The Pollution Characteristics and Full-Scale Risk Assessment of Coking Plant Soil Co-Contaminated with Polycyclic Aromatic Hydrocarbons and Heavy Metals

Soils in coal coking plants can contain both polycyclic aromatic hydrocarbons (PAHs) and heavy metals (HMs). In this study, we analyzed PAH-HM pollution of soil in a coking plant in Beijing, China using a risk quotient and Hakanson potential ecological risk assessment to evaluate the ecological risk of PAHs and HMs, respectively. In addition, a magnetic whole-cell bioreporter was used to detect ecological toxicity of soil samples. The ecological risk and ecological toxicity were also compared. We found serious PAH pollution in the samples as evidenced by total PAH values of up to 1,206.99 mg/kg that were mainly 4-ring PAH. Lead and chromium contamination was present at 245.83 and 169.60 mg/kg, respectively, which was higher than concentrations of other HMs, including arsenic, cadmium, and mercury. Most samples had PAH levels that could present a serious ecological risk, whereas nearly half of the samples had HM concentrations that would pose high ecological risks. In a bioreporter assay, the relative bioluminescence response ratio of soil samples ranged from 1.76 to 4.66, indicating that all samples showed ecological toxicity. In this study, we showed that bioreporters can be used to express the combined influence of all hazardous chemicals and demonstrated that bioreporters could be an efficient and rapid approach to assess biological toxicity of soils with co-contamination and provide a full-scale risk assessment of polluted soil combining risk assessment.