PAH-pools in soils along a PAH-deposition gradient.

The objectives of this study are to characterize different PAH-pools (soil horizons, microsites influenced by stem flow, aggregate core and surface fractions, particle size fractions) in soils affected by depositions. Three forest soils affected by the emissions of an aluminium plant near Ziar/Central Slovakia were sampled to analyze 20 PAHs. The organic layers have high concentrations of PAHs (40-200 mg kg(-1)), decreasing as soil depth and distance from the aluminium plant increases. At the two sites nearest to the plant PAH-concentrations are higher in microsites affected by stem flow than in microsites not influenced by stem flow. They are also higher in aggregate surface fractions than in aggregate core fractions and in bulk soil samples than in aggregates. Sand- and siltsize particles contain decreasing percentages of the sum PAH-concentrations as distance from the plant increases. This microscale heterogeneity affects PAH-availability and has to be considered when assessing environmental risks.