【作者】 陈蓉；

【导师】 徐卫红； 焦文涛；

【作者基本信息】 西南大学 ， 环境工程， 2016， 硕士

【摘要】 Cd在土壤系统中的污染过程具有隐蔽性、潜伏性、积累性和长期性,能通过食物链进入生物体,长期积累,从而危及人体健康。随着我国大规模的工业城市化进程,工业“三废”、污水灌溉、固体废弃物堆积、大气沉降以及农药和肥料的施用,我国农田Cd污染日益严重,菜地土壤Cd污染情况也不容乐观。我国农田土壤大多为中轻度污染的面源污染土壤。目前国内外常见的修复方法有物理工程修复、化学修复、生物修复和农业修复。在众多修复方法中,原位钝化修复技术成本低廉、操作方便、效果快速,在对污染土壤的治理中得到广泛应用,尤其对耕作土壤轻中度的面源污染的治理。生物炭具有很大的比表面积、表面能和结合重金属离子的作用,因此能够较好地去除和钝化土壤中的重金属。由无机-有机钝化剂混合制成的土壤调理剂,可以降低土壤中重金属的有效性。本研究以生物质炭和土壤调理剂为修复材料,通过吸附试验、土培试验和大田试验,分析生物质炭和土壤调理剂的吸附特性和对对小白菜的生长生理特性、Cd的积累及化学形态的影响,以及对土壤Cd形态及含量的影响。探讨生物质炭和土壤调理剂对Cd污染土壤的作用机制以及其对小白菜累积Cd的影响机制,找到生物质炭和土壤调理剂修复土壤的适宜添加量,以期为生物质炭和土壤调理剂修复Cd污染土壤的应用和蔬菜Cd污染的合理防治提供理论依据。主要结果如下:（1）从生物质炭和土壤调理剂的的比表面积与吸附前后的FE-SEM的扫描电镜和能谱分析可以知道,生物质炭表面光滑,炭层结构致密,有很多孔隙,且孔洞分布不均。土壤调理剂表面粗糙,形状极不规则,疏松多孔结构较多。两者吸附前后Cd元素质量百分含量明显增加,其他元素均有相应变化。生物质炭和土壤调理剂对Cd²⁺的吸附特性试验表明,生物质炭和土壤调理剂对Cd²⁺的吸附量随平衡液Cd²⁺浓度的升高而增大,其吸附曲线能用Langmuir等温线较好地拟合。生物质炭和土壤调理剂具有很大的吸附能力,吸附效率较高,能在短时间内达到平衡,其对Cd²⁺的吸附符合二级动力学模型。溶液p H对生物炭和土壤调理剂吸附Cd²⁺有较大的影响,在p H2⁹范围时,生物炭和土壤调理剂对Cd²⁺的吸附量随p H的增大而上升在p H>7时趋于平衡,其中在p H5⁷范围时,生物炭对Cd²⁺的吸附效果较好。（2）土培试验中,生物质炭和土壤调理剂及其复合配施处理均提高了小白菜地上部、根系和植株总干质量,小白菜的地上部、根系和总干重均随调理剂和生物质炭施加量的增加呈增长趋势。大多数情况下,施入土壤调理剂和生物质炭及其复合配施,小白菜叶绿素A、叶绿素B、叶绿素总量和类胡萝卜素的含量均显著提高。施加生物质炭和土壤调理剂均能使叶片CAT、SOD、POD活性和MDA含量都显著下降,并能提高小白菜还原糖百分含量、游离氨基酸含量和维生素C含量,降低了小白菜可食部位的硝酸盐含量,改善了小白菜的营养品质。（3）Cd在土培试验小白菜叶片中主要以氯化钠提取态（FNa Cl）和醋酸提取态（FHAc）存在。向Cd污染土壤上施加不同浓度的生物质炭和土壤调理剂均能显著降低叶片中FE、FW、FNa Cl、FHAc、FHCl和FR各形态的Cd含量和Cd总提取量,降幅分别为12.9%⁵8.9%,13.0%58.2%,6.6%⁵0.7%,16.3%⁴1.4%,13.3%⁴7.5%,7.7%39.1%和11.9%⁴8.0%。Cd主要积累在小白菜的根部。施加生物质炭和土壤调理剂及其复配后,小白菜植株各部位Cd含量以及植株Cd总积累量均有所下降。综合考虑Cd含量和Cd积累量,生物质炭和土壤调理剂降低了小白菜地上部Cd含量和Cd积累量以及植株总Cd积累量的作用以生物质炭>土壤调理剂。（4）土培试验土壤中Cd形态大小顺序为可交换态（EXC-Cd）>碳酸盐态（CAB-Cd）>残留态（RES-Cd）>铁锰氧化态（Fe Mn-Cd）>有机态（OM-Cd）。向Cd污染土壤中施加生物质炭和土壤调理剂,土壤中可交换态Cd（EXC-Cd）含量随施加量的增加而降低,而CAB-Cd、Fe Mn-Cd和OM-Cd则显著增加。生物质炭和土壤调理剂及其复配处理显著降低了土壤中Cd形态的总提取量,降幅均在5%左右。两种钝化剂复合配施比单施低浓度量（0.5%²%）的生物质炭和土壤调理剂的改良效果好。（5）大田试验中,Cd污染土壤上,施加不同浓度的生物质炭和土壤调理剂及其复合配施不同程度地降低了小白菜地上部和根系的Cd含量,其降低幅度分别为24.3%⁵2.2%和15.5%³4.3%,18.5%⁴0.9%和18.1%²8.5%,31.2%⁴1.5%和26.9%³3.2%。除T1处理和T/C 2:1处理有所增加外,施加土壤调理剂和生物质炭均能不同程度降低了小白菜地上部Cd积累量,且均随施加量的增加而降低。综合考虑Cd含量和Cd积累量,降低小白菜各部位和植株总Cd积累量的效果以生物质炭>土壤调理剂。（6）在矿区农田土壤中Cd形态大小顺序为可交换态（EXC-Cd）>残留态（RES-Cd）>碳酸盐态（CAB-Cd）>铁锰氧化态（Fe Mn-Cd）>有机态（OM-Cd）,其中可交换态（EXC-Cd）和残留态（RES-Cd）的Cd含量分别为1.565².953 mg·kg-1和1.118¹.425 mg·kg-1,分别占Cd总提取量29.0%⁴9.4%和18.7%²6.4%。生物质炭和土壤调理剂及其复配显著降低了土壤中Cd总提取量和可交换态Cd（EXC-Cd）含量,生物质炭的改良效果明显高于土壤调理剂;两种钝化剂混合配施以T/C 1:2处理效果较单施低浓度（0.5和1%）的生物质炭和土壤调理剂效果更好。（7）相关性分析中,小白菜地上部Cd含量与根系Cd含量的相关性达到极显著正相关水平（P<0.01）。小白菜地上部和根部个含量均与EXC-Cd极显著正相关（P<0.01）,与CAB-Cd、Fe Mn-Cd、OM-Cd和RES-Cd呈显著负相关（P<0.01）。土壤中EXC-Cd含量与CAB-Cd、Fe Mn-Cd、OM-Cd和RES-Cd含量呈显著负相关。更多还原

【Abstract】 The process of Cadmium（Cd） pollution in soil system has the characteristics of concealment, latent, accumulating and long-term. Cadmium goes into the organism through the food chain, and endangers human health after a long-term accumulation. Along with the large-scale industrial urbanization process of our country, cadmium is introduced into contaminated soils through industrial emission, atmospheric deposition, sewage irrigation, application of sludge and fertilizer contaminated with Cd, which results in the severe Cd pollution of the fields throughout China. Cadmium contaminated vegetable soils are also widespread in China, especially in suburban areas. Most of the non-point source polluted farmland soils in our country are mild or moderate pollution. Remediation technologies of soil Cd pollution mainly include engineering method, chemical remediation, phytoremediation and agronomic regulation. In numerous remediation methods, in situ remediation technology of passivation is low cost, easy to operate and has quick effect, which is widely used in contaminated soil, especially in mild or moderate polluted soils. Biochar has large specific surface area, surface energy and the role of binding heavy metal ions, so it is able to passivate heavy metals in soil. Soil conditioner made of inorganic-organic blend of passivating agents, can reduce the effectiveness of heavy metals in soil. In this research, through the adsorption experiment, pot and field experiments, the effects of biochar and soil conditioner on growth, physiological characteristics, Cd accumulation and chemical forms in pakchoi, as well as Cd chemical form in soil. We investigate the mechanism of biochar and soil conditioner on cadmium uptake by pakchoi, and find out the optimum adding amount of biochar and soil conditioner repairing soil, in order to provide theoretical foundation on Cd remediation. The main results are as follows:（1） In the scanning electron microscopy（SEM） and energy spectrum analysis, biochar was observed to have a smooth surface and dense carbon layer structure, with many voids and holes unevenly distributed; soil conditioner surface was found to be rough, highly irregular shape and have more porous structure. Both before and after the adsorption, the percentage of Cd element increased significantly, the percentages of the other elements have a corresponding change. Biochar and soil conditioners on Cd2 + adsorption tests showed that the Cd²⁺ adsorption capacity of biochar and soil conditioners increased with increasing Cd²⁺ concentration in the equilibrium solution, and the Cd²⁺ adsorption curve can be fitting well by Langmuir isotherm. Biochar and soil conditioner has large adsorption capacity, high adsorption efficiency, and they can achieve balance in a short time; the adsorption of Cd²⁺ is in accordance with the secondary dynamic model. Great influence of solution p H on Cd²⁺ adsorption by biochar and soil conditioners was found in our study. In the range of solution p H 2-9, Cd²⁺ adsorption capacity of biochar and soil conditioners increased with increasing solution p H first, and then tended to the balance. Higher Cd²⁺ adsorption capacities were observed at solution p H from 5 to 7.（2） In the pot experiment, the biochar and soil conditioners and their complex treatments increased the dry weight of shoot and root, and total plant dry mass in pakchoi. The dry weight of shoot and root, and total plant dry mass increase with increasing applied amount of the biochar and soil conditioners and their complex. In most cases, chlorophyll A, chlorophyll B, total chlorophyll and carotenoid content of pakchoi significantly increased by the soil conditioner and biochar and their complex. Applying biochar and soil conditioner into the contaminated soil can improve the nutritional quality of pakchoi, which not only significantly decrease the activities of CAT, SOD and POD, and MDA content in leaf of pakchoi, but also increase the content of reducing sugar, free amino acids and vitamin C content in pakchoi, and reduce the nitrate content.（3） The sodium chloride extraction（FNa Cl） and acetic acid extraction Cd（FHAc） were predominant forms of Cd in pakchoi leaves. Applying different concentrations of biochar and soil conditioner into the cadmium polluted soil significantly reduced the concentrations of FE, FW, FNa Cl, FHAc, FHCl, FR and the total extraction amount of Cd in the leaves by 12.9%- 58.9%, 13.0%-58.2%, 6.6%- 50.7%, 16.3%- 41.4%, 13.3%-47.5%, 7.7%-39.1% and 11.9%- 48.0%, respectively. Cadmium mainly accumulated in the roots of pakchoi. After the application of biochar and soil conditioner and their complex, Cd concentration of each tissue and plant total Cd accumulation of pakchoi decreased. Compared with two materials, the reducing effect on the concentration of Cd and the accumulation of Cd in shoot at biochar treatments were higher than those at soil conditioner treatments.（4） The order of concentration of Cd chemical forms in the pot soil was EXC-Cd>CAB-Cd > RES-Cd > Fe Mn-Cd > OM-Cd. The concentration of exchangeable Cd（EXC-Cd） in the soil decreased with increasing applied amount of biochar and soil conditioner and their complex. On the contrary, the concentrations of CAB-Cd, Fe Mn-Cd and OM-Cd significantly increased by applying biochar and soil conditioner. Biochar and soil conditioner and complex significantly reduced the total extraction amount of soil Cd by 5%. The reducing effect of the combined treatments of biochar and soil conditioneron the total extraction amount of soil Cd was better than that ofthe single treatments at low applied amount（from 0.5% to 2%）.（5） In the field experiment, applying different concentrations of biochar and soil conditioner and their complex in cadmium polluted soil variably reduced the concentration of Cd in shoot and root of pakchoi by 24.3%-52.2% and15.5%-34.3%, 18.5%-40.9% and18.1%-28.5%, 31.2%-41.5% and 26.9%-33.2%, respectively. Expect T1 and T/C2: 1 treatments increasing Cd accumulation, soil conditioner and biochar reduced Cd accumulation in shoot of pakchoi, and decreased with increasing applied amount of soil conditioner and biochar. Compared with two materials, the decreasing effect of biochar on Cd accumulation in each tissue and the total Cd of plant in pakchoi is higher than that of soil conditioner.（6） The order of Cd concentration of various chemical forms in the mining area was EXC-Cd>RES-Cd>CAB-Cd>Fe Mn-Cd>OM-Cd, and the concentrations of EXC-Cd and RES-Cd were 1.565-2.953 mg·kg-1 and 1.118-1.425 mg·kg-1, accounting for 29.0%-49.4% and 18.7%-26.4% of the total extraction amount of Cd, respectively. Concentration of EXC-Cd and the total extraction amount of soil Cd decreased by biochar and soil conditioner, and reducing effect of biochar was significantly higher than that of soil conditioner; reducing effect of the combined treatment（T/C1:2） was better than that in the single treatments at low applied amount（from 0.5% to 2%）.（7） In correlation analysis, Cd concentration in shoot of pakchoi was significantly positively correlated with root Cd concentration（P<0.01）. Significant positive correlations were found in Cd concentrations of shoot and root with concentration of EXC-Cd in soil（P<0.01）, while significant negative correlations were also observed in Cd concentrations of shoot and root with the concentrations of CAB-Cd, Fe Mn-Cd, OM-Cd and RES-Cd in soil（P<0.01）. The concentration of EXC-Cd was significantly negatively correlated with concentrations of CAB-Cd, Fe Mn-Cd, OM-Cd and RES-Cd in soil.更多还原