The Investigation On The Situation Of Contaminated Sites In Dalian And Study Of The Decision On Screening Levels

With the rapid development of economics and extension of cities, the structure and function of soil which is one of basic elements for ecosystem have been gradually changing in recent years. Currently, many industrial sites are moving out of the downtown based on city plans so that these lands function into the business and/or the residence. However, the pollution to underground water, generated by industry processes, varies with the change of the use of land and adversely affects human beings. Therefore, it is of great importance to conduct the environmental risk assessments in industrial sites.At present, as for the risk assessment to industrial sites, the corresponding method mainly relies on the reference of risk-assessment systems and models of USA and Netherland. Although the Ministry of Environment had put the<Technical Guide on risk assessment of polluted sites> into effect since the 1st of July in 2014, which provided the basic guidance in techniques for risk assessments to polluted sites in our country, there is no any another uniform principle for risk assessments to the soil pollution. Furthermore, the investigation and the assessment have been carried out for years in Dalian based on the Environmental risk assessment filter values for soils of site> which was issued in Beijing in 2011.However, the soil is of great difference among different areas so as to be unreasonable to adopt filter values for the risk assessment work on a basis of soils of Beijing. Therefore, it is necessary to conduct the research on risk-assessment falter values for soils in Dalian.(1) This study initially analyzes the relocation of 13 existed enterprises in Dalian, which are mainly in the area of Dalian Bay. In conclusion, among various typical pollutants and contents, the benzo (a) pyrene was beyond the limited value, which was with the maximum concentration of 0.848 mg/kg. And the excessive values were in the presence at a slag factory and a dyestuff factory, which reached the detected level of 79% and 84% respectively.(2) We proposed a method based on the acceptable risk level of cancer and non-cancer which applies counter calculation to get the concentration of soil pollutants under acceptable risk level and then to act as the screening level. Fitting the selected five typical pollutants cadmium, naphthalene, benzo (a) pyrene, benzene and ethylbenzene with screening values, the screening values of each substance were 0.064 mg/kg of benzo (a) pyrene, naphthalene of 2.14 mg/kg, cadmium of 13.36 mg/kg, ethylbenzene of 522 mg/kg, benzene of 0.062 mg/kg respectively.(3) We applied the fitted screening value to recalculate the site risk assessment for a chemical plant in Dalian. As a result, the health risk of benzene and benzo (a) pyrene were higher than that of the general acceptable risk level, and the contribution rate of two substances was analyzed.