Heavy Metal Pollution Characteristics Of An Abandoned Coking Plant And Study On Electrokinetic-Enhanced Plant Remediation Technology

With the development of China's society,the adjustment of industrial structure and the transformation of economic development mode,a large number of industrial enterprises have stopped production,closed or relocated,leaving a large number of heavy metal contaminated sites.This paper took an abandoned coking plant in Shanxi Province as the research object,studied the spatial distribution and risk assessment of heavy metals in the plant area,and studied remediation effects of three plants(ryegrass,alfalfa and ricinus)in a series of Pb contaminated soil by single plant phytoremediation and electrokinetic-enhanced phytoremediation,and explored the optimal electric parameters for improving phytoremediation efficiency in different Pb contaminated soils.The research results are as follows:(1)The characteristics of heavy metal pollution in the study area indicated that Pb pollution was the most serious;the ecological risk was strong,and Hg,Cd and Pb were the main contributing factors;the non-carcinogenic risk existed,the oral intake was the main route,As and Pb were the main contributing factors;the carcinogenic risk was within the acceptable range;the coking area was the most polluted area.Since Pb exceeded the standard most and was reflected in both ecological risk and non-carcinogenic risk,it could be treated as priority pollutant.(2)Single plant repair experiment showed that the enrichment coefficient and transport coefficient of alfalfa and ricinus were not correlated with soil Pb concentration,while the enrichment coefficient and transport coefficient of ryegrass were significantly correlated with soil Pb concentration.The accumulation of Pb in the plants was concentrated in the underground part,but alfalfa and ricinus had strong underground enrichment ability(BCF>1),while the underground part of ryegrass has no Pb enrichment ability(BCF<1);the absorption capacity of Pb in the plants was as follows: ricinus > ryegrass > alfalfa,and the maximumabsorption was under the condition of 300 mg/kg,400 mg/kg and 400 mg/kg,respectively.(3)Electrokinetic-enhanced phytoremediation experiment showed that electrokinetic effects were related to plant species and soil Pb concentrations.Electric action could increase the transport coefficient of ryegrass and ricinus,but has no significant effect on alfalfa;it could increase the enrichment coefficient of plants(ryegrass,alfalfa,ricinus)and promote the enrichment or accumulation of Pb,but it could not change the accumulation effect(BCF<1)to enrichment effect(BCF>1);the electric action can improve the Pb repair efficiency of ryegrass and ricinus in series of Pb contaminated soils,but only on the condition of 100mg/kg for alfalfa;the optimal electrokinetic conditions for improving the recovery efficiency were different in different Pb contaminated soils(100mg/kg,200mg/kg,300mg/kg,400mg/kg):they were T6,T6,T4,T2 for ryegrass,and T5,T5,T3,T6 for ricinus,and T4 was the best parameter for alfalfa on the condition of 100 mg/kg.The promoting effect of electric action on the plants was as follows: ricinus > ryegrass > alfalfa.