On the potential release rates of nutrient from internal sources: A comparative study of typical dredged and un-dredged areas, northwestern Lake Taihu

Abstract

Simulated research of internal loading release was carried out to assess the effects of sediment dredging on internal source release,and the basic properties of dredged and un-dredged sediments was also analyzed in this study. Intact sediment cores were collected from dredged and un-dredged sites in four areas including Bafang Port,Lvjiang Port,Moon Bay and Zhushan Bay,northwestern Lake Taihu. The results showed that the potential release rates of sediments can be efficiently prevented by dredging because of the internal loadings such as the loss on ignition,total nitrogen and ammonium nitrogen which were significantly lower after dredging. The potential release rates of ammonium in dredged sites of Bafang Port,Moon Bay and Zhushan Bay was 65. 3%,88. 8% and 21. 9%,respectively. The potential release rates of phosphorus in dredged sites of Bafang Port even showed negative(- 0. 35 mg/( m2·d)) which means the diffusion direction of phosphorus was from overlying water toward sediments. The release rates of phosphorus in dredged sites of Moon Bay and Zhushan Bay was 11. 3% and 50. 2% of the corresponding un-dredged sites.We also found that the potential release rates of ammonium and phosphorus in dredged sites of Lvjiang Port was significantly higher than those in un-dredged sites,which may be accounted for the reducing environment of water body and the high content of organic matter in sediments.