Research On Dissolved Inorganic Nitrogen Exchange At The Sediment-water Interface Of The Yangtze Estuarine Tidal Flats

Derived from intensive human activities such as fertilizer usage, fossil fuels combustion and sewage discharge in recent decades, aquatic environments in coastal areas all over the whorld have encountered serious dissolved inorganic nitrogen pollution, resulting in many existent and potential ecological and environmental issues such as water quality depravation, coastal eutrophication, ecological degradation, drinking water risk and so on. The Yangtze river is third biggest river in the world with a total catchment area about 18 million km~2 and a population more than 4 ×10~8 . In the past decades, increasing riverine nitrogen inputs due to gigantic loss of farmland nitrogen fertilizer and domestic sewage discharge have seriously influenced the Yangtze estuarine water qualities and the ecological security of the delta area. In the outer estuarine area, the frequency and the area of red tide have increased in past years. This issue has affected the economic and sustainable development of the Yangtze delta.As typical ecotone between terrestrial and oceanic ecosystems, the estuarine tidal flat is widely identified as one of the most valuable and vulnerable habitats with many particular characteristics such as powerful tidal and riverine hydrodynamic processes, frequent sediment transportation and matter exchange, acute physical and chemical gradients, and various organism species. The estuarine tidal flats have a series of environmental functions and ecological values, particularly it is recognized as a natural barrier in purifying terrigenous nitrogen input. However, extensive exploitations and developments in the Yangtze estuarine coastal zone in recent years have badly disturbed and destroyed tidal flat environments and ecosystems. In order to make proper use of estuarine tidal flat resources, protect estuarine tidal flat environments and ecological balance, prevent and cure estuarine eutrophication effectively, it is urgent to carry out systemic researches on the nutrient biogeochemical cycles and processes in the Yangtze estuarine coastal tidal flats. Studies on DIN Exchanges at the sediment-water interface of the Yangtze estuarine tidal flats is of global environment significance and in accordance with economic research demands for sustainable development in eastern coastal area of China.This dissertation was supported by the National Nature Science Key Foundation of China (No.40131020), National Nature Science Foundation of China (No. 40173030), the Science & Technology Department of Shanghai Program (Grant No.05DZ120007; Grant No.05JC14059), Shanghai Environmental Bureau Program; Shanghai Basic Science Research Key Program (No.02DJ14029), and Foundation for...