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” renders the 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.

New concepts for dynamic plant uptake models

“…[5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]). In most cases, the underlying different equations have been solved for steady-state and/or numerically for dynamic studies.…”

Using sludge on arable land - effect based levels and long-term accumulation for certain organic pollutants

“…Recently, dynamic models have been developed that accounts for root growth and diffusion in plants (e.g. Trapp et al, 2002;Trapp 2007). Those models were used by the Swedish EPA (Naturvårdsverket, 2009) in their model for guidevalues of contaminated soil.…”

“…For lipophilic compounds, the dynamic model predicted accumulation in carrots very well, whereas the equilibrium model overestimated accumulation by a factor of approximately 100-1000. There is also a dynamic model for potato (Trapp, 2007), showing that accumulation in potato is somewhat lower than in carrots. This is in agreement with field studies (Trapp et al, 2007;Samsoe-Peterson et al, 2002).…”

“…There is also a dynamic model for potato (Trapp, 2007), showing that accumulation in potato is somewhat lower than in carrots. This is in agreement with field studies (Trapp et al, 2007;Samsoe-Peterson et al, 2002). Because the equilibrium model significantly overestimates concentrations, the "carrot" model was used (Trapp, 2002) for the human intake calculations (see below) for all root vegetables and potato.…”

ModelPROBE: model driven soil probing, site assessment and evaluation

“…Other fully developed non-or minimal-invasive site survey techniques are not available at present. However, polar persistent chemicals are well known to be translocated from soil through roots to stem and leaves of plants (Trapp et al 2007). Sampling of wood and/or other vegetation parts can therefore be used to detect and monitor subsurface pollutants and natural attenuation processes (Larsen et al 2008).…”