Abstract: Suspended particulate matter in seawater was treated separately by high pressure digestion using sulfuric acid-potassium persulfate as the oxidant and soaking extraction in 1 mol/dm³ hydrochloric acid in order to dissolve total phosphorus and inorganic phosphorus respectively. The dissolved phosphorus was determined using phosphomolybdate blue spectrophotometry to calculate total and inorganic phosphorus in seawater suspended particulate matter and in sediments. Organic phosphorus was subsequently obtained by subtracting inorganic phosphorus from total phosphorus. The relative standard deviation was less than 1.44% when the concentration of PTP and PIP were (632.4～651.7)×10^－6 and (436.6～452.6)×10^－6 respectively. The recovery rate of PTP, PIP and POP were 97.2%～101.3%, 97.8%～100.4% and 97.3%～102.3% respectively. This analytical method can be used for determination of different forms of phosphorus in marine and estuarine sediment and in suspended particulate matter.

Key words: suspended particulate matter, phosphorus, total phosphorus, inorganic phosphorus, organic phosphorus, different forms of phosphorus, sea water