A fate model to predict the dynamics of bioavailability in soil in laboratory test 
systems

T. Jager, T.  Parkerton, D.  Letinksi, R. Manning, E. Febbo 

Vrije Universiteit Amsterdam, Department of Theoretical Biology, Amsterdam NL
ExxonMobil Biomedical Sciences, Ananadale, NJ, USA

SPME fibers are among the most promising analytical tools to predict the 
bioavailability of organic contaminants in environmental media. However, application 
to soil contamination presents difficulties due to the medium's low water content. 
Furthermore, bioavailability is a highly dynamic issue; both fibers and organisms 
require time to equilibrate which depends on the properties of the compound. To 
facilitate laboratory test design and analysis of soil bioaccumulation and toxicity 
experiments, we have developed a dynamic model for soil test systems. The model is 
based on the well-known multi-media fate models of the Mackay type. The modelled 
system comprises five compartments: soil, porewater, earthworm, air (headspace), and 
SPME fiber (either maintained in the soil headspace or in soil porewater). The model 
is calibrated using data on the accumulation of PAHs from soil to fibers and 
earthworms over time. Model results are discussed and used to provide 
recommendations regarding use of PDMS fibers as a biomimetic extraction device in 
soil toxicity tests.