Halloran LJS, Hunkeler D. Controls on the persistence of aqueous-phase groundwater contaminants in the presence of reactive back-diffusion.
Sci Total Environ 2020;
722:137749. [PMID:
32213436 DOI:
10.1016/j.scitotenv.2020.137749]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 03/03/2020] [Accepted: 03/03/2020] [Indexed: 06/10/2023]
Abstract
The persistence of groundwater contaminants is influenced by several interacting processes. Physical, physico-chemical, and (bio-)chemical processes all influence the transport of contaminants in the subsurface. However, for a given hydrogeological system, it is generally unclear to which degree each of these phenomena acts as a control on plume behaviour. Here, we present a comprehensive investigation of these processes and their influences on plume behaviour and persistence in layered sedimentary systems. We investigate different scenarios that represent fundamental configurations of common contaminant situations. A confined aquifer over- and underlain by aquitard layers is investigated in a source-removal scenario and a constant-source equilibrium scenario. Additionally, an aquitard overlain and underlain by high permeability units is investigated in a source-removal scenario. In these investigations, we vary layer thickness, as well as parameters governing advection, (back-)diffusion, sorption, and degradation. Extensive analysis of these results enables quantification of the influence of these parameters on maximum down-gradient concentration, plume persistence duration, and plume spatial extent. Finally, parameter space dimensionality reduction is used to establish trends and regimes in which certain processes dominate as controls. A lower limit to plume extent as a function of a novel constructed parameter is also determined. These results provide valuable quantitative information for the assessment of the fate of groundwater contaminants and are applicable to a wide range of aqueous-phase solutes.
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