| In China, the e-waste dismalting actives are almost crude and primitive, ignoring the safety of workers and leading serious pollution to the environment. For example, manual disassembling, open incineration and acid dipping, have lead serious environment pollution. Soil safety is vital as it is the sink of most pollutants and a part of the natural environment by human society.In this thesis, we first reviewed the research progress of phytroremediation and nZVI. Then, temporal and geographical changes in the concentrations of POPs and heavy metals in soil and sediments around a typical e-waste dismantling area were systematically were firstly investigated. Results showed that Guiyu are serious polluted by POPs and HMs, the environmental pollution rectification in this area is also severe.It can be confirmed that open burning site was demonstrated to be the pollution source of PAHs, PCBs and other pollutants, the other sites’concentration are vary as the distance from the open burning site.∑6-dioxin-like and∑CBs in all the soils increased gradually from the early stage of pollution to the peak of pollution. However, their concentrations in the three sites decreased in the following order:open burning site> printer roller dump site> rice field. The levels of HMs all higher than national standard (except Cr), and the mainly pollutants are Cd and Cu.Then, the indication between flower and soil pollution was discussed. The total flavonoids and Caffeic acid have correspondence relationship with the concentration of Pb and PCBs. For example, Cd middle and low concentration (0-10mg/kg), the Tagetes patula. Linn has more bud to blossom out and the color is bright. We built an early observing and monitoring system on soil pollution, which more intuitive, simple and low-cost.Further, we studied the potential of ornametal plants to phytroremediation e-waste pollution soil. The acute and chronic experiments were performed in the third part. NZVI, vermiculite-supported nZVI (Ⅵ-supported nZVI) and activated carbon supported nZVI (AC-supported nZVI) were selected to investigate the environmental toxicity effects on Impatiens balsamina and Tagetes patula Linn through short and long-term exposure. Our results demonstrated, for the first time, that modified nZVI (VI-and AC-supported) could alleviate the toxicity effect. nZVI effectively suppresses the aggregation effect, increasing surface area at the same time. They thought to deliver more reactivity with their surroundings than nZVI by effectively suppressing aggregattion effect. In soil culture, higher concentration (0.02%, w/w) shown obviously inhibitory effect on Impatiens balsamina, nearly stop developing after20days of exposure. This work provides important datas for the further application of nZVI remediation, even combined with plants in phytoremediation. However, the mechanisms of different nZVIs uptake inside plants seeds, distribution and accumulation are not clear and require further investigation.We studied the effect of nZVI on the remediation of PCBs on the combined pollution by Impatiens balsamina. Under the joint stress of Pb and PCBs, the antioxidative defense system of Impatiens balsamina played an important role in sustaining the balance between the production of ROS and the neutralization of antioxidants, and the plant showed good Pb tolerance and cumulative capacity. The dates of pot experiment indicated that, the plant showed good PCBs-Pb tolerance and cumulative capacity, and PCBs could stimulate the growth of plant. Impatiens balsamina showed the potential of remediation PCBs, the remove efficiency increased with the concentration of PCBs.0.05%(w/w) nZVI play a positiverole in phytroremediating PCBs. The PCB18,28have raised11.69and13.86%after grown three months. Vertical contrast between different months, it showed a dramatic increase of the removal efficiency during the first ten days and a moderate increase during day30(with17.19%and9.62%). It was slow down after day60. Prolong the growth of Impatiens balsamina, optimization the amount of nZVI and the way of addtion nZVI, could improve the performance further.Three different nano-sized zero-valent iron (nZVI) including nZVI, vermiculite-soupported nZVI (Ⅵ-soupported nZVI) and activated carbon soupported nZVI (AC-soupported nZVI) were selected to investigate the effects and uncover the mechanism on Tagetes patula Linn phytroremediation PCBs were carried in the fifth part. In the experimental range, the remove efficiency was increase along the PCBs concentraction. When the concentraction of Cd is lmg/kg, the effciency is only7.19%-11.67%(PCBs50μg/kg), higher to38.40-42.86% from19.23%-23.77%as the PCBs concentration increase from100μg/kg to500μg/kg. The removal efficiency (%) of nZVI treatments was higher than contorol. Among these, AC-soupported nZVI was the best, then Ⅵ-soupported nZVI. The possible reason was that loaded nZVI have definite shape, can surpess the agglomeration of nZVI and slowly the couse of oxidation. AC has more bonding sites than VI in the partical surface and inerface.The effect of three different nZVI on the enrichment of Pb was investigated by using the orthogonal experimental design. Different nZVI displayed different effect on the experiment. All in all, the addition of nZVI significantly reduced the Pb concentration in roots and shoots by decreasing the exchangeable and bioavailability Pb content, in Pb-contaminated soils. But the specific reasons should befurther studied.In conclusion, we planing to use three different nZVI as the enhancer, select PCBs, Pb and Cd were as objects, Impatiens balsamina and Tagetes patula Linn as the texted plants, pot experiments were carried out to discover the potential and repair mechanism of Pb/Cd-PCBs combined pollution soils with nano-phytoremediation method. These results provied theoretic basis and data support for further research. |
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