Environmental Assessment Of Polluted Ponds And Reduction Of Hexavalent Chromium

Polluted ponds is the gathering place of industrial wastewater and domestic sewage,which is harm to surrounding soil and groundwater seriously.Exposure pathways and potential risks of hexavalent chromium（Cr（VI））for human health in polluted ponds were evaluated through environmental surveys and risk assessments.The index of geoaccumulation was applied to analyze the impact of Cr（VI）in ecological environment.According to the pollution status of Cr（VI）in the polluted pond,the study of Cr（VI）reduction was carried out.Nanoscale zero-valent iron modified by poly（γ-glutamic acid）（nZVI@PGA）was prepared to evaluate the reduction performance of Cr（VI）.The performance of Cr（VI）reduction were investigated upon the change in several influencing factors.The main contents of this paper are shown as follows.（1）Environmental surveys and risk assessments of polluted pondThrough the initial data collection and field investigation,the pollution status of one pond in Heilongjiang was analyzed.According to the testing and analysis results,the maximum concentration of Cr（VI）in the bottom mud was 48 mg/kg,which exceeded the screening value of 5.7 mg/kg.Through exposure analysis and risk assessment,the carcinogenic risk index of Cr（VI）of the bottom mud was 8.83E-5,which exceeded the acceptable level for humans.According to the result of index of geoaccumulation,the risk level of maximum Cr（VI）concentration in the bottom mud reached level 6,belonging to a very seriously polluted area.（2）Reduction of Cr（VI）by nZVI@PGAnZVI@PGA showed an excellent reduction performance to Cr（VI）in aqueous solution.When the mass ratio of PGA/nZVI was 1:5,the reduction efficiency of nZVI@PGA can reach 97.3%,which was twice than nZVI in 30 min.By changing the p H,temperature and initial concentration of Cr（VI）in the reaction system,the effect of Cr（VI）reduction was investigated.In addition,the effects of Cr（VI）reduction were studied by adding NO₃^-,HCO₃^-,SO₄^2-,Cl^-and HA to the aqueous solution separately.The results showed that nZVI@PGA was still efficient for the Cr（VI）reduction with SO₄^2-,Cl^-and HA in the aqueous solution.