Seasonal Variation and Fluxes of Nutrients in the Lower Reaches of the Yellow River

Dissolved and particulate samples were collected from the low reaches of Yellow River i from March 2001 to February 2002 to determine the nutrient species.The variations and fluxes of nutrients were studied.The result showed that dissolved inorganic nitrogen(DIN)was the predominant species of TN.Nitrate was the predominant species in the Yellow River.No significantly relationship was found between nitrate and water discharge.The average concentration of nitrate was(260.6±84.0)μmol/L, which was significantly higher than the world background value.Particulate phosphorus was the predominant species of TP in the Yellow River,and it correlated well with suspended sediment discharge.The average concentration of particulate phosphorus was(16.2±22.9)μmol/L.The average concentration of phosphate was(0.42±0.20)μmol/L,which was relatively low and comparable to the world average level. The average concentration of silicate was(122.0±18.2)μmol/L.Yellow River input about 17 200 t of total nitrogen(TN)and 1 600 t of total phosphorus(TP)to the Bohai Sea.The highest fluxes were found in March for TN,March and September for TP and March for silicat,respectively.