| Diphenylarsinic acid(DPAA) is a new pollutants by arsenic contamination caused by leaking chemical weapons. more and more researchers have been concerned about the DPAA possessing high toxicity. Microorganisms may play an important role in DPAA repaired conversion processes. Now only two reports suggest bacteria can degrade the DPAA to arsenate in solution. However, to the best of our knowledge, the effects of environmental factors on degradation and the Study on microbial remediation of DPAA contaminated soil have not yet been explored. Arsenic hyperaccumulator, Pteris vittata L., is the ideal plant repair of arsenic contaminated. Our previous research get planting P. vittata can promote the removal of DPAA in soil. But the in-depth study of P. vittata absorption effect on DPAA did not have be start. For the removal of DPAA in soil, contaminated soil remediation, Establishment of microbial phytoremediation technology effective, this paper carried out the following research work, and achieved initial progress. Study on the degradation ability of bacterium Phyllobacterium myrsinacearum RC6 b on DPAA, study effects of pH value, iron, phosphate and the different effects of external carbon source on the degradation, a proposed degradation pathway was established through identification of the transformation products, Study of strain RC6 b repair effect of DPAA contaminated soil, establish determination of DPAA in P. vittata by high performance liquid chromatography, Verification of P. vittata absorption and transport capacity on DPAA and the transformation of DPAA in the plant, research strain RC6b- P. vittata combined remediation of DPAA contaminated soil. The above research explore the microbial- hyperaccumulator combined remediation of DPAA contaminated soil and provide scientific basis and a new technical way. The main results of this study include:1)DPAA can be effectively degraded by strain RC6 b, and by 28 d degrade, the degradation rate of DPAA was 72% in solution. PH and the content of iron have a significant influence on the degradation of DPAA, the degradation rate in acid(pH=4-6) are significantly higher than that in alkaline(pH=7-9), The rate of degradation and the iron content are appeared a positively related, and degradation rate in the concentration of 27 μmol/L is the maximum. Two benzene rings in DPAA have been hydroxy substituted one by one, and can eventually degrade to arsenate.2)Strain RC6 b could degrade the DPAA in soil effectively. Adding the RC6 b strain into contaminate soil after 60 d, Soil fluorescein two acetic acid esterase, dehydrogenase, soil microbial community functional diversity,and soil microbial community structure diversity are improved obviously, the ecological environment have be restore polluted soil effectively.3)A high performance liquid chromatography method was developed for the determination of diphenylarsinic Acid(DPAA)in P. vittata. After the sample was shaken in 0.1 mol/L Na2HPO4 solution for 4 h for the extraction and centrifuged at a high speed, the supernatant was passed through 0.22 μm filter membrane and the concentration of DPAA in the supernatant was determined by high performance liquid chromatography. The mobile phase was acetonitrile and 0.02 mol/L KH2PO4 solution(V/V= 16:84,pH= 2.7), the column temperature was set at 30 ℃, the flow speed was 1.0 mL/min, and the wavelength of ultraviolet detector was 220 nm. Linear relationship between values of peak area and concentration of diphenylarsinic acid was kept in the range of 0.2- 2 mg/L. The recovery rate, RSD(relative standard deviation) and MDL(method detection limit) were 98.49%- 98.80%, 0.97%- 4.60% and 2.74 mg/kg, respectively. The method can be operated easily, quantified accurately and widely used in research on remediation of DPAA contaminated soil with P. vittata.4)DPAA can be absorbed and transported in P. vittata, and the transformation is occurred in transportation to stem leaf, the PAA is one major transformation products, PAA and As(V) were detection in the roots stems and leaves, while DMA and As(III) was detected only in the leaf.5)Pteris vittata L and strain RC6 b both can effectively remove DPAA in soil, restore soil microbial community functional diversity and overall microbial activity, promote the recovery of ecological environment of soil, and the strain RC6 b can effectively promote the absorption of DPAA in soil by P. vittata, strain RC6b- Pteris vittata L combined repair have a better effect. |
