Study On Distribution And Benthic Fluxes Of Nutrients In Sediment Of The Yellow River Estuary Wetland

The estuarine and coastal tidal flat, as a typical transitional zone between land and ocean, is characterized by intense hydrodynamic conditions, frequent sediment transport and material exchange and high biodiversity, It has special environmental function and ecological values. The Yellow River estuary wetland is formed by the erosion of the sediment carried by Yellow River, which is the most complete, the most extensive and the most youngest new wetland ecosystem in the warm temperate of China. Because of its strong typicalness, the unique ecological environment and the rich natural resources, it attracts more and more attention of the researchers at home and abroad. Therefore, there are scientific and practical values to do research on the Yellow River estuary wetland.The paper was based on the surface sediment and the columnar sediment of Yellow River estuary wetland. The content and distribution characteristics of TN and TP in sediment and PO4-P, NH4-N, NO2-N, NO3-N and SiO3-Si in sediment pore water were discussed. Benthic exchange processes of nutrients at the sediment-water interface were measured according to the lab incubation experiments, and the influences to the exchange flux were discussed. This paper provides a basis for further research of nutrient migration, transformation and nutrient recycling in sediment of the Yellow River estuary wetland. The main conclusions are as follows:(1)The water content of sediment is 17.14-33.90%, and the median diameter of sediment is between 5.4 and 56.2μm. The main composition of sediment is silty sand, and the content of clay and sand are less. The distribution of water content of sediment and median diameter of sediment are contrary trend, and they has basic negative correlation, it means that the smaller of sediment particles, the stronger ability of sediments to hold water, and the moisture cotent of sediment are higher.(2) The concentration scopes of PO4-P in the surface sediment pore water ranges from 0.21 to 26.8μmol/L. The concentration scopes of NH4-N, NO2-N, NO3-N range from 12.13 to 580.3,0.40 to 143.0, and 0.06 to 4464μmol/L。The concentration of SiO3-Si ranges from 41.83 to 464.0μmol/L The concentration of TP and TN in sediment range from 8.10 to 42.43μg/g and 41.66 to 293.7μg/g, sediment particle size is the important influence factors to TP and TN, the smaller of sediment particles, the higher content of TP and TN. Besides, the inputs of exogenous particle nitrogen may affect the concentration of TN.(3) The concentration of PO4-P in marsh sediment pore water in Yellow River Estuary ranges from 0.18 to 2.18μmol/L. The vertical distribution of PO4-P first decreases with the depth, and then increases with the further increasing of depth.The concentrations of NH4-N, NO2-N, NO3-N and DIN in the sediment pore water range form 4.51-348.1,0.16-130.0, 1.71-2002,20.45-2314μmol/L. The concentration of inorganic nitrogen decreases with the depth. The concentration of SiO3-Si increases with the depth.The TP and TN in the sediment range from 4.54-43.07,11.69-293.7μg/g. The vertical distribution of TP and TN mainly decrease with the depth, which are affected by the sediment grain size.(4) According to the incubation experiment, the flux of nutrients between sediment and water are calculated, and factors that affect the exchange process are discussed. The results show that the fluxes of PO4-P, NH4-N, NO2-N, NO3-N and SiO3-Si between sediment and water are-0.30-0.045,-9.16-6.94,-1.20-2.10,-22.8-144,0-1.63 mmol/m2/d, respectively.The flux of nutrients are affected by salinity and redox environment.