Micro-ecological Effects Of Phthalate Ester Contaminated Soil And Research Of Fungi-plant Combined Remediation

The impacts of combined phthalate acid ester (PAE) contamination, including dimethyl phthalate (DMP), diethyl phthalate (DEP), and dioctyl phthalate (DOP), on soil microbial diversity were studied. The fungi-plant mode of PAEs bioremediation was also discussed. Research methods and results are as follows:(1) The impacts of combined PAEs contamination, including DMP, DEP and DOP, on farmland soil basal respiration and microbial diversity were studied by monitoring soil respiration, soil PAEs concentration and random amplified polymorphic DNA (RAPD) marker under laboratory simulation testing. The results showed that the soil basal respiration was activated by PAEs at an early stage, reaching a maximum value at 400 mg/kg PAEs treatment. However, this type of activation effect decreased with prolonged PAEs exposure time. In addition, the concentration of PAEs in the soil decreased, especially the DEP concentration. The Shannon-Weaver index of soil microbial community DNA sequence in all treatments was:0 mg/kg> 50 mg/kg> 100 mg/kg> 200 mg/kg> 400 mg/kg. Overall, the results indicated that the combined PAEs contamination in soil may stimulate soil basal respiration, but decrease soil microbial diversity.(2) Two PAEs degradation strains F2 and F3 were isolated from PAEs contaminated farmland soils, and DMP, DEP and DOP could be degraded at the same time by those two strains. The strains were identified as Fusarium oxysporm and Isaria sp. respectively. The optimum C:N of those strains was 20:1, and optimum pH was 7.0. The pH 5.0-7.0 was available for their survival. The biodegradation of PAEs in liquid and soil were studied by monitoring PAEs concentration and mycelium weight. The results showed that the concentration of PAEs in liquid culture medium decreased 66.20% in 7days (initial concentrations 300 mg/kg). The concentration of PAEs in the soils decreased 69.02% in 30days (initial concentrations 300 mg/kg). It is clearly that, those two strains were qualified for the biodegrading of combined PAEs contamination.(3) The degradation of PAEs in farmland soil was tested by monitoring plant biomass and height, PAEs concentration and DGGE. The fungi-plant mode of PAEs bioremediation was also discussed. The results showed that the growth of tomato and soybean was inhibited by PAEs, but no effect on vetiver. The soil basal respiration and fungi community were influence by adding PAEs, plants and inoculate fungi. Bands of F3 were no found in DGGE maps at the end of experiment in F3 inoculate soil. Synergistic effect on PAEs degradation was found between F3, indigenous microorganisms and plants. Compare of non-inoculate treatments, the average concentration of PAEs in pot soil was decreased 20.67% in inoculate treatments, and the average concentration of PAEs in plants was decreased 28.86% in inoculate treatments. It is clearly that, inoculate F3 enhance the biodegradation of PAEs in soil, and decline the accumulation of PAEs in plants. Three types of PAEs bioremediation mode were suggested.