Natural Attenuation of Chlorinated Solvents at a Complex Landfill Site

The objective of this study is to evaluate natural attenuation within groundwater at a landfill site located close to the city of Turin in Italy. The contaminants of concern found in the groundwater are primarily chlorinated aliphatic hydrocarbons (CAHs): PCE, TCE, DCE and VC, and metals such as iron, nickel and manganese. In particular, the daughter chlorinated compounds DCE and VC are present at high concentrations. The collection of groundwater biogeochemical data showed that two zones with distinct geochemical environment can be identified in the groundwater at the site. In the first zone aerobic conditions are found, while the second zone is charachterized by anaerobic conditions supporting a strongly reducing environment. Therefore, combined anaerobic and aerobic microbial processes are responsible for the degradation of chlorinated ethenes in the groundwater underlying the landfill. Also the metal contamination can be related to natural processes and, in particular, the high concentrations of dissolved iron and manganese are likely to be consequence of the biological activity, triggered by the organic load present in the landfill leachate.