Reactive contaminant infiltration under dynamic preferential flow

Darrell W.S. Tang*, Helen K. French, Anton Leijnse, Ruud P. Bartholomeus, Sjoerd E.A.T.M. van der Zee

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Biodegradation is an important mechanism of contaminant removal from soils. We use numerical simulations to study the contaminant transport in heterogeneous soils subject to transient flow conditions and anaerobic multicomponent biodegradation. These processes and their interactions affect contaminant travel times, the extent of reactant mixing, solute and microbial biomass distributions in the soil, and biodegradation outcomes. Especially when flux variations are large, the combination of soil heterogeneity and transient flow gives rise to dynamic preferential flow zones, which affects reactant mixing and biodegradation outcomes. Results show that soil heterogeneity may reduce contaminant leaching due to enhanced reactant mixing, especially when biodegradation is more limited by reactant mixing. Furthermore, unlike under steady-state flow, under transient flow soil heterogeneity does not substantially reduce contaminant residence times. As preferential flow zones change dynamically, the spatio-temporally averaged transport, mixing, and biodegradation experienced by various parts of contaminant plumes become homogenized. Therefore, knowing the initial biodegradation rate of a contaminant upon infiltration, and its mean residence time in the soil, enables a relative sensitivity analysis. This allows biodegradation outcomes of various scenarios to be approximately ranked, even under soil heterogeneity and transient flow, using information that is straightforward to measure or estimate in the field.

Original languageEnglish
Article number131111
JournalJournal of Hydrology
Volume634
DOIs
Publication statusPublished - May 2024

Keywords

  • Contaminant leaching
  • Heterogeneous soil
  • Multicomponent biodegradation
  • Preferential flow
  • Soil contamination
  • Transient flow

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