STEFAN TRAPP1 AND ALES KULHANEK2
1Environment & Resources DTU, Technical University of Denmark, DK-2800 Kongens Lyngby, E-mail: [email protected] 2Department of Environmental Chemistry, Institute of Chemical Technology, Technicka 5, Prague 160 00, Czech Republic
Keywords: Benzo(a)pyrene, bioconcentration, health risk, models, plant uptake, soil
Several risk assessment tools for contaminated soils have been developed, i.e. the Contaminated Land Exposure Assessment Model - CLEA (UK), CETOX (Denmark), CSOIL (The Netherlands), the Soil Screening Guidance - SSG (USA) or the (more general) European Union System for the Evaluation of Substances - EUSES (EU). Each of these tools uses a different approach for the calculation of the transfer into food . The methods differ, and the estimation of transfer into food has a very high uncertainty when calculating human exposure. Another shortcoming is that only one type of crop, usually green vegetables, is considered. However, green vegetables represent only a small fraction of vegetable food, compared to bread, potatoes, juice and other beverages. Besides this, the uptake into leaves does not necessarily correlate with uptake into other plant parts. The uptake and transport behavior of neutral organic compounds can be adequately described with the available theory . Plant specific models (leafy vegetables, root vegetables, fruits from trees) have been developed [3, 4, 5]. The results from crop-specific exposure assessment can not only provide more detailed information for risk management, they may also lead to different conclusions .
The objective of this chapter is to gain an insight into the underlyimg equations of the models, to show the similarities, but also the differences, and to compare the outcome to the empirical equation of Travis & Arms . Crop-specific models were developed by describing the basic processes of convective or diffusive uptake, chemical equilibrium between plant tissue (roots, wood, leaves, tubers) and surrounding soil or air, as well as fluxes inside the plants. This mechanistic principle of building is similar for all crop-specific models. However, processes and the parameterization depend on the type of crop (Figure 1). The models are briefly described below but for more detailed descriptions and the limits of applicability we refer the reader to the recent report of Sams0e-Petersen et al.  or published original work [3, 4, 5].
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