Abstract

 Biomimetic devices such as semipermeable membranes (SPMDs) and solid phase microextraction fibers (SPMEs) may be useful for investigating bioavailable organic contaminants in complex environmental matrices as they sample only weakly dissolved and easily-dissociated "available" molecules. Though both SPMDs and SPMEs passively sample organic compounds, their designs are quite different. SPMDs are layflat, thin-walled bags or comprised of low-density polyethylene filled with triolein lipid, whereas SPMEs are polymer-coated silica fibers. SPMEs have a number of advantages over SPMDs, including ease of use, expense, and sampling time. Through the use of lethal toxicity tests with invertebrates (Tubifex tubifex and Chironomus tentans) exposed to the explosive 2,4,6-trinitrotoluene in spiked waters and sediments, we calculated median lethal toxicity metrics (LC50s, LD50s) using three estimates of toxicant dose: external matrix concentration, body concentration, and amount adsorbed by polyacrylate SPMEs. LC50s calculated using sediment and water concentrations were highly variable (CV = 95%), probably due to the large differences in bioavailability between these matrices. Lethal toxicity metrics calculated using organism concentrations and SPME residues were much more precise, with CVs of 51 and 59%, respectively. This suggests that SPMEs and CBRs may provide an assessment of toxicity that accounts for environmental bioavailability. SPME analysis of sediment-associated organics is generally much easier, more rapid, less variable, and less expensive than biological tests. Thus, SPMEs have advantages over biological tests and may be a very powerful exposure assessment tool.