The Yellow River is the second longest river in China, which plays a very important role in the transportation of nutrients at the regional and even global scale. Water and sediment samples were collected at five sites located at the Gaocun to Lijin reaches along the Yellow River and the distribution characteristics of different phosphorus species were analyzed. The concentration of suspended particulate matter (SPM) in water ranged from 1.89 to 2.67 g·L-1 with an average of 2.26 g·L-1 in May and from 0.43 to 1.79 g·L-1 with an average of 1.21 g·L-1 in September. It almost had the same variation rule as the water flux, which reflects the influence of water flux on SPM transportation. The concentration of total phosphorus (TP) in water ranged from 0.05 to 2.31 mg·L-1 in May and from 0.03 to 0.1 mg·L-1 in September. Particulate phosphorus (PP) was the dominant TP species in both months, and TP and PP were significantly correlated (P<0.01), which implied that phosphorus loss in soil from Gaocun to Lijin reaches is still serious. Water runoff was positively correlated with TP and PP (P<0.05), but negatively correlated with total dissolved phosphorus (TDP) and dissolved inorganic phosphorus (DIP) (P<0.05, P<0.01, respectively). Increasing water runoff obviously increased the dilution of TDP and DIP. The concentration of SPM was negatively correlated with DIP (P<0.01), the adsorption of SPM on phosphorus was mainly the adsorption of DIP. The permanganate index in water was higher in fall suggesting more serious organic pollution and it was positively correlated with DIP (P<0.01). The phosphorus content in sediments was quite low in both months; the total phosphorus (TP) content in sediments ranged from 284.23 to 569.58 mg·kg-1 in May and from 287.97 to 355.39 mg·kg-1 in September. Calcium-bound phosphate (Ca-P) was the dominant species of inorganic phosphorus (IP). The labile organic phosphorus (L-OP) content was significantly correlated with runoff, SPM concentration, and permanganate index (P<0.01,P<0.05,P<0.01, respectively). The organic phosphorus (OP) content was significantly higher at the Lijin site in May, likely caused by the rainfall-runoff from the mining area around Lijin. The energy-based production activities from the Gaocun to Lijin reaches should also be further investigated.
Keywords: Yellow River; phosphorus; phosphorus fraction; sediments; water; water eutrophication.