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Soil heterogeneity effects on acid flushing of lead-contaminated soil

In English

Författare

Summary, in English

A compact model for evaluation of acid flushing of heavy-metal-contaminated soil in a small-scale on-site treatment plant is proposed. The model assumes that the soil was re-packed in a container after excavation resulting in a soil structure with heterogeneous and random physical and chemical properties. To evaluate the effects of heterogeneity on the efficiency of contaminant removal by acid flushing, a numerical analysis of lead transport in the heterogeneous soil medium was performed. The model examines cation exchange and surface complexation reactions involving three cations (Ca, Pb, and H) and one anion (Cl) in both dissolved and exchangeable forms, two Pb surface complexes (SOPbCl and SOPbOH), and one Cl surface complex (SOH2Cl). The transport of these species during flushing with acid in a synthetically generated two-dimensional heterogeneous soil was simulated in the model. Results indicated that the flushing fluid preferentially followed pathways with large permeability. The heterogeneous cation exchange capacity (CEC) distribution and surface complexation sites had a significant effect on the transport of dissolved species. Because the CEC was set to a relatively low value, Pb was adsorbed mainly as surface complexes (SOPbCl and SOPbOH). Simulation results suggest that blocks of low hydraulic conductivity located in the upper part of the model domain greatly impede solute transport. Ponding conditions did not significantly affect the efficiency of decontamination. The model and its results are useful in the design of small-scale treatment plants for acid flushing.

Publiceringsår

2008

Språk

Engelska

Sidor

121-134

Publikation/Tidskrift/Serie

Environmental Modeling and Assessment

Volym

13

Dokumenttyp

Artikel i tidskrift

Förlag

Springer

Ämne

  • Water Engineering

Nyckelord

  • numerical simulation
  • lead-contaminated soil
  • acid flushing
  • cation exchange
  • surface complexation

Status

Published

ISBN/ISSN/Övrigt

  • ISSN: 1573-2967