Roles of acetone-conditioning and lipid in sorption of organic contaminants.

Sorption of phenanthrene and 1-naphthol by a peat soil (PS) and its humic acid fractions (HAs) and humin (HM) was examined. Both phenanthrene and 1-naphthol consistently had decreased isotherm nonlinearity in the order PS > HA1 (first fraction) > HA7 (seventh fraction), due to decreased heterogeneity of soil organic matter (SOM). High isotherm nonlinearity of HM was attributed to the condensed structure of SOM in it. Acetone-conditioning increased sorption affinity and isotherm nonlinearity of HAs and HM for phenanthrene, and the conditioning effect was more pronounced at low solute concentrations. However, sorption of 1-naphthol by PS, HAs, and HM was insignificantly affected by acetone-conditioning, suggesting that 1-naphthol could have disparate distribution of sorbed sites from phenanthrene due to their structure and hydrophobicity difference. Lipid removal further increased sorption of phenanthrene and 1-naphthol by acetone-conditioned PS, HAs, and HM, due to increased accessibility of high-energy sites in SOM. Nonlinearity of phenanthrene and 1-naphthol also increased after lipid removal from the acetone-conditioned sorbents. In 1-naphthol- and phenanthrene-lipid competitive sorption systems, lipid had strong competition with phenanthrene, whereas 1-naphthol exhibited cooperative sorption with lipid on lipid-free PS, HAs, and HM, again showing the different sorption characteristics between phenanthrene and 1-naphthol.