The Primary Studies On Nitrogen And Phosphorus Cycling And Pollutant Refining In The Coastal Wetlands Of Of Yangtze Estuary

The coastal wetlands in the Yangtze Estuary with high biodiversity is one of the most important estuary wetlands in China, which are natural gene pool and high productivity system. But it is seriously impacted by human activities, such as wastewater discharge, reclamation, Three Gorges Reservoir project, water transferring project from south to north China, of which all would affect the wetland functions. So "the primary studies on nitrogen and phosphorus cycling and pollutant refining in the Yangtze Estuary coastal wetlands" would have important practical meaning.By setting sampling point for experimenting, monitoring in situ and analyzing in laboratory, we quantified the each stage of the nitrogen and phosphorus cycling, estimated the annual volume of nitrogen and phosphorus cycling in the Chongming Dongtan, and objectively evaluated the constructive coastal wetland system at Nanhui beach. We hope these studies can provide the academic bases for the sustainable development of the natural resources, environment and economy of the Yangtze Estuary wetlands. The results as follow:1. The studies on the nitrogen and phosphorus cycling in the coastal wetlandWhen the mass sand taken by Yangtze River water into the Estuary, partly was settled down the coastal wetlands in the Estuary. Particulate nitrogen and phosphorus can be decomposed to soluble inorganic nitrogen and phosphorus; partly soluble inorganic nitrogen and phosphorus in the seawater can be adsorbed by the soil. The kinetics of soil adsorb the dissolved inorganic phosphorus (DIP) and the ammonia nitrogen at the Jiuduansha in situ test point were ln(1-Si/12.106) = 0.01754t-0.2897, ln(1-Si/5.320)=0.05919t-0.58660. The net utilized rate of dissolved nitrogen and phosphorus by the vegetables in the coastal wetland was 13.59±10.40%, 14.75±5.16%. In winter, about 38.04±12.14% of nitrogen, 35.48±15.63 % of phosphorus in the above ground part of the vegetables was send to the underground part, about 53.32±10.43% of organic nitrogen and 51.55±7.16% of organic phosphorus in the litter was decomposed and released into the wetland.The sand kinetics experiments indicated that the annual net nitrogen and phosphorus input were 6.58×103t/a, 4.99×103t/a in the Chongming Dongtan respectively. In summer, the nitrogen and phosphorus in the vegetable each was 87.981t, 16.072t. In winter, 19.732t nitrogen and 4.038t phosphorus in the above ground vegetable was sent to the underground part, 13.644t nitrogen and 3.751t phosphorus of the rest of above ground part was decomposed and released into the Chongming Dongtan.2. The studies on the pollutant refining in coastal wetlandThe each average removal rates to total nitrogen, total phosphorus, chemical oxygen demand and dissolved inorganic phosphorus in the wastewater was 93.28%, 85.23%, 88.28% and 98.66% in the constructively coastal wetland acting as wastewater-treatment system at Nanhui beach.In the system, the vegetable can annually transfer 1.47t nitrogen and 0.458t phosphorus, this only account for the 2.42×10-4% of nitrogen and 6.43×10-4% of phosphorus in the annual inflows. So the vegetable has little direct effect to the removal.The main way of pollutant refining in the coastal wetland may be non-biological progress, for example, dilution by seawater, sedimentation of material, et al. The wastewater discharge increases the nitrogen and phosphorus content in soil, affected the water quality and partly vegetable growth.