Design and influence of an in-situ automated wiper system to improve DGT measurements of trace metals and mercury speciation in natural waters

Blondet I.; Raimbault V.; Prunier J.; Diaz K.; Graco M.; Ledesma J.; Carhuapoma W.; Point D. · Journal of Hazardous Materials Advances (2026) · DOI: 10.1016/j.hazadv.2026.101315

Resumen

Diffusive Gradients in Thin Films (DGT) are widely used for in situ measurement of trace metals and mercury species in natural waters. Long deployments, required for ultratrace analytes, often suffer from biofouling and particle accumulation, compromising measurement accuracy. This study presents an automated in situ miniwiper (MW) system designed to clean DGT surfaces during deployment. The MW was evaluated in two contrasting environments: (i) productive Peruvian coastal waters, to assess its impact on mercury speciation, and (ii) the particle-rich Nugu River (India), for trace metal and rare earth element (REE) measurements. In Peruvian waters, MW-equipped DGTs showed minimal biofilm over up to 68 days, while uncleaned DGTs exhibited significant biofouling, leading to 14–68% underestimation of mercury species. In the Nugu River, MW-DGTs effectively limited particle deposition, yielding concentrations for Al, Mn, Fe, Co, Cd, and REE in close agreement with discrete water samples, whereas uncleaned DGTs underestimated these values. The MW had little effect on Ni, Cu, and U. This study demonstrates that biofouling and particle accumulation can significantly bias DGT measurements, and the MW system provides a robust, operational solution for long-term monitoring.