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Environ Pollut. 2008 Dec;156(3):745-52. doi: 10.1016/j.envpol.2008.06.007. Epub 2008 Aug 6.

PAH desorption from river floodplain soils using supercritical fluid extraction.

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School of Resources and Environment Science, East China Normal University, Shanghai, China; Department of Environmental Geosciences, Vienna University, Althanstrasse 14, 1090 Vienna, Austria.


Sequential supercritical fluid extraction (SFE) was performed in order to estimate desorption of PAHs from river floodplain soils which contain coal and coal-derived particles. Original soils, soils' light fractions (rho<2 g cm(-3)), and <63 microm fractions were studied for PAHs' desorption kinetics. Desorption data were successfully described using a two-site model. Desorption rate constants were one order of magnitude lower than those of "slow" and "very slow" desorption rates from other studies. This suggests very slow and extremely slow desorption. Estimated time scales releasing 99% of total extractable contaminants ranged from decades for 2-4-ring PAHs and hundreds of years for 5-6-ring PAHs. We demonstrate that, despite high soil PAH concentrations which are due to coal and coal-derived particles, the general environmental risk is reduced by the very slow and extremely slow desorption rates.

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