Impact of soil amendments and the plant rhizosphere on PAH behaviour in soil

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  • Geoffrey Marchal, Center for Energy Resources Engineering, Technical University of Denmark, Denmark
  • Kilian E. C. Smith, Denmark
  • Philipp Mayer, Department of Environmental Engineering, Technical University of Denmark, Denmark
  • Lis Wollesen de Jonge
  • Ulrich G. Karlson, Department of Environmental Science, Aarhus University, Roskilde, Denmark
Carbonaceous soil amendments are applied to contaminated soils to strongly sorb polycyclic aromatic hydrocarbons (PAHs), reducing their freely dissolved concentrations (Cfree) and limiting uptake and toxicity. An agricultural soil spiked with 5 PAHs (phenanthridine, phenanthrene, anthracene, fluoranthene, and pyrene) was mixed with different soil amendments (activated carbon (AC), charcoal, or compost) and planted with radish (Raphanus sativus L.). For 2 months, Cfree, diffusive uptake, and chemical activities of PAHs were measured. For the AC, the Cfree and diffusive uptake of PAHs decreased up to 94% compared to the unamended soil after 1 week, and these reductions thereafter, remained throughout the experiment constant. The sum of chemical activities of the five PAHs was below the 0.01 to 0.1 threshold for baseline toxicity only for the AC amendment. In comparison, addition of charcoal led to rather modest reductions in the initial values of Cfree (between 37 and 61%) and diffusive uptake (between 31 and 72%). Conversely, compost had no effect on Cfree, and reduced the diffusive uptake as charcoal. The Cfree and diffusive fluxes were lower in the planted soil compare to the unplanted soil. No detectable amounts of PAHs were measured neither in the radish hypocotyl nor leaves over 60 days whatever the treatments. This finding suggests that adding AC, conversely to charcoal and compost, may reduce permanently acute toxicity and bioavailability of PAHs in agricultural soil, and plant-promoted microbial degradation may be a main mechanism of natural attenuation of PAHs.
Original languageEnglish
JournalEnvironmental Pollution
Pages (from-to)124-131
Publication statusPublished - 2014

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