Monitoring the evolution of abiotic and biotic processes vital to chlorinated compound degradation during remediation

Kocur, C., Reed, S., Wallace, S.J., Weber, K.

Dans les comptes rendus d’articles de la conférence: GeoNiagara 2021: 74th Canadian Geotechnical Conference; 14th joint with IAH-CNC

ABSTRACT: As the focus of the research community shifts towards novel contaminants and priorities realigned, it is easy to forget that technical challenges remain for the existing inventory of contaminated sites. Most practitioners would agree that their toolbox for management of complex chlorinated solvent sites is insufficient and incomplete. Although many sites can be effectively managed using current remediation technologies, there are examples where site complexity has foiled remediation efforts leading to costly investments in site characterization following remediation. This study presents an iterative approach of monitoring and remediation employing molecular biology tools (Illumina 16S rRNA metagenomic sequencing) alongside chemical reductants. The objective is to build evidence of the biotic and abiotic degradation processes as they evolve in the plume to shorten and shore up remediation outcomes. This study follows a dry cleaner facility that experienced about two decades of dissolution into a sandy aquifer. Despite delineation and site characterization, cleanup goals remain a challenge due to complex migration pathways that confound analysis. These complex contaminant pathways also present remediation challenges due to a high potential for back diffusion and long tailing of the plume regardless of source zone decisions. The challenges at such a site are not unique to chlorinated solvent sites and highlight the need for new tools and coordinated use of existing tools to characterize sites alongside remediation activities. Microscale zero valent iron (ZVI) was selected for pilot source zone remediation as well as targeted migration pathway treatment. This strong reductant was delivered through direct push tooling points and via existing monitoring wells. A Sulphidated ZVI product was selected for its specificity towards chlorinated compound degradation (as opposed to inefficient side reactions with water) along with its synergy with biotic and abiotic degradation processes that will be relied upon downgradient. Assessing the presence and abundance of certain microbial species via sequencing will help to characterize differences in microbial composition among sites. This pilot study allows for simultaneous characterization of the natural attenuation processes occurring in the plume while monitoring of source zone degradation processes that contribute to the plume.

Please include this code when submitting a data update: GEO2021_280

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