Phosphorus Forms And Fluxes Of The Suspended Particulate Matter In The Yellow Rive Downstream

Phosphorus (P) is an important nutrient, and it's essential for growth and propagates of organism. The primary source of P in ocean is from river input. P is existed in water column in both dissolved and particle form, and the particle P is the main input form by rivers. The particle P is existed in different chemical form with different physical and chemical properties and bioavailability. Grain size is an important factor which can impact both the content of different P in particles and transportation of particle P.The Yellow River is the second largest river in China, and its transportation is the principal source of most materials in Bohai Sea. The suspended particle matter (SPM) was collected both in Lijin station of the Yellow River monthly from January 2008 to December 2009 and during the period of Water and Sediment Regulation (WSR) in 2008 and 2009 and in different salinity areas of the Yellow River Estuary in September 2009. The contents of different form P in SPM were analyzed using the improved SEDEX method and the fluxes of different form P were estimated. The particle size separations were conducted for SPM samples collected from Lijin monthly in 2009 using water elutriation method. The mode of occurrence of P in different particle sizes SPM was analyzed.The results showed that, contents of phosphorus forms were closely related to grain size. The relationship between phosphorus forms and grain size was different in various salt areas, in freshwater, loosely adsorbed P, organic P, authigenic P and refractory P were preferentially associated with finer particles (such as clay-very fine silt and fine silt fractions), and detrital P was found in higher content in the larger size classes (such as medium silt and coarse silt).The flux of particulate phosphorus transported by the Yellow River was 40000 tons. Detrital P and authigenic P were the dominant forms of particulate phosphorus. 20 percent of particulate phosphorus was bio-available phosphorus. Without considering estuarine process,35 percent of particulate phosphorus and half of bio-available phosphorus were transported into the Bohai Sea, but the others deposited in estuary area.Water and sediment regulation was main period of phosphorus transported in a year. More than 30000 tons phosphorus were transported in that period, these were more than 75 percent of the whole year flux. In 2008 and 2009 water and sediment regulation period,83.5 percent and 66.8 percent of bio-available phosphorus were transported in the Yellow River.In different salt area, phosphorus forms were different. In low salt area, detrital phosphorus and authigenic phosphorus were the dominant forms of particulate phosphorus. In middle salt area, authigenic phosphorus detrital phosphorus and organic phosphorus were main forms, while loosely adsorbed phosphorus and organic phosphorus were main forms in high salt area.