Laboratory studies have been conducted to evaluate the relationship between wetland plant uptake, translocationa nd desorption-resistance of phenanthrene in sediments. The plants used in this study were a tree, black willow (Salix nigra), and the macrophyte, three-square bulrush (Scirpus olneyi). Sediments were prepared with material in reversibly and desorption-resistant fractions and exposed to plant uptake for several weeks using ~(14)C-labeled phenanthrene as tracer. Plant uptake (4-6percent of the added phenanthrene) was observed in sediment with the phenanthrene in a fully desorption-resistant state. The ability of two different wetland plant species to uptake phenanthrene from the desorption-resistant fraction of phenanthrene from sediment has been studied. Both plants appear to access the desorption-resistant phase to some extent. Two mechanisms appear to be important: the direct uptake of the porewater in equilibrium with the desorption-resistant phase and secondly, the sorption of the organic onto the root followed by uptake. A mathematical model to calculate the uptake from sediments considering the desorption-resistant fraction was derived. This model produces similar results to those obtained int he laboratory.
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