Characterizing natural degradation of tetrachloroethene (PCE) using a multidisciplinary approach
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RESEARCH ARTICLE
Characterizing natural degradation of tetrachloroethene (PCE) using a multidisciplinary approach ˚ kesson , Charlotte J. Sparrenbom, Catherine J. Paul, Sofia A Robin Jansson, Henry Holmstrand
Received: 8 June 2020 / Revised: 13 October 2020 / Accepted: 20 October 2020
Abstract A site in mid-western Sweden contaminated with chlorinated solvents originating from a previous dry cleaning facility, was investigated using conventional groundwater analysis combined with compound-specific isotope data of carbon, microbial DNA analysis, and geoelectrical tomography techniques. We show the value of this multidisciplinary approach, as the different results supported each interpretation, and show where natural degradation occurs at the site. The zone where natural degradation occurred was identified in the transition between two geological units, where the change in hydraulic conductivity may have facilitated biofilm formation and microbial activity. This observation was confirmed by all methods and the examination of the impact of geological conditions on the biotransformation process was facilitated by the unique combination of the applied methods. There is thus significant benefit from deploying an extended array of methods for these investigations, with the potential to reduce costs involved in remediation of contaminated sediment and groundwater. Keywords Chlorinated solvents Compound-Specific Isotope Analysis Geophysics Groundwater Natural degradation Quantitative Polymerase Chain Reaction
INTRODUCTION Chlorinated solvents are common contaminants of soil and groundwater at numerous sites of active and historical dry Electronic supplementary material The online version of this article (https://doi.org/10.1007/s13280-020-01418-5) contains supplementary material, which is available to authorized users.
cleaning facilities and industrial operations. Presently, nearly 3000 sites are known or suspected to be contaminated with chlorinated solvents in Sweden alone (SEPA 2015). Chlorinated solvents are dense non-aqueous phase liquids (DNAPLs), and this character gives them a special dispersal pattern and complex distribution that is controlled by local geological settings (Pankow and Cherry 1996). As these substances are harmful, and have been proved or are considered to be carcinogens (IARC 2014), sites contaminated with these solvents are highly prioritized for remediation. In situ remediation is recommended by the Swedish EPA as a more sustainable environmental strategy (SEPA 2014) than the traditional ‘‘dig and dump’’ treatment of contaminated sediments. However, in order to monitor and optimize this remediation, a reliable investigation methodology to validate the degradation progress is required. Complete biodegradation of PCE occurs in several ways, either by Dehalococcoides mccartyi alone or by a bacterial consortium where different bacteria carry out one or more steps of biodegradation (Stroo et al. 2013). D. mccartyi is the only bacterium known to be able to completely degrade PCE to ethe
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