Innovative receiving phase for Chemcatcher® passive sampler for phosphorus in the water environment: Calibration of sampling rate by water temperature and pH

Abstract

Passive sampling is a technique for monitoring orthophosphate (PO₄-P) in the water environment. Compared with traditional grab sampling followed by PO₄-P quantification, kinetic-type passive samplers such as Chemcatcher® express representative concentrations of PO₄-P as time-weighted average concentrations (C_TWA). They can also potentially evaluate much lower PO₄-P concentrations, but the available receiving phases of Chemcatcher® used for PO₄-P were extremely limited. We developed a new receiving phase, the PSfZS sheet, comprising a zirconium sulfate-surfactant micelle mesostructure and polysulfone matrix. We examined its performance in terms of PO₄-P sorption characteristics, PO₄-P selectivity, and PO₄-P sampling rate (R_s). Its capacity was adequate (12.0 μg-P/cm²) and selectivity for PO₄-P uptake was good. The R_s for PO₄-P increased with increasing water temperature (8.1-29.1 °C) and decreasing pH (4.1-9.7) in a laboratory calibration, and ranged from 5.27 × 10^-2 L/d to 1.66 × 10^-1 L/d. We placed the samplers in a municipal wastewater treatment plant, a shallow eutrophic lake, and an oligotrophic caldera lake. The R_s in the deployment sites was calibrated by monitored water temperature and pH. The estimated C_TWA of PO₄-P in the municipal wastewater treatment plant was similar to the averaged concentration of soluble reactive phosphorus determined by multiple grab samplings. In the lake deployments, we found that the new sampler can quantify C_TWA values of PO₄-P below 10 μg/L, and thus it provides more technical monitoring options and contributes to the conservation and management of the water environment.

Keywords: Eutrophication; Orthophosphate; Passive sampling; Soluble reactive phosphorus; Sorption; Zirconium.