Post-dredging effect assessment based on sediment chemical quality in urban rivers of Yangzhou.

Deteriorating of urban river environment in Yangzhou is gradually serious in recent years. Treatment measures including pollution source control, sewage interception, and sludge dredging have been carried out in recent years, but urban river environment is still poor. In order to ascertain the causes, post-dredging effects were assessed based on sediment chemical quality in urban rivers of Yangzhou. Results indicate that post-dredging effects are not ideal because of backward dredging technique and incomplete pollution control. Eutrophication degree is still relatively high for most of them and pollution degree of nutrients is total phosphorus (TP) > total nitrogen (TN) > organic matter (OM). Although the pollution of heavy metals is not serious, the major pollution factors Cd and Hg should still be monitored intensively in the sludge dredging for the toxic effect of heavy metals.