Stratification of chlorinated ethenes natural attenuation in an alluvial aquifer assessed by hydrochemical and biomolecular tools
Language English Country Great Britain, England Media print-electronic
Document type Journal Article
PubMed
28672697
DOI
10.1016/j.chemosphere.2017.06.100
PII: S0045-6535(17)31004-4
Knihovny.cz E-resources
- Keywords
- Biological markers, Chlorinated solvents, Hydrochemical markers, Indigenous microorganisms, Natural attenuation,
- MeSH
- Biodegradation, Environmental MeSH
- Water Pollutants, Chemical analysis MeSH
- Chloroflexi MeSH
- Ethylenes analysis MeSH
- Halogenation MeSH
- Environmental Monitoring * MeSH
- Groundwater chemistry MeSH
- Tetrachloroethylene chemistry MeSH
- High-Throughput Nucleotide Sequencing MeSH
- Iron analysis MeSH
- Publication type
- Journal Article MeSH
- Names of Substances
- Water Pollutants, Chemical MeSH
- ethylene MeSH Browser
- Ethylenes MeSH
- Tetrachloroethylene MeSH
- Iron MeSH
Biomolecular and hydrochemical tools were used to evaluate natural attenuation of chlorinated ethenes in a Quaternary alluvial aquifer located close to a historical source of large-scale tetrachloroethylene (PCE) contamination. Distinct stratification of redox zones was observed, despite the aquifer's small thickness (2.8 m). The uppermost zone of the target aquifer was characterised by oxygen- and nitrate-reducing conditions, with mixed iron- to sulphate-reducing conditions dominant in the lower zone, along with indications of methanogenesis. Natural attenuation of PCE was strongly influenced by redox heterogeneity, while higher levels of PCE degradation coincided with iron- to sulphate reducing conditions. Next generation sequencing of the middle and/or lower zones identified anaerobic bacteria (Firmicutes, Chloroflexi, Actinobacteria and Bacteroidetes) associated with reductive dechlorination. The relative abundance of dechlorinators (Dehalococcoides mccartyi, Dehalobacter sp.) identified by real-time PCR in soil from the lower levels supports the hypothesis that there is a significant potential for reductive dechlorination of PCE. Local conditions were insufficiently reducing for rapid complete dechlorination of PCE to harmless ethene. For reliable assessment of natural attenuation, or when designing monitoring or remedial systems, vertical stratification of key biological and hydrochemical markers should be analysed as standard, even in shallow aquifers.
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