title: Photo-transformation of pedogenic humic acid and consequences for Cd(II), Cu(II) and Pb(II) speciation and bioavailability to green microalga.
abstract: Humic substances (HS) play key role in toxic metal binding and protecting aquatic microorganisms from metal-induced stress. Any environmental changes that could alter HS concentration and reactivity can be expected to modify metal complexation and thus affect metal speciation and bioavailability to microalgae. The present study explores the influence of increased solar irradiance on the chemical structures and molecular weight of Elliott soil humic acid (EHA) and the associated consequences for Cd(II), Cu(II) and Pb(II) complexation and intracellular metal content in microalga. The results demonstrate that high radiance doses induce an oxidation of EHA with a formation of low molecular weight acids, an increase of -OH and -COOH group abundance, and a drop in EHA hydrodynamic size and molecular weight. The photo-induced structural changes are accompanied with a release of metal from M-EHA complexes and narrowing their size distribution, which in turn results in an increase of the intracellular Cd, Cu and Pb contents in microalga Chlamydomonas reinhardtii in agreement with the measured free metal ions concentrations.
authors.affiliation: Environmental Biogeochemistry and Ecotoxicology, Institute F.-A. Forel, Earth and Environmental Sciences, Faculty of Sciences, University of Geneva, 10, route de Suisse, CH-1290 Versoix, Switzerland. Electronic address: Isabelle.Worms@unige.ch.
authors.forename: Isabelle A M
authors.initials: IA
authors.lastname: Worms
authors.affiliation: Environmental Biogeochemistry and Ecotoxicology, Institute F.-A. Forel, Earth and Environmental Sciences, Faculty of Sciences, University of Geneva, 10, route de Suisse, CH-1290 Versoix, Switzerland.
authors.forename: David
authors.initials: D
authors.lastname: Adenmatten
authors.affiliation: Institute of Chemical Sciences and Engineering, School of Basic Sciences, Ecole Polytechnique Fédérale de Lausanne EPFL, Station 6, Switzerland.
authors.forename: Pascal
authors.initials: P
authors.lastname: Miéville
authors.affiliation: Process Engineering, Eawag, Ueberlandstrasse 133, 8600 Duebendorf, Switzerland.
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Traber
authors.affiliation: Environmental Biogeochemistry and Ecotoxicology, Institute F.-A. Forel, Earth and Environmental Sciences, Faculty of Sciences, University of Geneva, 10, route de Suisse, CH-1290 Versoix, Switzerland. Electronic address: vera.slaveykova@unige.ch.
authors.forename: Vera I
authors.initials: VI
authors.lastname: Slaveykova
mesh_terms: D001682:Biological Availability; D002104:Cadmium / Q000737:chemistry / Q000378:metabolism; D016825:Chlamydomonas reinhardtii / Q000378:metabolism*; D003300:Copper / Q000737:chemistry / Q000378:metabolism; D004785:Environmental Pollutants / Q000737:chemistry / Q000378:metabolism; D006812:Humic Substances; D007854:Lead / Q000737:chemistry / Q000378:metabolism; D019216:Metals, Heavy / Q000737:chemistry* / Q000378:metabolism*; D058086:Microalgae / Q000378:metabolism*; D055668:Photochemical Processes; D012987:Soil / Q000737:chemistry
chemical_list: D004785:Environmental Pollutants; D006812:Humic Substances; D019216:Metals, Heavy; D012987:Soil; D002104:Cadmium; D007854:Lead; D003300:Copper
keywords: Chlamydomonas reinhardtii; Dissolved organic matter; Flow field-flow fractionation; Metal bioavailability; Photooxidation; UV