| In this paper,a heavy metals contaminated site in Tianjin was taken as the research object.At first,the collection of survey informations and samples were completed,and the data was used on the health risk assessment of the contaminated site.The results of assessment for contaminated site showed that the environment risk of nickel beyond acceptable risk level,so the remediation target and technology must be determined.Specific content points were mentioned below:The sample points were determined mainly rely on the site information.The monitoring data showed that nickel in the site soil samples exceed the standard value.The characteristics of pollution distribution:In the horizontal direction,the points beyond the background value mainly focus on the south of site,and nickel content of the remaining points were in line with the background values;In the vertical direction,concentrations of nickel decrease with the increase of sampling depth,neverthless individual level was fluctuant,it may be attributed to artificial disturbances.On the basis of the residential land scenario,adults and children were taken as the receptors and the exposure pathways were as follows:oral intake,skin contact and inhalation.The model of health risk assessment was adopted to calculate carcinogenic risks and non-carcinogenic risks,the result of carcinogenic risks was 3.65×10-6 and the result of non-carcinogenic risks was 3.98,the results of risk characterization showed that,the content of nickel had already exceeded acceptable risk level,the works of remediation were needed to be carried out.The key works to implement remediation must be determine the risk control value.According to the guideline,the risk control value could be calculated out,but the guideline was based on the numerous conservative assumptions,which made the calculation of risk control value conservative;Verifying the risk control value through the human bioaccessibility experiment not only can avoid the harm to human health,but also provided there a reasonable remediation control value.After the relevant informations were taken into comprehensive consideration,the second way was selected and the value was determined as 491mg/kg and the earthwork was reduced to 3000 cubic meters.In the designated area,the contents of nickel were different,therefore the remediation technologies varied with the different degrees.The solidification/stabilization technologies were adopted when the pollution problem was serious.In another way,the stabilization technology could meet the requirements.According to the fact,the second way was applied.When 3%stabilizer was added to the soil,the concentration of soil leaching was lower than the detection limit and compressive strength could meet the standards,so it could be reused as subgrade soil near the industrial park. |
