Ceria oxide nanoparticle-based diffusive gradients in thin films for in situ measurement of dissolved reactive phosphorus in waters and sewage sludge

A passive sampling method based on diffusive gradients in thin films (DGT) using ceria oxide (CeO2) binding gel was developed for in situ measurement of dissolved reactive phosphorus (DRP). CeO2-based DGT showed excellent uptake performance for DRP, and the uptake mass was consistent with the predication by DGT equation. pH (4.2~9.4) and ionic strength (0.01~500 mM) had no effects on the uptake of DRP. Filed deployment of CeO2-DGT in reservoir water and seawater showed that the measureable concentrations of DRP were comparable to those obtained by grab sampling. CeO2-DGT was deployed in sewage sludge, and results showed the ratios (RS) between the concentration (CDGT) by CeO2-DGT and the concentration (CS) obtained by a traditional centrifugation method ranged from 0.23 to 0.58. This result indicated that sludge solid phase was a potential pool of DRP in sludge solution, and the DRP released from sludge solid phase could compensate partly the consumption of DRP at the interface of DGT device during the deployment. The ratios RS had positive correlation with the content of Fe (r = 0.847, p < 0.01) but were reversed with the level of Ca (r = − 0.879, p < 0.01) in sewage sludge. The proposed method provided a powerful tool for in situ measurement of DRP in natural waters and for release behavior of DRP in sludge.