不是十分显著,在加入质量分数为2%的石灰石土壤中,可以看到相比于未添加的和添加的1%质量分数的石灰石,对于重金属的吸收明显降低很多,其中对于重金属Zn和Cd减低了分别为32.7%和56.01%。而大于4%的质量分数浓度小白菜体内过氧化物酶和超氧化物歧化酶活性显著减低,而丙二醛及游离脯氨酸含量则持续升高。添加不同质量分数的石灰石能够在不同程度下降低重金属元素的在土壤及农作物的游离程度。综上所述,根据不同农作物对不同重金属吸收转化的差异,在重金属污染区土壤选择适当的农作物种类进行科学种植。达到了边生产边修复的目的,而且还提高了农作物的产量和质量,具有一定良好的生态效益和经济效益,也为西安市污灌区土壤环境质量评价和污灌区选种农作物提供理论依据。
[Abstract]:In this study, the soil and its corresponding three crops, cauliflower, radish and pakchoi, were studied in the farmland of Xichazhai Village sewage Irrigation area in the northern suburb of Xi'an, and the soil of the same area was selected as the background of the apple orchard area irrigated by groundwater. Soil quality and crop damage were evaluated by measuring soil particle composition pH, nitrogen, phosphorus, organic matter, catalase activity, plant height and leaf area. The total amount of heavy metals in farmland soil and the contents of heavy metals in different parts of three crops were determined respectively. Finally, the occurrence forms of heavy metals were extracted by Tessier definition and evaluated synthetically. The results showed that the contents of heavy metals in the soil of the study area were significantly higher than the standard, and the accumulative strength of different elements in the soil was obviously different. The order was CdZnPbCu.The content of four heavy metals in polluted soil was significantly different from that in unpolluted irrigation area (P0.01). (Raphanus sativus) and (Ottelia acuminata) of radish and cauliflower had good accumulative effect on CD and Cu, respectively. The effects of three crops on soil remediation in Xi'an sewage Irrigation area were as follows: the accumulation and distribution of heavy metals in different crop tissues of Brassica campestris (Brassica chinensis), was rhizome, and the exchangeable proportion of heavy metals in leaves and fruits was obviously different. The results showed that radish and cauliflower could easily absorb heavy metals in soil. The results of outdoor field remediation experiments showed that limestone could affect the physical and chemical properties of soil and reduce the bioavailability of heavy metal elements in soil by passivation so as to achieve an ideal remediation effect. Limestone of a certain mass fraction can promote the growth of plants, and exceed the maximum tolerance of plants, it can inhibit the growth of plants. When the limestone mass fraction was small, the plant height and leaf area were significantly promoted, and the higher concentration of limestone content was not conducive to plant growth. The effects of low concentration limestone content on catalase activity, superoxide dismutase activity, free proline content and malondialdehyde content were not significant. It can be seen that the absorption of heavy metals is much lower than that of limestone without adding and adding 1% mass fraction of heavy metals, among which Zn and CD are reduced by 32.7% and 56.01%, respectively. However, the activities of peroxidase and superoxide dismutase in Chinese cabbage were significantly decreased when the mass fraction concentration was more than 4%, while the content of malondialdehyde and free proline continued to increase. The addition of limestone with different mass fraction can reduce the dissociation of heavy metal elements in soil and crops to different extent. To sum up, according to the difference of absorption and transformation of different heavy metals by different crops, suitable crop types were selected for scientific planting in heavy metal contaminated areas. It has achieved the goal of repairing while producing, and has also improved the yield and quality of crops, which has certain good ecological and economic benefits. It also provides theoretical basis for evaluation of soil environmental quality and selection of crops in sewage irrigation area of Xi'an city.
【学位授予单位】：西北大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X53

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