Denitrification And N₂O Emission And Consumption At Coastal Tidal Flat, Yangtze Estuary

In recent decades, high intensity human activity, such as chemical fertilizer employment and drainage, induced the increase of nitrogen year after year which was transported into estuarine area. Quickly eutrophication in estuarine coastal water body is one of the serious globe environment problems in the world. Estuarine wetland is a natural barrier in purifying terrigenous pollutions and attenuating the riverine load to the sea, it plays a key role in controlling marine eutrophication and global nitrogen cycle. It was estimated that estuarine sediment could eliminate 10-60% territorial nitrogen load, among this, denitrification is an important process.As a key process of nitrogen cycle, denitrification is an important approach to transfer nitrogen in terrestrial and aquatic ecosystem into atmosphere, and has a key role on keeping nitrogen balance among the lithosphere, hydrosphere, biosphere and atmosphere. In the anoxic condition, nitrate will become electron acceptance instead of oxygen, much of it being converted into N₂ and a small proportion into N2O, and then enter into atmosphere. Because N₂ is abundant in the earth's atmosphere and inert, denitrification is considered as the most desirable means for nitrate removal from polluted and eutrophication water environment and this sink will never become saturation with nitrogen because of the nitrogen importing continuously.While N₂O is one of major atmospheric greenhouse gases, its greenhouse effect is prominent and has a long lifespan in the atmosphere, and thus has a large greenhouse wanning potential. At the same time it contributes to ozone destruction resulting in stratospheric ozone depletion, and at the bottom of stratosphere, it could be converted into NOx and then into HNO_x forming the acid precipitation. The converted production could also enhance the greenhouse effect. So in recent years, abundant attentions were put on the global N₂O emission and consumption flux and its concentration increasing in the atmosphere.In estuarine coastal area, terrigenous particular settle and deposit in this area by the land-sea interaction. The sediment is a huge pool of terrigenous nitrogen and carbon element. At the tidal flat, the growth and bury of plant make the tidal flat wetland as the important portion of global nitrogen and carbon pool. In the alluvial...