Source Estimation on Storm Runoff Load of Particulate Phosphorus by Chemical Sequential Extraction Techniques at Rain Events in Hikiji River

摘要

This research aimed the source identification of storm-runoff particulate phosphorus at rain events. At present, the achievement rate of the environmental standard in Japan for lakes is lower than that for the rivers that flow in and supposedly impact on the closed water systems. One of the reasons for this gap is uncertainty of the method to estimate the load. This study focused on the contribution of the phosphorus load to the river discharge during storm flow by considering adsorption of phosphorus matters on the solid phase of the sediment particle. We collected water samples at Ishikawa bridge of the Hikiji river during rainfall periods, from November sixteenth to eighteenth in 2017, with drastic change in water discharge. We measured the contents of particulate phosphorus for each of eight types by the sequential extraction technique. During baseflow period, the proportion of readily-available inorganic phosphorus and organic phosphorus, previously reported to be largely contained in algae, were at high level. On the other hand, as was previously reported, the carbonate-combining phosphorus which is most likely contained in the river bed sediment was distinctly discharged at peak time during the storm flow period.