title: Fifteen-year study of environmental dredging effect on variation of nitrogen and phosphorus exchange across the sediment-water interface of an urban lake.
abstract: Environmental dredging has been applied widely in Chinese lakes to reduce their internal nutrient loads. However, the efficacy of dredging to reduce internal loading of nitrogen (N) and phosphorus (P) and to improve water quality has been questioned by some researchers. In this study, the long-term (∼15 years) effects of dredging to reduce internal N and P loading in a closed, polluted urban lake were investigated. The results showed that the release of soluble reactive phosphorus (SRP) could be suppressed quickly after dredging, and that the dredging effect was sustained for about 18 months. A significant release of NH4+-N was discovered during the first 2-8 months after dredging, followed by maintenance of low-level release rates for about 21-32 months. The continuous inflowing of external pollution loading led to the increase in the release rates of SRP and NH4+-N. The external pollution loading was therefore reduced three years after dredging to strengthen the remediation effect. After that, high diffusive flux from the sediment was observed for both NH4+-N and SRP during summer seasons for about six years, followed by a decreasing trend. The NH4+-N concentration in the overlying water was reduced after the reduction of external loading, while a high concentration of SRP in the overlying water was still observed during summer seasons. In conclusion, the mid-term (<3 years) reduction of internal N and P loading could be achieved by dredging if the external pollution loading were not reduced. Achieving long-term control would require modification of external loading.
authors.affiliation: State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China.
authors.forename: Cheng
authors.initials: C
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, PR China.
authors.forename: Jicheng
authors.initials: J
authors.lastname: Zhong
authors.affiliation: State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, PR China.
authors.forename: Jianjun
authors.initials: J
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, PR China.
authors.forename: Lu
authors.initials: L
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, PR China. Electronic address: cxfan@niglas.ac.cn.
authors.forename: Chengxin
authors.initials: C
authors.lastname: Fan
mesh_terms: D002681:China; D002947:Cities; D004784:Environmental Monitoring; D052918:Environmental Restoration and Remediation / Q000706:statistics & numerical data*; D019015:Geologic Sediments / Q000737:chemistry*; D060106:Lakes / Q000737:chemistry*; D009584:Nitrogen / Q000032:analysis*; D058458:Nitrogen Cycle; D010758:Phosphorus / Q000032:analysis*; D012621:Seasons; D014874:Water Pollutants, Chemical / Q000032:analysis
chemical_list: D014874:Water Pollutants, Chemical; D010758:Phosphorus; D009584:Nitrogen
keywords: Exchange across sediment-water interface; External pollution loading; Long-term investigation; Nitrogen and phosphorus; Sediment dredging