Effects of depth of sediment dredging in urban rivers on release of nitrogen and phosphorus

The regularities of nitrogen and phosphorus nutrients released from the sediment of the Nanyuan River in Suzhou City at different depths of sediment dredging were studied by use of cylindrical specimens from the sediment.Some conclusions are drawn: the mass fraction of nitrogen decreases with the increase of the depth of the sediment;the mass fraction of TOC in the sediment and the amount of its release are of great influences on the accumulative release of the total amount of nitrogen;the release of nitrogen and phosphorus is closely related to the depth of sediment dredging,and the fluxes of nitrogen and phosphorus released from the interface of sediment and water are small when the depth of sediment dredging is 5cm or 15cm.