Research On The Risk Assessment Of A Contaminated Site And Remediation Technology

Due to the development of the city,We needs a large number of heavily polluting industrial enterprises and they need be moved into the industrial concentration area, so it left a lot of contaminated sitesaminated sites in city.The existence of these contaminated sites has caused harm to the natural environment and human health. It affect the development of land reuse, hinder the development of urban construction and local economy.In view of the situation of the site and the characteristics of pollutants, the reasonable method to evaluate and repair the site has become a hot issue today.This paper take a chromium contaminated site in Sichuan Province as the research object.And it has deeply research on three aspects that include the discovery, evaluation and treatment of contaminated sites. Taking risk assessment guidelines that issued by the state as the theoretical basis, localize the exposure parameters and model, analysis the rationality of selection of screening value,analysis parameter sensitivity to judge the rationality of the correction and comparative analysis the impact of the original guide(G) and the revised guidelines(M) on the cost.At last it carry on the experiment of repair technology to make the reasonable repair plan, and to discuss the best repair technology for the heavy polluted area.Achieved the following results:(1)According to "Sichuan Province National Physique Monitoring Bulletin in 2014 ", "Environmental Quality Bulletin" issued by the Sichuan Provincial Department of environmental protection, reference parameters of correction and model of foreign risk assessment standards.And carry on the uncertainty analysis of the correction of the height, weight, PM10, skin contact absorption efficiency factor, soil intake and other parameters and skin exposure model.Reasonable risk value was obtained, and it was found that children's weight, PM10 and soil intake had a great impact on the value of risk,so such data need to be valued based on the actual situation.(2)The calculated risk control values are compared with the national standards at all levels,the target value of soil remediation is determined based on ensuring human health.It is found that the setting filter value of Cr6+ is small in the draft of construction land,When we choose the filter value,we need to adjust it according to the actual situation.(3)According to the risk assessment results of G and M,it calculated the contribution rate. The results show that the difference between before and after about the total risk of contribution rate of each exposure path is very small,the result of the calculation is reasonable and credible.Because the risk control value of the original guide is greater than the revised guidelines,leading to repair work, the cost of the original guide are also higher than the revised guidelines. In the work, the model parameters are revised according to the actual situation, and the repair cost is reduced.(4)It determine the treatment of contaminated soil by ectopic solidification / stabilization and chemical reduction and chemical reduction in situ.The feasibility experiment was carried out, and the experimental results were obtained:The time of solidification and curing should be at least 21 days, 28 days is best;The effect of solidification is better when curing agent cement and soil mass ratio of more than 40%;The effect of reducing agent:Sodium sulfate > sodium sulfide> sodium sulfite;In the orthogonal experiment of three levels of cement, lime and Atetsumi factors,the ferrous sulfate is the main factor that affects the result of the experiment, and the cement is the secondary factor; The best remediation technology for each 200 g contaminated soil, cement should be taken 200 g, lime should be taken 100 g, ferrous sulfate dosage of 1.75 times the theoretical amount of reaction.The dosage of ferrous sulfate should be taken 1.75 times of the theoretical reaction.