Monitoring of persistent, lipophilic pollutants in water and sediment by solvent-filled dialysis membranes

Abstract

Dialysis membranes filled with solvents can be used to monitor persistent, lipophilic pollutants in marine and fresh water environments, to predict levels of bioavailable compounds in organisms, and to study bioaccumulation mechanisms. The membranes are filled with n-hexane and exposed for 1 to several weeks in the water or in the sediment. The solvent impregnates the membrane, makes it unsuitable for periphyton growth, and prevents bacterial degradation. The membranes can also be used in environments too polluted for biological indicators to survive. The use of membranes with a molecular weight cutoff of 1000 Da prevents substances of higher molecular weight from diffusing through their walls, thereby simplifying the cleanup procedure. Internal standards in the solvent can be quantified to ensure that the membrane functions properly during the exposure. Uptake and depuration of organochlorine residues by the membranes seem to be governed by equilibrium partitioning.