title: Natural dissolved organic matter mobilizes Cd but does not affect the Cd uptake by the green algae Pseudokirchneriella subcapitata (Korschikov) in resin buffered solutions.
abstract: Natural dissolved organic matter (DOM) can have contrasting effects on metal bioaccumulation in algae because of complexation reactions that reduce free metal ion concentrations and because of DOM adsorption to algal surfaces which promote metal adsorption. This study was set up to reveal the role of different natural DOM samples on cadmium (Cd) uptake by the green algae Pseudokirchneriella subcapitata (Korschikov). Six different DOM samples were collected from natural freshwater systems and isolated by reverse osmosis. In addition, one (13)C enriched DOM sample was isolated from soil to trace DOM adsorption to algae. Algae were exposed to standardized solutions with or without these DOM samples, each exposed at equal DOM concentrations and at equal non-toxic Cd(2+) activity (∼4 nM) that was buffered with a resin. The DOM increased total dissolved Cd by factors 3-16 due to complexation reactions at equal Cd(2+) activity. In contrast, the Cd uptake was unaffected by DOM or increased maximally 1.6 fold ((13)C enriched DOM). The (13)C analysis revealed that maximally 6% of algal C was derived from DOM and that this can explain the small increase in biomass Cd. It is concluded that free Cd(2+) and not DOM-complexed Cd is the main bioavailable form of Cd when solution Cd(2+) is well buffered.
authors.affiliation: Division Soil and Water Management, Department of Earth and Environmental Science, KU Leuven, Belgium. Electronic address: verheyenliesbeth@gmail.com.
authors.forename: Liesbeth
authors.initials: L
authors.lastname: Verheyen
authors.affiliation: Division Soil and Water Management, Department of Earth and Environmental Science, KU Leuven, Belgium. Electronic address: liske.versieren@ees.kuleuven.be.
authors.forename: Liske
authors.initials: L
authors.lastname: Versieren
authors.affiliation: Division Soil and Water Management, Department of Earth and Environmental Science, KU Leuven, Belgium. Electronic address: erik.smolders@ees.kuleuven.be.
authors.forename: Erik
authors.initials: E
authors.lastname: Smolders
mesh_terms: D002021:Buffers; D002104:Cadmium / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism*; D002247:Carbon Isotopes / Q000032:analysis; D000460:Chlorophyta / Q000737:chemistry* / Q000378:metabolism*; D005618:Fresh Water / Q000737:chemistry; D012987:Soil / Q000737:chemistry; D012996:Solutions; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D002021:Buffers; D002247:Carbon Isotopes; D012987:Soil; D012996:Solutions; D014874:Water Pollutants, Chemical; D002104:Cadmium
keywords: Cd uptake; Dissolved organic matter; Free ion activity model; Green algae; Resin buffering