PM19 Field-Based Effects Measures
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(PM294) Optimization of an in situ Toxicity Identification Evaluation (iTIE) Method.

Geyer, S1, Burton, G1, 1 Wright State University, Dayton, Ohio, United States

ABSTRACT- Determining causality in sediments contaminated with multiple chemicals is often important. Sediment sampling and manipulation for laboratory testing can alter chemistry, bioavailability and laboratory assays tend to alter exposures. An in situ Toxicity Identification Evaluation (iTIE) method was designed to identify dominant chemical class stressors (Burton and Nordstrom, Environ Toxicol Chem 2004). The focus of the current study was to optimize the previous iTIE design and examine the strengths and limitations of the method. The objectives were to: 1) establish sediment-size affects on porewater flow, 2) determine overlying water level limitations, 3) establish sorption coefficients of toxicant groups on chamber materials, and 4) validate iTIEs determinations of toxicant causality. The iTIE chambers operate via the Venturi pumping system which suctions test water through the treatment chamber and into the exposure chamber. The treatment chamber is packed with a differing treatment resin (Pond Care® zeolite for ammonia removal, Ambersorb® 563 for non-polar chemicals adsorption, Chelex® 100 for metals chelation, and polywool for reference chambers). Treatment differences were determined using Daphnia magna survival. Pore water flow delivery was improved using a modified multi-valve system, however, slight differences were noted between treatments and sediment types. The current design is limited to shallow, low to moderate current systems. Some sorption of chemical compounds occurred on the chamber materials, however, the continual porewater renewal reduced the importance of this loss. The iTIE treatment responses at contaminated field sites documented its effectiveness at determining causality, in a weight-of-evidence approach.

Key words: sediment toxicity, in situ, stressor identification, daphnia magna

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