Long-Term Monitoring of Bioavailable Copper in the Aquatic Environment Using a Resin-Filled Dialysis Membrane

Abstract

It has been demonstrated that only a relatively small portion of the total amount of metals in an aquatic system is biologically available. TO evaluate the ecotoxicity of the metals in a water body, the measurement of such a fraction is often critical (Wachnik 1988;Jonnalagadda and Rao 1993). A number of methods, including anodic stripping voltammetry have been developed for collecting information on metal speciation. None of them, however, can measure the biologically available fraction for routine monitoring purposes. This is due to both extremely low concentrations of such a fraction and shift of the equilibrium among species during the analysis (Tao 1987). Furthermore, most efforts on metal speciation have focused on the determination of the available metal concentration in a single grab sample. The level of individual species may, however, fluctuate randomly.The information on the overall bioavailability of the metals over a relatively long period of time is necessary for ecotoxicity assessment. This, however, cannot be provided by measured results from a limited number of samples collected individually. Sodergren (1987) used a dialysis membrane filled with organic solvent to simulate the absorption of organic pollutants by an organism. This technique was applied to predict the levels of bioavailable lipophilic pollutants in organisms and to study bioaccumulation mechanisms in aquatic environments (Sodergren 1990). A similar approach using dialysis with receiving resins was reported by Morrison (1987). A cellulose dialysis membrane, with a molecular weight cut-off of 1000 dalton, filled with Chelex-100 chelating resin was employed to simulate the slow membrane-limited metal transport process across a cell membrane. The method was tested for urban stormwater and other polluted waters. The membrane uptake rate, receiving resin uptake rate, as well as the relationship between metal uptake and rainfall duration were investigated. It was found that the metal uptake rates measured at three stormwater outfalls reflected the sporadic and variable nature of bioavailable metals in stormwater discharge (Morrison 1987(Morrison , 1989. The dialysisresin technique has also been employed to determine the free-ion fraction of cadmium in water samples (Berggren 1990). The purpose of the study was to measure the instant concentration of a single sample. Information on overall bioavailability of the metals cannot be provided by this approach.

Impact of Surface Water Conditions on Preservative Leaching and Aquatic Toxicity from Treated Wood Products

“…Free (hydrated) Cu 2+ ions present in natural waters tend to complex with inorganic and organic ligands such as CO 3 2- , OH - , and humic and fulvic acids ( − ) rendering Cu much less bioavailable to aquatic organisms and, as a result, less toxic ( 8 , − . The chemical characteristics of the solution in contact with treated wood can thus significantly impact the bioavailability and aquatic toxicity of the copper leached ( , ).…”