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The origin of speciation: Trace metal kinetics over natural water/sediment interfaces and the consequences for bioaccumulation

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Author: Vink, J.P.M.
Type:article
Date:2009
Institution: TNO Bouw en Ondergrond
Source:Environmental Pollution, 2, 157, 519-527
Identifier: 241373
doi: doi:10.1016/j.envpol.2008.09.037
Keywords: Geosciences · Availability · Biotic ligand model, Water Framework Directive · Free ion activity · Risk assessment · Uptake · Bio availabilities · Biotic ligand model, Water Framework Directive · Chemical conditions · Chironomus riparius · Exposure concentrations · Free ion activity · Free ions · Free metals · Geochemical conditions · Pore waters · Redox conditions · Sediment pore waters · Trace metals · Uptake · Bioaccumulation · Biochemistry · Cadmium compounds · Chemical speciation · Dissolution · Heavy metals · Ion exchange · Ions · Lead · Metal ions · Metals · Risk assessment · Risk management · Sedimentation · Sedimentology · Surface waters · Trace analysis · Trace elements · Water · Zinc · Heavy water

Abstract

The speciation of heavy metals was measured over a variety of natural and undisturbed water/sediment interfaces. Simultaneously, two benthic species (oligochaete Limnodrilus spp. and the midge Chironomus riparius) were exposed to these sediments. Under occurring redox conditions, free ion activities of trace metals Cd, Cu, Ni, Pb, and Zn were measured with a chelating exchange technique, while geochemical conditions (i.e., redox) remained in tact. Free ion activities were compared with total dissolved concentrations in pore waters and surface waters in order to relate speciation to bioaccumulation. Limnodrilus spp. and C. riparius have accumulation patterns that could be linked to time-dependent exposure concentrations, expressed as chemical speciation, in the surface water and the sediment's pore water. Concentrations of free metal ions in the overlying surface water, rather than in sediment pore water, proved to be the best predictor for uptake. For the first time, measurements are obtained from sediments without disturbing physical-chemical conditions and thus bioavailability, a major restriction of other studies so far. © 2008 Elsevier Ltd. All rights reserved.