Estimation of nutrient discharge from the Yangtze River to the East China Sea and the identification of nutrient sources.

Based on a time-series dataset and the mass balance method, the contributions of various sources to the nutrient discharges from the Yangtze River to the East China Sea are identified. The results indicate that the nutrient concentrations vary considerably among different sections of the Yangtze River. Non-point sources are an important source of nutrients to the Yangtze River, contributing about 36% and 63% of the nitrogen and phosphorus discharged into the East China Sea, respectively. Nutrient inputs from non-point sources vary among the sections of the Yangtze River, and the contributions of non-point sources increase from upstream to downstream. Considering the rice growing patterns in the Yangtze River Basin, the synchrony of rice tillering and the wet seasons might be an important cause of the high nutrient discharge from the non-point sources. Based on our calculations, a reduction of 0.99Tg per year in total nitrogen discharges from the Yangtze River would be needed to limit the occurrences of harmful algal blooms in the East China Sea to 15 times per year. The extensive construction of sewage treatment plants in urban areas may have only a limited effect on reducing the occurrences of harmful algal blooms in the future.

[1]  Z. Dai,et al.  Variation of riverine material loads and environmental consequences on the Changjiang (Yangtze) estuary in recent decades (1955-2008). , 2011, Environmental science & technology.

[2]  N. Rabalais,et al.  Future aquatic nutrient limitations. , 2003, Marine pollution bulletin.

[3]  Zhongyuan Chen,et al.  Yangtze River of China: historical analysis of discharge variability and sediment flux , 2001 .

[4]  John J. Walsh,et al.  Importance of continental margins in the marine biogeochemical cycling of carbon and nitrogen , 1991, Nature.

[5]  B. Jørgensen,et al.  Eutrophication: Definition, History and Effects , 2013 .

[6]  Zou Ying-bin.  Development of Cultivation Technology for Double Cropping Rice Along the Changjiang River Valley , 2011 .

[7]  Wenxian Guo,et al.  Agricultural non-point source pollution in the Yongding River Basin , 2014 .

[8]  Lei Gao,et al.  Nutrients and particulate organic matter discharged by the Changjiang (Yangtze River): Seasonal variations and temporal trends , 2012 .

[9]  Xiaoyong Shi,et al.  Increased nutrient loads from the Changjiang (Yangtze) River have led to increased Harmful Algal Blooms , 2014 .

[10]  Qianggong Zhang,et al.  Riverine nitrogen loss in the Tibetan Plateau and potential impacts of climate change. , 2016, The Science of the total environment.

[11]  J. Garnier,et al.  Nutrient (N, P) budgets for the Red River basin (Vietnam and China) , 2005 .

[12]  Xuejun Wang,et al.  Nutrient Loads Flowing into Coastal Waters from the Main Rivers of China (2006–2012) , 2015, Scientific Reports.

[13]  Kaiqin Xu,et al.  Long-term variations in dissolved silicate, nitrogen, and phosphorus flux from the Yangtze River into the East China Sea and impacts on estuarine ecosystem , 2007 .

[14]  S. L. Yang,et al.  Trends in annual discharge from the Yangtze River to the sea (1865–2004) / Tendances et épisodes extrêmes dans les débits annuels du Fleuve Yangtze débouchant dans la mer (1865–2004) , 2005 .

[15]  Zhigang Yu,et al.  Impacts of human activities on nutrient transports in the Huanghe (Yellow River) estuary , 2012 .

[16]  V. Smil.  Enriching the Earth: Fritz Haber, Carl Bosch, and the Transformation of World Food Production , 2000 .

[17]  Dennis P. Swaney,et al.  Regional nitrogen budgets and riverine N & P fluxes for the drainages to the North Atlantic Ocean: Natural and human influences , 1996 .

[18]  Howard R. Ernst.  Chesapeake Bay Blues: Science, Politics, and the Struggle to Save the Bay , 2003 .

[19]  R. Rosenberg,et al.  Spreading Dead Zones and Consequences for Marine Ecosystems , 2008, Science.

[20]  Baodong Wang.  Cultural eutrophication in the Changjiang (Yangtze River) plume: History and perspective , 2006 .

[21]  Sandip Mukhopadhyay,et al.  Fluxes of nutrients from the tropical River Hooghly at the land–ocean boundary of Sundarbans, NE Coast of Bay of Bengal, India , 2006 .

[22]  Gregory E. Schwarz,et al.  Regional interpretation of water‐quality monitoring data , 1997 .

[23]  S. M. Liu,et al.  Human impacts on the large world rivers: Would the Changjiang (Yangtze River) be an illustration? , 1999 .

[24]  R. E. Turner,et al.  Global patterns of dissolved N, P and Si in large rivers , 2003 .

[25]  Shu Gao,et al.  Changes in material fluxes from the Changjiang River and their implications on the adjoining continental shelf ecosystem , 2008 .

[26]  K. Sørensen,et al.  Input of organic carbon as determinant of nutrient fluxes, light climate and productivity in the Ob and Yenisey estuaries , 2010 .

[27]  S. Greenhalgh,et al.  EUTROPHICATION AND HYPOXIA IN COASTAL AREAS : A GLOBAL ASSESSMENT OF THE STATE OF KNOWLEDGE , 2008 .