Polycyclic Aromatic Hydrocarbons in Soil of the Canadian River Floodplain in Oklahoma.

The accumulation of polycyclic aromatic hydrocarbons (PAH) in soil, plants, and water may impart negative effects on ecosystem and human health.  We quantified the concentration and distribution of 41 PAH (n = 32), organic C, total N, and S (n = 140) and investigated PAH sources, using a chronosequence of floodplain soils under a natural vegetation succession.  Soil samples were collected between 0–260 cm depth in bare land (the control), wetland, forest, and grassland areas near a closed municipal landfill and an active asphalt plant (the contaminant sources), in the north bank of the Canadian River near Norman, Oklahoma.  Principal component, cluster, and correlation analysis were used to investigate the spatial distribution of PAH, in combination with diagnostic ratios to distinguish pyrogenic vs. petrogenic PAH suites.  Total PAH concentration (∑PAH) had a mean of 1300 ng/g, minimum of 16 ng/g, and maximum of 12,000 ng/g.  At 0–20 cm depth, ∑PAH was 3500 ± 1600 ng/g (mean ± 1 SE) near the contaminant sources.  The most common compounds were non-alkylated, high molecular weight PAH of pyrogenic origin, i.e. fluoranthene (17 %), pyrene (14 %), phenanthrene (9 %), benzo(b)fluoranthene (7 %), chrysene (6 %), and benzo(a)anthracene (5 %).  ∑PAH in the control (130 ± 23 ng/g) was comparable to reported concentrations for the rural Great Plains.  Perylene had a unique distribution pattern suggesting biological inputs.  The main PAH contamination mechanisms were likely atmospheric deposition due to asphalt production for 0–20 cm depth and past landfill operations at deeper depths.