The Process Research Of Microbial Method To Control Mercury-contaminated Farmland Soil

The high Hg²⁺-resistant fungal strain GX-10 was isolated from mercury-contaminated soil.As is shown by the results of ITS sequencing data,the fungal strain shares 99% conserved sequence with Scheffersomyces stipitis.The optimum fermentation condition was determined by fermentation tank.The experimental results show that the optimum fermentation condition is reached by temperature at 24-28?,ventilation at 2.4-2.8 m3/h,under this condition the strain grows well and the biomass is at a higher level;along with the fermentation,fungal concentration is more and more higher,stirring speed should be gradually increased in the range of 0-200 rpm.According to the fungal growth characteristics of different stages,The delay phase becomes shorter,the logarithmic phase becomes longer and the biomass increases rapidly after subsection control mode was used in the fermentation.Fungal growth curve is obtained by curve fitting with logistic mode.The effect of reaction time,pH,initial Hg²⁺ concentration,fungal dosages and temperature on Hg²⁺ removal by GX-10 was investigated,and the morphology of fungal strain GX-10 after Hg²⁺ adsorption was observed.The experimental results show that,the maximum adsorption of Hg²⁺ is reached by fungal dosages at 20 g/L,pH 5,temperature at 28 ?;the higher bio-adsorption of Hg²⁺ is 4.13 mg/kg.Hg²⁺ concentration could meet the national wastewater discharge standard after bio-adsorption of wastewater with not more than 0.5 mg/L Hg²⁺.SEM images show that GX-10 have an effective Hg²⁺ bio-adsorption and can produce stable precipitation structure.In order to obtain the best process conditions,we used the response surface methodology in dealing with wastewater with 20 mg/L Hg²⁺,the best process conditions was reached by temperature at 28?,pH 5,fungal dosages at 20 g/L.The experiment was operated in this condition,and the removal efficiency of Hg²⁺ was 95.332%,the predicted value was 94.431%,and the relative error was only 0.954%,so the optimization scheme is effective.The effect of fungal dosages on mercury immobilization in the soil and on mercury levels in pakchoi by GX-10 was investigated.The experimental results show that,residual mercury in the soil increases from 64.921% to 76.247%,up 11.326%;mercury levels in pakchoi decrease from 0.951 mg/kg to 0.248 mg/kg,down 73.92%.Fungus GX-10 can effectively immobilize mercury in the soil,realize the transformation of the unstable state mercury to stable state mercury,reduce the toxicity,migration and biological validity of mercury significantly.