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The Diffusive Gradients in Thin films (DGT) technique was used to analyse U, 226 Ra and other trace metals in stream water and soil porewater in a wetland in France impacted by uranium mining. High resolution profiles of metals in soil porewater obtained by DGT could be measured for the first time up to a depth of 75 cm by the construction of a novel DGT holder. In stream water, the DGT technique was compared to speciation carried out by filtration (0.45 μm) and ultrafiltration (UF) (500 kDa/100 kDa/10 kDa) and DGT porewater profiles were compared with piezometer data obtained in a parallel study. An increase in the trace concentrations of dissolved (0.45 μm) and particulate U, 226 Ra, and elements such as Al, Fe, Mn and Ba was observed in the stream water as it passes through the bog as a results of mobilization from the wetland. The porewater results indicate DGT labile metals species to be present in porewater and mobilization of uranium and other elements linked to the presence of enriched clays. In stream water, colloids and particles govern the behavior of U, Al and Fe, whereas Mn, Ba and Ra are essentially transported as truly dissolved metal species with DGT labile concentrations accounting for 100% of the dissolved fraction. The combined approaches of DGT and UF allow us to obtain a better understanding on the biogeochemical processes involved in the retention and mobility of U and 226 Ra in the wetland. [ABSTRACT FROM AUTHOR]

The Diffusive Gradients in Thin Films (DGT) technique using PIWBA resin (The Dow Chemical Company) was developed and validated for the measurement of uranium (U) concentration in natural and uranium mining influenced waters. The U uptake on the PIWBA resin gel was 97.3 ± 0.4% (batch method; V sol = 5 mL; [U] = 20 μg L −1 ; 0.01 M NaNO 3 ; pH = 7.0 ± 0.2). The optimal eluent was found to be HNO 3conc /70 °C with an elution efficiency of 88.9 ± 1.4%. The laboratory DGT investigation demonstrated that the PIWBA resin gel exhibits a very good performance across a wide range of pH (3–9) and ionic strength (0.001–0.7 M NaNO 3 ) at different time intervals. Neither effect of PO 4 3− (up to 1.72 × 10 −4 M), nor of HCO 3 − (up to 8.20 × 10 −3 M) on the quantitative measurement of uranium by DGT- PIWBA method were observed. Only at very high Ca 2+ (2.66 × 10 −4 M), and SO 4 2− (5.55 × 10 −4 M) concentration, the U uptake on DGT- PIWBA was appreciably lessened. In-situ DGT field evaluation was carried out in the vicinity of three former uranium mining sites in France (Loire-Atlantique and Herault departments), which employ different water treatment technologies and have different natural geochemical characteristics. There was a similar or inferior U uptake on DGT-Chelex ® -100 in comparison with the U accumulation on a DGT- PIWBA sampler. Most likely, the performance of Chelex ® -100 was negatively affected by a highly complex matrix of mining waters. The high concentration and identity of co-accumulating analytes, typical for the mining environment, did not have a substantial impact on the quantitative uptake of labile U species on DGT - PIWBA . The use of the polyphenol impregnated anion exchange resin leads to a significant advancement in the application and development of the DGT technique for determination of U in the vicinity of the former uranium mining sites. [ABSTRACT FROM AUTHOR]

The performance of the Diffusive Gradients in Thin films (DGT) technique with Chelex ® -100, Metsorb™ and Diphonix ® as binding phases was evaluated in the vicinity of the former uranium mining sites of Chardon and L'Ecarpière (Loire-Atlantique department in western France). This is the first time that the DGT technique with three different binding agents was employed for the aqueous U determination in the context of uranium mining environments. The fractionation and speciation of uranium were investigated using a multi-methodological approach using filtration (0.45 μm, 0.2 μm), ultrafiltration (500 kDa, 100 kDa and 10 kDa) coupled to geochemical speciation modelling ( PhreeQC ) and the DGT technique. The ultrafiltration data showed that at each sampling point uranium was present mostly in the 10 kDa truly dissolved fraction and the geochemical modelling speciation calculations indicated that U speciation was markedly predominated by CaUO 2 (CO 3 ) 3 2− . In natural waters, no significant difference was observed in terms of U uptake between Chelex ® -100 and Metsorb™, while similar or inferior U uptake was observed on Diphonix ® resin. In turn, at mining influenced sampling spots, the U accumulation on DGT-Diphonix ® was higher than on DGT-Chelex ® -100 and DGT-Metsorb™, probably because their performance was disturbed by the extreme composition of the mining waters. The use of Diphonix ® resin leads to a significant advance in the application and development of the DGT technique for determination of U in mining influenced environments. This investigation demonstrated that such multi-technique approach provides a better picture of U speciation and enables to assess more accurately the potentially bioavailable U pool. [ABSTRACT FROM AUTHOR]

A new resin- Diphonix ® in Diffusive Gradients in Thin Films (DGT) technique for the determination of uranium was investigated and compared with previously used binding phases for uranium, Chelex ® -100 and Metsorb™. The DGT gel preparation and the elution procedure were optimized for the new resin. The U uptake on Diphonix ® resin gel was 97.4 ± 1.5% (batch method; [U] = 20 μg L −1 ; 0.01 M NaNO 3 ; pH = 7.0 ± 0.2). The optimal eluent was found to be 1 M 1-hydroxyethane-1, 1-diphosphonic acid (HEDPA) with an elution efficiency of 80 ± 4.2%. Laboratory DGT study on U accumulation using a DGT samplers with Diphonix ® resin showed a very good performance across a wide range of pH (3–9) and ionic strength (0.001–0.7 M NaNO 3 ). Diffusion coefficients of uranium at different pH were determined using both, a diffusion cell and the DGT time-series, demonstrating the necessity of the implementation of the effective diffusion coefficients into U-DGT calculations. Diphonix ® resin gel exhibits greater U capacity than Chelex ® -100 and Metsorb™ binding phase gels (a Diphonix ® gel disc is not saturated, even with loading of 10.5 μmol U). Possible interferences with Ca 2+ (up to 1.33 × 10 −2 M), PO 4 3 − (up to 1.72 × 10 −4 M), SO 4 2 − (up to 4.44 × 10 −3 M) and HCO 3 − (up to 8.20 × 10 −3 M) on U-DGT uptake ([U] = 20 μg L −1 ) were investigated. No effect or minor effect of Ca 2+ , PO 4 3 − , SO 4 2 − , and HCO 3 − on the quantitative measurement of U by Diphonix ® -DGT was observed. The results of this study demonstrated the DGT technique with Diphonix ® resin is a reliable and robust method for the measurement of labile uranium species under laboratory conditions. [ABSTRACT FROM AUTHOR]

The analysis of platinum (Pt), palladium (Pd) and rhodium (Rh) in aquatic samples by the diffusive gradients in thin films (DGT) technique using chelating resins, specific designed for the accumulation of PGEs, namely Purolite S914, S920 and Italmatch Chemicals IONQUEST® MPX-317. may however, still be influenced by the accumulation of other elements such (Cu, Zn, Pb, etc.) which will be extracted simultaneously by the hot aqua regia extraction and interfere with the Inductively Coupled Plasma Mass Spectrometry (ICPMS) analysis of the Platinum Group Elements (PGEs). Selective extractions were investigated to release the interfering elements without loss of the Platinum Group Elements (PGEs) from the resin gels.. A rinse with deionized water removes over 95% of Sr and Rb and a second rinse with 0.05 mol L−1 H 2 SO 4 can be used to as a common eluent to remove an important fraction of the interfering elements from S920 and S914 without loss of PGEs but this results in loss of around 15% of the PGEs from MPX-317. It was shown that selective extractions can be used to remove specific interferences from each resin gel. Image 1 • Removal of interfering elements in analysis of PGEs by DGT and ICPMS was investigated. • Selective removal of Sr, Rb, Zr, Zn, Y, Mo, Cu, Cd, Pb and Hf was evaluated. • 0.05 M H 2 SO 4 effectively removed all interferences from S920 resin gel. • Most interferences removed with 0.05 M H 2 SO 4 from S914, except Cu. • No common eluent was found for MPX-317, selective elution possible. [ABSTRACT FROM AUTHOR]

The analysis of mercury in food presents a challenge for analytical chemists. Sample pre-treatment and the preconcentration of mercury prior to measurement are required, even when highly sensitive analytical methods are used. In this work, the Diffusive Gradients in Thin Films technique (DGT), combined with thermal decomposition gold amalgamation atomic absorption spectrometry (TDA-AAS), was investigated for the determination of the total dissolved mercury in fish sauces. Moreover, a new type of binding gel with Purolite S924 resin was used in DGT. Linearity assays for DGT provided determination coefficients around 0.995. Repeatability tests showed a relative standard deviation of less than 10%. pH values in the range of 3–6, as well as NaCl concentrations up to 50 g·L−1, did not affect the performance of DGT. The effective diffusion coefficient of mercury in five-fold diluted fish sauce was determined to be (3.42 ± 0.23)·10−6 cm2·s−1. Based on the 24 h deployment time of DGT, the limit of detection (LOD) for the investigated method was 0.071 µg·L−1. The proposed method, which combines DGT and TDA-AAS, allows for the analysis of fish sauces with mercury concentrations below the LOD of TDA-AAS, and significantly reduces the wear and corrosion of the TDA-AAS components. [ABSTRACT FROM AUTHOR]

The Diffusive Gradients in Thin Films (DGT) technique was developed for the first time for the platinum group elements (PGEs) platinum (Pt), palladium (Pd), and rhodium (Rh). Different chelating resins, specific designed for the accumulation of PGEs, namely Purolite S914, S920, S985, Italmatch Chemicals IONQUEST® MPX-317 and MP-102, were compared. The method development involved several different steps: 1) selection of an appropriate diffusive gel, 2) comparison of resins for the PGEs in terms of kinetics of uptake, 3) development of an efficient elution method for the PGEs from the resin gel, 4) Determination of diffusion coefficients for the PGEs in the diffusive gel, 5) Investigation of the influence of pH, ionic strength and dissolved organic matter on the diffusion coefficients and 6) study the selectivity of the tested resins gels in terms of potential interferences on the determination by ICPMS. Pt, Pd and Rh showed a linear accumulation over time for all resins and diffusion coefficients were independent of pH. The diffusion coefficient for Pt increased with increasing ionic strength (>0.5 M NaCl), but not for Pd and Rh. The interference study showed that Sr was the most important interferent for Rh and Pd and must be removed prior to analysis. The resins Purolite S914, Purolite S920, and Italmatch Chemicals IONQUEST® MPX-317 showed the best performance in terms of detection limits and separation of interferences. Using optimized procedures, the concentrations of Pt, Pd and Rh can be quantified at pg L−1 levels in natural waters for a 14 day deployment time. Image 1 • Development of the DGT technique for PGEs was made for the first time. • As resins Italmach IONQUEST® MPX-317, MP-102, Purolite S985, S914 and S920 were compared. • Resin gel preparation and elution methods were optimized. • No interactions were observed between Agarose as diffusive gel and PGEs in contrast to polyacrylamide. • Pt-resin gel performance follows the order MPX 317 > S914 ≥ S920 > MP 102 > S985. • Pd-resin gel performance follows the order S914 ≥ S920 > MPX317 > S985 > MP 102. • Rh-resin gel performance follows the order S920 > S914 > MPX 317 > S985 > MP 102. • Using optimized procedures PGEs could be measured at pg.L−1 levels in natural waters for a deployment time of two weeks. [ABSTRACT FROM AUTHOR]

Abstract: 3-Mercaptopropyl functionalized SBA-15 (SH-SBA) and 3-mercaptopropyl functionalized ethenylene bridged periodic mesoporous organosilica (SH-PMO) were included in a Diffusive Gradients in Thin film (DGT) probe and compared to similar commercially available resins also containing thiol functional groups, such as Sumichelate Q10R (SQR) and 3-mercaptopropyl functionalized silica gel (SH-KG), and also to the Chelex-100 resin for the determination of labile Hg concentrations. An agarose gel was used as the diffusive gel because the classic polyacrylamide gel shows more than 20% of Hg adsorption. According to our results, the Chelex-100 resin presents a much lower affinity for Hg than the thiol based resins. The non-linear accumulation profile of mercury with time for the Chelex-100 resin makes it in fact impossible to use Fick''s law for estimating the diffusion coefficient of Hg. The 4 other resins all show a linear accumulation profile of Hg with time. Although the highest accumulation rate is observed for SH-PMO followed by SQR, SH-SBA and SH-KG, these values do not differ very much. [Copyright &y& Elsevier]

The colloidal transport of trace (Fe, Al, Ba, Pb, Sr, U) and ultra-trace (226Ra) elements was studied in a mining environment. An original approach combining 0.45 μm filtered water sampling, the Diffusive Gradient in Thin films (DGT) technique, mineralogical characterization, and geochemical modelling was developed and tested at 17 sampling points. DGT was used for the truly dissolved fraction of the elements of interest, while the 0.45 μm filtration includes both colloidal and truly dissolved fractions (together referred to as total dissolved fraction). Results indicated a colloidal fraction for Al (up to 50%), Ba (up to 86%), and Fe (up to 99%) explained by the presence of submicrometric grains of kaolinite, barite, and ferrihydrite, respectively. Furthermore, the total dissolved 226Ra concentration in the water samples reached up to 10–25 Bq/L (1.2–3.0 10−12 mol/L) at 3 sampling points, while the truly dissolved aqueous 226Ra concentrations were in the mBq/L range. Such high total dissolved concentrations are explained by retention on colloidal barite, accounting for 95% of the total dissolved 226Ra concentration. The distribution of 226Ra between the truly dissolved and colloidal fractions was accurately reproduced using a (Ra x ,Ba 1-x)SO 4 solid solution, with values of the Guggenheim parameter a 0 close to ideality. 226Ra sorption on ferrihydrite and kaolinite, other minerals well known for their retention properties, could not explain the measured colloidal fractions despite their predominance. This illustrates the key role of barite in such environments. The measured concentrations of total dissolved U were very low at all the sampling points (<4.5 10−10 mol/L) and the colloidal fraction of U accounted for less than 65%. U sorption on ferrihydrite could account for the colloidal fraction. This original approach can be applied to other trace and ultra-trace elements to complement when necessary classical environmental surveys usually performed by filtration on 0.45 μm. [Display omitted] • An innovative approach was developed to assess the colloidal transport of 226Ra and U. • Water sampling, DGT, and solid characterization were combined with geochemical modelling. • 226Ra colloidal transport is explained by coprecipitation into barite. • This approach can be applied to other trace elements. [ABSTRACT FROM AUTHOR]

Abstract: High resolution profiles of trace elements (Fe, Mn, Co, As, Cu, Cr, Ni and Pb) were assessed using the DET (Diffusive Equilibrium in Thin films) and DGT (Diffusive Gradients in Thin films) techniques in silty, organically enriched, sub-tidal sediments of the Belgian coast during late winter and spring 2008. The general chemical properties of the sediments such as dissolved oxygen, pH, Eh and sulfide profiles, controlling precipitation/mobilization reactions, were determined with electrodes (pH and Eh) and microelectrodes (oxygen) and AgI-DGT probes (sulfide). Most trace elements show subsurface maxima and low concentrations beneath 8 cm of depth. The main physicochemical parameters controlling the vertical concentration profiles are dissolved oxygen and redox potential in the surface sediment and sulfide in the deeper sediment layers. Thermodynamic equilibrium calculations have been carried out verifying which solid phases can explain the dissolved trace metal concentrations. Seasonal variations of trace elements have been observed during the sampling period and sedimentation of fresh particulate organic matter (POM) derived from phytoplankton blooms appear to be the main cause of this temporal variability. Flux calculations based on DGT profiles (these fluxes are minimum ones) show that exchange fluxes of trace metals in February are slightly higher than in April. In addition, “DGT pistons” were deployed at the sediment water interface (SWI) to accumulate labile ions from below. This way all labile ions, binding onto the DGT Chelex resin, are pumped out of the pore waters and the solid sediment phase (only the mobile fraction). These results are a direct estimation of the amount of trace elements that can be released from the upper sediment to the water column (in the range of 4.4·10−5 to 0.10 mmol·m−2·d−1 for Co, Pb, Cr, As, Cu, Ni, Fe and Mn). [Copyright &y& Elsevier]

The sorption ability of Lewatit FO 36-DGT resin gel, which has been developed for arsenic determination, towards uranium was tested by batch experiments within this study for the first time. Since the uptake efficiency of uranium was 99.0 ± 0.4% and the maximum uptake capacity was not achieved even at the U spike of 1250 μg in the solution, the Lewatit FO 36 resin seems to be a suitable binding phase for DGT resin gels for the determination of uranium. The resin gel also does not display any significant sorption selectivity in favour of one element over another. A novel protocol for simultaneous elution of arsenic and uranium from Lewatit FO 36 resin gel was therefore proposed in this study. The elution efficiencies of 90.3 ± 3.9% and 85.2 ± 3.1% for As and U, respectively, were obtained using 5 mL of 1 M NaOH at 70 °C for 24 h. The comparison with the original elution protocol using microwave-assisted elution by 0.25 M NaOH and 0.17 M NaCl at 130 °C for 16 min indicates, that the novel elution protocol provides good results in the performance of arsenic elution and, in addition, allows simultaneous elution of uranium. Moreover, the elimination of NaCl from the elution process allows a fast and simple analysis of both elements using ICP-MS, and therefore, the Lewatit FO 36-DGT technique can become more commonplace among laboratories without the need to modify the analytical method as proposed in the original study. [Display omitted] • The Lewatit FO 36-DGT resin gel efficiently and simultaneously binds As and U. • A novel protocol for simultaneous elution of As and U from Lewatit FO 36 resin gel was proposed using 1 M NaOH at 70 °C. • New elution protocol allows a simple analysis of gel eluates by ICP-MS. [ABSTRACT FROM AUTHOR]