Comparison of Bioavailable Phosphorus in River Sediments and River Bed Sediments from Agricultural and Urban Rivers

Abstract

This study was carried out to determine the concentration of phosphorus in six rivers from agricultural and urban rivers and to compare the bioavailable phosphorus (BAP). Nutrients entering rivers are divided into suspended and dissolved state. In this study, BAP was measured by using ultrasonic extraction method. A 100 L sample was collected from six rivers, three agricultural rivers and three urban rivers to compare their BAP concentration. Measurement for two weather conditions, rain and no rain were taken. The results showed that BAP concentrations were high in Nishino river followed by Hamada, Umeda, Yagyu, Asakura and Uchibari river, with the concentration ranging from 0.1 to 1.00 mg/L. Agricultural rivers for both rain and no rain events were high in total phosphorus (TP) with the concentrations ranging from 0.50 to 1.09 mg/L. Particulate phosphorus (PP) concentration in the river sediment (RS) after a rain event was high compared to the PP during a no rain event. However, PP in river bed sediment (RBS) was high during a no rain event compared to the concentration of PP in the river sediment (RS). This may due to the accumulated and attached PP in the RBS (low flow of river water). Concentration of particulate bioavailable phosphorus (PBAP) in RS was ranging from 0.70 to 10.94 mg/g. In this study, it was found that the BAP concentration from agricultural rivers were high than the BAP concentration in urban rivers.