Enrichment of polycyclic aromatic hydrocarbons in forest soils near a blast furnace plant

Four different layers of soil were sampled at ten sites at increasing distances from a blast furnace plant. PAH concentrations decreased exponentially from moderately contaminated to background values. For each compound it was possible to distinguish between the source-related part, decreasing with increasing distance from the plant, and the background contribution. The relative contribution of PAHs differed between the source and the background profiles. PAH concentrations were found to be elevated up to a distance of 2 km from the boundary of the plant. The different layers of soil revealed a relative enrichment of PAHs with ageing of organic matter. This effect, which increased with the molecular weight of the compound, was used to estimate the half-life of PAHs in forest soil. Estimated DT(50)s ranged from 2 to 4 months for fluorene upto 1.9 to 3.4 years for benzo[b]fluoranthene.