Natural attenuation research at the contaminated megasite Zeitz

Monitored natural attenuation (MNA) as a possible remediation strategy has been intensively discussed over the last several years. However, in order to apply natural attenuation (NA) as a rational remediation option, suitable methods for the assessment and evaluation of the efficiency of these processes must be developed, the sustainability of the NA processes has to be demonstrated and regulatory and public acceptance has to be established. The RETZINA (Reference test site Zeitz for the implementation of the "Natural Attenuation" approach) -Project deals with the implementation of the MNA approach as a remediation concept at the heavily contaminated former industrial field site Zeitz (Germany). Due to the long history of industrial production, the multiple contaminant sources present and the large spatial extent, Zeitz is considered a contaminated megasite. The overall goal of the project is to incorporate novel site investigation methods into conventional strategies to improve site characterisation with respect to remediation measures relying on NA. Several investigation methods are being tested to examine temporal and spatial aspects of NA. In addition to conventional site investigation strategies, incorporation of new mass flux, toxicological and isotopic approaches form part of the research. Integral pumping tests yielded reliable data on mass fluxes through a control plane. The toxicological analysis gave new insights into contaminant interactions and the issue of multiple sources. Investigations of isotopic fractionation yielded increased confidence that NA is indeed ongoing at the site. Thus, the new methods gave more insight into the complexity of contaminant load and occurring degradation processes. Taken together, they strengthened the reliance on NA as a remediation option for this particular contamination at the megasite in context of the protection of water resources at the regional scale.