Novel DGT Method With Tri-metal Oxide Adsorbent For In Situ Spatiotemporal Flux Measurement Of Fluoride In Waters And Sediments

Natural mineral-water interface reactions drive ecosystem/global fluoride(F-)cycling.These small-scale processes prove challenging to monitoring due to mobilization being highly localized and variable;influenced by changing climate,hydrology,dissolution chemistries and pedogenosis.These release events could be captured in situ by the passive sampling technique,diffusive gradients in thin-films(DGT),providing a cost-effective and time-integrated measurement of F-mobilization.However,attempts to develop the method for F-have been unsuccessful due to the very restrictive operational ranges that most F--absorbents function within.A new hybrid-DGT technique for F-quantification containing a three-phase fine particle composite(Fe-Al-Ce,FAC)adsorbent was developed and evaluated.Sampler response was validated in laboratory and field deployments,passing solution chemistry QC within ionic strength and pH ranges of 0-200 mmol L-1 and 4.3-9.1,respectively,and exhibiting high sorption capacities(98±8 μg cm-2).FAC-DGT measurements adequately predicted up to weeklong averaged in situ F-fluvial fluxes in a freshwater river and F-concentrations in a wastewater treatment flume determined by high frequency active sampling.While,millimetre-scale diffusive fluxes across the sediment-water interface were modeled for three contrasting lake bed sediments from a F--enriched lake using the new FAC-DGT platform.