Toxicity identification evaluation of sediments in Liaohe River.

Liaohe River has received significant attention in the northeast region and even in the entire country. As part of a recently completed water quality assessment, a series of water column and sediment toxicity tests was performed throughout the watershed. In the current study, we subjected sediments from the Liaohe River to toxicity identification evaluation manipulations and tests for chronic toxicity with midge (Chironomus riparius), with survival as the end point. In Phase I, the sediments were treated with zeolite, cation-exchange resin, and powdered coconut charcoal. Results confirmed that ammonia compounds were the major contaminants in terms of toxicity, although toxic effects from metals were also a concern in at least three sites. In Phase II identification, chemical analysis provided a strong evidence that the metals As and Cd are the probable causes of toxicity in the sediments, without the influence of ammonia. Temporally, ammonia is responsible for the toxicity of the selected sediments.