Bioavailability of HOC depending on the colloidal state of humic substances: a case study with PCB-77 and Daphnia magna.
Condensed organic matter with higher affinity for hydrophobic organic compounds (HOC) is currently held responsible for slow desorption and concomitant lower bioavailabilities of HOC in sediments and soils. In an experiment with Daphnia magna and IHSS Peat Humic Acid (PHA), we showed that the bioconcentration factor (BCF) of 3,3',4,4'-tetrachlorobiphenyl (PCB-77) was directly related to the charge of the humic colloid, as predicted by the metal-humic binding model WHAM. Consistent with the type of binding to the humic acid (counter-ion accumulation vs. specific binding), increasing the concentration of Na+ and Ca2+ ions generated opposite effects on colloid charge and HOC binding by the humic acid. Condensation as a colloidal phenomenon in solution as well as on surfaces needs to be addressed as a contributor to lower bioavailabilities and, possibly, to slower desorption kinetics.
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Resource Centre for Environmental Technologies, CRP-Henri Tudor, Esch-sur-Alzette, G.-D. of Luxembourg, 66, Rue de Luxembourg, P.O. Box 144, 4002 Esch-sur-Alzette, Luxembourg. tom.galle@tudor.lu
Grégoire
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Wagner
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Bierl
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D000327:Adsorption; D000818:Animals; D001681:Biological Assay; D001682:Biological Availability; D003102:Colloids; D003621:Daphnia; D007700:Kinetics; D011078:Polychlorinated Biphenyls / Q000737:chemistry* / Q000493:pharmacokinetics*; D014874:Water Pollutants, Chemical / Q000493:pharmacokinetics*
D003102:Colloids; D014874:Water Pollutants, Chemical; D011078:Polychlorinated Biphenyls; C028451:3,4,3',4'-tetrachlorobiphenyl