Enhancement Effects Of Weak Electric Field On Uranium And Manganese Removal From Leachate Of Uranium Tailings Pond By Constructed Wetland

Under the effect of physics,chemistry and biological weathering,part of uranium and manganese of the uranium tailings will release into the uranium tailings pond.Under the action of rainfall and runoff,the leachate of uranium tailings will be produced,resulting in a larger area of radiation pollution.Once the uranium and manganese of leachate enter the food chain will them accumulate in the human body,posing a threat to human health.In addition,the leachate contained high concentration of pollutants such as chlorine,nitrate and sulfate.Therefore,the remediation of leachate from uranium tailings pond is an urgent problem needed to be solved.The constructed wetland(CW)model was constructed with white calamus(Acorus calamus L.)as the experimental plant.This article was basing on the research of the effect of different voltage gradient(VG)of direct-current weak electric fields(DCWEF)and different hydraulic retention time(HRT),different vertical water flow directions on the removal of uranium and manganese from the leachate of uranium tailings pond in CWs,the distribution characteristics of uranium and manganese in the CWs,the growth and physiological state of wetland plants,and so on.Results showed that with the application of DCWEF,the uranium and manganese concentrations of CW effluent met the emission standards,and the upwelling CWs with the enhancement of DCWEF were better than the downwelling ones.When the VG was 0.3 V/cm,in the upwelling CW,the removal rates of uranium,manganese,and nitrate were 97.03%,99.72%,99.30%,respectively;and the uranium,manganese,and nitrate concentrations of its effluent were 9.19 ?g/L,0.03 mg/L,and 2.69 mg/L,respectively.However,they made no difference to the concentration of chlorine and sulfate.Also,the distribution change of uranium and manganese in the constructed wetland and significant improvement of the enrichment capacity could be caused by the DCWEF.With a VG of 0.3V/cm,the uranium and manganese bioaccumulations of Calamus planted in the upwelling CWs were significantly increased by 43.59% and242.68%,reaching up to 169.71 mg/kg and 2911.00 mg/kg.Under this condition,the micro-bio-enrichment of uranium and manganese were significantly increased by 7.38% and 48.90%,reaching up to 67.45 mg/kg and 20294.49 mg/kg.Also,the uranium and manganese concentration of the salt scale accumulated on the surface of cathode affected by the DCWEF,up to 51.20 mg/kg and 653.11 mg/kg.Simultaneously,the quantity of uranium adsorbed on the matrix was reduced to 10.76%,while the quantity of manganese had no significant variation,compared with the upwelling CW with no DCWEF.According to the correlation analysis,it was found that in the progress of the remediation on the leachate from uranium tailings pond by CW,the variation of uranium,manganese,and nitrate concentrations performed the high correlation,and the Pearson correlation coefficient of uranium concentration between matrix and cathode surface was – 0.897,showing a highly negative correlation.Applying a DCWEF with a VG of 0.3 V/cm on the upwelling CW could alleviate the oxidative stress of plants suffered from the uranium and manganese by significantly improving the activity of superoxide dismutase(SOD)and the content of glutathione(GSH)for the decline of the malondialdehyde(MDA)and the increase of soluble sugar(SS).Summary,the couple of DCWEF and CW can achieve the high efficiency remediation of the leachate from uranium tailings pond.