Paul Wersin

Early diagenetic influences on iron transformations in a freshwater lake sediment

Chemical Geology, 1991

Wersin, P., H6hener, P., Giovanoli, R. and Stumm, W., 1991. Early diagenetic influences on iron t... more

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REDOX REACTIONS AT MINERAL-WATER INTERFACES-SPECTROSCOPIC STUDIES

by Paul Wersin and Michael Hochella

On the influence of carbonate in mineral dissolution: I. The thermodynamics and kinetics of hematite dissolution in bicarbonate solutions at T = 25° C

Geochimica Et Cosmochimica Acta, 1992

We have studied the thermodynamics and kinetics of hematite dissolution in bicarbonate solutions ... more We have studied the thermodynamics and kinetics of hematite dissolution in bicarbonate solutions under constant pCO 2 . The solubility of hematite is increased in the presence of bicarbonate. We have established that the complexes responsible for this increase are FeOHCO 3 (aq) and Fe ( CO 3 ) 2 - . The stability constants of these complexes at the

Dry deposition measurements using water as a receptor: A chemical approach

Water, Air, & Soil Pollution, 1993

The field measurement of dry deposition still represents a difficult task. In our approach, a 1 t... more The field measurement of dry deposition still represents a difficult task. In our approach, a 1 to 2 cm thick layer of water in a petri dish with a diameter of 22 cm, serves as a surrogate surface. The atmospheric constituents taken up by the water can be analyzed chemically by the same procedure as for the wet deposition samples. In contrast to solid surrogate surfaces, water exhibits the following advantageous properties: low and constant surface resistance, high sticking coefficient for aerosols, and predictable sorption behavior for gases. Consequently, the deposition rates measured to the wet surface are generally higher, by up to a factor of 4 for NH4 +, CI-, NO3-and SO42-, than those to a dry surface, but still smaller than the concurrent wet deposition rates. We observed the following average dry deposition rates in txmol m -2 d-l: NH4 + 48.3, Ca 2 § 40.7, Na + 15.8, Mg 2+ 8.4, K + 4.2, H-Aci 36.4; SO42-57.2, C1-39.2, NO 3-34.5, HSO 3-5.7, formate 4.0; acid soluble metals: Fe 2.8, Zn 0.60, Cu 0.11, Pb 0.073, Cd 0.0022. The soluble fraction of Zn, Cd, Cu, Pb and Fe in the dry deposition varied with the pH of the water phase corresponding to the adsorption tendency of these metals to oxide surfaces. The sampling method also allows tracing of regionally and locally emitted atmospheric pollutants. In our study the local pollution sources included road salting, construction work and a refuse incinerator. Finally, chemical reactions occurring in the atmosphere, such as the conversion of CI-to HC1 by HNO 3 or the oxidation of SO2, can be identified by evaluating the data. The method proposed is relevant to measure reproducibly the dry deposition of a variety of compounds to water bodies and moist vegetation.

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CO2 data on gas and pore water sampled in situ in the Opalinus Clay at the Mont Terri rock laboratory

Physics and Chemistry of the Earth, Parts A/B/C, 2008

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Modelling of the migration of trace elements along groundwater flowpaths by using a steady state approach application to the site at El Berrocal (Spain)

Journal of Contaminant Hydrology, 1997

The applications of geochemical modelling to natural water systems mostly rely upon the equilibri... more The applications of geochemical modelling to natural water systems mostly rely upon the equilibrium assumption. This is in principle justified for deep groundwater systems with long water residence times.In addition, trace element behaviour in these natural systems has been normally modelled by taking into account the precipitation and dissolution of individual trace element phases.Recent geochemical modelling work related to natural

Large-scale redox plume in glaciofluvial deposits due to sugar-factory wastes and wastewater at Aarberg, Switzerland

Hydrogeology Journal, 2001

The sugar factory at Aarberg, Switzerland, has processed about 18×10 6 metric tons of sugar beets... more The sugar factory at Aarberg, Switzerland, has processed about 18×10 6 metric tons of sugar beets in the last 100 years. This has been accompanied by releases of dissolved organic carbon to the groundwater, induced both by direct wastewater disposal until 1964 and by ongoing leakage from solid-waste deposits. Downgradient in the groundwater of the glaciofluvial aquifer, depletion of oxygen concentrations accompanied by low nitrate, high ammonium, dissolved Mn(II) and Fe(II) concentrations are observed. This study was aimed at developing a quantitative comprehension of theimpact of the leaking waste deposits on biogeochemical processes in the aquifer and on groundwater quality. The study includes a review of historical information, a survey of the hydrogeochemistry in the aquifer, the characterisation of riverwater infiltration rates with the radon method, establishment of a mass-balance model based on a numerical flow and transport model, and application of a stablecarbon-isotope method to show biodegradation of sugarwaste deposits in the aquifer. The investigations demonstrate that present emissions from waste deposits would not lead to the consumption of all the O 2 in the aquifer. The present occurrence of anoxic groundwater conditions is explained as a result of the long history of waste loading.

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From adsorption to precipitation: Sorption of Mn2+ on FeCO3(s)

Geochimica et Cosmochimica Acta, 1989

Sorption of Mn 2+ on siderite was investigated as a function of Mn concentration and time at cons... more

A surface complexation model of the carbonate mineral-aqueous solution interface

Geochimica et Cosmochimica Acta, 1993

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Surface charge of MnCO3and FeCO3

Geochimica et Cosmochimica Acta, 1990

The surface charge of two carbonate minerals (rhodochrosite, and siderite) was investigated as a ... more The surface charge of two carbonate minerals (rhodochrosite, and siderite) was investigated as a function of pH (4 to 8) and ionic strength (0.03, 0.1, and 1 .O mol dmp3 NaCl) under two different partial pressures of CO2 (0.5 and 0.005 atm). The acid/base titrations were performed with a flow-through reactor. This technique minimizes the contribution of dissolution and precipitation and thus allows the measurement of the surface charge to be performed.

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On the influence of carbonate in mineral dissolution: I. The thermodynamics and kinetics of hematite dissolution in bicarbonate solutions at

Geochimica et Cosmochimica Acta, 1992

We have studied the thermodynamics and kinetics of hematite dissolution in bicarbonate solutions ... more

Interaction between aqueous uranium (VI) and sulfide minerals: Spectroscopic evidence for sorption and reduction

by Michael Hochella and Paul Wersin

Geochimica et Cosmochimica Acta, 1994

2829 2830 P. Wersin et al

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Proton and Trivalent Metal Cation Binding by Dissolved Organic Matter in the Opalinus Clay and the Callovo-Oxfordian Formation

Environmental Science & Technology, 2008

We investigated the proton and trivalent metal binding of dissolved organic matter (DOM) in in si... more We investigated the proton and trivalent metal binding of dissolved organic matter (DOM) in in situ pore water and anoxic rock extracts of two potential host rocks for the disposal of radioactive waste, i.e., the Opalinus Clay (OPA) and the Callovo-Oxfordian formation (COx). The proton, curium, and europium binding properties of the OPA pore water and the extracted DOM of both rocks were studied with acid-base titrations, time-resolved laser fluorescence spectroscopy (TRLFS), and voltammetry, respectively. Protons were mostly buffered by inorganic compounds. DOM contributed to the total proton buffering capacity of the samples only to a small extent. Significant complexation of curium by DOM was observed for OPA pore water by TRFLS in contrast to little complexation by DOM detected in the OPA and COx extracts. The data on europium binding in OPA pore water were described by the presence of 14.3 microM organic ligands exhibiting a conditional affinity constant of log beta = 6.50. Calculations of europium speciation under in situ conditions indicated that carbonates largely controlled the speciation of europium in OPA and COx. In the OPA formation, the presence of DOM may enhance the solubility of europium by 5 x 10(-8) M, representing about one-third of total dissolvable europium.

Early diagenetic influences on iron transformations in a freshwater lake sediment

Chemical Geology, 1991

Wersin, P., H6hener, P., Giovanoli, R. and Stumm, W., 1991. Early diagenetic influences on iron t... more

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A kinetic model for iron diagenesis in a lake sediment

Chemical Geology, 1990

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Biogeochemical processes in a clay formation in situ experiment: Part E – Equilibrium controls on chemistry of pore water from the Opalinus Clay, Mont Terri Underground Research Laboratory, Switzerland

by Paul Wersin, Eric Gaucher, Simcha Stroes-Gascoyne, and Pierre Cannière

Applied Geochemistry, 2011

... fatty acids (PLFA) corresponding to 10 5 to 10 6 viable cells/g dry weight; detection of PLFA... more

Long-term diffusion experiment at Mont Terri: first results from field and laboratory data

Applied Clay Science, 2004

The diffusion of radionuclides is an important safety aspect for nuclear waste disposal in argill... more The diffusion of radionuclides is an important safety aspect for nuclear waste disposal in argillaceous host rocks. A longterm diffusion experiment, termed DI-A, is being carried out at the Mont Terri Rock Laboratory in the Opalinus Clay formation. The aim of this experiment is the understanding of the migration and sorption behaviour of cationic and anionic species in consolidated clays. This study reports on the experimental layout and the first results obtained from the DI-A experiment, which include the investigation of HTO, 22 Na + , Cs + , and I À migration during a period of 1 year by analysing these tracers in the water circulating in the borehole. In addition, results obtained from through-diffusion experiments on small-sized samples with HTO, I À , and 36 Cl À are presented.

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Sorption of uranium to sulfide minerals: Insight into redox reactions from spectroscopic analysis

by Paul Wersin and Michael Hochella

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