Characteristics and models for chlorohydrocarbon distribution in soils of Shanghai, China

A clear understanding of the distribution characteristics of contaminants in soils is a prerequisite for remediation of contaminated sites. However, investigations on the distributions of chlorohydrocarbon contaminants in the field are still rare. In this study, three contaminated sites in the urban area of Shanghai, China, were selected to investigate the spatial distribution characteristics of chlorohydrocarbon contaminants. The chlorohydrocarbon contaminant contents were obtained by sampling in the field and measuring in the laboratory. The chlorohydrocarbon contaminants even break through the relatively deeper soil layers due to their high density and low solubility in groundwater and then accumulate to a high content in the top surface of a specific layer, which can be a natural barrier for preventing contaminants from migrating downwards due to its relatively low permeability. The relationships between chlorohydrocarbon contaminant spatial distributions and soil layer features were analysed. By combining the zone maps of soil layer distributions, the characteristics of chlorohydrocarbon contaminant distributions and enrichment phenomena in three different zones corresponding to three different sites are discussed and summarised. Conceptual models for distributions of chlorohydrocarbon contaminants are also proposed for preliminary estimation of the maximum depth and the possible enrichment zones of chlorohydrocarbon contaminants.