Solid phase microextraction fibers for estimating the toxicity of nitroaromatic compounds

Solid phase microextraction fibers are useful for investigating bioavailable organic contaminants in complex environmental matrixes such as aquatic sediments. Solid phase microextraction fibers are polymer-coated silica fibers that sorb dissolved organic compounds from water and sediment. We investigated their concentrations as measures of exposure for 2,4,6-trinitrotoluene and its degradation products in acute sediment and water-only toxicity tests with Tubifex tubifex, Chironomus tentans, and Ceriodaphnia dubia. Results from these exposures allowed us to compare solid phase microextraction fibers concentrations to two conventional measures of toxicant dose: external matrix (water, sediment) and internal (organism) concentrations. Because trinitrotoluene degrades within sediment and organisms, doses based on sediment, water, and organism concentrations were calculated using the molar sum of trinitrotoluene and its nitroaromatic degradation products. Among species and matrixes, median lethal doses based on solid phase microextraction fiber and organism concentrations ranged from 12.6 to 55.3 (μmol nitroaromatic per ml polyacrylate and 83.4 to 172.3 nmol nitroaromatic per gram tissue, wet weight, respectively. In contrast to matrix concentrations, which are specific to sediment or water, both organism and solid phase microextraction fiber concentrations appeared to provide measures of dose independent of exposure scenario (sediment or water). Median lethal doses based on fiber concentrations in whole-sediment and water-only Tubifex tubifex toxicity tests were within a factor of 1.1 (18.7 and 21.3 (μmol nitroaromatic per ml polyacrylate, respectively). Median lethal doses based on organism concentrations were within a factor 1.4 for Chironomus tentans exposed in water-only or whole-sediment scenarios (118.0 and 83.4 nmol nitroaromatic per gram tissue, wet weight, respectively). Solid phase microextraction fibers may provide a powerful chemical estimate of exposure with which to understand bioavailability and toxicity of organic compounds to benthic organisms.