DGT-Induced Copper Flux Predicts Bioaccumulation and Toxicity to Bivalves in Sediments with Varying Properties Stuart L. Simpson,* ,† He ́ loïse Yverneau, †,‡ Anne Cremazy, †,§ Chad V. Jarolimek, † Helen L. Price, ∥ and Dianne F. Jolley ∥ † Centre for Environmental Contaminants Research, CSIRO Land and Water, Locked Bag 2007, Kirrawee, NSW 2234, Australia ‡ Ecole Nationale Supe ́ rieure de Chimie de Montpellier-National Graduate School of Chemistry of Montpellier, Montpellier 34296, France § Universite ́ de Bordeaux 1, 33600 Pessac, France ∥ School of Chemistry, University of Wollongong, NSW 2522, Australia * S Supporting Information ABSTRACT: Many regulatory frameworks for sediment quality assessment include consideration of contaminant bioavailability. However, the “snap-shots” of metal bioavailability provided by analyses of porewaters or acid-volatile sul fide- simultaneously extractable metal (AVS-SEM) relationships do not always contribute sufficient information. The use of inappropriate or inadequate information for assessing metal bioavailability in sediments may result in incorrect assessment decisions. The technique of diffusive gradients in thin films (DGT) enables the in situ measurement of metal concentrations in waters and fluxes from sediment porewaters. We utilized the DGT technique to interpret the bioavailability of copper to the benthic bivalve Tellina deltoidalis in sediments of varying properties contaminated with copper-based antifouling paint particles. For a concentration series of copper-paint contaminated sandy, silty-sand, and silty sediment types, DGT- probes were used to measure copper fluxes to the overlying water, at the sediment- water interface, and in deeper sediments. The overlying water copper concentrations and DGT-Cu fluxes were shown to provide excellent exposure concentration−response relationships in relation to lethal effects occurring to the copper-sensitive benthic bivalve, T. deltoidalis. The study demonstrates the strength of the DGT technique, which we expect will become frequently used for assessing metal bioavailability in sediments. ■ INTRODUCTION The technique of diffusive gradients in thin films (DGT) was developed to enable the in situ measurement of metal concentrations in waters 1 and fluxes from sediment pore- waters. 1,2 In a DGT device, dissolved metal species diffuse through a polyacrylamide gel layer and become trapped in a gel impregnated with a metal-exchange resin, which acts as a metal sink. 3 The removal of metals from sediment porewaters causes the concentration to decline immediately adjacent to the device. This localized decline could disturb the dynamic equilibrium between the sediment and metal in solution and induced release of metals to solution, 4 the extent of which will depend on the rate of metal resupply from the sediment solid phase to the porewater. If there is rapid resupply, metal concentrations in porewaters may be calculated from the DGT- accumulated metal concentration. However, when resupply from the sediments is limited, the DGT-flux provides information on the relative rate of remobilization of metals from sediments to the porewater. 5 Hence the DGT directly measures the flux of metal from the sediment during the deployment time, which reflects the concentration in the porewater, its diffusional transport, and the supply from the solid phase to solution. 6 It can be interpreted simply as the average porewater concentration at the interface of the device over the deployment period. The ability of DGT measurements to provide information on the localized remobilization of metals has been utilized to create high-resolution depth profiles of metals within sediments. 2,7 Such studies have demonstrated the heterogeneity of sediment environments, including the existence of microniches and to characterize zones of metal remobilization. 8−10 Existing methods for estimating the bioavailability of metals in sediments to benthic organisms have numerous limita- tions. 11,12 For example, the usefulness of chemical extractions that provide information on metal lability varies between metals and the degree of contamination and for the organism being studied. 13,14 Further to this, the equilibrium partitioning relationships between metals and acid-volatile sulfide (AVS) become less appropriate for organisms that create oxic/suboxic Received: April 4, 2012 Revised: July 14, 2012 Accepted: July 24, 2012 Published: July 24, 2012 Article pubs.acs.org/est © 2012 American Chemical Society 9038 dx.doi.org/10.1021/es301225d | Environ. Sci. Technol. 2012, 46, 9038−9046