The Study Of Biogeochemical Behavior Of Phosphorus In Yellow River Downstream And Estuary Wetland

Yellow River provides the main source of nutrients in the Bohai Sea as the second longest river in China and plays a significant impact on the ecology environment of the Bohai Sea. The river input is the major source of phosphorus in the Marine ecosystems, of which the main form is the particulate phosphorus, but most particles deposite in the mouth of the river and very few parts can enter the ocean. Phosphorus in particulate exists in different forms and the study on the forms of its existence can make better estimation on its potential impact on water environment. The phosphorus content varies with different sizes of suspended particles. A preliminary estimation of the transport flux of particulate phosphorus can be made according to the contents of phosphorus in different forms in suspended particulate with different sizes.Particles and water samples in the surface water were collected on the 20th during January to December in 2010 in Lijin and suspended particulates were classified using water grading device, and then contents of dissolved phosphorus in water and phosphorus in various forms in the suspended particulate after grading were studied. Surface water and suspended particles were collected during the water-sediment regulation in 2010 and then the contents of dissolved phosphorus in water and phosphorus of different forms in the suspended particulate were studied. Surface sediments and core sediments in the wetland of Yellow River estuary were collected in April 2009, and the forms of phosphorus in the sediment samples were analyzed using the modified SEDEX method. Fluxes of dissolved phosphorus and particulate phosphorus delivered by the Yellow River in 2010 were estimated. The main conclusions drawn by this paper were as follows: (1) In 2010, flux of dissolved phosphorus in the water of Yellow River Downstream showed a significant seasonal variation with higher in flood period while lower in dry period.(2) In the Yellow River Downstream, contents of phosphorus in different forms in suspended particulate were closely related to the particle sizes. The contents of loosely sorbed phosphorus, organic phosphorus and apatite phosphorus(Ap-P), were higher in fine particles, while content of detrital phosphorus ( De-P) was higher in coarse particles.(3)In 2010, flux of dissolved phosphorus in Yellow River was 330t and transport flux of particulate phosphorus was 115713t, which was 350 times that of dissolved phosphorus. Flux of bio-available phosphorus in the form of particulate was 26818t, which was 81 times that of the dissolved phosphorus. Phosphorus transported by Yellow River is mainly in the form of particulate. Particle sizes had a major impact on transport flux of the phosphorus. Contents of phosphorus in different forms were highest in the fine silt and clay, and they were the phosphorus that could be transported to the ocean.(4) Water-sediment regulation is the main period for the transport of phosphorus in a year by Yellow River and during this period the transport flux of particulate phosphorus arrived to 57 000 t which accounted for 49% of the annual flux and transport flux of bio-available phosphorus was 12 000 t which accounted for 47% of the annual flux.(5) Ap-P and De-P were the major existence forms of phosphorus in the wetland of Yellow River Estuary, the contents of which were more than 70% of all. Contents of phosphorus in various forms were closely related to particle sizes and content of organic matter.