An in situ toxicity identification evaluation method part I: Laboratory validation

Abstract

Identification of individual chemical groups is critical in evaluating sediment quality and fractionating these groups of chemicals in a mixture is important to determine the primary chemicals causing toxicity. The in situ toxicity identification evaluation (iTIE) is a novel method that was developed to fractionate chemicals in contaminated sediments and waters and assess toxicity organisms. The study objectives were to verify that the iTIE can help identify contaminant chemical classes and improve the toxicity assessment process; and compare the iTIE and U.S. Environmental Protection Agency's (U.S. EPA) toxicity identification evaluation (TIE) methods. The iTIE exposure chamber is powered by a portable air pump that suctions pore water, via a Venturi system, through selective sorption materials. After passing through the sorptive materials, the pore water passes into an exposure chamber containing Daphnia magna. The chemical sorption materials included Ambersorb 563 for nonpolar organic chemical adsorption, Chelex for metals chelation, and multiple zeolite types for ammonia adsorption. The laboratory studies were performed using water and sediments spiked with ammonia, cadmium, and fluoranthene. The laboratory validation of the iTIE approach showed that different classes of compounds readily could be separated via the resin treatments, resulting in significant differences in concentrations and thus exposures to in situ exposed organisms. Ammonia, cadmium, and fluoranthene were significantly removed by zeolite, Chelex, and Ambersorb, respectively. Although there was some cross-adsorption to the other nontarget resins, it was limited and allowed for treatment differences to be detected. Survival in the treatment resins exposed to the target compounds was as high as control survivals. A 24-h exposure period appeared optimal, allowing for replacement of initial culture water with pore waters, while longer exposures occasionally allowed for breakthrough of contaminants. The iTIE was more sensitive than the U.S. EPA TIE method, in that it detected toxicity more readily due to the greater loss of contaminant concentrations in the TIE manipulation process.