Journal article
The importance of transects for characterizing aged organic contaminant plumes in groundwater
Journal of contaminant hydrology, Vol.235, pp.103728-103728
11/2020
DOI: 10.1016/j.jconhyd.2020.103728
PMID: 33069942
Abstract
A complex mixture of dissolved organic contaminants, emanating from a many decades-old, residual, dense non-aqueous phase liquid (DNAPL) source, migrates through unconfined, moderately heterogeneous, glacial-derived sediments and sedimentary rock in a residential area of Dane County, Wisconsin, USA. A portion of this contaminant plume intersects a large man-made pond, roughly 400 m downgradient of the source zone. Depth-discrete, multilevel groundwater sampling, detailed sedimentological logs, and hydraulic head profiles were used to delineate the spatial distribution of hydraulic, geologic, organic contaminant, and redox hydrochemical conditions within the established plume along two transects immediately upgradient of the pond. Twenty-one contaminants were detected and classified into four major contaminant groups: chlorinated ethenes, chlorinated ethanes, aromatics (BTEX: benzene, toluene, ethylbenzene, xylene), and aliphatic ketones. Within the glacial sediments and shallow bedrock, zones of reductive dechlorination of chlorinated ethenes and ethanes were juxtaposed with zones of BTEX and ketone degradation. Spatial heterogeneity in the concentration and distribution of contaminant groups and redox conditions was observed over lateral distances of tens of meters and vertical distances of tens of centimeters along the two transects. Although the site was situated in a complex glacial depositional environment, lithologic and hydraulic heterogeneity surprisingly only had a modest influence on the spatial distribution of plume contaminants. Depth-discrete sampling along paired, closely spaced transects (~20 m apart) was essential to assess internal plume composition/concentration evolution along flow paths with strong attenuation over short migration distances. This study shows how paired, highly resolved transects can enhance understanding of transverse and longitudinal variability in areas where contaminant-induced redox conditions control reaction zones and strong plume attenuation.
•Transect-based multi-level sampling resolved complex contaminant distributions.•Delineation of steep contaminant concentration gradients and redox zonation.•Spatial variability in contaminant concentrations dominated by redox conditions.•Plume architecture mildly influenced by hydraulic and geologic heterogeneity.•Insights into rapid plume attenuation and strong mass discharge reduction near pond.
Details
- Title: Subtitle
- The importance of transects for characterizing aged organic contaminant plumes in groundwater
- Creators
- Colby M Steelman - University of GuelphJessica R Meyer - University of GuelphPhilipp Wanner - University of GuelphBenjamin J Swanson - University of GuelphOliver Conway-White - University of GuelphBeth L Parker - University of Guelph
- Resource Type
- Journal article
- Publication Details
- Journal of contaminant hydrology, Vol.235, pp.103728-103728
- Publisher
- Elsevier B.V
- DOI
- 10.1016/j.jconhyd.2020.103728
- PMID
- 33069942
- ISSN
- 0169-7722
- eISSN
- 1873-6009
- Grant note
- name: Solinst Canada Ltd.; name: Organic Geochemistry Lab; DOI: 10.13039/501100004490, name: University of Waterloo; name: Hydrite Chemical Co.; name: University Consortium for Field-Focused Groundwater Research
- Language
- English
- Date published
- 11/2020
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984229291102771
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