The toxicity of sediments from the black-odors river of wenzhou, china to the embryos of xenopus tropicalis

To evaluate the ecological risk of black-odors river, we measured the developmental toxicity of sediments in urban rivers of Wenzhou, China, with Xenopus tropicalis embryos. The sediments were seasonally collected from November, 2010 to August, 2011 at 7 sites in lower WenRui Tang River watershed of Wenzhou. The embryos were exposed to the sediment extracts for 48 h. All the embryos died in groups treated with extracts from S1 in autumn, spring and winter and from S3 in winter. The sediment extracts induced multiple malformations including bent notochord, enlarged proctodaeum, narrow fin and posterior anus in the embryos of X. tropicalis. The percentages of total malformation were more than 40% at 5 sites in autumn and winter, but they were less than 30% at all sites in spring and less than 10% at 5 sites in summer. The toxicity of sediments greatly decreased by ammonium removal. These results suggest that the sediments from some specific sites in urban rivers of Wenzhou had highly lethal effects and that the sediments from most sites showed teratogenic effects on amphibian embryos. Ammonium was the main contributor to the teratogenicity of sediments. The seasonal variations of toxicity of sediments might be related to the changes of seasonal precipitation.