Assessment of ammonia toxicity in contaminated sediments of the Upper Scheldt (Belgium): The development and application of toxicity identification evaluation procedures

The toxicity of sediment pore waters from 4 sites in the Upper Scheldt was characterized using modified Toxicity Identification Evaluation (TIE) procedures. The samples from all locations exhibited acute toxicity to the freshwater crustacean Thamnocephalus platyurus. The TIE approach was conducted using an enlarged battery of fractionation tests. Toxicity was removed or reduced sigmficantly by the cation exchange resins and the air-stripping test at pH 11. Additionally, increased toxicity was observed at higher pH while a reduced toxicity was found at a decreased pH. From these TIE studies, ammonia was identified as the dominant toxic agent.