【作者】 马伟芳；

【导师】 赵新华；

【作者基本信息】 天津大学 ， 环境工程， 2006， 博士

【摘要】 重金属-有机物复合污染底泥的植物修复是环境治理的热点和前沿领域,它利用超积累植物能从底泥中超量吸收重金属和降解有机物的特性,达到减少底泥中重金属和有机物含量之目的。目前复合污染植物修复的研究还很不完善,因此本文以天津市大沽排污河疏浚底泥为试验对象,通过盆栽试验,研究了玉米、印度芥菜、超积累油菜、紫花苜蓿、黑麦草、苋和不结球白菜等7种植物对复合污染疏浚底泥的修复情况及机理;并对天津市三大排污河沿岸的植物进行了筛选,为植物修复复合污染底泥或土壤提供了科学依据和理论基础。主要研究结果如下:适于底泥修复的植株种类为印度芥菜、黑麦草、玉米和紫花苜蓿;玉米和印度芥菜轮作对重金属积累效果和对底泥中有机物尤其是对氯苯的降解效果比黑麦草连茬、玉米和黑麦草互作、印度芥菜和黑麦草互作好。首次从理论上证明了重金属在植物体内的解毒机理为重金属螯合在配合体上,且配合体之间以及重金属和配合体形成架桥而聚集成团,形成金属结合蛋白或者沉淀积累在植物体内。柠檬酸和EDTA是能够加速植物修复进程的理想螯合剂。分次投加EDTA不仅可以加速植物修复,减弱EDTA的降解难题和EDTA-重金属螯合物的淋溶问题对环境的风险;还能减弱其带给底泥和环境的不利影响。首次发现分三次投加EDTA明显增加了底泥颗粒的粒径,降低了其比表面积,有利于底泥颗粒吸附重金属的释放,从理论上证明了受污染底泥实施加速植物修复的有效途径。建立了植物吸收、迁移与积累重金属的数学模型。基于MATLAB的ODE45,利用植物积累不同重金属的相关关系,对玉米积累不同重金属的数量随生长时间的变化情况进行了模拟和预测。通过模拟,不仅可以准确反应重金属在植物体内的吸收、迁移和积累的过程和机理,还可以预测植物积累重金属的数量及植物修复的最佳收获时间。沿岸植物调研发现了对Zn有较高的富集能力的新植物种类-红蓼、费菜和葎草,三者地上部分积累Zn量均大于地下,其中葎草地上部分积累的Zn量高达4614.11 mg/kg;蒲公英和小蓟地上部的Cd含量均高于根部Cd含量,而且富集系数均大于1,基本具备了超富集植物的特性,因此具备较大的继续研究价值。这些植物的发现为污染河道底泥的综合治理及底泥填埋厂的植被覆盖提供了依据。疏浚底泥园林应用,可促进植物生长,降低污染物进入食物链的风险性,又弥补了园林土壤贫瘠的不足,是城市疏浚底泥资源化的较为理想的出路。修复底泥农田利用,其重金属和有机污染物对地下水污染的潜在危险性大大降低。更多还原

【Abstract】 Phytoremediation is a new technique to clean up heavy metal-organic contaminated sediments or soils with some accumulators or hyperaccumulators which can take up heavy metal, transport and accumulate them in their above ground shoots. These plants also can decompose organic contaminants at the same time. While the mechanisms of phytoremediation for complex contaminated soils are not fully understood and the technology is not established yet. In order to solve the problem of ubiquitous polluted sewage rivers, pot experiment was conducted to study phytoremediation efficiency and mechanism of maize, Indian mustard, oilseed rape, Medicogo sativa L., Lolium multiflorum L., Amaranthus tricolor L., and Chinese cabbage in cleaning heavy metal-organic contaminated dredged sediments of Dagu sewage river. At the same time, the plant species were investigated in order to screen out native hyperaccumulators. The main results obtained were summarized as follows:Maize, Indian mustard, Medicogo sativa L., and Lolium multiflorum L. were screened out as feasible restoration species. Maize-indian mustard rotation system had the highest accumulation amounts to heavy metals and the best removal efficiency to organic contaminations (especially to chlorobenzene) among coatinuous stubbles Lolium multiflorum L., maize and Lolium multiflorum L. co-cropping, Indian mustard and Lolium multiflorum L. co-cropping and maize-indian mustard rotation system. One of the detoxification mechanisms was confirmed in the theory that multinuclear heavy metals chelated on ligand, and heavy metal accumulation in plant existed in the metal-organic clusters through the bridging of ligand and heavy metals for the first time.Citric acid and EDTA is suitable chaletor to improve phytoremediation effect. By adding EDTA in several times, it not only can accelerate phytoremediation effect, but also can abate side effect to sediment and environment because it can lighten the decomposing problem of EDTA and the eluviation risk of EDTA-heavy metals chelator to environment. The results were finded for the first time that by adding EDTA three times to sediment, the average particle size of sediment increased, while specific surface area and crystal lattice intensity decreased, which were contributed to the desorption of heavy metal from sediment particle.A model of heavy metal absorption, translocation and accumulation by plant was established to simulate the heavy metals accumulation process with growth time.Corresponding to the accumulation correlativity of heavy metals, using ODE45 solver of MATLAB simulated the accumulation process of maize to Zn, Pb, Cu, Ni, Cd. The model and simulation result provide scientific gist to know heavy metal absorption, translocation and accumulation mechanism of plants, to forecast heavy metals accumulation amount and to decide the optimal time of harvest and soil remediation.New Zn hyperaccumulator species were fined though investigation along the river which were Polygonum orietale L., S. aizoon L.., and Humulus scandens. The accumulation amount of Zn in the shoots was larger than in the roots among the three species. The highest accumulation amount was in the shoots of Humulus scandens, which attained 4614.11 mg/kg. The Cd accumulation amount in shoots of C. segetum Bge and Taraxacum mongolicum was higher than in roots. The hyperaccumulation coefficient was exceeded one in the two plants, which indicated that the two plants possessed the basic characteristic of hyperaccumulator and the value for further research. The discovery of this species provided the native plant to integratively phytoremediate the sewage river sediment and the vegetation category to cover the sediment fill plant.Horticultural application of dredged sediment can promote the growth of plant, which not only reduced the risk of contaminant entering food chain, but also fertilized the bareen gardens soil. This was a good way to turn dredged sewage river sediment into resource. The potential risk of heavy metal and organic contaminant to groundwater and environment was greatly reduced by application of phytoremediated sediment than unphytoremediated dredged sediment to farmland.更多还原