Developing a Method to Measure Bioavailable Phosphorus in River Water via Simultaneous Multisample Ultrasonic Extraction

Abstract

Abstract To reduce watershed eutrophication, measurements of bioavailable phosphorus (BAP) rather than total phosphorus (TP) are deemed critical. However, standard methods for direct and routine BAP measurement in river water have not been widely investigated. Therefore, in this study, a simultaneous multisample ultrasonic extraction method is proposed to measure total BAP (TBAP) in river water. Spike-and-recovery assessments showed that at least three repeated extractions are required to maintain accuracy. Results showed that sample P concentrations obtained using a 2-min extraction time and three extractions were consistent with theoretical values. Furthermore, the TBAP extraction results from custom samples containing different P sediment concentrations obtained under these conditions showed no significant differences between experimental and theoretical concentrations. Additionally, river water TBAP was quantified using the conventional and proposed method to examine the practicality of using the proposed method for simultaneous multisample ultrasonic extraction and to evaluate its adaptability to actual river water analysis. The extracted concentrations matched those obtained using the conventional method, in which total BAP is calculated as the sum of dissolved BAP and particulate BAP; no significant difference was observed between the concentrations. Ultrasonic extraction was considerably less time-consuming than the conventional method because more samples could be analyzed during a single run. Therefore, the simultaneous multisample ultrasonic extraction method proposed in this study can be used to directly quantify total BAP in river water.