Applied Geochemistry (v.47, #C)

Wellbore cement fracture evolution at the cement–basalt caprock interface during geologic carbon sequestration by Hun Bok Jung; Senthil Kabilan; James P. Carson; Andrew P. Kuprat; Wooyong Um; Paul Martin; Michael Dahl; Tyler Kafentzis; Tamas Varga; Sean Stephens; Bruce Arey; Kenneth C. Carroll; Alain Bonneville; Carlos A. Fernandez (1-16).
Composite Portland cement–basalt caprock cores with fractures, as well as neat Portland cement columns, were prepared to understand the geochemical and geomechanical effects on the integrity of wellbores with defects during geologic carbon sequestration. The samples were reacted with CO2–saturated groundwater at 50 °C and 10 MPa for 3 months under static conditions, while one cement–basalt core was subjected to mechanical stress at 2.7 MPa before the CO2 reaction. Micro-XRD and SEM–EDS data collected along the cement–basalt interface after 3-month reaction with CO2–saturated groundwater indicate that carbonation of cement matrix was extensive with the precipitation of calcite, aragonite, and vaterite, whereas the alteration of basalt caprock was minor. X-ray microtomography (XMT) provided three-dimensional (3-D) visualization of the opening and interconnection of cement fractures due to mechanical stress. Computational fluid dynamics (CFD) modeling further revealed that this stress led to the increase in fluid flow and hence permeability. After the CO2-reaction, XMT images displayed that calcium carbonate precipitation occurred extensively within the fractures in the cement matrix, but only partially along the fracture located at the cement–basalt interface. The 3-D visualization and CFD modeling also showed that the precipitation of calcium carbonate within the cement fractures after the CO2-reaction resulted in the disconnection of cement fractures and permeability decrease. The permeability calculated based on CFD modeling was in agreement with the experimentally determined permeability. This study demonstrates that XMT imaging coupled with CFD modeling represent a powerful tool to visualize and quantify fracture evolution and permeability change in geologic materials and to predict their behavior during geologic carbon sequestration or hydraulic fracturing for shale gas production and enhanced geothermal systems.

The adsorption of Eu(III) and Am(III) on Beishan granite: XPS, EPMA, batch and modeling study by Qiang Jin; Gang Wang; Mengtuan Ge; Zongyuan Chen; Wangsuo Wu; Zhijun Guo (17-24).
Display OmittedGranite has been chosen as a promising host rock for geological repository of high-level radioactive waste in many countries. However, the description of radionuclide adsorption on granite is subjected to its complicated composition and still a challenge. We studied the adsorption of Eu(III) and Am(III) on Beishan granite, a preliminary selection of host rock in China, as a function of pH, adsorbate concentration, ionic strength and the composition of background electrolytes. A surface complexation model was set up using Generalized Composite approach based on Eu(III) adsorption in NaCl electrolyte, supported by X-ray photoelectron spectroscopy and verified by Eu(III) adsorption in the presence of CO2 at P CO 2 = 10 - 3.58 atm and in CaCl2 electrolyte. The model was successfully extended to describe Am(III) adsorption in both NaCl and CaCl2 electrolytes. It was also found that temperature effect on Eu(III) adsorption was negligible at 25–80 °C, that the adsorption of Eu(III) on freshly crushed granite with “new” surfaces and aged granite with “old” surfaces were identical to each other, and that the presence of fulvic acid of 2–20 mg/L significantly declined the distribution coefficients of Eu(III) and Am(III) in high pH range. Electron probe micro analyses indicated that biotite had higher affinity for Eu(III) than other major minerals, such as oligoclase, quartz and orthoclase.

Evaluating the influence of road salt on water quality of Ohio rivers over time by Kelsey R. Dailey; Kathleen A. Welch; W. Berry Lyons (25-35).
Anthropogenic inputs have largely contributed to the increasing salinization of surface waters in central Ohio, USA. Major anthropogenic contributions to surface waters are chloride (Cl) and sodium (Na+), derived primarily from inputs such as road salt. In 2012–2013, central Ohio rivers were sampled and waters analyzed for comparison with historical data. Higher Cl and Na+ concentrations and fluxes were observed in late winter as a result of increased road salt application during winter months. Increases in both chloride/bromide (Cl/Br) ratios and nitrate (N-NO3 ) concentrations and fluxes were observed in March 2013 relative to June 2012, suggesting a mixture of road salt and fertilizer runoff influencing the rivers in late winter. For some rivers, increased Cl and Na+ concentrations and fluxes were observed at downstream sites near more urban areas of influence. Concentrations of Na+ were slightly lower than respective Cl concentrations (in equivalents). High Cl/Br mass ratios in the Ohio surface waters indicated the source of Cl was likely halite, or road salt. In addition, analysis of 36Cl/Cl ratios revealed low values suggestive of a substantial dissolved halite component, implying the addition of “old” Cl into the water system. Temporal trend analysis via the Mann–Kendall test identified increasing trends in Cl and Na+ concentration beginning in the 1960s at river locations with more complete historical datasets. An increasing trend in Cl flux through the 1960s was also identified in the Hocking River at Athens, Ohio. Our results were similar to other studies that examined road salt impacts in the northern US, but a lack of consistent long-term data hindered historical analysis for some rivers.

Black carbon (BC) in soils plays a key role of carrying hydrophobic pollutants like polycyclic aromatic hydrocarbons (PAHs). However, little is known about the spatial distribution, sources of BC and its relationship with PAHs in urban soils. We studied BC, total organic carbon (TOC) and PAHs concurrently in 77 soils collected from downtown area, suburban and rural area and industrial area of Shanghai, China. BC was determined by both chemical oxidation (dichromate oxidation, BCCr) and chemo-thermal oxidation (CTO-375, BCCTO). BC sources were identified qualitatively by BC/TOC concentration ratios and BC-cogenerated high molecular weight (HMW) PAH isomer ratios and quantitatively by principal component analysis followed by multiple linear regression (PCA-MLR). Results showed that BCCr concentration (4.65 g/kg on average) was significantly higher than BCCTO (1.91 g/kg on average) in Shanghai soils. BCCr concentrations in industrial area were significantly higher than those in other two. Stronger correlation was found between PAHs and TOC, BCCr than that between PAHs and BCCTO, which indicates the possibility of PAHs being carried by charcoal and other organic matters thus negating its exclusive dependence on soot. Charcoal was therefore suggested to be taken into account in studies of BC and its sorption of PAHs. BC/TOC ratios showed a mixed source of biomass burning and fossil fuel combustion. PCA scores of BC-cogenerated HMW PAHs isomer ratios in potential sources and soil samples clearly demonstrated that sources of BC in urban soils may fall into two categories: coal and biomass combustion, and traffic (oil combustion and tire wear). PCA-MLR of HMW PAHs concentrations in soil samples indicated that coal and oil combustion had the largest contribution to BC in urban soils while tire wear and biomass combustion were important in downtown and rural area, respectively, which indicated they were main sources of HMW PAHs and presumably of BC.

High-resolution stable carbon isotope monitoring indicates variable flow dynamic patterns in a deep saline aquifer at the Ketzin pilot site (Germany) by Martin E. Nowak; Robert van Geldern; Anssi Myrttinen; Martin Zimmer; Johannes A.C. Barth (44-51).
Stable isotopes of injected CO2 act as useful tracers in carbon capture and storage (CCS) because the CO2 itself is the carrier of the tracer signal and remains unaffected by sorption or partitioning effects. At the Ketzin pilot site (Germany), carbon stable isotope composition (δ13C) of injected CO2 at the injection well was analyzed over a time period of 4 months. Occurring isotope variances resulted from the injection of CO2 from two different sources (an oil refinery and a natural gas-reservoir). The two gases differed in their carbon isotope composition by more than 27‰. In order to find identifiable patterns of these variances in the reservoir, more than 250 CO2-samples were collected and analyzed for their carbon isotope ratios at an observation well 100 m distant from the injection well. An isotope ratio mass spectrometer connected to a modified Thermo Gasbench system allowed quick and cost effective isotope analyses of a high number of CO2 gas specimens. CO2 gas from the oil refinery (δ13C = −30.9‰, source A) was most frequently injected and dominated the reservoir δ13C values at the injection site. Sporadic injection of the CO2 from the natural gas-reservoir (δ13C = −3.5‰, source B) caused isotope shifts of up to +5‰ at the injection well. These variances provided a potential ideal tracer for CO2 migration behavior. Based on these findings, tracer input signals that were injected during the last 2 years of injection could be reconstructed with the aid of an isotope mixing model and CO2 delivery schedules. However, in contrast to the injection well, δ13C values at the observation well showed no variances and a constant value of −28.5‰ was measured at 600 m depth. This is in disagreement with signals that would be expected if the input signals from the injection would arrive at the observation well. The lack of isotope signals at the observation well suggests that parts of the reservoir are filled with CO2 that is immobilized.

The soils surrounding the Spektakel mine in the arid Okiep copper district of the Northern Cape Province, South Africa have been exposed to Cu containing acid mine drainage (AMD) for well over a century. This has led to acute soil contamination with Cu concentrations present as high as 10 wt%. Despite the sulphate-rich environment, associated with AMD, the Cu-hydroxy chloride mineral, atacamite [Cu2(OH)3Cl] is the exclusive secondary Cu mineral identified in the soils. Brochantite [Cu4(OH)6SO4], the sulphate equivalent was not detected. Evaporation is a major hydrologic process in the arid soil system, thus the chemical evolution of the saline, metal containing brine was determined both experimentally and using PHREEQC modelling in the presence and absence of calcite. In samples that evaporated in the absence of calcite, the pH of the evaporating solution progressively decreased to below 3.5, whereas the solution in contact with calcite retained a circumneutral pH throughout the evaporation process. Thus in the absence of calcite, evaporation alone will not favour the formation of Cu-hydroxy minerals. Chemical activities of the evaporating solutions were modelled using the SIT.dat database of PHREEQC. This allowed the inclusion of aqueous complexes into the activity calculations of the evaporating solutions. Contrary to the conservative molality evolution of sulphate, the evolution of the sulphate activity was substantially suppressed due to the formation of MgSO4 0 aqueous complexes. We propose that these MgSO4 0 aqueous complexes are responsible for the absence of brochantite whereas the conservative chloride ion is more available for secondary Cu mineral formation. This suggests that ion pairs and aqueous complexes play an important role in determining the speciation of evaporite minerals and should be included in the modelling of such systems.

We investigated the equilibrium chemistry and chemical speciation of S, Fe and metals (Co, Ni, Cu, Zn, Cd, and Pb) in eight full scale Continuous Stirred Tank Biogas Reactors (CSTBR). Five reactors were digesting mixtures of different organic wastes (referred to as Co-Digester; CD) and three were digesting Sewage Sludge (SS). Iron was continuously added to the CD reactors to remove sulfide produced during anaerobic digestion and SS was rich in Fe, amended for phosphate removal in wastewater treatment plants prior to anaerobic digestion. As a consequence of different S:Fe molar ratios (0.3–2.8), ferruginous (Fe(II)-dominated) conditions prevailed in SS reactors and sulfidic (S(-II)-dominated) conditions in CD reactors. In all reactors, the chemical speciation of S, as determined by S K-edge X-ray Absorption Near-Edge Structure spectroscopy, was dominated by FeS(s). Reduced organic S forms, consisting of RSH (thiol) and RSR (organic sulfide), were the second most abundant S species. Zero-valent S (elemental S, polysulfides, and possible traces of pyrite) was detected in all reactors, ranging between 6% and 26% of total S, with the highest proportion formed under ferruginous conditions. Thermodynamic modeling suggested that Fe in the aqueous phase was dominated by Fe(II)-thiol complexes under sulfidic conditions (CD reactors) and by Fe(II)-phosphate complexes under ferruginous conditions (SS reactors). Thiols, representing organic functional groups, and sulfide complexes were the major aqueous species of Co(II), Ni(II), Cd(II) and Pb(II) under sulfidic conditions. Under ferruginous conditions thiol complexes were still important, but carbonate and phosphate complexes in particular dominated the aqueous phase speciation of Co(II) and Ni(II). The aqueous phase speciation of Zn and Cu was dominated by Zn(II)-sulfide and Cu(I)-polysulfide complexes, respectively. The results highlights the importance of S:Fe molar ratio as a regulating factor for the chemical speciation of metals in biogas reactors which in turn is important for microbial trace metal uptake and growth as well as potential metal toxicity. Both these aspects are critical for a successful performance of biogas production process.

A batch reactor design for determining precipitation kinetics from an experimental (i.e. laboratory made) geothermal brine is presented. The purpose of the method is to improve techniques for predicting scaling risks in basin-hosted, enhanced geothermal systems (EGS). The method is applied to determining kinetic rate laws for alkali-earth metal sulfate precipitation in the Na–Ca–Ba–Sr–Cl–SO4–H2O system, which are a set of components commonly found in sedimentary basin brines, worldwide. The method of integral rates was used to determine alkali-earth metal precipitation kinetic rate laws for solutions reacting over 4 h at 75 °C and 150 °C. At 75 °C, the rate law for total sulfate precipitation is rate = 0.0137 * [SO4 2−]2. At 150 °C, the rate law for total sulfate precipitation is rate = 0.011 * [SO4 2−]2. All precipitants are found to be barite, with minor amounts of calcium and strontium incorporated into the barite structure. If only barite precipitation is considered, the rate coefficients become 0.045 and 0.025 at 75 °C and 150 °C, respectively. The precipitants’ specific reactive surface areas are estimated for each time step and temperature and are qualitatively observed to decrease as the reactions progress. The (1) the reaction order, (2) the rate coefficient and (3) the change in specific reactive surface area over time are the three parameters required to develop reactive transport models of mineral precipitation in a geothermal power plant. All three of these parameters can be determined with the method employed in this study. Results from these experiments confirm previous results that precipitation kinetics are dependent on both starting concentrations and background salinities. Experiments designed to predict scaling risks in real geothermal systems require adjustments to the method presented herein, specifically (1) experimental fluids must more closely approximate real geothermal brines, (2) a larger reactor is required to produce a greater precipitant mass and (3) full quantitative assessment of the precipitants’ specific reactive surface area are required to reduce the error of these measurements.

Display OmittedLow-pH Fe(II) oxidation can be exploited for the treatment of acid mine drainage (AMD). However, natural or engineered terraced iron formations (TIFs) are underutilized for AMD treatment because of uncertainties with respect to treatment performance. To address this problem we measured the rates of Fe(II) oxidation multiple times at eight sites in the Appalachian Bituminous Coal Basin and at three sites in the Iberian Pyrite Belt (IPB). Longitudinal geochemical transects were measured downstream of emergent anoxic AMD sources. Water velocities were measured at each sampling location and used to transform concentration versus distance profiles into concentration versus travel time for kinetic analysis of field data. Zero-order Fe(II) oxidation rates ranged from 8.60 to 81.3 × 10−7  mol L−1  s−1 at the Appalachian sites and 13.1 to 67.9 × 10−7  mol L−1  s−1 at the IPB sites. First-order Fe(II) oxidation rate constants ranged from 0.035 to 0.399 min−1 at the Appalachian sites and 0.003 to 0.010 min−1 at the IPB sites. Faster rates of Fe(II) oxidation were measured at two sites (one in Appalachia and one in IPB) where the emergent pH values were the lowest and little to no oxidative precipitation of Fe(III) occurred. Laboratory-based rates of Fe(II) oxidation were measured with TIF sediments and emergent AMD collected from seven Appalachian sites. First-order laboratory rate constants normalized to sediment biomass concentrations (measured by phospholipid fatty acids; PLFA) were positively correlated to first-order field rate constants. Biomass composition was relatively similar between all sites, and predominately comprised of proteobacteria and general PLFAs. A zero-order lab-based removal rate for dissolved Fe(T) was used to calculate area-based design criteria of 2.6–8.7 g Fe day−1  m−2 (GDM) for both natural and engineered TIFs.

Display OmittedThe mobility of toxic metals in soils or sediments is of great concern to scientists and environmentalists since it directly affects the bioavailability of metals and their movement to surface and ground waters. In this study, a multi-surface soil speciation model for Cd (II) and Pb (II) was developed to predict the partition of metals on various soil solid components (e.g. soil organic matter (SOM), oxide mineral, and clay mineral). In previous study, the sorption of metal cations on SOM and oxide minerals has been evaluated by thermodynamically based surface complexation model. However, metal binding to soil clay fractions was normally treated in a simplistic manner: only cation exchange reactions were considered and exchange coefficient was assumed unity. In this study, the binding of metals onto clays was described by a two-site surface sorption model (a basal surface site and an edge site). The model was checked by predicting the adsorption behavior of Cd (II) and Pb (II) onto three selected Chinese soils as a function of pH and ionic strengths. Results showed that the proposed model more accurately predicted the metal adsorption on soils under studied condition, especially in low ionic strength condition, suggesting that adsorption of metals to soil clay fractions need to be considered more carefully when modeling the partition of trace elements in soils. The developed soil speciation model will be useful when evaluating the movement and bioavailability of toxic metals in soil environment.

Large variability of trace element mass fractions determined by ICP-SFMS in ice core samples from worldwide high altitude glaciers by Chiara Uglietti; Paolo Gabrielli; John W. Olesik; Anthony Lutton; Lonnie G. Thompson (109-121).
We quantified leaching and mass fractions of trace elements in melted acidified ice core samples measured by Inductively Coupled Plasma Sector Field Mass Spectrometry (ICP-SFMS). This assessment was conducted using nine ice core sections retrieved from various high-altitude drilling sites in South America, Africa, Asia and Europe.Twenty trace elements (Ag, Al, As, Bi, Cd, Co, Cr, Cu, Fe, Mn, Mo, Pb, Rb, Sb, Sn, Ti, Tl, U, V and Zn) were determined. During a 1½ month acid leaching period our assessment shows distinct increases in the concentration of various trace elements (10% for Cd; 30% for Pb; 50–80% for As, Cu, Mo, Mn, Tl and U; 80–90% for Bi, Rb, Sb, Sn and Zn; 100–160% for Al, Cr, Co, Ti and V; 200% for Fe). The exception is Ag, which shows a 50% decrease. We found that the observed relative increases in trace element concentrations are: (i) independent of the absolute trace element concentrations and micro-particle levels/size of the samples, and (ii) unlikely to affect reconstructions of the crustal/non-crustal origin of trace elements based on the use of the crustal enrichment factor.After 1½ months of leaching, the measured trace element concentrations were found to be only a fraction of the estimated total concentration and that the mass fractions determined vary largely from element to element (on average 80–90% for As and Mn; 50–70% for U, Fe, Ti and Tl; 20–50% for Al, Cd, Co, Cr, Cu, Mo, Pb, Rb, V and Zn; 15% for Bi and 2% for Ag). These observations imply: (i) a significant underestimation of the mass fluxes of these trace elements to high altitude glaciers and (ii) a likely dependency of the mass fractions on the typical crystallographic position of each trace element within the micro-particles contained in the ice core samples.

Environmental impact of a granite processing factory as source of naturally occurring radionuclides by J. Guillén; J.J. Tejado; A. Baeza; A. Salas; J.G. Muñoz-Muñoz (122-129).
The extraction and processing of ornamental stone, and granite in particular, generates a huge amount of wastes, which are usually disposed into slag heaps and subjected to weathering. Granite can present high content of naturally occurring radionuclides (40K, 226,228Ra, 234,238U, 210Po, and 228,230,232Th). A small-scale granite processing company was selected, and the generated wastes, mainly scraps and slurries, presented almost the same activity levels, since only physical processes (cutting) were used. Uranium and 40K content in the water used in the factory as coolant were enhanced regarding its original value, as a consequence of its contact with the slurries. Other physico-chemical parameters of the water (pH, conductivity, Cl, K, Na, Mg) also increased. The environmental behavior of naturally occurring radionuclides contained in solid wastes, scraps and slurries, were assessed by means of a sequential extraction procedure. Uranium in scraps and slurries was mainly associated with diluted-acid (HCl 1 M), concentrated-acid (HCl 6 M), and residual fractions; while 40K was almost exclusively associated with the residual fraction. The readily bioavailable fraction (water soluble + exchangeable) in scrap and slurry were lower than 20%, and decreased in the following order: 226,228Ra >  234,238U >  40K »  210Po ≈  228,230,232Th.

Redox reaction of aqueous selenite with As-rich pyrite from Jiguanshan ore mine (China): Reaction products and pathway by Mingliang Kang; Fabrizio Bardelli; Laurent Charlet; Antoine Géhin; Andrey Shchukarev; Fanrong Chen; Marie-Christine Morel; Bin Ma; Chunli Liu (130-140).
The interaction of an As-rich natural pyrite (FeS2.08As0.043) with aqueous Se(IV) was investigated as a function of pH, ferrous iron concentration, and reaction time. Arsenic is often the most abundant minor constituent of natural pyrite, and is believed to substitute for S in the pyrite structure. EXAFS measurements confirmed the presence of AsS dianion group, with arsenic in the same local configuration as in the arsenopyrite. Speciation studies indicated that Se(0) was the unique reduction product in the pH range 5.05–8.65 over a reaction period of >1 month, while trace amounts of FeSeO3 might be formed at pH ⩾ 6.10. At pH > 6.07, the formation of Fe(III)-(oxyhydr)oxide is kinetically favored, and it consumed nearly all the aqueous iron, including the extra added Fe2+, thereby inhibiting the formation of the thermodynamically most stable product: FeSe2. After oxidation by Se(IV), the occurrence of surface S0, significant aqueous sulfur deficit, and excessive leaching of arsenic in solution, indicate the preferential release of As impurity via arsenopyrite oxidation. The data suggest that the polysulfide-elemental sulfur pathway, which prevails in acid-soluble metal sulfides, is an important pathway in the oxidation of As-rich pyrite, in addition to the thiosulfate pathway for acid-insoluble pyrite. Control experiments on As-free natural pyrite further support this mechanism. This study confirms the potential of reductive precipitation to attenuate the mobility of Se in the environment and demonstrates that minor elements commonly present in natural pyrite can play a significant role on its dissolution pathway.

Stable isotope fractionation of chlorine during the precipitation of single chloride minerals by Chongguang Luo; Yingkai Xiao; Hanjie Wen; Haizhou Ma; Yunqi Ma; Yanling Zhang; Yuxu Zhang; Maoyong He (141-149).
Display OmittedIn order to better understand chlorine isotopic variations during brine evolution, experiments were designed to determine the changes in the chlorine isotope composition (δ37Cl value) during evaporations of solutions containing NaCl, KCl and MgCl2⋅6H2O at 28 ± 2 °C. Three evaporation experiments were conducted in a clean environment. The precipitate and brine samples were collected during the evaporation, and the chlorine isotopic ratios of the samples were determined using an improved thermal ionisation mass spectrometry procedure based on Cs2Cl+ ion measurement. The results are as follows: the mean fractionation factors of the three solutions are α Na  = 1.00055, α K  = 1.00025, and α Mg  = 1.00012, respectively, where α Na, α K and α Mg are the fractionation factors between salts (NaCl, KCl and MgCl2⋅6H2O) and saturated solutions. The results showed that the δ 37Cl values of precipitate and coexisting brine samples decrease during the precipitation of single chloride minerals. The residual brine was a 35Cl reservoir for different single chloride solutions. New chlorine isotopic evolution curve during seawater evaporation were also calculated. The results indicated that during the primary precipitation stage of halite, δ 37Cl decreased continuously, and the most important thing is that this trend continues during the final stages when Mg–salts begin to precipitate.

Carbamazepine breakthrough as indicator for specific vulnerability of karst springs: Application on the Jeita spring, Lebanon by Joanna Doummar; Tobias Geyer; Michael Baierl; Karsten Nödler; Tobias Licha; Martin Sauter (150-156).
The pharmaceutical drug carbamazepine is considered an effective wastewater marker. The varying concentration of this drug was analyzed in a mature karst spring following a precipitation event. The results show that carbamazepine is an indicator of wastewater entering the system through a fast flow pathway, leading to an increase of the drug concentrations in spring water shortly after a strong rainfall event. The analysis of the breakthrough curve of carbamazepine along with the electrical conductivity signal and major ions chemograph allowed the development of a conceptual model for precipitation event-based flow and transport in the investigated karst system. Furthermore the amount of newly recharged water and the mass of carbamazepine reaching the aquifer system during the event could be estimated using a simple mixing approach. The distance between the karst spring and the potential carbamazepine source was estimated by the combination of results from artificial tracer tests and the carbamazepine breakthrough curve. The assessment of spring responses to precipitation event using persistent drugs like carbamazepine helps assess the effect of waste water contamination at a spring and gives therefore insights to the specific vulnerability of a karst spring.

Natural tracers in Senonian–Eocene formations for detecting interconnection between aquifers by Michael Zilberbrand; Eliyahu Rosenthal; Gabriel Weinberger (157-169).
Relatively high concentrations of dissolved bio-Barium and bio-silica in groundwater in Paleocene–Eocene carbonate aquifers caused by the Paleocene–Eocene thermal maximum are proposed as tracers for delineating zones of leakage into adjacent aquifers. In fresh, oxidized and not thermal groundwater (within a narrow range of temperatures) these tracers can be considered as conservative. In addition, certain trace elements (U, Mo, Se and Tl) of phosphates widespread in Senonian carbonate strata are suggested to serve as tracers of water originating from these sediments. The locally increased concentrations of these trace elements in groundwater of a carbonate aquifer underlying the Senonian strata were also proposed as tracers of water leakage from above. The proposed tracers of water in Eocene and Senonian strata have been used for delineating zones of local leakage into the underlying Turonian aquifer in the Yarkon-Taninim basin (YTB) of Israel. Results of geochemical survey of 208 wells in the Turonian aquifer of the YTB were used for Pearson’s correlation and Principal Component Analysis (PCA) for detection of interconnection zones. PCA revealed 4 factors explaining up to 86% of variance in groundwater chemistry in the Turonian carbonate aquifer. Two factors, first – with high loadings of Ba and SiO2, and second – with high loadings of U, Mo, Se and Tl, were interpreted to be related to local groundwater leakage from Eocene strata into the Turonian aquifer, fast and slow, respectively. Mapping of these two factors enabled delineation of areas where local inflow of water from the Eocene aquitard exists.

Seasonal variations of arsenic at the sediment–water interface of Poyang Lake, China by Tianlong Deng; Yi Wu; Xiaoping Yu; Yafei Guo; Yu-Wei Chen; Nelson Belzile (170-176).
Arsenic species including arsenite, arsenate, and organic arsenic were measured in the porewaters collected from Poyang Lake, the largest freshwater lake of China. The vertical distributions of dissolved arsenic species and some diagenetic constituents [Fe(II), Mn(II), S(−II)] were also obtained in the same porewater samples in summer and winter. In sediments the concentration profiles of total As and As species bound to Fe–Mn oxyhydroxides and to organic matter were also determined along with the concentrations of Fe, Mn and S in different extractable fractions. Results indicate that, in the summer season, the concentrations of total dissolved As varying from 3.9 to 55.8 μg/L in sediments were higher than those (5.3–15.7 μg/L) measured in the winter season, while the concentrations of total As species in the solid phase varied between 10.97 and 25.32 mg/kg and between 7.84 and 30.52 mg/kg on a dry weight basis in summer and winter, respectively. Seasonal profiles of dissolved As suggest downward and upward diffusion, and the flux of dissolved As across the sediment–water interface (SWI) in summer and winter were estimated at 3.88 mg/m2  a and 0.79 mg/m2  a, respectively. Based on porewater profiles and sediment phase data, the main geochemical behavior of As was controlled by adsorption/desorption, precipitation and molecular diffusion. The solubility and migration of inorganic As are controlled by Fe–Mn oxyhydroxides in summer whereas they appear to be more likely controlled by both amorphous Fe–Mn oxyhydroxides and sulfides in winter. A better knowledge of the cycle of As in Poyang Lake is essential to a better management of its hydrology and for the environmental protection of biota in the lake.

Effect of major cation water composition on the ion exchange of Np(V) on montmorillonite: NpO2 +–Na+–K+–Ca2 +–Mg2+ selectivity coefficients by Ana Benedicto; James D. Begg; Pihong Zhao; Annie B. Kersting; Tiziana Missana; Mavrik Zavarin (177-185).
Np(V) sorption was examined in pH 4.5 colloidal suspensions of nominally homoionic montmorillonite (Na-, K-, Ca- and Mg-montmorillonite). Ionic exchange on permanent charge sites was studied as a function of ionic strength (0.1, 0.01 and 0.001 M) and background electrolyte (NaCl, KCl, CaCl2 and MgCl2). An ion exchange model was developed using the FIT4FD program, which considered all experimental data simultaneously: Np sorption data, major cation composition of the electrolyte and associated uncertainties. The model was developed to be consistent with the ion exchange selectivity coefficients between the major cations reported in the literature and led to the following recommended selectivity coefficients for Np(V) ion exchange according to the Vanselow convention: log K V Na + NpO 2 + = - 0.20 , log K V K + NpO 2 + = - 0.46 , log K V Ca 2 + NpO 2 + = - 0.57 , log K V Mg 2 + NpO 2 + = - 0.57 . Both the experimental data and the estimated selectivity coefficients in this study are consistent with the limited Np(V) ion exchange and sorption data reported in the literature. The results indicate that, as expected, low ionic strengths favor Np(V) sorption when ion exchange is the main sorption mechanism (i.e. acidic to neutral pHs) and that the divalent cations Ca2+ and Mg2+ may be important in limiting Np(V) ionic exchange on montmorillonite.

In this study, we report for the first time lanthanum and gadolinium anomalies at the catchment scale (Rhine-Meuse River system) together with the partitioning of their anthropogenic contents between the dissolved and the particulate phases. We compare the dissolved and total REE patterns of samples taken at 9 locations in the Rhine Branches including Lobith (situated at the German–Dutch border where the Rhine is not yet divided in three Branches), in surface water fed by the Rhine Branches (canals and lake IJsselmeer and Ketelmeer) and 3 locations where the water is derived from the river Meuse (originating from Belgium and France).We demonstrate that the anthropogenic input of lanthanum in the German part of the Rhine River identified by Kulaksiz and Bau (2011) can be traced in the complex Rhine-Meuse Delta up to the North Sea. In the Dutch Branches of the Rhine River, in contrast to the German part of the Rhine River, the anthropogenic lanthanum (LaANTHRO) is mainly present in the particulate phase (SPM) and not in the dissolved phase (defined as the <0.45 μm fraction). In the Meuse River no anthropogenic lanthanum was found. The amount of LaANTHRO transported by the Rhine River at the Lobith station (German–Dutch border) varies from 2008 to 2010 between 3.7 and 5.2 tons/y in the dissolved phase, and between 28.8 and 37.4 tons/y in the particulate phase. However, a big discrepancy is evidenced when we compare the LaANTHRO load calculated on bases of the total water samples with the LaANTHRO load calculated as the sum of the particulate and dissolved load: the total LaANTHRO load is roughly 2 times larger than the LaANTHRO load calculated as the sum of the dissolved and particulate LaANTHRO load. The difference between the two calculated fluxes is most likely caused by not sampling the finest fraction of the particulate pool in the SPM samples with an overflow centrifuge.The anthropogenic gadolinium identified by high gadolinium anomalies in the REE patterns originates from numerous point sources (waste water treatment plant effluents) and can thus be considered as diffuse pollution when compared to anthropogenic lanthanum clearly resulting from a single source. The amount of anthropogenic gadolinium measured in the dissolved phase (main carrier of Gd) increases or decreases along the Rhine and Meuse Rivers depending whether or not the mixing water contains anthropogenic gadolinium, i.e. receives waste water effluents.

Sequestration of Cd(II) and Ni(II) ions on fungal manganese oxides associated with Mn(II) oxidase activity by Jianing Chang; Yukinori Tani; Hirotaka Naitou; Naoyuki Miyata; Haruhiko Seyama (198-208).
Display OmittedThe sequestration of Ni(II) and Cd(II) by biogenic manganese oxides (BMOs) in cultures of an Mn(II)-oxidizing fungus, Acremonium strictum strain KR21-2, was examined. In batch culture experiments, Ni(II) and Cd(II) were sequestered concurrently with the formation of BMOs with initial concentrations of ⩾30 μM Ni(II) and ⩾50 μM Cd(II). The coexistence of Ni(II) and Cd(II) at higher concentrations caused minor Mn oxide precipitation, and most of the metal ions remained in solution. An assay of Mn(II)-oxidizing activity using a concentrated crude solution of Mn(II) oxidase revealed that in association with BMO, enzymatic activity was maintained even at higher concentrations of Ni(II) and Cd(II) (⩾500 μM), while activity was lower in the absence of BMO. BMOs formed in 1 mM Mn(II) efficiently sequestered Ni(II) and Cd(II) at concentrations up to 1 mM at pH 7.0 with maximum sorption capacities of 25.8 mol% for Ni(II) and 25.0 mol% for Cd(II) relative to Mn oxide under aerobic conditions, without observable release of Mn(II). Meanwhile, BMOs heated to 85 °C to inactivate the associated Mn(II) oxidase released significant amounts of Mn(II) and had lower sequestration efficiencies. Thus, the Mn(II) oxidase associated with newly formed BMOs progressively oxidized Mn(II), which was released through ion exchange at the surface and hence reduced competitive sorption. The results of repeated treatments of newly formed and heated BMOs in Ni(II) or Cd(II) solution (∼1 mM) with excess Mn(II) (∼1 mM) demonstrated that the associated enzymatic activity is a prerequisite for continuous sequestration.

Geochemical characteristics of an urban river: Influences of an anthropogenic landscape by Nicholas P. Connor; Stephanie Sarraino; Deborah E. Frantz; Karen Bushaw-Newton; Stephen E. MacAvoy (209-216).
The Anacostia River in Washington, DC is among the ten most contaminated rivers in the USA, containing sewage, metals, PAHs, and PCBs. Seventy-five percent of its watershed is urban or impervious. The biogeochemical characteristics of urban rivers, including the Anacostia, remain largely unstudied. Here we examine the base-flow geochemistry of the tidal freshwater Anacostia over a two-year period (April 2010–April 2012), concentrating on water chemistry (pH, hardness, SAR, alkalinity, Ca, Mg, Na, K, Fe, Mn, Zn, Al, Ba, Ni, total P, S, Sr, NO3 , NH4 +, PO4 3 ) at 3 locations in the stream. Anacostia pH is between 7.3 and 8.2, indicating rapid buffering of precipitation (pH 4.9). Mean NO3 was generally between 1.1 and 1.3 mg/L, although occasionally concentrations increased to 3–4 mg/L at all sites. Ammonium was very low generally 0.0–0.3 mg/L with occasional peaks of 1.5–3.9 mg/L downstream. A Principle Components Analysis (PCA) of stream chemistry showed two components that explained two-thirds of the data variance. One component was correlated with Ca, Mg, Na, and hardness, all associated with bedrock or concrete dissolution. A second component was correlated with NH4 +, NO3 , K and associated with nutrients. Na and Ca had the highest concentrations. This trend has been observed in other urban streams, suggesting urban stream syndrome and dissolution of concrete. Plotting Na/(Na + Ca) versus total dissolved solids indicates contributions from groundwater, but also produces a signature that is dramatically different from major world rivers. The data presented here demonstrates the need for understanding the geochemistry of highly urbanized systems and the extent to which urban inputs drive stream chemistry.