Extending the functionality of the slurry ferrihydrite-DGT method: Performance evaluation for the measurement of vanadate, arsenate, antimonate and molybdate in water

Abstract

The monitoring of oxyanions in waters, presents significant challenges due to their relatively low concentrations, and a characteristically changeable/unstable/reactive geochemistry with high spatial and temporal turnover. This results in a very heterogeneous pattern of mobility and bioavailability, which is difficult to capture reliably and in a cost effective manner. The diffusive gradients in thin-films (DGT) technique is a popular analytical tool for testing water quality, primarily because it provides a time-integrated measurement. However, to date, the most widely used DGT configuration for oxyanion sampling, the slurry ferrihydrite binding layer (SF-DGT) has only been fully characterized for phosphate. Confirmatory testing of the functional range of ionic strengths, pH, deployment times and ionic competition effects, that the SF-DGT's operates within has not been carried out, but is addressed in this study for V, As, Sb, and Mo. In this study SF-DGT Sb measurements functioned over the largest range of conditions (ionic strength, 0.1-500 mM; pH 3.86-9.90), while ionic strengths above 100 and 500 mM were found to be problematic for As and Mo, respectively. Low pH (below 4) caused inferences with V, conversely As and Mo determination faltered/deviated from predicted responses in pH conditions of ∼9. SF-DGT measurements adequately predicted up to weeklong averaged in situ metal oxyanion concentrations in a freshwater river. This study concludes that the SF-DGT configuration is highly suitable for pollution monitoring applications in freshwater systems for key oxyanion species.

Passive sampler measurements of inorganic arsenic species in environmental waters: A comparison between 3-mercapto-silica, ferrihydrite, Metsorb®, zinc ferrite, and zirconium dioxide binding gels

“…For total As, numerous studies have shown that the DGT performances of the 3MP, Fh, Metsorb ® , and/or ZrO2 binding gels were comparable in laboratory over 40 -120 h of deployment in freshwater[3,9,12,41,42], similarly to what has been observed in the present study. On the contrary, in binding gels up to 40-96 h of deployment time.…”

Evolution of the reactive surface area of ferrihydrite: time, pH, and temperature dependency of growth by Ostwald ripening

“…For this reason, it is used and widely studied as model material to elucidate the adsorption of cations, anions, and organic matter. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] The surface area of ferrihydrite is an essential characteristic particularly from the perspective of surface complexation modelling. One reason is that ferrihydrite particles are usually charged.…”

The Study of Phosphate Release from Artificial Sediment into Water Body Using Diffusive Gradient in Thin Film (DGT) Device in Oxic Condition

“…Therefore, in situ techniques for measuring phosphorous needs to developed. Diffusive Gradient in Thin Film (DGT) technique has been developed for in situ measurements of vanadate, arsenate, antimonate, and molybdate in water [14], methyl mercury in rice plants [15], reactive phosphorus species in natural water, sediment and soil [16] and others. The principle of phosphate measurement using the DGT technique is based on the diffusion of phosphate species through the polyacrylamide gel layer and then bound by the ferrihydrite layer embedded in the next gel layer [17].…”