Selection Of Phytoremediation Species For PAHs Polluted Soils And Study On The Micro-ecological Characteristics In Plant Rhizosphere

It is worldwide concerned to prevent and remediate soil organic pollution, conserve the soil environment, and realize sustainable utilization of soil resources. It is also very important to select high efficiency plants for remediation of organic polluted soils, to elucidate the processes and mechanisms of phytoremediation, and to understand the rhizosphere micro-ecological characteristics of the remediation plants in polluted soils, which would provide scientific basis for developing fast and cost-effective technologies for control and remediation of organic polluted soils.This dissertation revealed the hazards of PAHs-contaminated soil, reviewed the present research status on phytoremediation of soil organic pollution, summarized the mechanism and affecting factors of phytoremediation, and elaborated the selecting for high performance remediating plants and their rhizosphere effect response during remediating processes. Based on these, species in Poaceae and Fabaceae family were studied for selection according to the remediating effectiveness of the species in PAHs spiked soils. Moreover, the micro-ecological characteristics in rhizosphere during phytoremediation were also studied. Major results are as follows:(1) Under treatments of 10 and 50 mg B[a]P kg^-1, the degradation rates of B[a]P with plants were 66.9～69.6% and 72.3～77.0% in an unpolluted soil after 120 days, whereas the rates without plant were 57.4% and 67.7%, respectively. Under treatments of 50 mg B[a]P kg^-1, the degradation rates of PAHs with plants were 77.1～77.6% in a polluted soil after 90 days, whereas the rate without plant was 73.5%. B[a]P in freshly-spiked soils would be dissipated much easier by phytoremediation than that in aged polluted soils. Both Medicago sativa and Lolium multiflorum can effectively remediate PAHs polluted soils.(2) The rhizosphere effects enhenced the total water-extractable carbon, increased microbial biomass carbon, promoted activities of polyphenol oxidase and dehydrogenase with the interaction of added B[a]P, and thereby promoted the PAHs dissipation in soils.(3) With the purpose of illustration the mechanism of PAHs dissipation in the rhizosphere, this study used phospholipid fatty acid (PLFA) profiles to reveal the response of soil microbial communities. The microbes characterized by 16:1w5c, 18:1w5c, 18:1w9c, and 10Me18:0 played positive roles during the PAH dissipation in soils. Both pollutant and plants altered the profile of microbial communities in polluted soils.