Uptake of Organic Contaminants from Soil into Vegetables and Fruits - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 384

concentration vector C (0) for the next period. This refers to concentrations in any
compartment (i.e. soil, roots and leaves).
9.4.5 Input Data for the Root and Leaf Model
Input data are the same for the steady state and the dynamic model version and are
mostly taken from the carrot model (Trapp 2002 ) and the leafy vegetables model
(Trapp and Matthies 1995 ) (Table 9.1 ).
9.5 Influence of Contaminant-Specific Parameters
The uptake of contaminants into plants and their accumulation depends on
contaminant-specific parameters. The importance of some of these parameters is
investigated in this section by using the models described before. Also, experimen-
tal results are reported, not only with the intention to give a review, but also in order
to confirm (or to falsify) the processes and the principal outcomes of the model sim-
ulations. Many experimental studies on plant uptake of organic contaminants are
available, but most of them are from laboratory or greenhouse experiments, and the
results may not always be applicable to field conditions. Results from field studies,
however, are less often published. This may be due to high expenses, analytical diffi-
culties or other research priorities. But a reason may also be that the results of uptake
studies from outdoors often show a very large variation and are difficult to interpret.
9.5.1 K OW on Accumulation in Roots and Potatoes
Figure 9.5 shows the calculated concentration in roots (steady-state solution
Eq. 9.22 ) and potatoes (Trapp et al. 2007a ) for a constant soil concentration of 1 mg
kg − 1 (wet weight). The most relevant contaminant-specific parameter in the root
and potato model is the log K OW , which is varied from 0 (polar contaminants) to 8
(super-lipophilic contaminants). The concentrations are compared to the concentra-
tions resulting from the equilibrium partition coefficient approach ( RCF ,Eqs. 9.5
and 9.10 ) and to the Travis and Arms-regression (“T&A”, Eq. 9.3 ). For very polar
contaminants, the concentration in roots and potatoes is predicted to be higher than
the concentration in soil. This is because very polar contaminants are mainly found
in aqueous phases, and roots and potatoes contain usually more water (up to 95%)
than soil (about 30%). For more lipophilic contaminants, the RCF (here related to
soil, i.e. RCF / K SW ) approaches a value of 1, due to the similar sorption capacity of
roots and soil.
For polar contaminants, the regression of T&A and the two dynamic models
give results close to the equilibrium ( RCF ). With increasing lipophilicity, the pre-
dicted concentration decreases and the deviation from equilibrium increases. The