Study On Distribution Of Heavy Metals In Contaminated Sites After The Removal Of The Coating Factory

Currently, with the rapid development of urbanization and continuous expansion of urban regions, industrial enterprises in the central areas need to be relocated in order to meet the requirements of urban development. After the relocation, the land field that the enterprises formally occupied might be polluted by the chemicals produced in the production process, which will threaten the human health. Therefore, before the recycle of land it is necessary to conduct a comprehensive assessment on its legacy pollutants and provide a reliable scientific basis for the land restoration and recycle. In order to meet the requirements of urban transformation, a coating factory named A in Chongqing relocated and the pollution of heavy metals in the soil need to be investigated. Two batches of soil samples were collected from the land field. The first batch is from the five screening sampling points that were chosen according to the original function partition of the company. The second batch is from nine screening sampling points that were chosen according to the survey results of the first batch. Flame atomic absorption spectrophotometer was used to analyze the content of the five types of heavy metals in the soil samples.The conclusions are as follows:(1)The contents of five heavy metals in the top layer soil(0-20 cm) from five screening sampling areas are greatly different, resulting in various degree of pollution. Additionally, the pollution by the five types of heavy metals are unevenly distributed in each area. The degree of pollution is decreasing as follows: road > production area > raw material storage area > end product storage area > central square. The road was the most greatly polluted area, especially the whole exposed soil from both sides of the hardened road to the edge of production and storage areas.(2)In the top layer soil(0-20 cm) of the key pollution area(i.e. road), the contents of five types of heavy metals varied little and distributed much more evenly than that between different areas. The pollution was mainly caused by materials falling down during their transportation. The vertical migration distribution of heavy metals become unevenly, and their contents also decreased with land depth. The content of heavy metals in top layer soil(0-20 cm) and superficial soil(20-40 cm) shows an obviously positive correlation. The RAF results indicate that one heavy metal in all the sampling areas has similar vertical migration capability, and the capability was not related to the type of heavy metals.(3)The results showed that the content of Cr was lower than A level, the content of Cu, Zn and Cd was in A-B level, and the content of Pb was lower than A level except one sampling area(in A-B level). The pollution depth in some area is beyond 40 cm. It is suggested that utilization direction of the land field should be limited or adjusted according to the Exhibition Standards(provisional)(HJ350-2007).