Applied Geochemistry (v.23, #8)
Resuspension of urban soils as a persistent source of lead poisoning in children: A review and new directions by Mark A.S. Laidlaw; Gabriel M. Filippelli (2021-2039).
Urban soils act as the repository for a number of environmental burdens, including Pb. Significant attention has been devoted to reducing Pb burdens to children with outstanding success, but the fact that blood Pb levels above 10 μg/dL are disproportionately found in children living in many USA cities (15–20% in some cities compared to a national average of less than 2%) indicates that not all of the sources have been eliminated. Although the health risk of fine particulates has begun to raise concerns in cities, little attention has been paid to Pb associated with these particulates and the potential role of this pathway for continued Pb burdens of urban youth. This review summarizes recent work on particulate resuspension and the role of resuspension of Pb-enriched urban soils as a continued source of bio-available Pb both outside and inside homes, then presents recent efforts to model Pb burdens to children based on the atmospheric parameters that drive particulate resuspension. A strong seasonal relationship is found between atmospheric particulate loading and blood Pb levels in children, and new particulate loading models are presented for a range of US cities involved in the Interagency Monitoring of Protected Visual Environments (IMPROVE) program. These seasonal particulate loading models have implications for a number of respiratory health impacts, but can also be used to calculate seasonal patterns in bio-available Pb redistribution onto contact surfaces (the primary pathway for ingestion-related uptake in toddlers) and assist clinicians in interpreting time-specific blood Pb tests.
Integrated hydrochemical assessment of the Quaternary alluvial aquifer of the Guadalquivir River, southern Spain by M. Lorite-Herrera; R. Jiménez-Espinosa; J. Jiménez-Millán; K.M. Hiscock (2040-2054).
The alluvial aquifer of the Guadalquivir River comprises shallow Quaternary deposits located in the central-eastern part of the Province of Jaén in southern Spain, where groundwater resources are used mainly for crop irrigation in an important agricultural area. In order to establish the baseline hydrochemical conditions and processes determining the groundwater quality, groundwater and river water samples were collected as part of an integrated investigation that coupled multivariate statistical analysis with hydrochemical methods to identify and interpret the groundwater chemistry of the aquifer system. Three main hydrochemical types (Mg–Ca–HCO3, Ca–Mg–SO4–HCO3–Cl and Na–Ca–Mg–Cl–SO4) were identified. Further interpretation, using R-mode principal components analysis (PCA) conducted with 13 hydrochemical variables, identified two principal components which explain ⅔ of the variance in the original data. In combination with the hydrochemical interpretation, mineralogical analyses of the aquifer sediment together with inverse geochemical modelling using NETPATH showed that dedolomitization (calcite precipitation and dolomite dissolution driven by gypsum dissolution) is the principal hydrochemical process controlling the regional groundwater chemistry. Other processes such as silicate weathering, ion exchange, mixing between river water and groundwater, and agricultural practices also affect the groundwater chemistry.
Mercury pollution from artisanal mercury mining in Tongren, Guizhou, China by Ping Li; Xinbin Feng; Lihai Shang; Guangle Qiu; Bo Meng; Peng Liang; Hua Zhang (2055-2064).
Concentrations of total Hg (T-Hg) were measured in mine waste, stream water, soil and moss samples collected from the Tongren area, Guizhou, China to identify potential Hg contamination to local environments, which has resulted from artisanal Hg mining. Mine waste contained high T-Hg concentrations, ranging from 1.8 to 900 mg/kg. High concentrations of Hg were also found in the leachates of mine waste, confirming that mine waste contains significant water-soluble Hg compounds. Total Hg distribution patterns in soil profiles showed that top soil is contaminated with Hg, which has been derived from atmospheric deposition. Data suggest that organic matter plays an important role in the binding and transport of Hg in soil. Elevated T-Hg concentrations (5.9–44 mg/kg) in moss samples suggest that atmospheric deposition is the dominant source of Hg to local terrestrial ecosystems. Concentrations of T-Hg were highly elevated in stream water samples, varying from 92 to 2300 ng/L. Particulate Hg in water constituted a large proportion of the T-Hg and played a major role in Hg transport. Methyl–Hg (Me–Hg) concentrations in the water samples was as high as 7.9 ng/L. Data indicate that Hg contamination is dominantly from artisanal Hg mining in the study area, but the extent of Hg contamination is dependent on the mining history and the scale of artisanal Hg mining.
Methodology for bounding calculations of nuclear criticality of fissile material accumulations external to a waste container at Yucca Mountain, Nevada by Jean-Philippe Nicot (2065-2081).
The possibility of nuclear criticality, however remote, in the vicinity of the proposed repository at Yucca Mountain, Nevada generates justified concerns and may impact the performance of the repository. A heuristic approach is presented here for determining the amount, spatial distribution and other characteristics of fissile material accumulation in the rock beneath a waste package that could contribute to such an event. This study is concerned primarily with waste packages containing special spent fuel from the Department of Energy and high-level nuclear waste glass. Mixing with less alkaline waters and the subsequent drop in pH is the mechanism that is most efficient for precipitating fissile material from the waste package internal leachate, in contrast to natural deposits in which redox changes are the main precipitation driver. External accumulation size is determined by (1) computing the chemical composition of the leachate leaving a package as its internal materials degrade (with the batch geochemical code EQ3/6), (2) determining precipitation of fissile material into mineral phases (using the 1D geochemical code PHREEQC) as the effluent mixes with percolation water, and (3) heuristically scaling results to a 3D volume and computing the criticality coefficient (using the code MCNP). Loci for accumulation are the multiple lithophysal cavities and the fracture system. A bounding conservative approach is used by necessity in Step 3. Nuclear criticality is sensitive to small variations in the distribution of fissile material and parameters of natural systems vary by orders of magnitude. Because the most likely combinations of parameters are not conducive to nuclear criticality, this study focuses on extreme values of parameter probabilistic distributions, such as limited flow into the package associated with a large percolation rate, combinations of material degradation rates favoring actinide release, and very high host-rock porosity values. By considering these combinations, most favorable to criticality but unlikely, it was concluded that external nuclear criticality is not a concern at the proposed repository.
Iodine in Chinese coals and its geochemistry during coalification by Daishe Wu; Haiwen Deng; Baoshan Zheng; Wuyi Wang; Xiuyi Tang; Huayun Xiao (2082-2090).
To determine the I distribution in Chinese coals, a nationwide survey was undertaken based on the distribution, periods of formation, rank and production yields of various coal deposits. A total of 305 coal samples were collected and their I contents were determined by catalytic spectrophotometry with pyrohydrolysis. The geochemistry of I during coalification (including both peat diagenesis and coal metamorphism) was assessed. It was found that the I contents of Chinese coals range from 0.04 mg kg–1 to 39.5 mg kg–1 and exhibit a lognormal distribution, with a geometric mean of 1.27 mg kg–1. Statistical correlation analysis and the observation that I contents increase with coal rank indicate that coal I is chalcophile in nature, and not generally organically bound. When peat developed into lignite through diagenesis, 95–99.9% of the original I was lost. The composition and structure of clay minerals present in the coal were controlled by the original depositional environment. The higher the I content of coals, the more likely the original sediments were affected by a marine environment. Iodine contents increased from lignite through sub-bituminous and bituminous coals to anthracite. This indicates that coal absorbed excess I from hydrothermal fluids during metamorphism (including geothermal metamorphism and telemagmatic metamorphism). The telemagmatic metamorphism was caused by magmatic activities that depended on the specific geological structure of the region. In China, most high-rank coals were formed by telemagmatic metamorphism.
Geochemistry of regional aquifer systems hosted by carbonate-evaporite formations in Umbria and southern Tuscany (central Italy) by Francesco Frondini (2091-2104).
In central Italy Mesozoic carbonates represent the principal reservoir of freshwater of the region. The hydrogeological setting is linked to the geological evolution of the Apennine chain and is generally characterised by a lower aquifer and one or more shallower aquifers separated by thin aquicludes. In these systems, groundwater composition is the result of a complex array of regional and local geochemical processes. The main geochemical processes are the dissolution of calcite, the influx of deeply derived CO2 related to a regional process of mantle degassing, dedolomitization and mixing with deep saline fluids. The occurrence of saline fluids, characterised by a Na–Cl(HCO3) composition, is related to the presence of a deep regional aquifer at the base of Mesozoic carbonates. The extremely high pCO2 values computed for the saline waters suggest that the deep aquifer is also a structural trap for the mantle derived CO2 during its ascent towards the surface. In central Italy, geological and geophysical data highlight the presence of two different crustal sectors: the eastern sector, where the geometry of the Apennine thrust belt is still preserved, and the western sector, where the compressive structures are dislocated by important extensional deformations. In the western sector, the normal faults disrupting the compressive structures allow the mixing of the deep Na–Cl(HCO3) fluids with the shallow groundwater causing a salinity increase and the natural deterioration of groundwater quality.
Denitrification in intact sediment cores from a constructed wetland: Examining the isotope pairing technique by Kyle S. Herrman; Jeffrey R. White (2105-2112).
Constructed wetlands aid in the removal of NO 3 - from surface waters due to enhanced rates of denitrification. In this study intact sediment cores from a constructed wetland were used to measure denitrification rates via the isotope pairing technique and to compare with denitrification rates measured via a mass balance of NO 3 - disappearance from the water column. The traditional application of the isotope pairing technique calls for the use of mechanical mixing to ensure the transfer of tracer 15 NO 3 - into the sediments. However, artificial mixing can disrupt natural redox processes near the sediment–water interface, and thus may yield rates that are not representative of field conditions. The objective of this study was to examine the applicability of the isotope pairing technique for intact sediment cores and to determine the adjustments that may be necessary in such applications. The 15 NO 3 - was added to the overlying water of intact sediment cores and was transported into sediments only by natural diffusion processes. Using Br− as a conservative tracer, it was determined that passive diffusion alone allowed 27% of the added compound to reach the zone of denitrification in the sediments. Using these results, the enrichment factor (ε) used in the isotope pairing technique was adjusted to account for this effect. Also, it was determined that agitation of the cores at the end of the incubations was necessary to release residual 15N-labelled N2 gas entrained in the sediment matrix. Only after accounting for these two factors did the denitrification rate from the isotope pairing technique agree with mass balance calculations. The isotope pairing technique can be used to quantify denitrification in intact sediment cores if diffusion limitations are quantified and entrained N2 is released from the sediment matrix before final isotope analyses are conducted.
Characterisation and evaluation of reference materials for black carbon analysis using elemental composition, colour, BET surface area and 13C NMR spectroscopy by Karen Hammes; Ronald J. Smernik; Jan O. Skjemstad; Michael W.I. Schmidt (2113-2122).
A recent comparative exercise found that different black carbon (BC) quantification methods produced widely varying results for a set of BC reference materials that included three laboratory-produced BC-rich materials, five environmental BC matrices and four samples of non-BC organic matter. This variation was attributed to a range of physical and chemical properties of the samples that could, in various ways, result in the over- or under-detection of BC in some or all of the techniques. Here the most pertinent chemical and physical characteristics of the samples are presented, including elemental analysis, lightness measurements, BET surface area measurements and 13C NMR analysis. Amongst the BC-rich materials, soot and char could be distinguished from one another mainly on the basis of H/C and O/C ratios, NMR observability and BET surface area. The results indicate that the aromatic structures in the soot are more highly condensed, and this explains why some BC quantification techniques detect these two materials differently. The non-BC potentially interfering materials were shown to share properties with the BC-rich materials (high C content, low lightness values and high aromaticity) that are used for certain BC quantification methods. This may lead to overestimation of BC unless these interfering materials are removed during pre-treatment. The environmental matrices were found to have relatively high amounts of metal oxides that have the potential to catalyse or inhibit thermal and chemical reactions during BC analysis.
Accurate determination of Fe(II) concentrations in the presence of a very high soluble Fe(III) background by Youri Gendel; Ori Lahav (2123-2129).
Analytical methods used for determining dissolved Fe(II) often yield inaccurate results in the presence of high Fe(III) concentrations. Accurate analysis of Fe(II) in solution when it is less than 1% of the total dissolved Fe concentration (FeT) is sometimes required in both geochemical and environmental studies. For example, such analysis is imperative for obtaining the ratio Fe(II)/Fe(III) in rocks, soils and sediments, for determining the kinetic constants of Fe(II) oxidation in chemical or biochemical systems operating at low pH, and is also important in environmental engineering projects, e.g. for proper control of the regeneration step (oxidation of Fe(II) into Fe(III)) applied in ferric-based gas desulphurization processes. In this work a method capable of yielding accurate Fe(II) concentrations at Fe(II) to FeT ratios as low as 0.05% is presented. The method is based on a pretreatment procedure designed to separate Fe(II) species from Fe(III) species in solution without changing the original Fe(II) concentration. Once separated, a modified phenanthroline method is used to determine the Fe(II) concentration, in the virtual absence of Fe(III) species. The pretreatment procedure consists of pH elevation to pH 4.2–4.65 using NaHCO3 under N2(g) environment, followed by filtration of the solid ferric oxides formed, and subsequent acidification of the Fe(II)-containing filtrate. Accuracy of Fe(II) analyses obtained for samples (Fe(II)/FeT ratios between 2% and 0.05%) to which the described pretreatment was applied was >95%. Elevating pH to above 4.65 during pretreatment was shown to result in a higher error in Fe(II) determination, likely resulting from adsorption of Fe(II) species and their removal from solution with the ferric oxide precipitate.
A method for determining both diffusion and sorption coefficients of rock medium within a few days by adopting a micro-reactor technique by Keita Okuyama; Akira Sasahira; Kenji Noshita; Toshiaki Ohe (2130-2136).
Migration properties characterized by physico-chemical factors such as distribution coefficient (K d) and diffusion coefficient (D e) are of great concern in performance assessment of high-level radioactive waste disposal in a deep geologic environment. These coefficients are normally obtained with different sample geometries using conventional methods, i.e., crushed samples by the batch sorption method for K d determination and block samples by the through-diffusion method for D e. A size dependence on both K d and D e has been reported and an additional correction due to size difference is required to maintain consistency of the data set. A fast method was developed, hereafter referred to as the micro-channel method, to determine both the sorption coefficient (R d) and D e using non-crushed rock sample by adopting the micro-reactor technique. In this method, a radionuclide solution is injected into a micro-channel (20 mm length, 4 mm width, 160 μm depth), which is in contact with a plate-shaped rock sample. A part of the injected radionuclide can diffuse into the rock matrix and/or adsorb on the rock surface and this results in an inlet-outlet concentration difference. A breakthrough curve is easily obtained with a short observation period because the injection amount is extremely small and is comparable to that escaping by diffusion into the matrix. The breakthrough curve is analyzed by a two-dimensional diffusion-advection equation to evaluate R d and D e.In the present study, tritiated water (specific activity, 1.2 × 104 Bq/mL; pH, 6) was injected into the micro-channel, and the breakthrough curve of 3H obtained. A series of experiments was carried out by changing the flow rate of the tritiated water (2.6 × 10−5–7.7 × 10−4 m/s). Rock samples were biotite granite from the Makabe area, Japan. The diffusion coefficient evaluated by least squares fitting to the numerical solutions (D e = 1.5 × 10−11 m2/s) agreed well with that obtained by the through-diffusion method (1.3 × 10−11 m2/s). The breakthrough curve of Cs ([Cs] = 1.0 × 10−7 mol/L, pH 6) labeled with 134Cs (specific activity adjusted to 4.9 × 101 Bq/mL) was also obtained. A nearly constant R d value (5.5 × 10−2 m3/kg) was found when the flow rate was less than 2.5 × 10−4 m/s. This implied that the sorption equilibrium is reached and K d is obtained by the present method. This value was almost identical to K d obtained by the batch sorption method (5.0 × 10−2 m3/kg), but the testing period was very different; 1 day and 7 days, respectively. It is concluded that application of the micro-channel method provided advantages when compared with the conventional methods.
Uranium removal from groundwater using hydroxyapatite by Franz Georg Simon; Vera Biermann; Burkhard Peplinski (2137-2145).
The present work shows that U can be effectively removed from groundwater using permeable reactive barriers with hydroxyapatite (HAP) as reactive material. The main factor influencing the removal processes is the composition of the groundwater, namely the concentration of Ca and carbonate. Sorption of U onto the HAP surface seems to be the dominant removal process with the possibility of remobilisation. Newly formed U-phosphate minerals were detected by ESEM/EDX and XRD in samples with high U content indicating either a dissolution-precipitation mechanism or sorption onto the apatite surface followed by alteration of the structure. The formed U-phosphate minerals are stable under common groundwater conditions and can be remobilised only at high pH-values and high carbonate concentrations.
Mixing-induced groundwater denitrification beneath a manured field in southern Alberta, Canada by J.E. McCallum; M.C. Ryan; B. Mayer; S.J. Rodvang (2146-2155).
Contamination of shallow groundwater by NO 3 - from manure may occur under fields where manure is spread as fertilizer and for disposal. Attenuation of NO 3 - in groundwater occurs through denitrification under certain conditions, or NO 3 - -contaminated younger groundwater may mix with older groundwater, lowering the NO 3 - concentration. In this study, δ15N and δ18O values of NO 3 - , and δ18O and δ2H values in groundwater under a manured field were evaluated to determine if groundwater NO 3 - concentrations were influenced through mixing of shallower, manure-impacted groundwater with older groundwater, or if denitrification was reducing NO 3 - concentrations. The younger groundwater showed clear evidence of manure impact with elevated Cl− (∼85 mg L−1) and NO 3 - concentrations (∼50 mg NO3–N L−1), and δ15N and δ18O values of NO 3 - consistent with a manure source. Vertical hydraulic gradients and δ18O and δ2H values in groundwater suggest older, more reduced groundwater is upwelling locally and mixing with the shallow groundwater. Decreasing NO3:Cl ratios, decreasing dissolved O2 concentrations, and increasing δ15N and δ18O values of NO 3 - suggest that denitrification occurs locally in the aquifer. The extent of denitrification is proportional to the fraction of deeper groundwater in the aquifer. Denitrification apparently does not proceed in the younger, manure-impacted groundwater in the absence of mixing.
Rapid transport of anthropogenic lead through soils in southeast Missouri by Panjai Prapaipong; Colin W. Enssle; Julie D. Morris; Everett L. Shock; Rachel E. Lindvall (2156-2170).
To investigate Pb transport and cycling, soils from the forest floor and cores from White Oaks (Quercus alba L.) were collected near a Pb smelter in SE Missouri at varying depths from the surface and varying distances. Lead concentrations in soil samples at the surface drop dramatically with distance from approximately 1500 mg/kg at less than 2 km from the smelter to around 100 mg/kg at localities greater than 2 km from the smelter. Lead contents in tree rings are below 0.5 mg/kg in samples dated prior to 1970, and rapidly increase in 1975–1990 samples. Isotopic compositions of soils and tree rings exhibit systematic variations of Pb isotopic compositions with depth and tree ring age. Distinguishable isotopic signatures for Pb sources allowed quantification of the contribution of smelter Pb to the soils. At depths where Pb concentrations decreased and approached constant values (10–25 cm, 10–30 mg/kg), 50–90%, 40–50% and 10–50% of the Pb could be derived from the smelter for the samples at locations less than 2, 2–4 and over 4 km from the smelter, respectively. The remaining portion was attributable to automobile emission and bedrock sources. Because the smelter operated from 1963 to 2003 and samples were collected in 1999, it is estimated that smelter Pb infiltrates at rates of ∼1 cm/yr (30 cm in 30 yr). At distances less than 1.5 km from the smelter, even though Pb concentrations become asymptotic at a depth of ∼30 cm, isotopic evidence suggests that Pb has migrated below this depth, presumably through exchange with naturally occurring Pb in the soil matrix. This implies that soils heavily polluted by Pb can exceed their Pb carrying capacity, which could have potential impacts on shallow groundwater systems and risk further exposure to human and ecological receptors.
Prospective scenarios for water quality and ecological status in Lake Sete Cidades (Portugal): The integration of mathematical modelling in decision processes by G. Martins; D.C. Ribeiro; D. Pacheco; J.V. Cruz; R. Cunha; V. Gonçalves; R. Nogueira; A.G. Brito (2171-2181).
The design of alternative strategies for water and ecological quality protection at the Lake Verde of Sete Cidades should be coupled with the assessment of future trophic states. Therefore, a mathematical model was developed to make prospective scenarios to reduce the risk of environmental degradation of the lake, and a modified Psenner scheme was used to characterize P distribution in the sediments. The model was able to describe thermal stratification, nutrient cycling (P, NH4 and NO3), dissolved O2, and phytoplankton dynamics in the water column and adjacent sediment layers. Internal P recycling, resulting from thermal stratification and sediment anoxia, was identified as the main cause for the increase of P concentration in the hypolimnion followed by slow transfer to the epilimnion (about 20 μg/L annual average). Cyanobacteria blooms during spring were explained by the availability of P and increased water temperature verified during this season. The most sensitive model parameter was sediment porosity. This parameter has a direct effect in dissolved O2 and P profiles and also in phytoplankton biomass. Finally, different water quality restoration scenarios were identified and their effectiveness assessed. Without the adoption of remediation measures (scenario control), Lake Verde water quality would deteriorate with annual average concentrations of total P and phytoplankton biomass (dry matter) reaching 34 μg/L and 2 mg/L, respectively, after 10 years of simulation. The reduction of P loads (scenario PORAL) into the lake would improve water quality comparatively to the scenario control, reducing the annual average concentrations of total P from 34 μg/L to 26 μg/L and of phytoplankton from 2 mg/L down to 1.4 mg/L after 10 years of simulation. In scenario sediments, corresponding to a decrease in the organic content of the sediments, a reduction in the concentrations of total P and phytoplankton is expected in the first two years of simulation, but this effect, would be attenuated throughout the years due to organic matter sedimentation. The best strategy is obtained by combining external and internal measures for P remediation. Finally, it is recommended that the model be used to integrate the results of water quality monitoring and watershed management plans.
Groundwater characterisation and modelling of water–rock interaction in an argillaceous formation (Tournemire, France) by C. Beaucaire; J.-L. Michelot; S. Savoye; J. Cabrera (2182-2197).
Chemical (Na, K, Mg, Ca, Cl, SO4, HCO3, Si, Al, Fe, Mn, TOC) and isotopic (18O[H2O], 2H[H2O], 3H[H2O], 14C[DIC], 13C[DIC], 34S[SO4], 18O[SO4]) data were obtained on groundwater collected from fractures inside the consolidated argillaceous formation of Tournemire (Aveyron) and from the aquifers surrounding this formation. Because of the very low transmissivity of such fractures (10−10 m2 s−1), specific devices were developed, for limiting out-gassing and air-contamination of groundwater during the sampling. Two modelling approaches are proposed to account for the chemical evolution of fracture groundwater from Na–Cl–HCO3 to Na–SO4 type. The first one is based on mineral equilibria only and the second one also takes into account the ion-exchange reactions. The two modelling approaches are able to reproduce K+ concentrations and they led to an almost constant pCO2 (10−2.6 atm), which only depends on equilibrium with the calcite–dolomite–kaolinite–quartz assemblage. The modelling of Na+, Ca2+ and HCO 3 + behaviours is improved by taking the ion-exchange reactions into account.In some boreholes, the time evolution of the chemical composition of fluids was greatly influenced by SO4 reduction combined with oxidation of dissolved organic C. The isotopic composition of aqueous SO4 in fracture groundwater confirms that SO4 reduction processes have occurred since the drilling of these boreholes, but also previously, during the natural evolution of groundwater. These redox reactions constitute a source of aqueous inorganic C that has to be considered in the computation of groundwater “ages” with 14C. For the studied fracture groundwaters, the maximum age estimates range from 17 to 29 ka. This shows that fractures may induce relatively fast groundwater flow, compared to the very long migration times that are calculated by only considering diffusive transport in the rock microporosity.
Cluster analysis applied to regional geochemical data: Problems and possibilities by Matthias Templ; Peter Filzmoser; Clemens Reimann (2198-2213).
Cluster analysis can be used to group samples and to develop ideas about the multivariate geochemistry of the data set at hand. Due to the complex nature of regional geochemical data (neither normal nor log-normal, strongly skewed, often multi-modal data distributions, data closure), cluster analysis results often strongly depend on the preparation of the data (e.g. choice of the transformation) and on the clustering algorithm selected. Different variants of cluster analysis can lead to surprisingly different cluster centroids, cluster sizes and classifications even when using exactly the same input data. Cluster analysis should not be misused as a statistical “proof” of certain relationships in the data. The use of cluster analysis as an exploratory data analysis tool requires a powerful program system to test different data preparation, processing and clustering methods, including the ability to present the results in a number of easy to grasp graphics. Such a tool has been developed as a package for the R statistical software. Two example data sets from geochemistry are used to demonstrate how the results change with different data preparation and clustering methods. A data set from S-Norway with a known number of clusters and cluster membership is used to test the performance of different clustering and data preparation techniques. For a complex data set from the Kola Peninsula, cluster analysis is applied to explore regional data structures.
Zero-valent iron and organic carbon mixtures for remediation of acid mine drainage: Batch experiments by Matthew B.J. Lindsay; Carol J. Ptacek; David W. Blowes; W. Douglas Gould (2214-2225).
A series of laboratory batch experiments was conducted to evaluate the potential for treatment of acid mine drainage (AMD) using organic C (OC) mixtures amended by zero-valent Fe (Fe0). Modest increases in SO4 reduction rates (SRRs) of up to 15% were achieved by augmenting OC materials with 5 and 10 dry wt% Fe0. However, OC was essential for supporting SO4 reducing bacteria (SRB) and therefore SO4 reduction. This observation suggests a general absence of autotrophic SRB which can utilize H2 as an electron donor. Sulfate reduction rates (SRRs), calculated using a mass-based approach, ranged from −12.9 to −14.9 nmol L−1 d−1 g−1 OC. Elevated populations of SRB, iron reducing bacteria (IRB), and acid producing (fermentative) bacteria (APB) were present in all mixtures containing OC. Effective removal of Fe (91.6–97.6%), Zn (>99.9%), Cd (>99.9%), Ni (>99.9%), Co (>99.9%), and Pb (>95%) was observed in all reactive mixtures containing OC. Abiotic metal removal was achieved with Fe0 only, however Fe, Co and Mn removal was less effective in the absence of OC. Secondary disordered mackinawite [Fe1+x S] was observed in field-emission scanning electron microscopy (FE-SEM) backscatter electron micrographs of mixtures that generated SO4 reduction. Energy dispersive X-ray (EDX) spectroscopy revealed that Fe–S precipitates were Fe-rich for mixtures containing OC and Fe0, and S-rich in the absence of Fe0 amendment. Sulfur K-edges determined by synchrotron-radiation based bulk X-ray absorption near-edge structure (XANES) spectroscopy indicate solid-phase S was in a reduced form in all mixtures containing OC. Pre-edge peaks on XANES spectra suggest tetragonal S coordination, which is consistent with the presence of an Fe–S phase such as mackinawite. The addition of Fe0 enhanced AMD remediation over the duration of these experiments, however long-term evaluation is required to identify optimal Fe0 and OC mixtures.
Evidence for cross formational hot brine flow from integrated 87Sr/86Sr, REE and fluid inclusions of the Ordovician veins in Central Tarim, China by Chunfang Cai; Kaikai Li; Hongtao Li; Baoshou Zhang (2226-2235).
Rare earth elements, δ 34S, 87Sr/86Sr and δ 18O were determined, and fluid inclusions were analyzed of fracture filling barite, anhydrite, fluorite, calcite and quartz from Upper Ordovician carbonates in Central Tarim, China. The aim was to assess the origin, evolution and flow of fluid in the fractures. There was mixing of relatively hot Ba-rich and 87Sr-rich fluid with in situ basinal water and fresh water which was relatively cool and more radiogenic. The hotter fluid is hydrothermal as indicated by homogenization temperatures (HTs) about 20 °C higher than the formation, and was most likely derived from Precambrian to Lower Cambrian clastic rocks or/and from the basement through faults. This is because almost all of 87Sr/86Sr ratios of late stage fracture-fillings (mainly 0.70889–0.71036) and present brines are higher than that of Upper Ordovician limestones. The hydrothermal fluid was enriched in F−, Eu2+, Ba2+, Sr2+ and Zn2+ during migration as indicated by the positive relationships of Eu to Sr, Ba and Zn. When the hydrothermal fluid mixed with local basinal water, it precipitated isotopically-normal S anhydrite, fluorite and calcite with positive Eu anomalies. The precipitation of these Ca-minerals was followed by thermochemical SO4 reduction (TSR) of dissolved sulphates by hydrocarbons. It was likely that only part of the SO 4 2 - was reduced and the generated H2S leaked out, thus barite deposited from residual SO 4 2 - has abnormally high δ 34S values from 42‰ to 47‰ and the generated H2S is isotopically light from 15‰ to 18‰. Subsequently, hydrothermal fluid was likely to have mixed with relatively cool and more 87Sr-rich freshwater, resulting in precipitation of quartz and fluorite with salinities as low as 0.5 wt% NaCl equiv. and 87Sr/86Sr ratios up to 0.71036.
Arsenic release from biotite into a Holocene groundwater aquifer in Bangladesh by Ashraf Ali Seddique; Harue Masuda; Muneki Mitamura; Keiji Shinoda; Toshiro Yamanaka; Takaaki Itai; Teruyuki Maruoka; Kenji Uesugi; Kazi Matin Ahmed; Dipak Kumar Biswas (2236-2248).
Continuous core sediments (to a depth of 90.1 m) taken at a transitional area of Holocene and Pleistocene deposits in Sonargaon, Bangladesh were characterized for their mineralogy and chemistry. Among the sediments of the lower part of the Holocene aquifer (depth: 18–29 m), where most domestic wells are installed, As is mostly fixed in biotite and organic phases. A positive correlation of As concentration with those of Al and Fe but not that of total organic C clearly suggests that biotite is a primary source of As. Although microbial reduction–dissolution of As-containing Fe oxyhydroxides is thought to cause As-enriched groundwater in the Ganges–Brahmaputra–Meghna delta plain, the authors conclude that chemical weathering of biotite is the primary formation mechanism and prevailing reducing conditions contribute to the expansion of As-enriched groundwater in the study area.
Secondary phase formation on UO2 in phosphate media by A. Rey; J. Giménez; I. Casas; F. Clarens; J. de Pablo (2249-2255).
The dissolution of UO2 (a chemical analog of uraninite and of spent nuclear fuel) has been studied by using a flow-through reactor. The UO2 dissolution rates at total PO 4 3 - concentrations of 10−4, 10−5, and 10−6 mol dm−3 have been determined to be: 1.3 × 10−10 mol m−2 s−1, 6.7 × 10−11 mol m−2 s−1, and 2.0 × 10−11 mol m−2 s−1, respectively. The dissolution rates determined are found to be higher than the ones determined for similar carbonate concentrations. Moreover, the surface of the UO2 has been studied in static tests by means of the scanning force microscopy technique (SFM) in order to follow the formation of any secondary solid phase on its surface. The formation of chernikovite (H2(UO2)2(PO4)2 · 8H2O) has been observed at a 10−4 M total PO 4 3 - concentration, while no uranyl-phosphate secondary phases have been found at lower PO 4 3 - concentrations. In experiments performed in the presence of both carbonate and phosphate, no precipitation of secondary phases has been observed. It is postulated that this is due to the formation of the highly stable uranyl-carbonate complexes in solution.
Effect of iron and carbonation on the diffusion of iodine and rhenium in waste encasement concrete and soil fill material under hydraulically unsaturated conditions by Dawn M. Wellman; Kent E. Parker; Laura Powers; Greg A. Whyatt; Libby N. Clayton; Shas V. Mattigod; Marcus I. Wood (2256-2271).
Assessing long-term performance of Category 3 cement wasteforms and accurate prediction for radionuclide encasement requires knowledge of the radionuclide–cement interactions and mechanisms of retention (i.e. sorption or precipitation). A set of sediment-concrete half-cell diffusion experiments was conducted under unsaturated conditions (4% and 7% by weight moisture content) using carbonated and non-carbonated concrete–soil half cells. Results indicate the behavior of Re and I release was comparable within a given half-cell test. Diffusivity in soil is a function of moisture content; a 3% increase in moisture content affords a one to two order of magnitude increase in diffusivity. Release of I and Re was 1–3 orders of magnitude less from non-carbonated, relative to carbonated, concrete monoliths. Inclusion of Fe in non-carbonate monoliths resulted in the lowest concrete diffusivity values for both I and Re. This suggests that in the presence of Fe, I and Re are converted to reduced species, which are less soluble and better retained within the concrete monolith. The release of I and Re was greatest from Fe-bearing, carbonated concrete monoliths, suggesting carbonation negates the effect of Fe on the retention of I and Re within concrete monoliths. This is likely due to enhanced formation of microcracks in the presence of Fe, which provide preferential paths for contaminant migration. Although the release of I and Re were greatest from carbonated concrete monoliths containing Fe, the migration of I and Re within a given half cell is dependent on the moisture content, soil diffusivity, and diffusing species.
Anaerobic decomposition of tropical soils and plant material: Implication for the CO2 and CH4 budget of the Petit Saut Reservoir by Frédéric Guérin; Gwenaël Abril; Alexis de Junet; Marie-Paule Bonnet (2272-2283).
Tropical hydroelectric reservoirs contribute significantly to atmospheric CH4 and CO2 emissions. To evaluate the contribution of the mineralization of the flooded soils and biomass to these atmospheric gas emissions, field and laboratory experiments were conducted. Cores were retrieved inform the littoral zone of the Petit Saut Reservoir (French Guiana), flooded 10 a prior to sampling, and different soils and plant material in the tropical forest surrounding the reservoir. All the samples were flooded and incubated in anoxic conditions in the dark at 30 °C. The potential CH4 and CO2 production rates were determined. Soils and plant material from the tropical forest were incubated over one year and the production measurements were performed at a frequency of 1–5 months. Methane and CO2 production rates of soils and littoral sediments were linearly correlated to the organic C (OC) content of the slurries. The slopes of the relationships were 2.6 × 10 2 ± 5.6 × 10 1 nmol ( CH 4 ) g OC ( dry ) - 1 h - 1 and 3.5 × 10 2 ± 6.9 × 10 1 nmol ( CO 2 ) g OC ( dry ) - 1 h - 1 . For plant material, no relationship between the production rates and the OC content was found and on average over the year of incubation, production rates were 2.4 × 10 3 ± 1 × 10 3 nmol ( CH 4 ) g OC ( dry ) - 1 h - 1 and 3.9 × 10 3 ± 5 × 10 3 nmol ( CO 2 ) g OC ( dry ) - 1 h - 1 , which is one order of magnitude higher than the mineralization of the soils and sediments. Extrapolated at the scale of the Petit Saut Reservoir over 10 a, these results show that the mineralization of the soil and the plant biomass initially flooded contributed to 75–95% of the total C emissions to the atmosphere since the flooding of the reservoir. Methane: CO2 molar ratios were 3 times higher for anaerobic decomposition than atmospheric emissions, quantitatively consistent with aerobic CH4 oxidation.
Carbon sources and signals through time in an Alpine groundwater Basin, Sagehen California by Erik D. Blumhagen; Jordan F. Clark (2284-2291).
In 2003, chlorofluorocarbon (CFC) apparent ages, major ion chemistry and C isotopes were determined in nine springs from Sagehen Basin, a high elevation watershed in the eastern Sierra Nevada. Springs with similar apparent ages, which ranged between 15 and 45 a, had very similar chemistry despite being found in different areas of the watershed. In agreement with earlier studies, concentrations of rock-derived cations (Ca2+ and Na+), conductivity, temperature and pH increase with apparent age, documenting the chemical evolution of this groundwater system. In contrast with the cation data, δ13C and ΣCO2 show no correlation with apparent age. δ13C displays a strong linear relationship with 1/ΣCO2 (R 2 = 0.91). This is consistent with results from a previously developed soil respiration/diffusion model. Spring radiocarbon content ranged between 85 and 110 pmc and varied with apparent age, whereby the youngest groundwater has the highest radiocarbon values. The spring radiocarbon is set by the soil pCO2 and its trend can be best described assuming the soil CO2 is composed of a mixture of 50–66% fast- (15–25 a) and 33–50% slow- (4 ka) cycling components. These results are consistent with previous soil C studies. The C isotope data indicate that in Sagehen Basin the groundwater ΣCO2 is inherited from the soil zone with little, if any, contribution from the dissolution of disseminated calcite.
Carbonation of alkaline paper mill waste to reduce CO2 greenhouse gas emissions into the atmosphere by R. Pérez-López; G. Montes-Hernandez; J.M. Nieto; F. Renard; L. Charlet (2292-2300).
The global warming of Earth’s near-surface, air and oceans in recent decades is a direct consequence of anthropogenic emission of greenhouse gases into the atmosphere such as CO2, CH4, N2O and CFCs. The CO2 emissions contribute approximately 60% to this climate change. This study investigates experimentally the aqueous carbonation mechanisms of an alkaline paper mill waste containing about 55 wt% portlandite (Ca(OH)2) as a possible mineralogical CO2 sequestration process. The overall carbonation reaction includes the following steps: (1) Ca release from portlandite dissolution, (2) CO2 dissolution in water and (3) CaCO3 precipitation. This CO2 sequestration mechanism was supported by geochemical modelling of final solutions using PHREEQC software, and observations by scanning electron microscope and X-ray diffraction of final reaction products. According to the experimental protocol, the system proposed would favour the total capture of approx. 218 kg of CO2 into stable calcite/ton of paper waste, independently of initial CO2 pressure. The final product from the carbonation process is a calcite (ca. 100 wt%)-water dispersion. Indeed, the total captured CO2 mineralized as calcite could be stored in degraded soils or even used for diverse industrial applications. This result demonstrates the possibility of using the alkaline liquid–solid waste for CO2 mitigation and reduction of greenhouse effect gases into the atmosphere.
Chemical controls on the solubility, speciation and mobility of lanthanum at near surface conditions: A geochemical modeling study by Ziya S. Cetiner; Yongliang Xiong (2301-2315).
Recent experimental determinations of the solubility products of common rare earth minerals such as monazite and xenotime and stability constants for chloride, sulfate, carbonate and hydroxide complexes provide a basis to model quantitatively the solubility, and therefore the mobility, of rare earth elements (REE) at near surface conditions. Data on the mobility of REE and stabilities of REE complexes at near-neutral conditions are of importance to safe nuclear waste disposal, and environmental monitoring. The aim of this study is to understand REE speciation and solubility of a given REE in natural environments. In this study, a series of formation constants for La aqueous complexes are recommended by using the specific interaction theory (SIT) for extrapolation to infinite dilution. Then, a thermodynamic model has been employed for calculation of the solubility and speciation of La in soil solutions reacted with the La end-member of mineral monazite (LaPO4), and other La-bearing solid phases including amorphous lanthanum hydroxide (La(OH)3, am) and different La carbonates, as a function of various inorganic and organic ligand concentrations. Calculations were carried out at near-neutral pH (pH 5.5–8.5) and 25 °C at atmospheric CO2 partial pressure. The model takes account of the species: La3+, LaCl2+, LaCl 2 + , LaCl 3 0 , LaCl 4 - , LaSO 4 + , La ( SO 4 ) 2 - , LaCO 3 + , La ( CO 3 ) 2 - , LaHCO 3 2 + , La(OH)2+, LaOx+, La ( Ox ) 2 - , LaAc2+ and La ( Ac ) 2 - (where Ox2− = oxalate and Ac− = acetate).The calculations indicate that the La species that dominate at pH 5.5–8.5 in the baseline model soil solution (BMSS) include La3+, LaOx+, LaSO 4 + , LaCO 3 + and La ( CO 3 ) 2 - in order of increasing importance as pH rises. The solubility of monazite in the BMSS remains less than ∼3 × 10−9 M, exhibiting a minimum of ∼2 × 10−12 M at pH 7.5. The calculations quantitatively demonstrate that the concentrations of La controlled by the solubility of other La-bearing solid phases are many orders of magnitude higher than those controlled by monazite in the pH range from 5.5 to 8.5, suggesting that monazite is likely to be the solubility-controlling phase at this pH range. The calculations also suggest that significant mobility of La (and other REE) is unlikely because high water–rock ratios on the order of at least 104 (mass ratio) are required to move 50% of the La from a soil. An increase in concentration of oxalate by one order of magnitude from that of the baseline model solution results in the dominance of LaOx+ at pH 5.5–7.5. Similarly, the increase in concentration of SO 4 2 - by one order of magnitude makes LaSO 4 + the dominant species at pH 5.5–7.5. Above pH 7.5, carbonate complexes are important. The increase in oxalate or SO 4 2 - concentrations by one order of magnitude can enhance the solubility of monazite by a factor of up to about 6 below neutral pH, in comparison with that in the baseline model soil solution. From pH 7.0 to 8.5, the solubility of monazite in the soil solutions with higher concentrations of oxalate or SO 4 2 - is similar, or almost identical, to that in the BMSS.
Galvanic interactions between metal sulfide minerals in a flowing system: Implications for mines environmental restoration by Qingyou Liu; Heping Li; Li Zhou (2316-2323).
Managing mine water that has been contaminated with metal sulfide minerals due to galvanic corrosion is becoming an increasingly important environmental problem. Here, galvanic corrosion was investigated by studying galvanic interactions between pyrite–chalcopyrite and pyrite–galena in flowing mediums such as mine discharge water and flowing rainwater. The results showed that the corrosion current density of pyrite–galena is greater than that of pyrite–chalcopyrite under identical conditions. The corrosion current density of the galvanic cell tends to increase with increasing concentrations of strongly oxidizing ions (e.g., Fe3+) in the flowing medium, whereas the existence of non-oxidizing and non-reducing ions (e.g., Na+) have no obvious influence on the galvanic cell. In addition, the corrosion current density increases with increasing flow rate. Using the galvanic model, mixed potential theory and Butler–Volmer equation, the experimental results were explained theoretically. Because these experiments were performed under conditions very similar to those seen in mine discharge water and flowing rainwater, these results have direct implications for the future management and control of environmental pollution from mining operations.
Multivariate analysis of contamination in the mining district of Linares (Jaén, Spain) by J. Martínez López; J. Llamas Borrajo; E. De Miguel García; J. Rey Arrans; Ma C. Hidalgo Estévez; A.J. Sáez Castillo (2324-2336).
Historically, a significant level of mining activity has taken place in the batholite-related metalogenic enclave of Linares (Jaén province, Spain), associated with Pb–Ag, Cu, Zn and Fe sulphides and Ba sulphate mineralization, though mining here has now been abandoned. Additionally, the area features a significant amount of urban, industrial and agricultural activities. These considerations, taken together, explain the need to assess the levels of concentration of trace elements and to determine their relationship with geogenic and anthropogenic factors. For geochemical characterisation of the soil, the region has been divided into 126 grid squares with an area of 1 km2. For each grid square, 32 trace elements have been analysed. Elemental concentrations of Cu, Pb, Zn, As and Mn have been included in statistical analyses. According to the reference levels established by the Regional Government (Junta de Andalucía), soils in a large part of the study area require amendment applications. The comparison of the mean content for each grid square with the reference levels reveals a significant degree of contamination of the soil by Cu (719 mg kg−1), Pb (22,964 mg kg−1) and As (100 mg kg−1) in those grid squares affected by metallurgic activities. By means of factor analysis, four scores have been identified which together account for 80% of the variance observed. The first score is highly correlated with the logarithms of the variables Fe, Th, La, Ti, Al, Na, K, Zr, Y, Nb, Be and Sc. It is a “natural” factor that indicates the type of soil matrix (fundamentally granites and, to a lesser degree, Triassic materials). The second score shows high correlation with the logarithms of the variables Mo, Cu, Pb, Zn, Ag, Co, Mn, As, Cd, Sb, Ba, W and Sn, and is the “metallization” factor related to the mineralization that has been exploited. The third score is mainly determined by the logarithms of the variables Sr, Ca and Mg. This is a “natural” factor that indicates a type of carbonate soil matrix (Miocene). Finally, the fourth factor groups the logarithms of the variables Ni, V and Cr, elements that are associated with the combustion of fossil fuels. Analysis of the patterns of each of the factors identified enabled achieving a global characterisation of the study area. Cluster analysis of the observations showed there to be five clusters relating to the grid squares, differentiated by lithologies and degrees of contamination. These clusters are used to determine the background of granite and to calculate the anomalous load.
Origin of groundwater salinity and hydrogeochemical processes in a confined coastal aquifer: Case of the Rhône delta (Southern France) by Veronique de Montety; Olivier Radakovitch; Christine Vallet-Coulomb; Bernard Blavoux; Daniel Hermitte; Vincent Valles (2337-2349).
The Rhône delta, South of France (Camargue, 750 km2) is a coastal saline wetland located along the Mediterranean Sea. The confined aquifer of this delta shows high values of electrical conductivity rising from the north (4 mS/cm) to the shoreline (58 mS/cm). This work aims to identify the origin of groundwater salinity and the geochemical processes occurring in this coastal confined aquifer according to the degree of salinity. A natural tracing approach is considered using monthly sampling in 8 piezometers for chemical and isotopic analyses (18O, 2H, 13CTDIC). Ionic and isotopic ratios demonstrate that strong salinities are due to a simple mixing between Mediterranean seawater and freshwater; seawater contribution reaches up to 98% at 8 km from the shoreline. Seawater intrusion induces a particular groundwater chemistry which varies with the degree of seawater contribution: (1) In the less saline part of the aquifer (seawater contribution <20%), the intrusion induces an increase of Na+ in groundwater leading to Ca2+/Na+ exchange processes. The δ13CTDIC analyses show that matrix exchange processes most likely occur for the less saline samples. (2) In the saline part of the aquifer (seawater contribution >20%), the intrusion induces SO4 reduction which is confirmed by highly depleted δ13CTDIC values (up to −19‰). The δ13CTDIC also reveals that methanogenesis processes may occur in the most reductive part of the aquifer. Due to SO4 reduction, the intrusion induces a shift in carbonate equilibrium leading to supersaturation with respect to dolomite and/or magnesian calcite. Thus carbonate precipitation may occur in the area strongly influenced by seawater.
Monitoring and modelling of the solid-solution partitioning of metals and As in a river floodplain redox sequence by Thomas J. Schröder; Willem H. van Riemsdijk; Sjoerd E.A.T.M. van der Zee; Jos P.M. Vink (2350-2363).
For a period of 2 a, pore water composition in a heavily contaminated river floodplain soil was monitored in situ. Pore water samples were collected 12 times over all seasons in a profile ranging from aerobic to sulphidic redox conditions, and As, Cd, Cr, Cu, Pb, Zn, Mn, Fe, Ca, Cl, SO4, DOC, IOC and pH were determined. The variability of pH, IOC, DOC and Ca was found to be rather small during the year and within the profile (rsd < 0.04, 0.16, 0.24 and 0.22, respectively). The temporal variability of the metal and As concentrations was small, too, whereas changes with depth were distinct. Under sulphidic conditions, concentrations were below 1 μg L−1 (Cd, Cu, Pb) or 10 μg L−1 (Zn, As). The data set was compared with results from a geochemical model that was fully parameterised from literature data and included equilibrium speciation, sorption and mineral dissolution. The general pattern of the solid–solution partitioning of Cd, Cu, Zn and As in the profile was predicted well by mechanistic geochemical modelling on the basis of solid phase composition. Metals strongly bound to organic matter such as Cd and Cu were predicted better than metals mainly present within a mineral. Detailed information regarding the presence of colloidal Fe and Mn in pore water might improve the prediction of the solid–solution partitioning of a number of metals. The study also indicates that the chemical behaviour of Pb is still not understood sufficiently.
Redox front formation in an uplifting sedimentary rock sequence: An analogue for redox-controlling processes in the geosphere around deep geological repositories for radioactive waste by H. Yoshida; R. Metcalfe; K. Yamamoto; Y. Murakami; D. Hoshii; A. Kanekiyo; T. Naganuma; T. Hayashi (2364-2381).
Subsurface redox fronts control the mobilization and fixation of many trace elements, including potential pollutants such as certain radionuclides. Any safety assessment for a deep geological repository for radioactive wastes needs to take into account adequately the long-term redox processes in the geosphere surrounding the repository. To build confidence in understanding these processes, a redox front in a reduced siliceous sedimentary rock distributed in an uplifting area in Japan has been studied in detail. Geochemical analyses show increased concentrations of Fe and trace elements, including rare earth elements (REEs), at the redox front, even though concentrations of reduced rock matrix constituents show little change. Detailed SEM observations revealed that fossilized microorganisms composed of amorphous granules made exclusively of Fe and Si occur in the rock’s pore space. Microbial 16S rDNA analysis suggests that there is presently a zonation of different bacterial groups within the redox band, and bacterial zonation played an important role in the concentration of Fe-oxyhydroxides at the redox front. These water–rock–microbe interactions can be considered analogous to the processes occurring in the redox fronts that would develop around geological repositories for radioactive waste. Once formed, the Fe-oxyhydroxides within such a front would be preserved even after reducing conditions resume following repository closure.
Isotopic composition of sulfate as a tracer of natural and anthropogenic influences on groundwater geochemistry in an urban sandstone aquifer, Birmingham, UK by Simon Bottrell; John Tellam; Rebecca Bartlett; Anwen Hughes (2382-2394).
Development and management of urban groundwater resources is limited in practice by a lack of knowledge of the nature, distribution and sources of groundwater contamination in an urban aquifer that may have had complex land use and abstraction history. Sulfate is associated with many of the solute sources to urban groundwater and in this study the use of dual isotope (δ18O and δ34S) “fingerprinting” of SO 4 2 - in groundwater to assess the contribution of different sources to urban groundwater is investigated. Groundwater (70 locations) and surface water samples from the city of Birmingham on the Triassic Sherwood sandstone aquifer have been analyzed for inorganic chemical and SO 4 2 - isotopic composition. Isotopic compositions of SO 4 2 - associated with various solute sources have also been determined. Sulfate derived from pyrite oxidation during recharge through Quaternary Drift deposits is characteristically depleted in 18O and 34S compared to other sources and is ubiquitous in unconfined zone groundwater, though the contribution from this source has increased markedly following draw down induced by abstraction from the aquifer. In unpolluted groundwaters other SO 4 2 - sources are dissolution of evaporite minerals (confined zone) and rainfall (unconfined zone). Unfortunately, SO 4 2 - isotopic composition cannot distinguish between made-ground (i.e. artificial man-made ground, usually demolition waste) and sewage sources of SO 4 2 - , which constitute the major contributions to SO 4 2 - in polluted urban groundwater at most sites. Contributions of SO 4 2 - from spilt industrial acids do have a distinctive isotopic composition seen at many metal-working and former metal-working sites. Estimates of solute contributions derived from these sources derived in this way provide a useful check on the “calibration” of aquifer and pollutant flux recharge models for urban groundwater.
A detailed pyrolysis-GC/MS analysis of a black carbon-rich acidic colluvial soil (Atlantic ranker) from NW Spain by Joeri Kaal; Antonio Martínez-Cortizas; Klaas G.J. Nierop; Peter Buurman (2395-2405).
Despite the potentially large contribution of black carbon (BC) to the recalcitrant soil organic matter pool, the molecular-level composition of aged BC has hardly been investigated. Pyrolysis-GC/MS, which provides structural information on complex mixtures of organic matter, was applied to the NaOH-extractable organic matter of an acidic colluvial soil (Atlantic ranker) sampled with high resolution (5 cm) that harbours a fire record of at least 8.5 ka. Additionally, 5 charcoal samples from selected soil layers were characterised using pyrolysis-GC/MS for comparison. Pyrolysis-GC/MS allowed distinguishing between BC and non-charred organic matter. It is argued that a large proportion of the polycyclic aromatic hydrocarbons (PAHs), benzenes and benzonitrile in the pyrolysates of the extractable organic matter, together accounting for 21–54% of total identified peak area, derived from BC. In charcoal samples, these compounds accounted for 60–98% of the pyrolysis products. The large quantity of BC in almost all samples suggested a key role of fire in Holocene soil evolution. The high C content of the soil (up to 136 g C kg−1 soil) may be attributed to the presence of recalcitrant organic C as BC, in addition to the sorptive preservation processes traditionally held responsible for long-term C storage in acid soils. Interactions between reactive Al hydroxides and BC could explain the longevity of BC in the soil. This work is the first thorough pyrolysis-GC/MS based study on ancient fire-affected organic matter.
Ion microprobe Sr isotope analysis of carbonates with about 5 μm spatial resolution: An example from an ayu otolith by Yuji Sano; Kotaro Shirai; Naoto Takahata; Hiroshi Amakawa; Tsuguo Otake (2406-2413).
A high lateral resolution secondary ion mass spectrometer (NanoSIMS NS50 ion microprobe) has been used to measure 87Sr/86Sr ratios in natural CaCO3 samples. A ∼2 nA O− primary beam was used to sputter a 5–7-μm diameter crater on the sample surface and secondary positive ions were extracted for mass analysis using an accelerating voltage of 8 kV and a Mattauch–Herzog geometry. The multi-collector system was adjusted to detect 43Ca+ (by a detector EM#2), 80 Ca 2 + (EM#3), 86Sr+ (EM#4), and 87Sr+ (EM#4b) ions at the same time. Then the magnetic field was scanned for the EM#4 to detect 85Rb+, 86Sr+ and 87Sr+, while the EM#4b can measure 86Sr+, 87Sr+ and 88Sr+, respectively. A mass resolution of 3600 at 10% peak height was attained with a flat peak top, while the sensitivity of Sr was about 10 cps/nA/ppm. An aragonite sample (coral skeleton standard; JCp-1) was used as a reference for Sr isotope ratio calibration. Repeated analyses of the JCp-1 show that the 87Sr/86Sr ratio agrees well with the seawater signature within a precision of 0.3‰ at 2σ, after the series of corrections such as the Ca dimer, 87Rb, and a mass bias estimated by the 88Sr/86Sr ratio. The method was applied to an otolith (ear-stone) from ayu (Plecoglossus altivelis altivelis) collected from the Yodo river, Japan. Although experimental errors are relatively large, up to 3‰ at 2σ, the ratios of the core region are higher than the seawater signature while more distal values agree well with seawater. The very outermost part again shows the relatively higher 87Sr/86Sr ratios. The spatial variation of 87Sr/86Sr ratios was consistent with amphidromous migration of the fish, namely, born in the lake and grown in the coastal sea and finally collected in a river.
Field trial using bone meal amendments to remediate mine waste derived soil contaminated with zinc, lead and cadmium by I.R. Sneddon; M. Orueetxebarria; M.E. Hodson; P.F. Schofield; E. Valsami-Jones (2414-2424).
Bone meal amendments are being considered as a remediation method for metal-contaminated wastes. In various forms (biogenic, geogenic or synthetic), apatite, the principal mineral constituent of bone, has shown promise as an amendment to remediate metal-contaminated soils via the formation of insoluble phosphates of Pb and possibly other metals. The efficacy of commercially available bovine bone meal in this role was investigated in a field trial at Nenthead, Cumbria with a mine waste derived soil contaminated with Zn, Pb and Cd. Two 5 m2 plots were set up; the first as a control and the second, a treatment plot where the soil was thoroughly mixed with bone meal to a depth of 50 cm at a soil to amendment ratio of 25:1 by weight. An array of soil solution samplers (Rhizon SMS™) were installed in both plots and the soil pore water was collected and analysed for Ca, Cd, Zn and Pb regularly over a period of 2 a. Concurrently with the field trial, a laboratory trial with 800 mm high and 100 mm wide leaching columns was conducted using identical samplers and with soil from the field site.A substantial release of Zn, Pb, Cd and Ca was observed associated with the bone meal treatment. This release was transient in the case of the leaching columns, and showed seasonal variation in the case of the field trial. It is proposed that this effect resulted from metal complexation with organic acids released during breakdown of the bone meal organic fraction and was facilitated by the relatively high soil pH of 7.6–8.0. Even after this transient release effect had subsided or when incinerated bone meal was substituted in order to eliminate the organic fraction, no detectable decrease in dissolved metals was observed and no P was detected in solution, in contrast with an earlier small column laboratory study. It is concluded that due to the relative insolubility of apatite at above-neutral pH, the rate of supply of phosphate to soil solution was insufficient to result in significant precipitation of metal phosphates and that this may limit the effectiveness of the method to more acidic soils.
Stable carbon and oxygen isotope investigation in historical lime mortar and plaster – Results from field and experimental study by B. Kosednar-Legenstein; M. Dietzel; A. Leis; K. Stingl (2425-2437).
Lime mortar and plaster were sampled from Roman, medieval and early modern buildings in Styria. The historical lime mortar and plaster consist of calcite formed in the matrix during setting and various aggregates. The stable C and O isotopic composition of the calcite matrix was analyzed to get knowledge about the environmental conditions during calcite formation. The δ 13Cmatrix and δ 18Omatrix values range from −31 to 0‰ and −26 to −3‰(VPDB), respectively. Obviously, such a range of isotope values does not represent the local natural limestone assumed to be used for producing the mortar and plaster. In an ideal case, the calcite matrix in lime mortar and plaster is isotopically lighter in the exterior vs. the interior mortar layer according to the relationship δ 18Omatrix = 0.61 · δ 13Cmatrix − 3.3 (VPDB). Calcite precipitation by uptake of gaseous CO2 into alkaline Ca(OH)2 solutions shows a similar relationship, δ 18Ocalcite = 0.67 · δ 13Ccalcite − 6.4 (VPDB). Both relationships indicate that the 13C/12C and 18O/16O values of the calcite reflect the setting behaviour of the lime mortar and plaster. Initially, CO2 from the atmosphere is fixed as calcite, which is accompanied by kinetic isotope fractionation mostly due to the hydroxylation of CO2 (δ 13Cmatrix ≈ −25‰ and δ 18Omatrix ≈ −20‰). As calcite formation continued the remaining gaseous CO2 is subsequently enriched in 13C and 18O causing later formed calcite to be isotopically heavier along the setting path in the matrix. Deviations from such an ideal isotopic behaviour may be due to the evolution of H2O, e.g. evaporation, the source of CO2, e.g. from biogenic origin, relicts of the natural limestone, and secondary effects, such as recrystallization of calcite. The results of the field and experimental study suggest that isotope values can be used as overall proxies to decipher the origin of carbonate and the formation conditions of calcite in the matrix of ancient and recent lime mortar and plaster. Moreover, these proxies can be used to select calcite matrix from historical lime mortar and plaster for 14C dating.
Identification of sources and causes of leakage on a zoned earth dam in northern Taiwan: Hydrological and isotopic evidence by Tsung-Ren Peng; Chung-Ho Wang (2438-2451).
Seepage through an earth dam body must be regulated as a well–planned process, if it is not properly managed, the abnormal seepage may cause dam failure. This study employed stable isotopic and statistical methods to identify the source and cause of an abnormal leakage on the zoned earth dam of the Xin–Shan reservoir located in northern Taiwan. Water samples from the dam area over a 2-a period were collected and analyzed for their stable O and H isotope compositions. In addition, a 4-a period of hydrological data, including rainfall, reservoir level, well level, seepage of filter drainage and leakage, were statistically analyzed with a stepwise multiple regression approach. Both the stable isotopic and hydrological results indicate that the abnormal leakage on the dam shell comes from the filter drainage in the dam. The reason for abnormal leakage is due to unexpected and significant precipitation–sourced water flowing into the dam’s body. The dam filter fails to drain out the incoming water sufficiently, thus generating the abnormal seepage. In addition, the defect in the dam filter may also cause the drainage filter to drain off reservoir seepage inadequately. Therefore, it is suggested that checking the filter function and preventing excessive precipitation–sourced water from flowing into the dam are the two top priorities for the follow-up remedial strategy of the dam.
High-sensitive measurement of uranium LIII-edge X-ray absorption near-edge structure (XANES) for the determination of the oxidation states of uranium in crustal materials by Yuhei Yamamoto; Yoshio Takahashi; Yutaka Kanai; Yoshio Watanabe; Tomoya Uruga; Hajime Tanida; Yasuko Terada; Hiroshi Shimizu (2452-2461).
The uranium LIII-edge XANES spectra for natural rocks at the concentration range of 0.96–124 mg kg−1 were measured using a log spiral bent crystal Laue analyzer (BCLA) combined with a multi-element Ge detector. It was found that the quality of the XANES spectra using the BCLA was greatly improved due to a reduction of interfering fluorescence from major components such as Rb and Sr. The ratio of signal to background intensities in the U LIII-edge XANES spectra increased by a factor of 2.9–17 with the use of the BCLA, which greatly enhanced the detection limit for the speciation of the oxidation states of U or the U(IV)/U(VI) ratio of natural samples. In addition, it was demonstrated that the fluorescence XANES method coupled with the BCLA enable determination of the speciation of U for various natural samples such as acidic igneous rocks, ferromanganese nodules, sediments, and some sedimentary rocks such as shale and limestone.
High arsenic and boron concentrations in groundwaters related to mining activity in the Bigadiç borate deposits (Western Turkey) by Ünsal Gemici; Gültekin Tarcan; Cahit Helvacı; A. Melis Somay (2462-2476).
This study documents the environmental impacts of borate mines in Bigadiç district, which are the largest colemanite and ulexite deposits in the world. Borate-bearing formations have affected the concentrations of some contaminants in groundwater. Groundwater quality is directly related to the borate zones in the mines as a result of water–rock interaction processes. Calcium is the dominant cation and waters are Ca–SO4 and HCO3 type in the mine (Tülü borate mine) from which colemanite is produced. However in the Simav and Acep Borate Mines, ulexite and colemanite minerals are produced and waters from these open pit mines are Na–HCO3–SO4 types. High SO4 concentrations (reaching 519 mg/L) might be explained by the existence of anhydrite, gypsum and celestite minerals in the borate zone. Groundwater from tuff and borate strata showed relatively low pH values (7–8) compared to surface and mine waters (>8). EC values ranged from 270 to 2850 μS/cm. Boron and As were the two important contaminants determined in the groundwaters around the Bigadiç borate mines. Arsenic is the major pollutant and it ranged from 33 to 911 μg/L in the groundwater samples. The concentrations of B in the study area ranged from 0.05 to 391 mg/L. The highest B concentrations were detected at the mine areas. The extension of the borate zones in the aquifer systems is the essential factor in the enrichment of B and As, and some major and trace elements in groundwaters are directly related to the leaching of the host rock which are mainly composed of tuffs and limestones. According to drinking water standards, all of the samples exceed the tolerance limit for As. Copper, Mn, Zn and Li values are enriched but do not exceed the drinking water standards. Sulfate, Al and Fe concentrations are above the drinking water standard for the groundwater samples.
In situ arsenic removal in an alkaline clastic aquifer by Alan H. Welch; Kenneth G. Stollenwerk; Angela P. Paul; Douglas K. Maurer; Keith J. Halford (2477-2495).
In situ removal of As from ground water used for water supply has been accomplished elsewhere in circum-neutral ground water containing high dissolved Fe(II) concentrations. The objective of this study was to evaluate in situ As ground-water treatment approaches in alkaline ground-water (pH > 8) that contains low dissolved Fe (<a few tens of μg/L). The low dissolved Fe content limits development of significant Fe-oxide and the high-pH limits As adsorption onto Fe-oxide. The chemistries of ground water in the two aquifers studied are similar except for the inorganic As species. Although total inorganic As concentrations were similar, one aquifer has dominantly aqueous As(III) and the other has mostly As(V). Dissolved O2, Fe(II), and HCl were added to water and injected into the two aquifers to form Fe-oxide and lower the pH to remove As. Cycles of injection and withdrawal involved varying Fe(II) concentrations in the injectate. The As concentrations in water withdrawn from the two aquifers were as low as 1 and 6 μg/L, with greater As removal from the aquifer containing As(V). However, Fe and Mn concentrations increased to levels greater than US drinking water standards during some of the withdrawal periods. A balance between As removal and maintenance of low Fe and Mn concentrations may be a design consideration if this approach is used for public-supply systems. The ability to lower As concentrations in situ in high-pH ground water should have broad applicability because similar high-As ground water is present in many parts of the world.
Major and trace element geochemistry in Zeekoevlei, South Africa: A lacustrine record of present and past processes by Supriyo Kumar Das; Joyanto Routh; Alakendra N. Roychoudhury; J. Val Klump (2496-2511).
This study reports a multi-parameter geochemical investigation in water and sediments of a shallow hyper-eutrophic urban freshwater coastal lake, Zeekoevlei, in South Africa. Zeekoevlei receives a greater fraction of dissolved major and trace elements from natural sources (e.g., chemical weathering and sea salt). Fertilizers, agricultural wastes, raw sewage effluents and road runoff in contrast, constitute the predominant anthropogenic sources, which supply As, Cd, Cu, Pb and Zn in this lake. The overall low dissolved metal load results from negligible industrial pollution, high pH and elevated metal uptake by phytoplankton. However, the surface sediments are highly polluted with Pb, Cd and Zn. Wind-induced sediment resuspension results in increased particulate and dissolved element concentrations in bottom waters. Low C/N ratio (10) indicates primarily an algal source for the sedimentary organic matter. Variation in sedimentary organic C content with depth indicates a change in primary productivity in response to historical events (e.g., seepage from wastewater treatment plant, dredging and urbanization). Primary productivity controls the enrichment of most of the metals in sediments, and elevated productivity with higher accumulation of planktonic debris (and siltation) results in increased element concentration in surface and deeper sediments. Aluminium, Fe and/or Mn oxy-hydroxides, clay minerals and calcareous sediments also play an important role in adsorbing metals in Zeekoevlei sediments.
by Richard K. Glanzman (2512-2513).
Comment on “The biosphere: A homogeniser of Pb-isotope signals” by C. Reimann, B. Flem, A. Arnoldussen, P. Englmaier, T.E. Finne, F. Koller and Ø. Nordgulen by William Shotyk (2514-2518).
Comment on “The biosphere: A homogeniser of Pb-isotope signals” by C. Reimann, B. Flem, A. Arnoldussen, P. Englmaier, T.E. Finne, F. Koller and Ø. Nordgulen by Richard Bindler (2519-2526).
Reply to the comments on “The biosphere: A homogenizer of Pb-isotope signals” by Richard Bindler and William Shotyk by Clemens Reimann; Belinda Flem; Arnold Arnoldussen; Peter Englmaier; Tor Erik Finne; Friedrich Koller; Øystein Nordgulen (2527-2535).