Applied Geochemistry (v.27, #3)

Selenium in volcanic environments: A review by Geerke H. Floor; Gabriela Román-Ross (517-531).
Display Omitted► Selenium has a narrow range between toxic and essential concentrations. ► Selenium is volatilized and transferred to the environment during volcanic activity. ► There is a lack of high quality Se data in volcanic soils and waters. ► Sorption processes seems to control the Se behavior in soils. ► Hydrothermal activity impacts Se concentrations in groundwaters.Selenium is a chemical element with major environmental implications, due to the extremely narrow range between essential and toxic concentrations. Volcanoes emit significant amounts of Se, which has an enormous impact on the Se cycle and potentially human and animal health. This paper presents a broad overview of the current state of knowledge of major aspects of volcanic derived Se, focussing on the processes in soils and aquifers.Volcanic soils, formed when volcanic products weather rapidly, display peculiar characteristics. Selenium contents can be relatively high (1–2 orders of magnitude higher) compared to the worldwide average (0.4 mg/kg), but often with low mobility. The soils can be impacted by local deposition of volcanic emissions, which are enriched in Se due to volatilization in the magma chamber. It seems that the chemical fate of Se in volcanic soils is controlled by sorption processes on poorly crystalline phases, which presence depends on the parental materials and weathering. These sorption processes also determine leaching to groundwaters. Some volcanic aquifers have Se concentrations above the WHO guideline of 10 μg/L. This might also be related to geothermal activity.In spite of the well documented interest on Se during the last decades a significant number of uncertainties exist on the behavior of this fascinating element. A preliminary model of the Se cycle around volcanoes can be constructed, but the well-known analytical problems associated with Se determinations have produced a lack of reliable information on some processes involved in the chemical interaction between soils and water. This review, therefore, also aims to identify the processes where new efforts are needed to produce good quality data to be compared and integrated in global models.

Lead and lead isotopes in agricultural soils of Europe – The continental perspective by Clemens Reimann; Belinda Flem; Karl Fabian; Manfred Birke; Anna Ladenberger; Philippe Négrel; Alecos Demetriades; Jurian Hoogewerff (532-542).
► Pb concentrations are reported in agricultural soils at the European scale. ► A map of a Pb isotope ratio landscape covering a continent is presented. ► Results define the soil geochemical Pb background for Europe. ► Baseline data for forensic and environmental studies are provided.Lead isotopes are widely used for age dating, for tracking sources of melts, sediments, Pb products, food and animals and for studying atmospheric Pb contamination. For the first time, a map of a Pb isotope landscape at the continental-scale is presented. Agricultural soil samples (Ap-horizon, 0–20 cm) collected at an average density of 1 site/2500 km2 were analysed for Pb concentration and Pb isotopes (206Pb, 207Pb, 208Pb). Lead concentrations vary from 1.6 to 1309 mg/kg, with a median of 16 mg/kg. Isotopic ratios of 206Pb/207Pb range from 1.116 to 1.727 with a median of 1.202. The new data define the soil geochemical Pb background for European agricultural soil, providing crucial information for geological, environmental and forensic sciences, public health, environmental policy and mineral exploration. The European continental-scale patterns of Pb concentrations and Pb isotopes show a high variability dominated by geology and influenced by climate. Lead concentration anomalies mark most of the known mineralised areas throughout Europe. Some local Pb anomalies have a distinct anthropogenic origin.

Floodplain deposits: A geochemical archive of flood history – A case study on the River Rhine, Germany by Z.A. Berner; S. Bleeck-Schmidt; D. Stüben; T. Neumann; M. Fuchs; M. Lehmann (543-561).
► River discharge and composition of suspended material are correlated. ► Compositional gradients in floodplain sediments are correlative with flood intensities. ► Comparison of OSL ages and historically documented flood events.Based on the correlation between discharge and carbonate content of the suspended load of the River Rhine, Germany, a systematic geochemical, mineralogical and granulometric study was carried out to verify whether this geochemical signal is transferred to floodplain deposits and in what way these sediments and their chemostratigraphic characterization can be used as a tool for the reconstruction of the river flood history. The analysis of the time resolved changes in the composition of particulate matter during a flood event revealed that the increase of carbonate content (represented by CaO, Sr) with discharge was coupled to a simultaneous decrease in the relative amount of siliciclastics (K2O, Rb). The association of these two groups of diametrical parameters with specific grain size fractions (carbonates with 40–200 μm; siliciclastics with >200 μm) were found to be slightly shifted relative to each other and showed different gradients during the surging and fading flood wave. This, together with the covariance of elements pertaining to minerals with different density (e.g., carbonate and heavy minerals) suggests a chemical response to the changes in discharge, which is controlled primarily by hydraulic equivalence rather than grain size. There is also a time lag between the amount of suspended load and discharge, with a maximum in suspended load shortly after the peak discharge, when the flood has already started to abate. The flood plain sediments have similar composition to the suspended load, suggesting the direct transfer of the geochemical flood signal to the floodplain sediments.Three lithological units could be distinguished in a 240 cm long sediment core collected from the floodplain. Grain-size and geochemical composition indicate that only the top of the section (20–70 cm) represents sediments deposited in an abandoned channel of the river and may have preserved the geochemical flood signals as identified during actual flood events. The comparison of the chemostratigraphy of this part of the section (estimated with optical stimulated luminescence to be deposited between ca. 1650 and 1920), with a record of historically documented inundations, however, yielded only poor agreement. The possible reasons for this inconsistency are discussed and suggestions are made for continuing investigations.

Major and trace metal mobility during weathering of mine tailings: Implications for floodplain soils by David Kossoff; Karen A. Hudson-Edwards; William E. Dubbin; Maria Alfredsson (562-576).
► Magnitudes and mechanisms of metal mobility during tailings weathering were determined. ► By the end of the weathering experiments all leachates had pH of ∼2. ► Release of Ca, Cu, Mg, Mn and Na and retention of Al, K, Sr, Sn and Ti was observed. ► Dissolution of primary sulfides and silicates controls metal mobility. ► The release of tailings to floodplains should be severely limited or prohibited.Mine tailings discharged to river systems have the potential to release significant quantities of major and trace metals to waters and soils when weathered. To provide data on the mechanisms and magnitudes of short- and long-term tailings weathering and its influence on floodplain environments, three calendar year-long column leaching experiments that incorporated tailings from Potosí, Bolivia, and soil from unaffected downstream floodplains, were carried out. These experiments were designed to model 20 cycles of wet and dry season conditions. Two duplicate columns modeled sub-aerial tailings weathering alone, a third modeled the effects of long-term floodplain tailings contamination and a fourth modeled that of a tailings dam spill on a previously contaminated floodplain. As far as was practical local climatic conditions were modeled. Chemical analysis of the leachate and column solids, optical mineralogy, XRD, SEM, EPMA, BCR and water-soluble chemical extractions and speciation modeling were carried out to determine the processes responsible for the leaching of Al, Ca, Cu, K, Na, Mg, Mn, Sn, Sr and Ti. Over the 20 cycles, the pH declined to a floor of ca. 2 in all columns. Calcium, Cu, Mg, Mn and Na showed significant cumulative losses of up to 100%, 60%, 30%, 95% and 40%, respectively, compared to those of Al, K, Sr, Sn and Ti, which were up to 3%, 1.5%, 5%, 1% and 0.05%, respectively. The high losses are attributed to the dissolution of relatively soluble minerals such as biotite, and oxidation of chalcopyrite and Cu-sulfosalts, while low losses are attributed to the presence of sparingly soluble minerals such as svanbergite, cassiterite and rutile. These results strongly suggest that the release of tailings to floodplains should be limited or prohibited, and that all tailings should be removed from floodplains following dam spills.

Mineralogical and chemical evolution of ochreous precipitates from the Libiola Fe–Cu-sulfide mine (Eastern Liguria, Italy) by Pietro Marescotti; Cristina Carbone; Paola Comodi; Francesco Frondini; Gabriella Lucchetti (577-589).
► Mineralogy and chemistry of ochreous precipitates in acid mine drainage systems. ► Role of Fe-oxyhydroxides in controlling acid mine drainage chemistry. ► Factors controlling Fe-oxyhydroxide precipitation and transformation.The mineralogical and chemical evolution of ochreous precipitates forming from acid mine drainage (AMD) from the abandoned Libiola Fe–Cu-sulfide mine (Eastern Liguria, Italy) was followed through a multianalytical approach (XRD, TEM, XRF, ICP) applied to surface precipitates and associated waters collected from several mine adits. The mineralogy of the precipitates changed significantly as a consequence of the variations of the chemical parameters of the circulating solutions (mainly pH, Eh, and sulfate concentrations) which, in turn, were mainly controlled by mixing with unpolluted stream and rill waters of the mining area. A progressive transition from jarosite-, to schwertmannite-, to goethite-, to ferrihydrite-, to amorphous-dominated precipitates was observed, mainly as a consequence of an increase in the pH of the associated solutions. This mineralogical evolution agrees well with the aqueous speciation and Eh–pH stability calculations performed on the waters associated with the different precipitate types. Furthermore, TEM analysis indicated that metastable pristine phases (schwertmannite) tend to transform progressively to well-crystallized more stable species, here represented by goethite. The comparison of the water chemistry and the crystal chemistry of the different precipitates showed a significant decrease in the Zn, Cu, Ni, Co contents in waters where the coexisting precipitates were almost exclusively composed of goethite. The distribution of V, Sr, As concentrations within the different precipitates showed that the most efficient scavenging phase for these elements was jarosite, whereas ferrihydrite efficiently took up Pb ions, and schwermannite acted as a natural sink for Cr.The comparative analysis of the precipitates and waters of the Libiola mining area indicated that the authigenic Fe-oxyhydroxides play an important role in controlling the composition of the highly polluted AMD waters, but this role as “cleaning agents” was mostly ephemeral. Minor pH–Eh oscillations facilitated quick mineralogical transformations, via dissolution–reprecipitation or solid state transformation, which, in turn, controlled the trace elements that were mobilized or permanently stored within the solid phases.

► Schwertmannite transformation is strongly triggered by enhancing aqueous pH. ► Schwertmannite transformed incompletely to goethite even after 120 days at pH 8. ► Only <2% of sorbed As(III) get released and inhibits schwertmannite transformation. ► Aqueous pH inversely affect As(III) release which re-adsorbed within 40 days ageing. ► Prolonged schwertmannite exposure in alkaline media brings high sulfate loading.Schwertmannite (SHM) precipitated from acid mine drainage often contains high levels of As(III). The present study is aimed at understanding the fate of As(III) preadsorbed to bio-synthesized schwertmannite (0.92 wt% As(III)) during transformation, compared with SHM devoid of As(III). Ageing experiments were conducted at room temperature in controlled reactors for 120 days at pH 5, 6, 7 and 8. Transformation was indicated by a steady SO 4 2 - release of ⩾90% of solid phase SO 4 2 - at pH 8 after 75 days from both specimens. The SO 4 2 - release correlated with OH consumption, indicating OH - – SO 4 2 - exchange and was facilitated as pH increased from 5 to 8. No significant structural change could be indicated after 75 days using XRD, IR spectroscopy and scanning electron microscopy, suggesting the formation of an initial transformation product of low crystallinity. Incomplete ripening of the transformation product was determined after 120 days with traces of ferrihydrite and goethite in As(III)-free specimens, which was more prominent at higher pH. Significant release of sorbed As (1.9 wt% at pH 5) could be detected during the initial phase of the transformation of As-containing SHM which was rapidly readsorbed probably to the new phase. No detectable ripening occurred after 120 days at lower pH values in the case of As(III)-sorbed specimens indicating an inhibitory effect of As on the nucleation of new phases.

Arsenic and antimony contamination of waters, stream sediments and soils in the vicinity of abandoned antimony mines in the Western Carpathians, Slovakia by Edgar Hiller; Bronislava Lalinská; Martin Chovan; Ľubomír Jurkovič; Tomáš Klimko; Michal Jankulár; Róbert Hovorič; Peter Šottník; Renáta Fľaková; Zlatica Ženišová; Ivana Ondrejková (598-614).
► We study antimony and arsenic environmental contamination in five abandoned Sb mines. ► High concentrations of both metalloids were found in all environmental compartments. ► Discharged waters from adits and impoundments represent a source of both, As and Sb. ► Sb is more soluble than As in most solid samples regardless of their sources.Environmental contamination with As and Sb caused by past mining activities at Sb mines is a significant problem in Slovakia. This study is focused on the environmental effects of the 5 abandoned Sb mines on water, stream sediment and soil since the mines are situated in the close vicinity of residential areas. Samples of mine wastes, various types of waters, stream sediments, soils, and leachates of the mine wastes, stream sediments and selected soils were analyzed for As and Sb to evaluate their geochemical dispersion from the mines. Mine wastes collected at the mine sites contained up to 5166 mg/kg As and 9861 mg/kg Sb. Arsenic in mine wastes was associated mostly with Fe oxides, whereas Sb was present frequently in the form of individual Sb, Sb(Fe) and Fe(Sb) oxides. Waters of different types such as groundwater, surface waters and mine waters, all contained elevated concentrations of As and Sb, reaching up to 2150 μg/L As and 9300 μg/L Sb, and had circum-neutral pH values because of the buffering capacity of abundant Ca- and Mg-carbonates. The concentrations of Sb in several household wells are a cause for concern, exceeding the Sb drinking water limit of 5 μg/L by as much as 25 times. Some attenuation of the As and Sb concentrations in mine and impoundment waters was expected because of the deposition of metalloids onto hydrous ferric oxides built up below adit entrances and impoundment discharges. These HFOs contained >20 wt.% As and 1.5 wt.% Sb. Stream sediments and soils have also been contaminated by As and Sb with the peak concentrations generally found near open adits and mine wastes. In addition to the discharged waters from open adits, the significant source of As and Sb contamination are waste-rock dumps and tailings impoundments. Leachates from mine wastes contained as much as 8400 μg/L As and 4060 μg/L Sb, suggesting that the mine wastes would have a great potential to contaminate the downstream environment. Moreover, the results of water leaching tests showed that Sb was released from the solids more efficiently than As under oxidizing conditions. This might partly explain the predominance of Sb over As in most water samples.

Arsenic accumulation and speciation in plants from different habitats by Claes Bergqvist; Maria Greger (615-622).
► Submerged plants have a higher accumulation capacity of As than terrestrial and emergent plants. ► The As accumulation factor decreases with increasing soil As concentration. ► Even though submerged soil contains primarily arsenite submerged plants contains more arsenate. ► Even though arid soil contains more arsenate than arsenite terrestrial plants contains more arsenite than arenate.Understanding As accumulation in plants is necessary in order to alleviate problems with As in the environment and to improve sustainable As phytotechnologies. To find suitable candidates for phytoremediation purposes and to investigate specific accumulation patterns due to growth habitat and plant groups, As accumulation in 124 plant species collected from different habitats and speciation in 6 of these plant species, was determined. The data show that submerged plants have a higher accumulation than emergent and terrestrial plants. The As concentration in terrestrial and emergent plants were correlated with the [As]soil, while the accumulation factor correlated negatively with [As]soil. Gymnosperms had a high [As]shoot:[As]root ratio. The inorganic As species, arsenate and arsenite were found in plants from all habitats and methylarsonic acid (MMA) in all but one plant species. Arsenate predominated in submerged plants. The results suggest that the habitat and the [As]soil have a strong influence on the As accumulation in plants and that submerged plants and/or gymnosperms might be suitable for phytoremediation of As.

► Historical iron slag is chemically dominated by Al2O3, Cao, MgO, and SiO2. ► Some samples are enriched in elements such as As, Cd, Cu, and Mn. ► Mineralogy is pyroxene, olivine, iron metal, glass; some melilite, spinel, sulfides. ► Al, Cu, Fe, and Mn leached during simulated weathering. ► Partitioning of elements among phases affects their potential release to environment.The Hopewell Furnace National Historic Site in southeastern Pennsylvania, which features an Fe smelter that was operational in the 18th and 19th centuries, is dominated by three slag piles. Pile 1 slag, from the Hopewell Furnace, and pile 2 slag, likely from the nearby Cornwall Furnace, were both produced in cold-blast charcoal-fired smelters. In contrast, pile 3 slag was produced in an anthracite furnace. Ore samples from the nearby Jones and Hopewell mines that fed the smelter are mainly magnetite-rich with some sulfides (pyrite, chalcopyrite, sphalerite) and accessory silicates (quartz, garnet, feldspar, and clay minerals). Slag piles 1 and 2 are similar mineralogically containing predominantly skeletal and dendritic aluminian diopside and augite, skeletal forsteritic olivine, glass, rounded blebs of metallic Fe, and exotic quartz. Olivine is a major phase in all samples from pile 2, whereas it occurs in only a few samples from pile 1. Samples of the <2 mm-size fraction of surface composite slag material or crushed slag from at depth in piles 1 and 2 are mineralogically similar to the large surface slag fragments from those piles with the addition of phases such as feldspars, Fe oxides, and clay minerals that are either secondary weathering products or entrained from the underlying bedrock. Pile 3 slag contains mostly skeletal forsteritic olivine and Ti-bearing aluminian diopside, dendritic or fine-grained subhedral melilite, glass, euhedral spinel, metallic Fe, alabandite–oldhamite solid solution, as well as a sparse Ti carbonitride phase. The bulk chemistry of the slag is dominated by Al2O3 (8.5–16.2 wt.%), CaO (8.2–26.2 wt.%), MgO (4.2–24.7 wt.%), and SiO2 (36.4–59.8 wt.%), constituting between 81% and 97% of the mass of the samples. Piles 1 and 2 are chemically similar; pile 1 slag overall contains the highest Fe2O3, K2O and MnO, and the lowest MgO concentrations. Pile 3 slag is high in Al2O3, CaO and S, and low in Fe2O3, K2O and SiO2 compared to the other piles. In general, piles 1 and 2 are chemically similar to each other, whereas pile 3 is distinct – a conclusion that reflects their mineralogy. The similarities and differences among piles in terms of mineralogy and major element chemistry result from the different smelting conditions under which the slag formed and include the fuel source, the composition of the ore and flux, the type of blast (cold versus hot), which affects the furnace temperature, and other beneficiation methods.The three distinct slag piles at Hopewell are enriched in numerous trace elements, such as As (up to 12 mg/kg), Cd (up to 0.4 mg/kg), Co (up to 31.8 mg/kg), Cu (up to 647 mg/kg), Mn (up to 0.69 wt.%), Pb (up to 172 mg/kg) and Zn (up to 393 mg/kg), together with Fe (13.9 wt.%), when compared to the average for the continental crust, with the <2 mm-size fraction commonly containing the highest concentrations. Enrichments in various elements (e.g., Cd, Co, Cu, Pb, Zn) were also found in the ore samples. Despite these enrichments, comparison of bulk chemistry trace-element concentrations to the environmental guidelines suggests most elements are likely not problematic with the exception of As, Co, Fe and Mn. Leachate tests that simulate weathering indicate Fe (up to 973 μg/L) and Mn (up to 133 μg/L) are readily released in potentially harmful concentrations compared to secondary drinking water and some aquatic ecosystem toxicity criteria. Aluminum and Cu, although not high in the solid compared to environmental guidelines, also exceed relevant criteria in leachate extracts with maximum concentrations of 2700 μg/L and 17.7 μg/L, respectively. In contrast, As and Co, which are significant in the solids, are not leached in concentrations that exceed guidelines (i.e., 3 μg/L or less for both elements). The weathering rates of the Fe metal and Fe oxides, which host Cu and some Fe, are likely higher than the silicate glass, which hosts the majority of Al, Mn and some Fe, and the crystalline silicates and spinels affecting which elements and how much are released into the environment and surrounding aquatic ecosystem. The mineral assemblages and their chemical composition, the bulk sample chemistry, and leachability of trace elements are all important components in understanding the potential environmental impacts of the slag piles.

► Determination of present Cr(VI) inventory of a Cr(VI) contaminated site. ► Comparison of aq. Cr(VI) concentrations with solubility of identified Cr(VI) minerals. ► Demonstration of naturally occurring Cr(VI) reduction with Cr isotope measurements. ► Quantification of current extent of naturally occurring Cr(VI) reduction. ► Presentation of first δ53Cr data of subsoil samples of a Cr(VI) contaminated site.The risk of groundwater contamination by chromate at a former chromite ore processing industrial site in Rivera (Switzerland) was assessed by determining subsoil Cr(VI) concentrations and tracking naturally occurring Cr(VI) reduction with Cr isotopes. Using a hot alkaline extraction procedure, a total Cr(VI) contamination of several 1000 kg was estimated. Jarosite, KFe3((SO4) x (CrO4)1− x )2(OH)6, and chromatite (CaCrO4) were identified as Cr(VI) bearing mineral phases using XRD, both limiting groundwater Cr(VI) concentrations. To track assumed Cr(VI) reduction at field scale δ53Cr values of contaminated subsoil samples in addition to groundwater δ53Cr data are used for the first time. The measurements showed a fractionation of groundwater δ53Cr values towards positive values and subsoil δ53Cr towards negative values confirming reduction of soluble Cr(VI) to insoluble Cr(III). Using a Rayleigh fractionation model, a current Cr(VI) reduction efficiency of approximately 31% along a 120 m long flow path was estimated at an average linear groundwater velocity of 3.3 m/d. Groundwater and subsoil δ53Cr values were compared with a site specific Rayleigh fractionation model proposing that subsoil δ53Cr values can possibly be used to track previous higher Cr(VI) reduction efficiency during the period of industrial activity. The findings strongly favor monitored natural attenuation to be part of the required site remediation measures.

► Development of a 2D reactive transport model of a Cr(VI) contaminated site. ► Model incorporation of site mineralogy, Cr isotopes, water chemistry and site hydrology. ► Simulation of measured present day Cr(VI) concentrations and δ 53Cr values. ► Prediction of Cr(VI) plumes for alternate remediation strategies. ► Prediction of remaining time with ongoing subsoil Cr(VI) contamination.A 2D horizontal reactive transport model of a chromate-contaminated site near Rivera, Switzerland, was developed using the computer code CrunchFlow to evaluate site remediation strategies. Transport processes were defined according to the results of an existing hydrological model, and the definition of geochemical (reactive) processes is based on the results of a detailed mineralogical and geochemical site characterization leading to a comprehensive conceptual site model. Kinetics of naturally occurring Cr(VI) reduction by Fe(II) and natural solid organic matter is quantified by fitting measured Cr isotope ratios to a modeled 1D section along the best constrained flow line. The simulation of Cr isotope fractionation was also incorporated into the 2D model. Simulation of the measured present day Cr(VI) plume and δ 53Cr value distribution was used for the 2D model calibration and corresponds to a situation where only monitored natural attenuation (MNA) is occurring. Other 2D model runs simulate alternate excavation scenarios. The simulations show that with an excavation of the top 2–4 m the groundwater Cr(VI) plume can be minimized, and that a deeper excavation depth only diminishes the plume if all the contaminants can be removed. A combination of an excavation of the top 2–4 m and monitoring of the ongoing natural Cr(VI) reduction is suggested as the most ecological and economical remediation strategy, even though a remaining time period with ongoing subsoil Cr(VI) contamination in the order of 1 ka is predicted.

Neuro-fuzzy modeling based genetic algorithms for identification of geochemical anomalies in mining geochemistry by Mansour Ziaii; Faramarz Doulati Ardejani; Mahdi Ziaei; Ali A. Soleymani (663-676).
► Developing a genetic algorithm based neuro-fuzzy model in mining geochemistry. ► Recognition of local-scale blind mineralization in different geochemical landscape. ► Identification of Deh-Salm in Iran as the most important porphyry mineralization.A genetic algorithm (GA)-based neuro-fuzzy approach is used for identification of geochemical anomalies by implementing a Takagi, Sugeno and Kang (TSK) type fuzzy inference system in a 5-layered feed-forward adaptive artificial neural network. This paper investigates the effectiveness of GA-based neuro-fuzzy for separating zone dispersed mineralization (ZDM) from blind mineralization, and its application for identification of geochemical anomalies in the arid landscape of the Lut metallogenic province in eastern Iran. Other classification algorithms such as metallometry, zonality, criteria, and back-propagation artificial neural network classifiers are also used for comparison. The genetic operators are carefully designed to optimize the artificial neural network, avoiding premature convergence and permutation problems. The results show that the GA-based hybrid neuro-fuzzy model can provide accurate results in comparison with those results obtained by other techniques. Neuro-fuzzy and GA-based neuro-fuzzy techniques appear to be well-suited for routine exploration geochemistry applications. In conjunction with statistics and conventional mathematical methods, hybrid approaches can be developed and may prove a step forward in the practice of applied geochemistry.

Display Omitted► Li, B and their isotopes are mainly controlled by water/rock interactions. ► The input of seawater is negligible in these geothermal waters. ► Sr isotope compositions are in agreement with local magmatic bedrocks.Chemical and isotopic data for 23 geothermal water samples collected in New Zealand within the Taupo Volcanic Zone (TVZ) are reported. Major and trace elements including Li, B and Sr and their isotopic compositions (δ7Li, δ11B, 87Sr/86Sr) were determined in high temperature geothermal waters collected from deep boreholes in different geothermal fields (Ohaaki, Wairakei, Mokai, Kawerau and Rotokawa geothermal systems). Lithium concentrations are high (from 4.5 to 19.9 mg/L) and Li isotopic compositions (δ7Li) are homogeneous, ranging between −0.5‰ and +1.4‰. In particular, it is noteworthy that, except for the samples from the Kawerau geothermal field having slightly higher δ7Li values (+1.4%), the other geothermal waters have a near constant δ7Li signature around a mean value of 0‰ ± 0.6 (2σ, n  = 21). Boron concentrations are also high and relatively homogeneous for the geothermal samples, falling between 17.5 and 82.1 mg/L. Boron isotopic compositions (δ11B) are all negative, and display a range between −6.7‰ and −1.9‰. These B isotope compositions are in agreement with those of the Ngawha geothermal field in New Zealand. Lithium and B isotope signatures are in a good agreement with a fluid signature mainly derived from water/rock interaction involving magmatic rocks with no evidence of seawater input. On the other hand, Sr concentrations are lower and more heterogeneous and fall between 2 and 165 μg/L. The 87Sr/86Sr ratios range from 0.70549 to 0.70961. These Sr isotope compositions overlap those of the Rotorua geothermal field in New Zealand, confirming that some geothermal waters (with more radiogenic Sr) have interacted with bedrocks from the metasedimentary basement. Each of these isotope systems on their own reveals important information about particular aspects of either water source or water/rock interaction processes, but, considered together, provide a more integrated understanding of the geothermal systems from the TVZ in New Zealand.

The origin of thermal waters in the northeastern part of the Eger Rift, Czech Republic by Tereza Dupalová; Ondra Sracek; Zbyněk Vencelides; Karel Žák (689-702).
► Thermal waters in this part of the Eger Rift are formed by mixing. ► Investigation confirmed an input of endogenous CO2. ► High mineralization ground water shows a maximum CO2 input. ► Input of solutes is linked to the presence of paleo-brines in bedrock.An investigation of the thermal waters in the Ústí nad Labem area in the northeastern part of the Eger Rift has been carried out, with the principal objective of determining their origin. Waters from geothermal reservoirs in the aquifers of the Bohemian Cretaceous Basin (BCB) from depths of 240 to 616 m are exploited here. For comparison, thermal waters of the adjacent Teplice Spa area were also incorporated into the study. Results based on water chemistry and isotopes indicate mixing of groundwater from aquifers of the BCB with groundwater derived from underlying crystalline rocks of the Erzgebirge Mts. Unlike thermal waters in Děčín, which are of Ca–HCO3 type, there are two types of thermal waters in Ústí nad Labem, Na–HCO3–Cl–SO4 type with high TDS values and Na–Ca–HCO3–SO4 type with low TDS values. Carbon isotope data, speciation calculations, and inverse geochemical modeling suggest a significant input of endogenous CO2 at Ústí nad Labem in the case of high TDS groundwaters. Besides CO2 input, both silicate dissolution and cation exchange coupled with dissolution of carbonates may explain the origin of high TDS thermal waters equally well. This is a consequence of similar δ13C and 14C values in endogenous CO2 and carbonates (both sources have 14C of 0 pmc, endogenous CO2 δ13C around −3‰, carbonates in the range from −5‰ to +3‰ V-PDB). The source of Cl seems to be relict brine formed in Tertiary lakes, which infiltrated into the deep rift zone and is being flushed out. The difference between high and low TDS groundwaters in Ústí nad Labem is caused by location of the high mineralization groundwater wells in CO2 emanation centers linked to channel-like conduits. This results in high dissolution rates of minerals and in different δ13C(DIC) and 14C(DIC) fingerprints. A combined δ34S and δ18O study of dissolved SO4 indicates multiple SO4 sources, involving SO4 from relict brines and oxidation of H2S. The study clearly demonstrates potential problems encountered at sites with multiple sources of C, where several evolutionary groundwater scenarios are possible.

► Recharge areas and flow-paths of water are detectable by conjoint analyses of stable isotopes and REY-pattern in groundwater. ► In semi-arid regions highly disturbed by faults in which intricate inter-aquifer flow occurs exercised method is worthwhile. ► A non-invasive system-knowledge is fundamental for smart water resources management. ► Identifying hydrogeological components is prerequisite do develop sustainable exploitation strategies. ► In areas with scarce groundwater but different societies the above items become highly politically.The Bet She’an and Harod Valleys in Israel are regional recipients and mixing zones for groundwater draining from a multiple aquifer system, which includes carbonate and basalt aquifers and deep-seated pressurized brines. The aquifers drain through two types of outlets, distinct and mixed. The latter type is mainly conditioned by the occurrence of fault-blocks related to the Jordan Rift system, which act as connecting media between the aquifers and facilitate interaquifer flow. Conjoint application of rare earth element distribution and water isotopes enables detection of the local areas replenishment by rainfall infiltration and, in connection with the position of wells or springs, the identification of groundwater flow paths. Once stationary equilibria are established changes of REY composition between REY in groundwater and their surface adsorption, are negligible. In areas with little soil coverage and vegetation even recharge over young Tertiary and diagenetic Cretaceous limestones is distinguishable by their REY distribution patterns. Groundwater recharged over Tertiary limestones show higher REY abundance and more significant Ce anomalies than those derived from the Cretaceous limestones. Weathering of alkali olivine basalts leads to REY patterns in groundwater depleted in the middle REE. The improved knowledge of the hydrological systems is thought to be useful for regional hydrogeological modeling and for designing rational water management schemes.

Discrimination between different water bodies from a multilayered aquifer (Kaluvelly watershed, India): Trace element signature by Nathalie Gassama; Haino Uwe Kasper; Aline Dia; Constantin Cocirta; Martine Bouhnik-LeCoz (715-728).
► Trace elements were measured in aquifer formations and related groundwaters. ► Redox-sensitive elements cannot be used as tracers because of pumping. ► Soluble elements can be tracers if they occur in little type of minerals. ► Na versus Ti and Ca versus Ti allow differentiating between water sources.In the multilayered aquifer of Kaluvelly (India), comprising various sedimentary layers overlying a charnockitic basement, concentrations of trace elements were measured in aquifer formations and in groundwaters to identify geochemical tracers for water bodies. The two main sandstones (Cuddalore and Vanur) originate from the charnockites and the Cuddalore sandstone has experienced lateritization. In the studied area, two charnockite end-members were identified: a dioritic and a granitic one. Mineralogical composition and whole-rock Ti concentrations confirmed the charnockite which displayed the granitic composition as the parent rock of the two sandstones. Titanium distribution indicates that the Cuddalore sandstone originates from a more intense weathering of the parent material than the Vanur sandstone. Despite extensive differences in trace element contents recorded in aquifer formations, only a few trace elements were suitable to distinguish the water bodies. Among soluble elements, Li (in the Vanur aquifer) and Ba (in the charnockite and carbonaceous aquifers) can be used as tracers. As the input of these elements in solution is mainly regulated by the available stock, for a given mineralogical origin there is a direct link between the aquifer formation composition and water signature. With the exception of As, concentrations of redox-sensitive elements were not preserved during pumping because of oxidation, preventing their use as tracers. Low-mobility elements such as La, Ce, Th, Zr, Nb, Hf, or Ta were too insoluble to be detected in waters and/or to record the aquifer formation signature. Their input in solution was not regulated by the available stock but by the dissolution rate of rock-forming minerals. Only Ti can be used to distinguish between two out of the three aquifers (charnockite and Vanur). The specific behavior of Ti recorded in these waters may be linked to rutile inclusions within plagioclases and to the influence of climate on Ti solubility.

Occurrence and geochemistry of radium in water from principal drinking-water aquifer systems of the United States by Zoltan Szabo; Vincent T. dePaul; Jeffrey M. Fischer; Thomas F. Kraemer; Eric Jacobsen (729-752).
226Ra plus 228Ra exceed 0.185 Bq/L in seven eastern and central USA principal aquifers. ► Radium concentration was highest in low pH and anoxic waters. ► Geochemical environments and low aquifer sorption capacity controlled Ra occurrence. ► Alpha recoil affected the presence of 224Ra in western USA principal aquifers. ► Differences in Ra isotope ratios depended upon geology of the principal aquifer.A total of 1270 raw-water samples (before treatment) were collected from 15 principal and other major aquifer systems (PAs) used for drinking water in 45 states in all major physiographic provinces of the USA and analyzed for concentrations of the Ra isotopes 224Ra, 226Ra and 228Ra establishing the framework for evaluating Ra occurrence. The US Environmental Protection Agency Maximum Contaminant Level (MCL) of 0.185 Bq/L (5 pCi/L) for combined Ra (226Ra plus 228Ra) for drinking water was exceeded in 4.02% (39 of 971) of samples for which both 226Ra and 228Ra were determined, or in 3.15% (40 of 1266) of the samples in which at least one isotope concentration (226Ra or 228Ra) was determined. The maximum concentration of combined Ra was 0.755 Bq/L (20.4 pCi/L) in water from the North Atlantic Coastal Plain quartzose sand aquifer system. All the exceedences of the MCL for combined Ra occurred in water samples from the following 7 PAs (in order of decreasing relative frequency of occurrence): the Midcontinent and Ozark Plateau Cambro-Ordovician dolomites and sandstones, the North Atlantic Coastal Plain, the Floridan, the crystalline rocks (granitic, metamorphic) of New England, the Mesozoic basins of the Appalachian Piedmont, the Gulf Coastal Plain, and the glacial sands and gravels (highest concentrations in New England).The concentration of Ra was consistently controlled by geochemical properties of the aquifer systems, with the highest concentrations most likely to be present where, as a consequence of the geochemical environment, adsorption of the Ra was slightly decreased. The result is a slight relative increase in Ra mobility, especially notable in aquifers with poor sorptive capacity (Fe-oxide-poor quartzose sands and carbonates), even if Ra is not abundant in the aquifer solids. The most common occurrence of elevated Ra throughout the USA occurred in anoxic water (low dissolved-O2) with high concentrations of Fe or Mn, and in places, high concentrations of the competing ions Ca, Mg, Ba and Sr, and occasionally of dissolved solids, K, SO4 and HCO3. The other water type to frequently contain elevated concentrations of the Ra radioisotopes was acidic (low pH), and had in places, high concentrations of NO3 and other acid anions, and on occasion, of the competing divalent cations, Mn and Al. One or the other of these broad water types was commonly present in each of the PAs in which elevated concentrations of combined Ra occurred. Concentrations of 226Ra or 228Ra or combined Ra correlated significantly with those of the above listed water-quality constituents (on the basis of the non-parametric Spearman correlation technique) and loaded on principal components describing the above water types from the entire data set and for samples from the PAs with the highest combined Ra concentrations.Concentrations of 224Ra and 226Ra were significantly correlated to those of 228Ra (Spearman’s rank correlation coefficient, +0.236 and +0.326, respectively). Activity ratios of 224Ra/228Ra in the water samples were mostly near 1 when concentrations of both isotopes were greater than or equal to 0.037 Bq/L (1 pCi/L), the level above which analytical results were most reliable. Co-occurrence among these highest concentrations of the Ra radionuclides was most likely in those PAs where chemical conditions are most conducive to Ra mobility (e.g. acidic North Atlantic Coastal Plain). The concentrations of 224Ra were occasionally greater than 0.037 Bq/L and the ratios of 224Ra/228Ra were generally highest in the PAs composed of alluvial sands and Cretaceous/Tertiary sandstones from the western USA, likely because concentrations of 224Ra are enhanced in solution relative to those of 228Ra by alpha recoil from the aquifer matrix. Rapid adsorption of the two Ra isotopes (controlled by the alkaline and oxic aquifer geochemistry) combined with preferential faster recoil of 224Ra generates a 224Ra/228Ra ratio much greater than 1. The 228Ra/226Ra activity ratio was locally variable, and was generally lower than 1 (226Ra rich) in samples from PAs with carbonate bedrock, but was typically greater than 1 (228Ra rich) in PAs composed of unconsolidated sand.

Hydrogeochemistry approach to the identification of flow components under the descending limb conditions of a hydrograph (Corbeira stream, Spain) by Juciene Andrade Figueiredo; Eldemar Albuquerque Menor; Maria Teresa Taboada-Castro; Maria Mercedes Taboada-Castro; Luís Drude Lacerda (753-759).
► The PP/DP ratio allows identifying flow components without direct support of hydrographs. ► Mean PP/DP values establish hydrogeochemistry signatures in descending limb of the hydrograph. ► The method is valid for application in others small catchments under temperate climate.This paper presents a method based on hydrogeochemical signatures for the identification of flow components, from the descending limb to the baseflow, without the direct support of hydrographs. The proposed model was built using chemical analysis of waters from a small agro-forestry catchment having a temperate climate. The sampling was performed every 15 days at the Corbeira stream outlet, from 2004 to 2008. A statistical approach was used with particulate P/dissolved P (PP/DP) values, resulting in a global histogram, within which mini-Gaussian distributions were highlighted. The mean of each group of highlighted PP/DP values, as well as all other selected analytical parameters, were calculated and plotted in Cartesian diagrams. The results showed the hydrogeochemical signatures of the Corbeira stream in the descending limb to baseflow conditions. Scatterplots of the migration of particulate matter showed linear regressions forming α  ≠ 0 to the X-axis, while dissolved compounds showed parallel linearity (α  = 0) in relation to the same axis. Deflections in the linear behavior point to significant changes in the chemical concentrations from different types of aqueous inputs. Flow components in the descending limb show distinct ranges along the X-axis: the mean PP/DP values. The ranges varying from 3.3 to 2.0 correspond to its upper phases from 2.0 to 0.9 suggests mixtures between inflows and from 0.9 to 0.3 denote subsurface flow dominance. Finally, PP/DP < 0.3 indicates exclusive baseflow conditions. These intervals are specific to the Corbeira catchment as a consequence of its geographical characteristics and should be numerically different from the proposed method if applied to other catchments. However, this method remains valid for application in other small catchments as the PP/DP ranges in the descending limb are defined by the relative behavior between the linear correlations from the hydrogeochemical concentrations plotted in a Cartesian diagram.

Silver and lead in high-altitude lake sediments: Proxies for climate changes and human activities by Marion Garçon; Catherine Chauvel; Emmanuel Chapron; Xavier Faïn; Mingfang Lin; Sylvain Campillo; Sarah Bureau; Marc Desmet; Marie-Christine Bailly-Maître; Laurent Charlet (760-773).
► We present trace-element contents and Pb isotopic ratios in sediments from high-altitude lake in the French Alps. ► Pb and Ag contents are dominated by input from a lead–silver vein located few meters from the lakeshore. ► Advances of glaciers produced sediments with high Ag–Pb contents and Pb/U ratios due to increased erosion of the vein. ► Reduced glacier activity led to the formation of organic-rich sediments with high U and As contents and low Pb/U ratios. ► Medieval mining activities are marked by huge Ag concentration peaks.High-altitude lake sediments are often used as archives for environmental changes and their chemical and isotopic compositions provide significant constraints on natural and anthropogenic long-term changes that have occurred in their catchment area. Here, trace-element concentrations and Pb isotopes are presented for two sedimentary cores from Lake Blanc Huez in the French Alps, to trace the impact of climate changes and human activities over the Holocene. Lead and Ag contents are very high and clearly dominated by input from a Pb–Ag vein located a few meters from the lakeshore, a vein that also buffers the Pb isotopes. Mining of this vein in medieval times is recorded in the corresponding lake sediments with high Ag content coupled with high Pb/U ratio. These chemical characteristics can be used to constrain the major Holocene climate changes. Significant advances of glaciers next to the lake produced sediments with Ag and Pb concentration peaks and high Pb/U ratios due to accelerated erosion of the Pb–Ag vein, similar to the effects of the medieval mining. In contrast, reduced glacier activity led to the formation of organic-rich sediments with high U and As contents and low Pb/U ratios. More generally, the observed combination of chemical changes could be used elsewhere to decipher environmental changes over long periods of time.

► Both inorganic and organic iodine species studied in twelve geologic samples. ► Batch and column approaches used to study sorption, degradation, and transport. ► MeI is weakly sorbed, but degradation varied greatly in media with different OM. ► Iodate sorbed more strongly than iodide, sorption of 4-iodoaniline related to OM.Iodine is an important element in studies of human nutrition to combat I deficiency disorders, and in protection of the environment and human health from anthropogenic release of radioactive I. Biogeochemical cycling of I in the subsurface environment is complex, because it occurs in multiple oxidation states and as inorganic and organic species that may be volatile, hydrophilic and biophilic. Predicting the fate and transport of anthropogenic radioiodine deposited from the atmosphere or released into the subsurface requires knowledge of the sorption and degradation behavior of the various I species that may interact with soils and sediments. In this study, sorption, degradation, and transport behavior of I species (iodide, iodate, methyl iodide, and 4-iodoaniline) were examined in 12 geologic samples of differing physico-chemical characteristics, collected at numerous nuclear facilities in the USA. In particular, this work focuses on the sorption and degradation behavior of CH3I in geologic media, for which few studies are available, even though it is recognized as an important gaseous form of I in the marine atmosphere, and as a major form released from nuclear fuel reprocessing facilities and during nuclear accidents. Results from complementary batch and column experiments show that different I species exhibit very different sorption and transport behavior in geologic media. Sorption of I is in general minimal, but a low concentration (5 × 10−13  M) of radioactive 125I is found to be strongly sorbed onto samples with high organic matter. Sorption of IO 3 - is consistently greater than that of I, and sorption of 4-iodoaniline is generally strong and seems to be related to the amount of organic matter in the media. Methyl iodide is weakly sorbed onto 12 geologic samples with a distribution coefficient of about 1 mL/g, but its degradation varies greatly as a function of organic matter content, with a regression line of t 1/2  = 0.084 × OM + 0.088 (R 2  = 0.898, N  = 6) where t 1/2 is the degradation half-life and OM is the organic matter content. These results will be useful in predicting the mobility of anthropogenic radioactive I deposited on a soil surface, and highlight the fact that it will exhibit different residence times according to its original chemical form and to the composition of host sediments.

Armouring of well cement in H2S–CO2 saturated brine by calcite coating – Experiments and numerical modelling by Nicolas Jacquemet; Jacques Pironon; Vincent Lagneau; Jérémie Saint-Marc (782-795).
Display Omitted► Experimental testing of well cement reactivity/durability within H2S–CO2 brine. ► CSH carbonation by CO2 and ferrite sulfidation by H2S. ► Evidence of cement armouring and clogging due to CaCO3 precipitates.The active acid gas (H2S–CO2 mixture) injection operations in North America provide practical experience for the operators in charge of industrial scale CO2 geological storage sites. Potential leakage via wells and their environmental impacts make well construction durability an issue for efficiency/safety of gas geological storage. In such operations, the well cement is in contact with reservoir brines and the injected gas, meaning that gas–water–solid chemical reactions may change the physical properties of the cement and its ability to confine the gas downhole. The cement-forming Calcium silicate hydrates carbonation (by CO2) and ferrite sulfidation (by H2S) reactions are expected. The main objective of this study is to determine their consequences on cement mineralogy and transfer ability. Fifteen and 60 days duration batch experiments were performed in which well cement bars were immersed in brine itself caped by a H2S–CO2 phase at 500 bar–120 °C. Scanning electron microscopy including observations/analyses and elemental mapping, mineralogical mapping by micro-Raman spectroscopy, X-ray diffraction and water porosimetry were used to characterize the aged cement. Speciation by micro-Raman spectroscopy of brine trapped within synthetic fluid inclusions were also performed. The expected calcium silicate hydrates carbonation and ferrite sulfidation reactions were evidenced. Furthermore, armouring of the cement through the fast creation of a non-porous calcite coating, global porosity decrease of the cement (clogging) and mineral assemblage conservation were demonstrated. The low W/R ratio of the experimental system (allowing the cement to buffer the interstitial and external solution pH at basic values) and mixed species diffusion and chemical reactions are proposed to explain these features. This interpretation is confirmed by reactive transport modelling performed with the HYTEC code. The observed cement armouring, clogging and mineral assemblage conservation suggest that the tested cement has improved transfer properties in the experimental conditions. This work suggests that in both acid gas and CO2 geological storage, clogging of cement or at least mineral assemblage conservation and slowing of carbonation progress could occur in near-well zones where slight water flow occurs e.g. in the vicinity of caprock shales.

► Chemical evolution during rock weathering of granitoids overlaps with their magmatic chemical variation. ► Many classical weathering indices are obscured for the rocks in the wide granitic area. ► A cancellation method of the magmatic influence from weathering index is proposed.Quantitative determination of the degree of chemical weathering of rocks is a fundamental task in environmental and engineering geology, and many weathering indices based on whole-rock chemistry have been proposed. However, most classical indices are of limited application to granitoids in a wide area, because these lithotypes generally exhibit wide chemical variation arising from their petrogenesis. The chemical evolution produced during rock weathering, therefore, overprints pre-existing magmatic chemical variation. This problem can cause many classical weathering indices to yield misleading results. This study proposes a method that compensates for the influence of petrogenesis on calculation of the weathering index. The method is based on a bivariate plot of the magmatic chemical variation (MCV) in granitoids, and the degree of chemical weathering (DCW). The MCV axis must be based on an element that reflects magmatic processes and is also relatively immobile during rock weathering. In this study TiO2 contents are utilized for the MCV. The DCW axis is fundamentally defined by the ratios of more-mobile to less-mobile elements during weathering, and hence many classical indices can be applied. The improved value of the degree of chemical weathering (DCWi) for a weathered rock is derived by: DCW i = s × ( MCV CV - MCV 1 ) + DCW 1 where MCV1 is the measured composition (e.g. TiO2 content) of the weathered rock. DCW1 denotes the ratios of more-mobile to less-mobile elements of the weathered rock. The “s” parameter is the slope of the least square linear regression for fresh granitoids in the MCV–DCW relationship. MCVCV is a correction factor which is given by the average point on the MCV axis (e.g. average TiO2) of the fresh rocks. This method is useful for evaluating the degree of weathering of various granitoids, and enhances the practical application of many weathering indices.

► We investigate n-alkanes and their hydrogen isotopes in plants from an arid region. ► Average chain length values of n-alkane are closely related to plant species. ► Evaporation of lake water influences δD values of n-alkanes in aquatic plants. ► Humidity and rainfall affect δD values of n-alkanes in terrestrial plants. ► δD values of n-alkane in aquatic and terrestrial plants record source water δD values.Various aquatic plants from Lake Qinghai, the largest inland saline lake in China, and terrestrial plants from the surrounding area were investigated for the distribution of n-alkanes and their δD values. The n-alkanes in the samples range from C15 to C33 with C preference index (CPI) values of 4.0–29.7. The n-C23 or n-C25 alkane is the dominant compound in the aquatic submerged plants. The aquatic emergent and terrestrial plants have an abundance maximum at n-C27, n-C29 or n-C31. The average chain length (ACL) values, ranging from 26.0 to 29.6, are closely related to the plant species. The n-alkanes from the aquatic plants have mean δD values of −169‰ to −121‰ and those from the terrestrial plants values of −173‰ to −109‰. The H isotopic composition (δD) and fractionation differ significantly among the plants studied. Comparison shows that additional evaporative enrichment of the lake water associated with saline lakes and humidity influence the δD values of the n-alkanes in aquatic and terrestrial plants, respectively. The mean δD values of n-alkanes in the plants decrease with increasing ACL value. The n-alkanes from the different types of plants are more depleted in D relative to environmental water and those from aquatic plants (with a mean value of −143‰) have a greater isotopic fractionation than terrestrial plants (mean value −113‰).