Laboratory studies to characterize the efficacy of sand capping a coal tar-contaminated sediment

Seunghun Hyun, Chad T. Jafvert, Linda S. Lee, P. Suresh C. Rao

Research output: Contribution to journalArticlepeer-review

24 Citations (Scopus)


Placement of a microbial active sand cap on a coal tar-contaminated river sediment has been suggested as a cost effective remediation strategy. This approach assumes that the flux of contaminants from the sediment is sufficiently balanced by oxygen and nutrient fluxes into the sand layer such that microbial activity will reduce contaminant concentrations within the new benthic zone and reduce the contaminant flux to the water column. The dynamics of such a system were evaluated using batch and column studies with microbial communities from tar-contaminated sediment under different aeration and nutrient inputs. In a 30-d batch degradation study on aqueous extracts of coal tar sediment, oxygen and nutrient concentrations were found to be key parameters controlling the degradation rates of polycyclic aromatic hydrocarbons (PAHs). For the five PAHs monitored (naphthalene, fluorene, phenanthrene, anthracene, and pyrene), degradation rates were inversely proportional to molecular size. For the column studies, where three columns were packed with a 20-cm sand layer on the top of a 5 cm of sediment layer, flow was established to sand layers with (1) aerated water, (2) N2 sparged water, or (3) HgCl2-sterilized N2 sparged water. After steady-state conditions, PAH concentrations in effluents were the lowest in the aerated column, except for pyrene, whose concentration was invariant with all effluents. These laboratory scale studies support that if sufficient aeration can be achieved in the field through either active and passive means, the resulting microbially active sand layer can improve the water quality of the benthic zone and reduce the flux of many, but not all, PAHs to the water column.

Original languageEnglish
Pages (from-to)1621-1631
Number of pages11
Issue number10
Publication statusPublished - 2006 Jun
Externally publishedYes

Bibliographical note

Funding Information:
This study was supported by funds provided by NiSource Inc., Merrillville, IN and Purdue University.


  • Coal tar
  • NAPL
  • Polycyclic aromatic hydrocarbons
  • Sand cap
  • Sediment

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • General Chemistry
  • Pollution
  • Health, Toxicology and Mutagenesis


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