title: Diffusion of PAH in potato and carrot slices and application for a potato model.
abstract: A method for quantifying the effect of medium composition on the diffusive mass transfer of hydrophobic organic chemicals through thin layers was applied to plant tissue. The method employs two silicone disks, one serving as source and one as sink for a series of PAHs diffusing through thin layers of water, potato tissue, and carrot tissue. Naphthalene, phenanthrene, anthracene, and fluoranthene served as model substances. Their transfer from source to sink disk was measured by HPLC to determine a velocity rate constant proportional to the diffusive conductivity. The diffusive flux through the plant tissue was modeled using Fick's first law of diffusion. Both the experimental results and the model suggest that mass transfer through plant tissue occurs predominantly through pore water and that, therefore, the mass transfer ratio between plant tissue and water is independent of the hydrophobicity of the chemical. The findings of this study provide a convenient method to estimate the diffusion of nonvolatile organic chemicals through various plant materials. The application to a radial diffusion model suggests that "growth dilution" rendersthe concentration of highly hydrophobic chemicals in potatoes below their equilibrium partitioning level. This is in agreement with field results for the bioconcentration of PAHs in potatoes.
authors.affiliation: Institute of Environment & Resources, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark. stt@er.dtu.dk
authors.forename: Stefan
authors.initials: S
authors.lastname: Trapp
authors.forename: Anita
authors.initials: A
authors.lastname: Cammarano
authors.forename: Ettore
authors.initials: E
authors.lastname: Capri
authors.forename: Fredrik
authors.initials: F
authors.lastname: Reichenberg
authors.forename: Philipp
authors.initials: P
authors.lastname: Mayer
mesh_terms: D018552:Daucus carota / Q000737:chemistry; D004058:Diffusion; D008962:Models, Theoretical; D011084:Polycyclic Aromatic Hydrocarbons / Q000737:chemistry* / Q000378:metabolism; D012989:Soil Pollutants / Q000737:chemistry* / Q000378:metabolism; D011198:Solanum tuberosum / Q000737:chemistry* / Q000378:metabolism
chemical_list: D011084:Polycyclic Aromatic Hydrocarbons; D012989:Soil Pollutants