title: Exceptionally strong sorption of infochemicals to activated carbon reduces their bioavailability to fish.
abstract: The addition of activated carbon (AC) to sediments is a relatively new approach to remediate contaminated sites. Activated carbon strongly sorbs hydrophobic organic contaminants, thereby reducing their bioavailability and uptake in organisms. Because of its high sorption capacity, AC might, however, also sorb other chemicals that are not contaminants but instead have ecological functions. Examples of such compounds are infochemicals or pheromones (i.e., compounds serving as chemical inter- and intraspecies information vectors). The present study investigated the sorption of 2 known infochemicals, hypoxanthine-3-N-oxide (H3NO) and pyridine-N-oxide (PNO), to 5 different powdered ACs. Sorption isotherms of these low-molecular-weight, polar fish kairomone substances appeared highly nonlinear, with logarithmic Freundlich sorption coefficients of up to 7.6. At physiologically relevant concentrations, sorption was up to 7 to 9 orders of magnitude stronger than expected on the basis of hydrophobic forces only (i.e., the compounds' log octanol-water partition coefficient, being approximately -1), indicating exceptionally strong binding to specific sites. This binding effectively reduced the bioavailability of H3NO to Sarasa goldfish, as was shown in a behavioral assay. The present study demonstrates the previously unrecognized potential of AC to sorb ecologically relevant chemicals. Whether this potential may lead to subtle, unwanted ecological effects in the field will have to be investigated in more detail during future research.
authors.affiliation: Institute for Risk Assessment Sciences, Utrecht University, Utrecht, the Netherlands.
authors.forename: Michiel T O
authors.initials: MT
authors.lastname: Jonker
authors.forename: Louise
authors.initials: L
authors.lastname: van Mourik
mesh_terms: D000327:Adsorption; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D002606:Charcoal / Q000737:chemistry*; D006054:Goldfish / Q000502:physiology*; D057927:Hydrophobic and Hydrophilic Interactions; D007042:Hypoxanthines / Q000737:chemistry* / Q000378:metabolism / Q000633:toxicity; D011208:Powders; D011725:Pyridines / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry* / Q000378:metabolism / Q000633:toxicity
chemical_list: D007042:Hypoxanthines; D011208:Powders; D011725:Pyridines; D014874:Water Pollutants, Chemical; D002606:Charcoal; C013229:pyridine N-oxide; C017423:hypoxanthine 3-oxide
keywords: Activated carbon; Goldfish; Kairomones; Sediment remediation; Sorption