Natural Attenuation in Streambed Sediment Receiving Chlorinated Solvents from Underlying Fracture Networks.
Contaminant discharge from fractured bedrock formations remains a remediation challenge. We applied an integrated approach to assess the natural attenuation potential of sediment that forms the transition zone between upwelling groundwater from a chlorinated solvent-contaminated fractured bedrock aquifer and the receiving surface water. In situ measurements demonstrated that reductive dechlorination in the sediment attenuated chlorinated compounds before reaching the water column. Microcosms established with creek sediment or in situ incubated Bio-Sep beads degraded C1-C3chlorinated solvents to less-chlorinated or innocuous products. Quantitative PCR and 16S rRNA gene amplicon sequencing revealed the abundance and spatial distribution of known dechlorinator biomarker genes within the creek sediment and demonstrated that multiple dechlorinator populations degrading chlorinated C1-C3alkanes and alkenes co-inhabit the sediment. Phylogenetic classification of bacterial and archaeal sequences indicated a relatively uniform distribution over spatial (300 m horizontally) scale, but Dehalococcoides and Dehalobacter were more abundant in deeper sediment, where 5.7 ± 0.4 × 105and 5.4 ± 0.9 × 10616S rRNA gene copies per g of sediment, respectively, were measured. The microbiological and hydrogeological characterization demonstrated that microbial processes at the fractured bedrock-sediment interface were crucial for preventing contaminants reaching the water column, emphasizing the relevance of this critical zone environment for contaminant attenuation.
Burcu
B
Şimşir
Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences , Shenyang, Liaoning 110016, China.
Jun
J
Yan
Department of Microbiology, University of Massachusetts , Amherst, Massachusetts 01002, United States.
Jeongdae
http://orcid.org/0000-0002-6871-5366
J
Im
Geosyntec Consultants , Knoxville, Tennessee 37922, United States.
Duane
D
Graves
Frank E
http://orcid.org/0000-0002-9797-4279
FE
Löffler
D001673:Biodegradation, Environmental; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics*; D012997:Solvents; D014874:Water Pollutants, Chemical
D012336:RNA, Ribosomal, 16S; D012997:Solvents; D014874:Water Pollutants, Chemical