Investigation In Remediation Of Phenanthrene-and Tricyclazole-contaminated Soil Using Compost

This thesis mainly focuses on the application of the produced compost to remediate the phenanthrene- and/or tricyclazole- contaminated soils as well as variations of microbial community structure, some enzyme activities during the process of remediation, and the kinetics based on the experimental data. The results obtained are shown as in follows:1. In this study, the process parameters, activities of characterized enzymes, shift in microbial population and community structure were investigated during composting the stimulated municipal solid waste (MSW). The results showed that the temperature was the dominant factor to lead the composting during the whole compost process, and and it showed a noticeable influenced on the enzymatic activity and microbial communities. At the stable stage of compost process, the catabolic activity, enzyme activity and microbial population and diversity was got a prominent improvement, as which was high enough to perform remediation of contaminated soil.2. Composted Municipal Solid Waste (CMSW) and Spent Mushroom Compost (SMC) were taken as additives for remediating phenanthrene- and tricyclazole- polluted soil. The HPLC analysis on concentration of pollutants demonstrated that the CMSW and SMC both could improve the degradation process of phenanthrene in soil by shortening the lag phase, increasing the degrading rate, while SMC resulted in a more rapid biodegradation of phenanthrene with different initial concentrations, compared with CMSW.A less than 18% of the added tricyclazole was removed within 56 days in soil and soil/CMSW mixture, whereas an increased removal rate to 33% in soil/SMC was recorded, and the removal rate was proved to be negatively related with the initial concentration of tricyclazole. It might be due to the enhanced toxicity of added pollutant, which inhibited the growth and activity of corresponding degrader.3. As one of phenanthrene analogues, tricyclazole was found to inhibit the growth of phenanthrene-degrading strains ZX4 even in lower dose (30 mg L^-1) with an obviously prolonged lag phase. Further studies revealed that the influence from tricyclazole was positively related with its concentration and the growth of most of phenanthrene degraders was prominently delayed at 60 mg L" of tricyclazole. With 60 mg kg^-1 of tricyclazole, the population of PAH degrader rose slowly following a 2 weeks lag. However, tricyclazole generated no negative effect on PAH degrader in soil/SMC mixture, where the population of degrader rose quickly in similar trend as the control, without any obvious delay.Based on HPLC detection, tricyclazole was proved with a prominent inhibition effect on degradation of phenanthrene in soil with a prolonged lag phase of degradation, and phenanthrene was removed linearly but exponentially without tricyclazole.The concentration of phenanthrene in both soil/SMC remediation systems was diminished at exponential rate. It was deduced that SMC could not only get ride of the inhibition of tricyclazole on growth of PAH degrader, but dispel the influence on degradation of phenanthrene generated by tricyclazole likewise.In other way, a negative influence was observed on the degradation of tricyclazole at the presence of phenanthrene. It might due to the effect of firstly utilizing phenanthrene by microbial degrader or the enhanced toxicity of total pollutants.4. The investigation on variation of Catalase, polyphenol Oxidase, respiration activity and population of PAH degrader revealed that SMC improved the activities of many microbes and enzymes which were not significantly affected by contaminants, but produced no impact on succession of PAH degrader. Instead, the population of PAH degraders was mainly affected by the properties and concentration of the pollutants.Despite the rich humus in SMC, extraction analysis of phenanthrene and tricyclazole in SMC indicated that SMC only resulted in slight adsorption rate of both pollutants.5. As an indicator of the degradation potential of PAHs, C23O activity, determined with MPN-PCR showed a significant correlationship with PAH degraders (R²=0.871, p<0.01) and could reflect the variation of phenanthrene in both environments. On the other hand, no influence was observed via the added tricyclazole.An analysis on variation of microbial communities with DGGE implied that the microorganisms were also under control of phenanthrene, due to its enormous toxicity. In phenanthrene contaminated samples, microbial diversity was negatively correlated with the concentration of pollutants.On the contrary, fungal communities in contaminated samples did not response to the pollutants rapidly, but differed with each other according with the type and concentration of pollutants in the end of the remediation. In both soil/SMC mixtures, the populations and diversity of xenobiotic-degrading fungi were increased comparing to the soil samples, due to the addition of SMC containing abundant catabolic fungi.6. Glutathione S-transferases (GSTs) were found in most of microorganisms, with a variety of evidences about their ability on catabolism of many xenobiotics in cell. Two types of GSTs were identified by DGGE analysis, one was the related phenanthrene degradation and the other was not. Therefore, the ELISA on concentration of GST in environments might reflect the total amount of GST.The content of GSTs was not significantly affected by added pollutants either phenanthrene or tricyclazole contaminated samples, but varied with the degradation of each contaminants. In general, the content of GST could indicate the catabolism of pollutants, rather than the residue.