Application of an unsteady state environmental distribution model to a decadal time series of PAH concentrations in Central Europe

To explain observed decadal trends in concentrations of polycyclic aromatic hydrocarbons (PAHs) in soil at the Košetice observatory, Czech Republic, an environmental distribution model for persistent organic pollutants (POPs) based on the fugacity approach was developed. Weekly air concentrations were used as input data for the unsteady state model and concentrations in soil were calculated. In general, agreement between measured and predicted soil concentrations of PAHs was observed. Temporal trends in PAH concentrations in Košetice can be related to changes in residential heating. Predicted soil concentrations of volatile PAHs namely acenaphthylene, fluorene and phenanthrene are in better correspondence with observed data than concentrations of less volatile PAHs i.e. dibenzo(ah)anthracene, benzo(a)pyrene and benzo(ghi)perylene. These discrepancies between model results and field data are probably a result of a simplified description of degradation and aging processes in soil. The results from our dynamic multicompartmental model confirmed our hypothesis about unsteady state conditions between the air and soil, and suggested that a commonly used simple steady state model should be only applied as a predictive tool in a small region when local sources and sinks are well described.