Development and Validation of a New Dgt Technique Using the Novel Crygel for Measuring Dissolved Hg(Ii) in the Estuary

The complex seawater matrix has significantly influenced the determination of estuarine dissolved Hg(II), hindering its monitoring and risk assessment. In this work, the SiO2-SH-DGT assembled by the SiO2-SH crygel as the novel binding phase was developed to tackle this problem. The uniform dispersed of the crygel into the binding gel was advantageous for achieving remarkable and comparable capacity. The estimated diffusion coefficient (D) was 1.45-3.08 times of the existing research. The CDGT/CSOL was within the range of 0.91-1.06 under variable conditions, namely pH (3-9), ionic strengths (10-800 mM), and a low level of humic acid, as well as in the seawater matrix (Na+, Ca2+, Cl-), which demonstrated SiO2-SH-DGT was insensitive to the environmental factors. However, the high content of Mg2+ did interfere with its performance, the mechanism was manifested as competitive adsorption and diffusion. Therefore, the correction model based on CMg was successfully established by calibrating accumulated mass M' and D', its high accuracy was further verified at static and dynamic Hg(II) concentrations in the lab, the CDGT kept high conformity with CSOL. Finally, SiO2-SH-DGT was deployed in the three typically aquaculture areas in Beibu Gulf, field trials achieved the actual Hg(II) level to be 1.52-5.38 ng/L with consideration of DBL theory. The finding of this research could provide a new thought and the technical support for metallic pollution monitoring in estuary maricultural areas