Geochemical characteristics of phosphorus near the Huanghe River estuary

An improved sequential extraction method was used to extract and determine 7 forms of phosphorus exchangeable or loosely sorbed P (Ads P), aluminum bound P (Al P), iron bound P (Fe P), occluded P (Occ P), authigenic apatite plus biogenic apatite plus CaCO 3- associated P (CFAP P), detrital apatite P (FAP P), and organic bound P (Org P) in suspended matter and surface sediments of the Huanghe River (Yellow River), its estuary and nearby shelf. The concentrations of dissolved inorganic and organic P in river water were also determined. A dissolved P flux of 1.6 billion grams per year, solubilized P flux of 281 billion grams per year, and buried P flux of 588 billion grams per year from the Huanghe River to the Bohai Sea were calculated using the concentrations of P determined in the water column, suspended matter and sediments. Due to the high suspended load and low discharge of the Huanghe River, the direct contribution of dissolved P carried in solution by it to the Bohai Sea is minor compared to the solubilized P released from the suspended matter and sediments. More than two thirds of the total P transported by the Huanghe River is deposited and buried in marine sediments. Decomposition of riverine organic matter which releases organic bound P is an essential source of dissolved/solubilized P in the sea.