This study proposes an advanced leaching method using organic acids to recover rare earth elements(REEs)from NdFeB permanent magnets from end-of-life computers hard disk drives(HDDs).The end-oflife HDDs were first dis...This study proposes an advanced leaching method using organic acids to recover rare earth elements(REEs)from NdFeB permanent magnets from end-of-life computers hard disk drives(HDDs).The end-oflife HDDs were first dismantled in order to recover NdFeB magnets,which were then thermally demagnetized at 350℃during 30 min before crushing in a ball mill under inert atmosphere.Scanning electron microscopy/energy dispersive X-ray spectroscopy(SEM/EDS)analyses performed on the NdFeB magnets show the heterogeneous structure containing the major matric phase Nd_(2)Fe_(14)B and the REEsrich phase containing Nd and Pr oxides.Additionally,X-ray diffraction(XRD)and Mossbauer spectroscopy(MS)analyses on the ground NdFeB magnet show that grinding NdFeB magnets under inert atmosphere helps to minimize its oxidation.Chemical analysis shows that the composition of the ground sample is Nd:22.8 wt%,Pr:3.3 wt%,Dy:1.2 wt%,Fe:62.6 wt%,Co:1.5 wt%,B:0.9 wt%,Ni:0.6 wt%.Diagrams of speciation and equilibrium phases(E_(h) vs.pH)were calculated to determine the predominance of the formed species in the REEs-organic acids systems.The influence of the organic acid type(acetic acid,formic acid,citric acid and tartaric acid),the acid concentration(10 vol%,up to saturation),and the solid/liquid(S/L)ratio(0.5%-10%)on NdFeB magnets leaching was investigated employing an optimal experimental design conceived by the statistical software JMP.Acetic acid(CH_(3)COOH)shows the highest leaching performance of REEs,allowing leaching yields over 90%for Nd,Dy and Pr in the acid concentration range of 1.6-10 mol/L and the S/L ratio range of 0.5%-5%at a temperature of 60℃.The results presented in this investigation suggest that REEs can be recovered from magnets of end-of-life HDDs using an eco-friendly method assisted by organic acids.展开更多
The East African Rift system （EARS） provides a unique system with the juxtaposition of two contrasting yet simultaneously formed rift branches, the eastern, magma-rich, and the western, magma-poor, on either sides o...The East African Rift system （EARS） provides a unique system with the juxtaposition of two contrasting yet simultaneously formed rift branches, the eastern, magma-rich, and the western, magma-poor, on either sides of the old thick Tanzanian craton embedded in a younger lithosphere. Data on the pre-rifr, syn-rift and post-rift far-field volcanic and tectonic activity show that the EARS formed in the context of the interaction between a deep mantle plume and a horizontally and vertically heterogeneous lithosphere under far-field tectonic extension. We bring quantitative insights into this evolution by implementing high-resolution 3D thermo-mechanical numerical deformation models of a lithosphere of realistic rheology. The models focus on the central part of the EARS. We explore scenarios of plumelithosphere interaction with plumes of various size and initial position rising beneath a tectonically pre-stretched lithosphere. We test the impact of the inherited rheological discontinuities （suture zones） along the craton borders, of the rheological structure, of lithosphere plate thickness variations, and of physical and mechanical contrasts between the craton and the embedding lithosphere. Our experiments indicate that the ascending plume material is deflected by the cratonic keel and preferentially channeled along one of its sides, leading to the formation of a large rift zone along the eastern side of the craton, with significant magmatic activity and substantial melt amount derived from the mantle plume material. We show that the observed asymmetry of the central EARS, with coeval amagmatic （western） and magmatic （eastern） branches, can be explained by the splitting of warm material rising from a broad plume head whose initial position is slightly shifted to the eastern side of the craton. In that case, neither a mechanical weakness of the contact between the craton and the embedding lithosphere nor the presence of second plume are required to produce simulations that match observations. This result reconciles the passive and active rift models and demonstrates the possibility of development of both magmatic and amagmatic rifts in identical geotectonic environments.展开更多
Plant communities play an important role in the C-sink function of peatlands. However,global change and local perturbations are expected to modify peatland plant communities,leading to a shift from Sphagnum mosses to ...Plant communities play an important role in the C-sink function of peatlands. However,global change and local perturbations are expected to modify peatland plant communities,leading to a shift from Sphagnum mosses to vascular plants. Most studies have focused on the direct effects of modification in plant communities or of global change(such as climate warming, N fertilization) in peatlands without considering interactions between these disturbances that may alter peatlands' C function. We set up a mesocosm experiment to investigate how Greenhouse Gas(CO_2, CH_4, N_2O) fluxes, and dissolved organic carbon(DOC)and total dissolved N(TN) contents are affected by a shift from Sphagnum mosses to Molinia caerulea dominated peatlands combined with N fertilization. Increasing N deposition did not alter the C fluxes(CO_2 exchanges, CH_4 emissions) or DOC content. The lack of N effect on the C cycle seems due to the capacity of Sphagnum to efficiently immobilize N. Nevertheless, N supply increased the N_2O emissions, which were also controlled by the plant communities with the presence of Molinia caerulea reducing N_2O emissions in the Sphagnum mesocosms. Our study highlights the role of the vegetation composition on the C and N fluxes in peatlands and their responses to the N deposition. Future research should now consider the climate change in interaction to plants community modifications due to their controls of peatland sensitivity to environmental conditions.展开更多
More than 2,000,000 tons of silica nanoparticles (NPs) are produced annually in the world to cover the needs of nanotechnologies. Inevitably, a quantity of NPs, will be in industrial discharges and domestic, or even i...More than 2,000,000 tons of silica nanoparticles (NPs) are produced annually in the world to cover the needs of nanotechnologies. Inevitably, a quantity of NPs, will be in industrial discharges and domestic, or even in water resources. Share their high surface reactivity, these NPs may also carry with them through a specific adsorption of other toxic chemical pollutants inherent to the industrial sectors. To preserve public health and the environment from this pollution, it is necessary to remedy the potential pollution. In this context, the main motivation of this work is to answer this environmental issue by proposing a scheme of remediation based on the use of a conventional treatment process. The process of elimination nanoparticles by coagulation/flocculation was selected for its simplicity and also for its universal use. The NPs of industrial silica S30R50 were used as support to develop the process. The optimization of coagulation/flocculation, was greatly facilitated by the use of laser diffraction online. This technique allowed to follow the dynamic character of the treatment and to determine the size and the most relevant textural parameters (density, porosity and fractal dimension) of the flocs depending on the nature of the used reagents. The critical concentrations of different coagulants and flocculants used were determined by electrophoresis and turbidity. The ratio of their charge density/molecular weight has conditioned the quality of separation, the floc size and their texture. Excellent coagulation/flocculation performances are reached using organic reagents authorized by the Directorate General for Health of several countries. After optimization of the process, the size distributions are between 10 μm and 1 mm, with fractal dimensions (compactness) ranging from 2.3 to 2.5. The performances obtained show that the use of cationic polymers is a promising potential route to treat other types of NPs. The treatment proposed to reach a ratio of average diameters dFloc/dNP of 3500, and therefore it facilitates the elimination of these NPs agglomerated by filtration.展开更多
Real-time methods to monitor stable isotope ratios of CO_2 are needed to identify biogeochemical origins of CO_2 emissions from the soil–air interface. An isotope ratio infra-red spectrometer（IRIS） has been develop...Real-time methods to monitor stable isotope ratios of CO_2 are needed to identify biogeochemical origins of CO_2 emissions from the soil–air interface. An isotope ratio infra-red spectrometer（IRIS） has been developed to measure CO_2 mixing ratio with δ~13C isotopic signature, in addition to mixing ratios of other greenhouse gases（CH_4, N2_O）. The original aspects of the instrument as well as its precision and accuracy for the determination of the isotopic signature δ~13C of CO_2 are discussed. A first application to biodegradation of hydrocarbons is presented, tested on a hydrocarbon contaminated site under aerobic bio-treatment. CO_2 flux measurements using closed chamber method is combined with the determination of the isotopic signature δ~13C of the CO_2 emission to propose a non-intrusive method to monitor in situ biodegradation of hydrocarbons. In the contaminated area, high CO_2 emissions have been measured with an isotopic signature δ~13C suggesting that CO_2 comes from petroleum hydrocarbon biodegradation.This first field implementation shows that rapid and accurate measurement of isotopic signature of CO_2 emissions is particularly useful in assessing the contribution of contaminant degradation to the measured CO_2 efflux and is promising as a monitoring tool for aerobic bio-treatment.展开更多
The chemistry of subsurface water bodies is difficult to understand unless precipitation chemistry and atmospheric processes are taken into consideration. Limited pioneer work has been carried out on considering preci...The chemistry of subsurface water bodies is difficult to understand unless precipitation chemistry and atmospheric processes are taken into consideration. Limited pioneer work has been carried out on considering precipitation chemistry.Polluted zone delineation is very much significant before the planning for any of the remedial measures.The dual contamination is a common problem noticed展开更多
The impact of population pressure has been observed on several systems,groundwater resource is one among them.Mismanagement and over-exploitation has not only caused the decline of groundwater levels but also causes d...The impact of population pressure has been observed on several systems,groundwater resource is one among them.Mismanagement and over-exploitation has not only caused the decline of groundwater levels but also causes deterioration in water quality. Fluoride is one of such parameters where impact of over exploitation has been observed.Fluoride is展开更多
This study aims to uses paleomagnetic and anisotropy of magnetic susceptibility(AMS)methods to recognize the initial deposit position and to track the paleoflow at the origin of an iron skarn-related deposit.The Yaman...This study aims to uses paleomagnetic and anisotropy of magnetic susceptibility(AMS)methods to recognize the initial deposit position and to track the paleoflow at the origin of an iron skarn-related deposit.The Yamansu deposit is located in eastern Tianshan(Charvet,2007).This province has a substantial mining potential for Fe–(Cu)skarn,Cu–Ni and V–Ti orthomagmatic deposits,and orogenic Au lodes(Branquet et al.,2012;Zhang et a.,2005;Mao et al.,2005).Recent publication dates the Yamansu deposit at 323 Ma,and uses this deposit to define a model of Submarine Volcanogenic Iron Oxide(SVIO)deposits(Hou et al.,展开更多
From the study of the Strengbach and Ringelbach watersheds we propose to illustrate the interest of combining the geochemical tracing and geochemical modeling approaches on surface and deep borehole waters,to decipher...From the study of the Strengbach and Ringelbach watersheds we propose to illustrate the interest of combining the geochemical tracing and geochemical modeling approaches on surface and deep borehole waters,to decipher the diversity of the water flow and the associated water–rock interactions in such elementary mountainous catchments. The results point to a clear geochemical typology of waters depending on the water circulations(deep vs. hypodermic) within the substratum.展开更多
Natural organic matter(NOM)is known to play an important role in the transport and binding of trace metal elements in aquatic and soil systems.Thallium is a pollutant for which the extent of the role played by NOM is ...Natural organic matter(NOM)is known to play an important role in the transport and binding of trace metal elements in aquatic and soil systems.Thallium is a pollutant for which the extent of the role played by NOM is poorly known.Consequently,this study investigates thallium(Ⅰ)and its complexation to a purified humic substance as proxy for NOM.Experiments were performed with the Donnan Membrane Technique to separate,for the first time,the free Tl^+ion from its complexed form in the bulk solution.Various pH and concentrations were investigated at constant ionic strength and constant NOM proxy concentrations in solution.Experimental results were described with NICA-Donnan model.Thallium complexation was compared to silver complexation using literature data and using the same NICA-Donnan formalism.Parameters for these two cations(Tl^+and Ag^+)are reported in this article,for the first time.Results display low thallium complexation to the NOM proxy while silver competes with divalent cations for the NOM binding sites.Calculated speciation for dissolved thallium highlights the dominance of free thallium(Tl^+)in solution whereas Tl-NOM complexes contribute roughly 15%to total Tl(Ⅰ)species in river and lake type waters.Similar results are obtained for soil solutions,Tl-bound to NOM<30%of total,from UK soils with different land use and geochemistry.展开更多
基金Project supported by the Occitanie region(RETREAt project-ALDOCT 000443)the French geological survey(BRGM)。
文摘This study proposes an advanced leaching method using organic acids to recover rare earth elements(REEs)from NdFeB permanent magnets from end-of-life computers hard disk drives(HDDs).The end-oflife HDDs were first dismantled in order to recover NdFeB magnets,which were then thermally demagnetized at 350℃during 30 min before crushing in a ball mill under inert atmosphere.Scanning electron microscopy/energy dispersive X-ray spectroscopy(SEM/EDS)analyses performed on the NdFeB magnets show the heterogeneous structure containing the major matric phase Nd_(2)Fe_(14)B and the REEsrich phase containing Nd and Pr oxides.Additionally,X-ray diffraction(XRD)and Mossbauer spectroscopy(MS)analyses on the ground NdFeB magnet show that grinding NdFeB magnets under inert atmosphere helps to minimize its oxidation.Chemical analysis shows that the composition of the ground sample is Nd:22.8 wt%,Pr:3.3 wt%,Dy:1.2 wt%,Fe:62.6 wt%,Co:1.5 wt%,B:0.9 wt%,Ni:0.6 wt%.Diagrams of speciation and equilibrium phases(E_(h) vs.pH)were calculated to determine the predominance of the formed species in the REEs-organic acids systems.The influence of the organic acid type(acetic acid,formic acid,citric acid and tartaric acid),the acid concentration(10 vol%,up to saturation),and the solid/liquid(S/L)ratio(0.5%-10%)on NdFeB magnets leaching was investigated employing an optimal experimental design conceived by the statistical software JMP.Acetic acid(CH_(3)COOH)shows the highest leaching performance of REEs,allowing leaching yields over 90%for Nd,Dy and Pr in the acid concentration range of 1.6-10 mol/L and the S/L ratio range of 0.5%-5%at a temperature of 60℃.The results presented in this investigation suggest that REEs can be recovered from magnets of end-of-life HDDs using an eco-friendly method assisted by organic acids.
基金co-funded by a U.S.National Science Foundation(Grant EAR-0538119)to E.Calaisthe Advanced ERC(Grant 290864 RHEOLITH)to E.Burov and A.Koptev+2 种基金the Royal Academy of Netherlands visiting professor grant to E.Burovthe UPMC visiting professor grant to S.Cloetinghperformed on the ERC-funded SGI Ulysse cluster of ISTEP
文摘The East African Rift system （EARS） provides a unique system with the juxtaposition of two contrasting yet simultaneously formed rift branches, the eastern, magma-rich, and the western, magma-poor, on either sides of the old thick Tanzanian craton embedded in a younger lithosphere. Data on the pre-rifr, syn-rift and post-rift far-field volcanic and tectonic activity show that the EARS formed in the context of the interaction between a deep mantle plume and a horizontally and vertically heterogeneous lithosphere under far-field tectonic extension. We bring quantitative insights into this evolution by implementing high-resolution 3D thermo-mechanical numerical deformation models of a lithosphere of realistic rheology. The models focus on the central part of the EARS. We explore scenarios of plumelithosphere interaction with plumes of various size and initial position rising beneath a tectonically pre-stretched lithosphere. We test the impact of the inherited rheological discontinuities （suture zones） along the craton borders, of the rheological structure, of lithosphere plate thickness variations, and of physical and mechanical contrasts between the craton and the embedding lithosphere. Our experiments indicate that the ascending plume material is deflected by the cratonic keel and preferentially channeled along one of its sides, leading to the formation of a large rift zone along the eastern side of the craton, with significant magmatic activity and substantial melt amount derived from the mantle plume material. We show that the observed asymmetry of the central EARS, with coeval amagmatic （western） and magmatic （eastern） branches, can be explained by the splitting of warm material rising from a broad plume head whose initial position is slightly shifted to the eastern side of the craton. In that case, neither a mechanical weakness of the contact between the craton and the embedding lithosphere nor the presence of second plume are required to produce simulations that match observations. This result reconciles the passive and active rift models and demonstrates the possibility of development of both magmatic and amagmatic rifts in identical geotectonic environments.
基金research conducted in the Labex VOLTAIRE (ANR-10-LABX-100-01)the financial support provided to the PIVOTS project by the Région Centre–Val de Loire:ARD 2020 program,CPER 2015-2020,the European Union who invests in Centre-Val de Loire with the European Regional Development Fundsupported by the AMIS(FAte and IMpact of AtmospherIc PollutantS)project funded by the European Union,under the Marie Curie Actions IRSES(International Research Staff Exchange Scheme),within the Seventh Framework ProgrammeFP7-PEOPLE-2011-IRSES
文摘Plant communities play an important role in the C-sink function of peatlands. However,global change and local perturbations are expected to modify peatland plant communities,leading to a shift from Sphagnum mosses to vascular plants. Most studies have focused on the direct effects of modification in plant communities or of global change(such as climate warming, N fertilization) in peatlands without considering interactions between these disturbances that may alter peatlands' C function. We set up a mesocosm experiment to investigate how Greenhouse Gas(CO_2, CH_4, N_2O) fluxes, and dissolved organic carbon(DOC)and total dissolved N(TN) contents are affected by a shift from Sphagnum mosses to Molinia caerulea dominated peatlands combined with N fertilization. Increasing N deposition did not alter the C fluxes(CO_2 exchanges, CH_4 emissions) or DOC content. The lack of N effect on the C cycle seems due to the capacity of Sphagnum to efficiently immobilize N. Nevertheless, N supply increased the N_2O emissions, which were also controlled by the plant communities with the presence of Molinia caerulea reducing N_2O emissions in the Sphagnum mesocosms. Our study highlights the role of the vegetation composition on the C and N fluxes in peatlands and their responses to the N deposition. Future research should now consider the climate change in interaction to plants community modifications due to their controls of peatland sensitivity to environmental conditions.
文摘More than 2,000,000 tons of silica nanoparticles (NPs) are produced annually in the world to cover the needs of nanotechnologies. Inevitably, a quantity of NPs, will be in industrial discharges and domestic, or even in water resources. Share their high surface reactivity, these NPs may also carry with them through a specific adsorption of other toxic chemical pollutants inherent to the industrial sectors. To preserve public health and the environment from this pollution, it is necessary to remedy the potential pollution. In this context, the main motivation of this work is to answer this environmental issue by proposing a scheme of remediation based on the use of a conventional treatment process. The process of elimination nanoparticles by coagulation/flocculation was selected for its simplicity and also for its universal use. The NPs of industrial silica S30R50 were used as support to develop the process. The optimization of coagulation/flocculation, was greatly facilitated by the use of laser diffraction online. This technique allowed to follow the dynamic character of the treatment and to determine the size and the most relevant textural parameters (density, porosity and fractal dimension) of the flocs depending on the nature of the used reagents. The critical concentrations of different coagulants and flocculants used were determined by electrophoresis and turbidity. The ratio of their charge density/molecular weight has conditioned the quality of separation, the floc size and their texture. Excellent coagulation/flocculation performances are reached using organic reagents authorized by the Directorate General for Health of several countries. After optimization of the process, the size distributions are between 10 μm and 1 mm, with fractal dimensions (compactness) ranging from 2.3 to 2.5. The performances obtained show that the use of cationic polymers is a promising potential route to treat other types of NPs. The treatment proposed to reach a ratio of average diameters dFloc/dNP of 3500, and therefore it facilitates the elimination of these NPs agglomerated by filtration.
基金ECOTECH BIOPHY (Optimisation de procédés de BIOdépollution des eaux souterraines contaminées par des hydrocarbures par un monitoring géo PHYsique et analyse de gaz en ligne) (ANR-10-ECOT-014)LABEX VOLTAIRE (LABoratoire d'EXcellence VOLatils-Terre,Atmosphère et Interactions - Ressources et Environnement) (ANR-10-LABX-100-01)supported by the AMIS (FAte and IMpact of Atmospher Ic Pollutant S) project funded by the European Union,under the Marie Curie Actions IRSES (International Research Staff Exchange Scheme),within the Seventh Framework Programme FP7-PEOPLE-2011-IRSES
文摘Real-time methods to monitor stable isotope ratios of CO_2 are needed to identify biogeochemical origins of CO_2 emissions from the soil–air interface. An isotope ratio infra-red spectrometer（IRIS） has been developed to measure CO_2 mixing ratio with δ~13C isotopic signature, in addition to mixing ratios of other greenhouse gases（CH_4, N2_O）. The original aspects of the instrument as well as its precision and accuracy for the determination of the isotopic signature δ~13C of CO_2 are discussed. A first application to biodegradation of hydrocarbons is presented, tested on a hydrocarbon contaminated site under aerobic bio-treatment. CO_2 flux measurements using closed chamber method is combined with the determination of the isotopic signature δ~13C of the CO_2 emission to propose a non-intrusive method to monitor in situ biodegradation of hydrocarbons. In the contaminated area, high CO_2 emissions have been measured with an isotopic signature δ~13C suggesting that CO_2 comes from petroleum hydrocarbon biodegradation.This first field implementation shows that rapid and accurate measurement of isotopic signature of CO_2 emissions is particularly useful in assessing the contribution of contaminant degradation to the measured CO_2 efflux and is promising as a monitoring tool for aerobic bio-treatment.
文摘The chemistry of subsurface water bodies is difficult to understand unless precipitation chemistry and atmospheric processes are taken into consideration. Limited pioneer work has been carried out on considering precipitation chemistry.Polluted zone delineation is very much significant before the planning for any of the remedial measures.The dual contamination is a common problem noticed
文摘The impact of population pressure has been observed on several systems,groundwater resource is one among them.Mismanagement and over-exploitation has not only caused the decline of groundwater levels but also causes deterioration in water quality. Fluoride is one of such parameters where impact of over exploitation has been observed.Fluoride is
基金This work was carried out in the frame of Bioshale （European project contract NMP2-CT-2004 505 710）. The authors acknowledge the financial support given to this project by the European Commission under the Sixth Framework Programme for Research and Development. We wish to thank H. Karas （president of KGHM Cuprum） and D. Morin （BRGM） who initiated this project in 2003 and TVK and KGHM Polska Miedz S. A. for their support during the project. We also wish to thank the representatives of our various partners and the members of the executive board for their contributions to the work reported in this paper： Thierry Auge and Dominique Morin （BRGM） Jan Pasava and Anna Vymazalova （CGS）+10 种基金 Andrzej Grotowski and Barbara Pakulska （Cuprum） Franz Glombitza and Jana Pinka （GEOS） Jorg Langwaldt and Lasse Ahonen （GTK） Kirsti Loukola-Ruskeeniemi and Olof Forsen （HUT） Witold Charewicz, Tomasz Chmielewski, Andrzej Luszczkiewicz and Zygmunt Sadowski （PWR） Jesus Palma and Francisco Sanchez （TR） Stoyan Groudev and Irena Spasova （UMGS） Teresa Farbiszewska and Jadwiga Farbiszewska-Kiczma （UO） Barrie Johnson and Kevin Hallberg （UWB） Aleksandra Sklodowska and Renata Matlak0wska （UW-FB） Paul Norris （Warwick） and all our colleagues from the different organisation who participated in this project.
文摘This study aims to uses paleomagnetic and anisotropy of magnetic susceptibility(AMS)methods to recognize the initial deposit position and to track the paleoflow at the origin of an iron skarn-related deposit.The Yamansu deposit is located in eastern Tianshan(Charvet,2007).This province has a substantial mining potential for Fe–(Cu)skarn,Cu–Ni and V–Ti orthomagmatic deposits,and orogenic Au lodes(Branquet et al.,2012;Zhang et a.,2005;Mao et al.,2005).Recent publication dates the Yamansu deposit at 323 Ma,and uses this deposit to define a model of Submarine Volcanogenic Iron Oxide(SVIO)deposits(Hou et al.,
基金financially supported by funding from the CPER-Alsace REALISE program,the Equipex program CRITEX,the CNRS SOERE RBV and the LABEX"G-Eau-Thermie profonde"funding from the French ANR Program under grant agreement ANR-15-CE06-0014(Projet CANTAREAlsace)
文摘From the study of the Strengbach and Ringelbach watersheds we propose to illustrate the interest of combining the geochemical tracing and geochemical modeling approaches on surface and deep borehole waters,to decipher the diversity of the water flow and the associated water–rock interactions in such elementary mountainous catchments. The results point to a clear geochemical typology of waters depending on the water circulations(deep vs. hypodermic) within the substratum.
基金IRSN,CEA,BRGM and IPGP for funding this research Grant n°DEN 3841supported by IPGP multidisciplinary program PARIby Region Ile de France SESAME Grant no.12015908。
文摘Natural organic matter(NOM)is known to play an important role in the transport and binding of trace metal elements in aquatic and soil systems.Thallium is a pollutant for which the extent of the role played by NOM is poorly known.Consequently,this study investigates thallium(Ⅰ)and its complexation to a purified humic substance as proxy for NOM.Experiments were performed with the Donnan Membrane Technique to separate,for the first time,the free Tl^+ion from its complexed form in the bulk solution.Various pH and concentrations were investigated at constant ionic strength and constant NOM proxy concentrations in solution.Experimental results were described with NICA-Donnan model.Thallium complexation was compared to silver complexation using literature data and using the same NICA-Donnan formalism.Parameters for these two cations(Tl^+and Ag^+)are reported in this article,for the first time.Results display low thallium complexation to the NOM proxy while silver competes with divalent cations for the NOM binding sites.Calculated speciation for dissolved thallium highlights the dominance of free thallium(Tl^+)in solution whereas Tl-NOM complexes contribute roughly 15%to total Tl(Ⅰ)species in river and lake type waters.Similar results are obtained for soil solutions,Tl-bound to NOM<30%of total,from UK soils with different land use and geochemistry.
