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(046) Sorption of non-polar organic compounds by natural organic matter in soils and sediments: an overview. van Noort, Paul1, 1 ABSTRACT- Several investigators have observed sorption isotherms for organic compounds in soils and sediments to become increasingly non-linear on increasing contact time. Other investigators observed in situ distributions over sediment and water to exceed expectations based on equilibrium partitioning considerations by several orders of magnitude. Desorption has been found to be characterised by a fast initial release followed by a much slower release. Now, there is general consensus that adsorption at specific sites in natural organic matter occurs in addition to linear (ab)sorption. Adsorption at these specific sites has been explained in terms of sorption in holes in perhaps rearranging glassy natural organic matter. Others advanced sorption by soot-like material or high-surface carbonaceous materials as an explanation. It will be argued that all adsorption phenomena can be explained in terms of a combination of sorption at both low-energy non-planar sites such as in flexible holes in glassy natural organic matter and high-energy planar sites such as in graphitic soot-like material. Key words: sorption, soil, sediment, organic |
