In situ electrokinetic remediation of soil co-contaminated with trace elements and polycyclic aromatic hydrocarbons

Sammanfattning: Sites contaminated with polycyclic aromatic hydrocarbons can be simultaneously contaminated with trace elements. Co-contaminated soil is considered a complex problem since inorganic and organic contaminants behave differently and thereby often require different remediation strategies. Despite the fact that co-contaminated soils are a common problem, existing research on remediation of contaminated soil mostly focuses on either organic or inorganic contaminants. In the present study, the possibilities of electrokinetic remediation as an alternative to commonly used remediation technologies was investigated. An experiment was setup to evaluate the effects of electrokinetic remediation on both polycyclic aromatic hydrocarbons and trace elements, such as arsenic, cadmium, chromium, copper, lead and zinc, simultaneously. The experiment was performed in 12 litre large plexiglass cells. Two cells with electrokinetic treatment, equipped with iron electrodes, to amend the soil with iron via intentional corrosion of the electrodes, and one control. The cells were filled with contaminated soil and deionized water was pumped through the cells to simulate a groundwater flow. The experiment ran for two months, during which pore water was sampled weekly and simulated groundwater monthly, to monitor changes in contaminant concentrations. Soil samples were taken at the start and at the end of the experiment. Results showed that the concentration of polycyclic aromatic hydrocarbons in the simulated groundwater decreased from 0.39 ± 0.15 μg L-1 to 0.12 ± 0.064 μg L-1 during the experiment. However, at the point of writing, samples of soil at the end of the experiment has not yet been analysed for concentration of polycyclic aromatic hydrocarbons, something that needs to be done to validate previously described results. In terms of the trace elements, the applied method did not increase their mobility, nor did it decrease it. Moreover, the trace elements behaved similarly in the control cell as in the treatment cells. This was observed for all the tested trace elements, indicating that electrokinetic remediation in this particulate case may be a suitable remediation technology for organic, but not that successful for inorganic contaminants. In regard to this, further research is required to establish whether electrokinetic remediation is a promising remediation technology for co- contaminated soil and how it can be optimized to ensure remediation success for both organic and inorganic contaminants.