Influence of Sediment Dredging on Nitrogen and Phosphorus Release in Fubao Bay of Dianchi Lake, China

Fubao Bay lies in the northeast part of Dianchi Lake with highly polluted by contamination input from the Daqing and Haihe rivers, and hyper-eutrophication and algae blooming appeared in this bay. A laboratory experiment was carried out through a six-month incubation of undredged (control) and dredged cores to study the effect of sediment dredging on nitrogen and phosphorus release from the sediment. During the experiment, dredging the upper 30 cm layer could efficiently reduce the organic matter, microbial activity, alkaline phosphatase activity and different phosphorus forms in the sediment. The results showed that the sediment, whether dredging or undredging, was the source of NR4+-N and PO43--P for the water. The NH4+-N and PO43--P fluxes of the undredged sediment ranged from 245.6 to 461.6 mg/m(2).d and 2.21 to 3.22 mg/m(2).d, respectively. The dredged sediment made the fluxes to decrease to 46.1 to 154.7 mg/m(2).d and 0.38 to 1.22 mg/m(2).d, respectively. The fluxes of the dredged cores were sharply lower than those of the control. Dredging can be considered as a useful measure for rehabilitating the aquatic ecosystem of our study site.