Applied Geochemistry (v.45, #C)
Abundance and speciation of iron across a subtropical tidal marsh of the Min River Estuary in the East China Sea by Min Luo; Cong-Sheng Zeng; Chuang Tong; Jia-Fang Huang; Qiang Yu; Yan-Bin Guo; Shu-Hua Wang (1-13).
Iron has profound influence on anaerobic organic matter oxidation and Fe–S–C biogeochemical cycling in tidal marshes. To examine the abundance and speciation of iron, six iron species (poor crystalline Fe(III), crystalline Fe(III), non-sulfidic Fe(II), porewater Fe2+, FeS, and FeS2) were investigated in a cross transect (span = 250 m, depth = ∼1.2 m) in a tidal marsh of the Min River Estuary in the East China Sea. The results suggested that sediment characteristics, pH, redox condition, conductivity, chloride, sulfate, and organic matter create a highly heterogeneous geochemical framework in the cross transect. Correspondingly, the zonation of iron species differed significantly across the tidal marsh. Poor crystalline Fe(III) (48 ± 24 μmol g−1) and crystalline Fe(III) (75 ± 32 μmol g−1) accumulated on the surface of the high-tide zone and decreased with elevation. The non-sulfidic Fe(II) minerals (140 ± 61 μmol g−1) accounted for the largest proportion of the six iron species. The porewater Fe2+ was enriched within the deep layer of the upland region (pH = 6.2–6.5) and exhibited a maximum of 11.49 mM. The aqueous sulfide concentration was below detection. FeS (39 ± 6 μmol g−1) and FeS2 (57 ± 25 μmol g−1) accumulated closer to the lower extremity. Tidal water brought O2 and removed certain amounts of dissolved organic carbon, dissolved inorganic carbon, and Fe(III)-bearing particles in an element budget during tidal inundation. Variations of topography, tidal hydrology, seawater intrusion, and organic matter altered the dominant organic matter oxidation pathway and further affected iron mineralization.
Estimated thermodynamic properties of NaFeS2 and erdite (NaFeS2:2H2O) by Arnault Lassin; Patrice Piantone; Catherine Crouzet; Françoise Bodénan; Philippe Blanc (14-24).
The main by-products of a lead-recovery process from waste are scoriaceous sodium–iron sulphides, whose storage is problematic due to their great reactivity with air and water. The objective of this work was to complete thermodynamic databases with a totally new set of properties for the two major components: NaFeS2 and erdite (NaFeS2:2H2O). The solubility product of erdite was measured at 20 °C in a batch reactor. It is −38.0 ± 0.3 when the reaction is written as a function of the predominant species at the experimental conditions: NaFeS 2 : 2 H 2 O + 0.5 H 2 O = HFeO 2 - + 1.875 HS - + 0.125 SO 4 = + Na + + 2.125 H + . The resulting standard Gibbs free energy of formation of erdite from elements is −809.76 kJ/mol at 25 °C and 1 bar. An original calculation procedure, relying on a combination of different theoretical models, then allowed the determination of the standard Gibbs free energies of formation of NaFeS2 and of the water of hydration for transforming NaFeS2 into erdite. At 25 °C and 1 bar, they are −322.85 and −243.46 kJ/mol respectively. The other standard thermodynamic properties (enthalpy, entropy, and heat capacity) of erdite are −922.04 kJ/mol, 232.6 J/(mol K) and 175.7 J/(mol K), respectively. For NaFeS2, they are −331.33 kJ/mol, 114.3 J/(mol K) and 97.7 J/(mol K), respectively. For the water of hydration they are −295.36 kJ/mol, 59.2 J/(mol K) and 39.0 J/(mol K), respectively.
Transport of perfluorocarbon tracers and carbon dioxide in sediment columns – Evaluating the application of PFC tracers for CO2 leakage detection by L. Zhong; J.E. Amonette; A.V. Mitroshkov; K.B. Olsen (25-32).
Perfluorocarbon compounds (PFCs) have high chemical and thermal stability, low background levels in natural systems, and easy detectability. They are proposed as tracers for monitoring potential CO2 leakage associated with geological carbon sequestration (GCS). The fate of the PFCs in porous media, and in particular, the transport of these compounds relative to CO2 gas in geological formations, has not been thoroughly studied. We conducted column tests to study the transport of perfluoro-methylcyclo-pentane (PMCP), perfluoro-methylcyclo-hexane (PMCH), ortho-perfluoro-dimethylcyclo-hexane (ortho-PDCH), and perfluoro-trimethylcyclo-hexane (PTCH) gas tracers in a variety of porous media. The influence of water content and sediment minerals on the retardation of the tracers was tested. The transport of PFC tracers relative to 13CO2 and the conservative tracer sulfur hexafluoride (SF6) was also investigated. Results show that at high water content, the PFCs and SF6 transported together. In dry and low-water-content sediments, however, the PFCs were retarded relative to SF6 with the degree of retardation increasing with the molecular weight of the PFC. When water was present in the medium, the transport of CO2 was greatly retarded compared to SF6 and the PFC tracers. However, in dry laboratory sediments, the migration of CO2 was slightly faster than all the tracers. The type of minerals in the sediments also had a significant impact on the fate of the tracers. In order to use the PFC tracer data obtained from the ground surface or shallow subsurface in a GCS site to precisely interpret the extent and magnitude of CO2 leakage, the retardation of the tracers and the interaction of CO2 with the reservoir overlying formation water should be carefully quantified.
A multiple-tracer approach to understanding regional groundwater flow in the Snake Valley area of the eastern Great Basin, USA by Philip M. Gardner; Victor M. Heilweil (33-49).
Groundwater in Snake Valley and surrounding basins in the eastern Great Basin province of the western United States is being targeted for large-scale groundwater extraction and export. Concern about declining groundwater levels and spring flows in western Utah as a result of the proposed groundwater withdrawals has led to efforts that have improved the understanding of this regional groundwater flow system. In this study, environmental tracers (δ 2H, δ 18O, 3H, 14C, 3He, 4He, 20Ne, 40Ar, 84Kr, and 129Xe) and major ions from 142 sites were evaluated to investigate groundwater recharge and flow-path characteristics. With few exceptions, δ 2H and δ 18O show that most valley groundwater has similar ratios to mountain springs, indicating recharge is dominated by relatively high-altitude precipitation. The spatial distribution of 3H, terrigenic helium (4Heterr), and 3H/3He ages shows that modern groundwater (<60 yr) in valley aquifers is found only in the western third of the study area. Pleistocene and late-Holocene groundwater is found in the eastern parts of the study area. The age of Pleistocene groundwater is supported by minimum adjusted radiocarbon ages of up to 32 ka. Noble gas recharge temperatures (NGTs) are generally 1–11 °C in Snake and southern Spring Valleys and >11 °C to the east of Snake Valley and indicate a hydraulic discontinuity between Snake and Tule Valleys across the northern Confusion Range. The combination of NGTs and 4Heterr shows that the majority of Snake Valley groundwater discharges as springs, evapotranspiration, and well withdrawals within Snake Valley rather than continuing northeastward to discharge at either Fish Springs or the Great Salt Lake Playa. The refined understanding of groundwater recharge and flow paths acquired from this multi-tracer investigation has broad implications for interbasin subsurface flow estimates and future groundwater development.
Hydrogeochemical characterisation and modelling of groundwaters in a potential geological repository for spent nuclear fuel in crystalline rocks (Laxemar, Sweden) by María J. Gimeno; Luis F. Auqué; Patricia Acero; Javier B. Gómez (50-71).
Two sites in the eastern coast of Sweden have been investigated by the Swedish Nuclear Fuel and Waste Management Company (SKB), within the framework of the site characterisation programme, as possible candidates for hosting the proposed repository for the long-term storage of spent nuclear fuel: Forsmark and Laxemar. This study presents the main results concerning the hydrogeochemical characterisation of the groundwaters in the second site, Laxemar. The distribution of the main chemical variables in groundwaters are shown and interpreted in combination with the results from speciation–solubility and reaction-path simulations, together with the available mineralogical information. The results indicate that the main processes determining the overall geochemical evolution of the Laxemar groundwaters are advective/diffusive mixing and water–rock interactions driven by past and present climatic changes inducing the input of different recharge waters over time (glacial meltwater, old marine water and modern meteoric water) and affecting the preexisting very old saline groundwaters in the bedrock. The superimposed effects of these mixing events, deduced from the behaviour of the conservative elements (Cl and δ18O), have generated a rather steep salinity gradient in the groundwater system, with diluted waters in the upper part, brackish waters in the middle, and saline waters in the lower part of the bedrock.The resultant successive disequilibrium states imposed by mixing have conditioned the water–rock interaction processes that have affected the non-conservative elements to different degrees. The main chemical reactions found to be important in controlling some of the variability of these elements and some important parameters like pH and alkalinity, are: aluminosilicate and carbonate dissolution/precipitation, quartz and fluorite equilibrium, cation exchange, and gypsum dissolution. These reactions and their importance in the system are presented in this paper.Once the main hydrogeochemical features of the Laxemar groundwaters and the potentially controlling water–rock interactions in the system have been identified and justified with the help of thermodynamic simulations, a general geochemical conceptual model has been proposed. This model will be used as the basis for predicting the future evolution of the groundwater chemistry as an essential part of the safety assessment of the future repository.
Dynamics and origin of atmospheric CH4 in a Polish metropolitan area characterized by wetlands by M. Górka; D. Lewicka-Szczebak; R. Fuß; M. Jakubiak; M.O. Jędrysek (72-81).
The aim of this study was to assess the natural and anthropogenic input of methane (CH4) to the urban atmosphere of Wrocław (South West Poland). The study is based on the combined use of quantitative (measurement of concentrations) and qualitative analyses (analysis of stable carbon isotopic compositions). Air samples were collected every three weeks in 2011 from 15 sampling points distributed evenly over the city area. The methane concentration varied from 1859 ppb to 7691 ppb, with a mean annual value of 2096 ppb. Carbon isotopic composition of methane δ13C(CH4) varied from −61.5‰ to −37.8‰ with average of −48.1‰. The dominant CH4 source was biogenic, namely, the methane produced at sewage irrigation fields (man made biogenic emissions) and local wetlands (natural biogenic input). During the growing season emitted CH4 spread to considerable distances, depending on the prevailing meteorological conditions. During the cold period, biogenic input was negligible and other anthropogenic sources (biomass burning and city network gas) of methane could be observed.
Role of an impermeable layer in controlling groundwater chemistry in a basaltic aquifer beneath an agricultural field, Jeju Island, South Korea by Hee-Won Jung; Seong-Taek Yun; Kyoung-Ho Kim; Sang-Sil Oh; Kyung-Goo Kang (82-93).
Hydrochemical data (major cations and anions, and trace metals such as Fe, Mn and V) of groundwater (n = 144) were collected from 15 pre-existing wells in the Gosan area, along the southwestern coast of Jeju Island, South Korea, between January and October 2010. These were used to investigate the spatio-temporal variability of groundwater quality in a basaltic aquifer beneath an agricultural field. In the western part of the study area, an impermeable clay-rich layer (Gosan Formation) overlies the basaltic aquifer, prohibiting direct recharge from rainwater infiltration and allowing a shallow perched aquifer to form above the formation. Robust Principal Component Analysis (ROBPCA) was performed to investigate the hydrochemical characteristics. Twenty-seven outlying samples were separated from the total dataset; among these, 17 samples reflected seawater effects, and seven samples reflected abnormally high impacts from agricultural contamination. For the rest regular observations (n = 117) and a good leverage point, ROBPCA showed that principal component (PC) 1 effectively distinguishes uncontaminated water from those samples reflecting agricultural contamination. Variables with positive PC 1 loadings (TDS, Ca, Mg, NO3, SO4, and Cl) indicate agricultural contamination, while negative PC 1 loadings (pH, Na, K, HCO3 and V) possibly indicate basalt weathering. Samples with chemistry controlled by agricultural contamination are restricted to the eastern part of the study area, while uncontaminated water is predominantly observed in the western part where the Gosan Formation occurs. Such a distinct spatial pattern indicates that overall groundwater quality is regulated by the occurrence of the impermeable formation. Groundwater samples from wells near the edge of the Gosan Formation show seasonal fluctuations in water quality, with factor scores that indicates uncontaminated water in the dry season (January to April), and agricultural contamination in the wet season (May to October). This suggests that groundwater below the marginal part of the impermeable layer is seasonally contaminated by a temporal extension of the pollution front during the wet season, even though the impermeable layer plays a role as a natural barrier to protect groundwater from the infiltration of surface contaminants. This study also shows the advantage of ROBPCA to successfully identify spatio-temporal variation of groundwater quality in an area where diverse hydrochemical processes are coexisting and anormalous samples occur.
Understanding the hydrochemical evolution of a coastal dune system in SW England using a multiple tracer technique by Debbie Allen; W. George Darling; Peter J. Williams; Charlie J. Stratford; Nick S. Robins (94-104).
An improved knowledge of the hydrology of coastal dune systems is desirable for successful management of their diverse ecology under a changing climate. As a near-pristine coastal dune spit system, Braunton Burrows (SW England) is an ideal location for the study of the natural processes governing recharge to the dune groundwater system and the evolution of its water quality. Whereas previous investigations have tended to focus on inter-dune slacks, this study has also given attention to infiltration through the high dunes. Cores were taken through dunes and the resulting sand samples processed to provide information on grain size distribution and porewater chemistry. Groundwater samples were obtained from beneath dunes and slacks. A variety of geochemical techniques were applied including hydrochemistry, stable isotopes and residence time indicators. The unsaturated zone profiles indicate the existence of piston flow recharge with an infiltration rate of 0.75–1 m/yr, although faster rates probably also occur locally. Groundwater beneath the high dunes gave ages in the range 13–16 yr, compared to the dune slack groundwater ages of 5–7 yr, and an age of 22 yr for groundwater from the underlying mudstone aquifer. The chemistry of waters in both unsaturated and saturated zones is dominated by Ca and HCO3, supplemented by variable amounts of other ions derived from marine aerosols and limited reaction with sand grains and their coatings. The main chemical evolution of the porewaters occurs rapidly through the mobilisation of surface salt crusts and dissolution of shell carbonate. This situation changes little in the underlying groundwater, though an evolution towards reducing conditions increases the concentrations of redox-sensitive species such as Fe and Mn. The rapid chemical evolution of the infiltrating water means that its composition will respond quickly to changes in the supply of shell material and/or marine salts, which are possible consequences of climate change. However, the residence time measurements suggest the dune aquifer has a relatively long turnover time which will to some extent buffer such changes. The results of the present study should be transferable to natural dune systems in similar coastal situations.
Geochemical controls of iodine uptake and transport in Savannah River Site subsurface sediments by Hilary P. Emerson; Chen Xu; Yi-Fang Ho; S. Zhang; Kathleen A. Schwehr; Michael Lilley; Daniel I. Kaplan; Peter H. Santschi; Brian A. Powell (105-113).
Display OmittedBecause iodine-129 has a half-life of nearly 16 million years, poses major health threats, and can be mobile in the environment, it is important to use the best estimates for kinetics of sorption in risk assessment models. Previous work estimating the iodine sorption has not allowed for samples to reach full equilibrium and field studies have reported significant fractions of up to three major species of iodine; therefore, further research into the kinetics of iodine sorption to sediments is warranted. The objective of this study is to investigate the kinetics of iodine sorption in the presence of subsurface upland sediments and wetland sediments from an area within an 129I plume at the Savannah River Site in Aiken, SC. Batch sorption studies for these systems took longer than 8 weeks to reach equilibrium, which is significant as previous studies did not reach such timescales. In addition, experiments were conducted under oxic and anoxic conditions. Results confirm that there are three species present in these systems (iodide, iodate, and organo-iodine) with a majority as organo-iodine species at equilibrium for systems with high organic matter content. It is notable that the anoxic conditions exhibited reduced sorption for the iodate species to wetland sediment with high organic matter.
Evaluation of the ability of ferrihydrite to bind heavy metal ions: Based on formation environment, adsorption reversibility and ageing by Shan Meng; Huanling Wang; Hui Liu; Caihong Yang; Yu Wei; Denglu Hou (114-119).
Ferrihydrites prepared by three procedures exhibit different adsorption capacity and affinity for Cu(II) ions.Display OmittedBinding ability of heavy metal ions on the surface of environmental minerals may greatly affect the local chemical properties, long-range interactions, surface reactivity, and bioavailability of metal ions in the aquatic environment. In this work, three ferrihydrites (Fh-1, Fh-2 and Fh-3) were prepared by different clearly defined procedures. Among them, the formation condition of Fh-3 is close to that of ferrihydrite in natural environment. The adsorption characteristics of the Cu(II) ions on the three ferrihydrites were investigated. The affinity of three ferrihydrites to Cu(II) ions was evaluated based on pH-sorption edge curves, Langmuir and Freundlich model parameters, adsorption–desorption isotherms and ageing of ferrihydrite adsorbed Cu(II). The results indicate that the maximum adsorption capacity for Cu(II) was found to be 8.74, 13.33 and 14.39 mg g−1 for Fh-1, Fh-2 and Fh-3, respectively. Fh-2 and Fh-3 have stronger affinity than Fh-1 to adsorb Cu(II) ions. The experimental data were well fitted by double layer surface complexation model. The sorption differences of Cu(II) on the three Fhs were investigated by results gained from the simulation.
Spatial prediction of blood lead levels in children in Toledo, OH using fuzzy sets and the site-specific IEUBK model by Lauren R. Stewart; John R. Farver; Pece V. Gorsevski; Jeffrey G. Miner (120-129).
Lead poisoning in young children remains a concern in many urban areas, even 30 years after the banning of Pb-based paint and leaded gasoline. In 2010, 16.6% of 6550 children tested in Toledo, OH had blood lead levels (BLLs) above the Centers for Disease Control (CDC) lead poisoning reference level of 5 μg/dL. The aim of this study was to spatially quantify the risk of lead poisoning to children in Toledo, OH and to reduce lead poisoning risk through educational outreach and citizen science.The educational outreach component of the study was implemented through the sampling strategy. Students in Toledo area schools were instructed on proper USEPA soil sampling guidelines and were asked to collect soil samples from their residential yards. A subsample of 81 soils was analyzed for total lead and bioavailable lead. Site-specific total lead and bioavailability data were used in the USEPA Integrated Exposure Uptake and Biokinetic (IEUBK) model to predict BLLs. Predicted BLLs were then used to extract expert knowledge for development of an index model using analytical hierarchy process (AHP) and weighted linear combination (WLC). Expert knowledge was used to standardize predictor datasets and to produce continuous BLL risk for each predictor variable. Fuzzy sets were implemented in the model to account for uncertainties in the sampling method.It was found that 8.6% of sampled sites had total soil lead concentrations above the USEPA action level of 400 mg/kg, but 28.4% of soil samples yielded predicted elevated BLLs, suggesting the action level is set too high. The spatial variables influencing risk of lead poisoning from most important to least important were age of housing, road density, percent impervious surfaces, home value, household income and soil type. The highest risk for lead poisoning was in the city center and decreased moving towards the rural areas surrounding the city. The index model paired with the unique outreach driven sampling approach proved successful both at providing quality soil samples and educating the community about the ongoing risks of lead in soil.
Ground water colloid properties from the Bangombé system by Claude Degueldre; Marcus Laaksoharju (130-143).
Comparison of lanthanide concentrations associated with the colloid phase (400–50 nm): BAX03(Col) (this work), with the so called “dissolved” (<450 nm): BAX03(GW) (Stille et al., 2003), leachates from particles (>450 nm): BAX03(Leach) (Stille et al., 2003) from the rock: BAX03R(Leach) (Stille et al., 2003), and from the reactor zone: BAX03(Rock1180) (Hidaka et al., 2005).Display OmittedThe concentration and the role of colloids in the transport of elements in the vicinity of a fossil reactor at Bangombé, Gabon, were assessed. Colloid sampling was conducted in seven boreholes around and in the extinguished natural reactor. The ground waters are of Na–Mg–Ca–HCO3 type, with variable salinities, pH 4.6–6.8 and anaerobic Eh values. Filtered ground water and colloid samples were taken from the reactor and the surroundings. Filtered fluids and colloid samples collected on membranes and resuspended in solution were analysed by ICP-MS and ICP-AES in order to examine the element association in the colloid phase within the size range 3000 to 400 to 50 nm. The colloid concentrations for the size 400 to 50 nm range from 80 to 300 ng ml−1. They consist of silica particles associated with ferrihydrite coated with organics. Trace element results show that metals including Pb, Sc, Y, La, Ce, Pr, Nd, Bi, Th and U are associated to various degrees with the colloid phase. The distribution ratios of these trace elements between the water and the colloid phase (Kp) were experimentally determined. The high Pb distribution ratios of 10+7 ml g−1 are specifically discussed. Values range from 10+6 to 10+5 ml g−1for the trivalent elements (Sc, Y, La, Ce, … , Bi). For uranium, a Kp of the order of 10+5 ml g−1 may be calculated and compared with data gained using the surface complexation model. These Kp values suggest that the uranium is partially sorbed or associated with ground water colloids. Measurements from the reactor zone show that about 2–4% of the uranium is associated with the colloid phase, which contributes partially to the uranium transport. The rather low colloid concentrations are due to the relatively high concentrations of Ca, Mg and Na in these quasi-neutral waters. These soluble elements contribute to the attachment of the colloids, restricting their transport. This indicates that the colloid phase may not be an important transport medium for the radionuclides in the Bangombé system if their association is reversible. The Bangombé colloid results are compared with those studied for other systems.
Effects of alteration product precipitation on glass dissolution by Denis M. Strachan; James J. Neeway (144-157).
Understanding the mechanisms that control the durability of nuclear waste glass is paramount if reliable models are to be constructed so that the glass dissolution rate in a given geological repository can be calculated. Presently, it is agreed that (boro)silicate glasses dissolve in water at a rate dependent on the solution concentration of orthosilicic acid (H4SiO4) with higher [H4SiO4] leading to lower dissolution rates. Once the reaction has slowed as a result of the buildup of H4SiO4, another increase in the rate has been observed that corresponds to the precipitation of certain silica-bearing alteration products. However, it has also been observed that the concentration of silica-bearing solution species does not significantly decrease, indicating saturation, while other glass tracer elements concentrations continue to increase, indicating that the glass is still dissolving. In this study, we have used the Geochemist’s Workbench code to investigate the relationship between glass dissolution rates and the precipitation rate of a representative zeolitic silica-bearing alteration product, analcime [Na(AlSi2O6)⋅H2O]. To simplify the calculations, we suppressed all alteration products except analcime, gibbsite (Al(OH)3), and amorphous silica. The pseudo-equilibrium-constant matrix for amorphous silica was substituted for the glass pseudo-equilibrium-constant matrix because it has been shown that silicate glasses act as a silica-only solid with respect to kinetic considerations. In this article, we present the results of our calculations of the glass dissolution rate at different values for the analcime precipitation rate constant and the effects of varying the glass dissolution rate constant at a constant analcime precipitation rate constant. From the simulations we conclude, firstly, that the rate of glass dissolution is dependent on the kinetics of formation of the zeolitic phase. Therefore, the kinetics of secondary phase formation is an important parameter that should be taken into account in future glass dissolution modeling efforts. Secondly, the results indicate that, in the absence of a gel layer, the glass dissolution rate controls the rate of analcime precipitation in the long term. The meaning of these results pertinent to long-term glass durability is discussed.
Reactivity of the calcite–water-interface, from molecular scale processes to geochemical engineering by Frank Heberling; Dirk Bosbach; Jörg-Detlef Eckhardt; Uwe Fischer; Jens Glowacky; Michael Haist; Utz Kramar; Steffen Loos; Harald S. Müller; Thomas Neumann; Christopher Pust; Thorsten Schäfer; Jan Stelling; Marko Ukrainczyk; Victor Vinograd; Marijan Vučak; Björn Winkler (158-190).
Surface reactions on calcite play an important role in geochemical and environmental systems, as well as many areas of industry. In this review, we present investigations of calcite that were performed in the frame of the joint research project “RECAWA” (reactivity of calcite–water-interfaces: molecular process understanding for technical applications). As indicated by the project title, work within the project comprised a large range of length scales. The molecular scale structure of the calcite (1 0 4)–water-interface is refined based on surface diffraction data. Structural details are related to surface charging phenomena, and a simplified basic stern surface complexation model is proposed. As an example for trace metal interactions with calcite surfaces we review and present new spectroscopic and macroscopic experimental results on Selenium interactions with calcite. Results demonstrate that selenate (SeO4 2−) shows no significant interaction with calcite at our experimental conditions, while selenite (SeO3 2−) adsorbs at the calcite surface and can be incorporated into the calcite structure. Atomistic calculations are used to assess the thermodynamics of sulfate (SO4 2−), selenate (SeO4 2−), and selenite (SeO3 2−) partitioning in calcite and aragonite. The results show that incorporation of these oxo-anions into the calcite structure is so highly endothermic that incorporation is practically impossible at bulk equilibrium and standard conditions. This indicates that entrapment processes are involved when coprecipitation is observed experimentally. The relevance of nano-scale surface features is addressed in an investigation of calcite growth and precipitation in the presence of phosphonates, demonstrating the influence of phosphonates on the morphology of growth spirals and macroscopic growth rates. It is investigated how physical properties of limestone containing cement suspensions may influence the workability of the cement suspensions and thus the efficacy of limestone in industrial applications. The largest scale is reached in iron filtration experiments in a water-purification-pilot-plant using limestone as filter material, which appeared to be highly effective for removing iron from drinking water. Investigations presented cover a whole series of methods to study the calcite–water-interface. Many calcite related topics are addressed, demonstrating how broad the field of calcite–water-interface research is and how manifold the applications are, for which calcite–water-interface phenomena are of major relevance.
High-technology metals as emerging contaminants: Strong increase of anthropogenic gadolinium levels in tap water of Berlin, Germany, from 2009 to 2012 by N. Tepe; M. Romero; M. Bau (191-197).
The distribution of rare earth elements (REE) in tap water sampled in December 2012 in Berlin, Germany, is characterized by anomalously high levels of gadolinium (Gd). While the western districts of the city show strong anthropogenic positive Gd anomalies in REE distribution patterns, the eastern districts are (almost) unaffected. This contamination with anthropogenic Gd results from Gd-based contrast agents used in Magnetic Resonance Imaging, that enter rivers, groundwater and eventually tap water via the clear water effluent from wastewater treatment plants. While the spatial distribution of anthropogenic Gd in 2012 confirms results of an earlier study in 2009 (Kulaksiz and Bau, 2011a), anthropogenic Gd concentrations have increased between 1.5- and 11.5-fold in just three years. This confirms predictions based upon the increase of anthropogenic Gd concentrations in the Havel River over the past two decades and the time it takes the water to migrate from the Havel River to the groundwater production wells. Anomalously high levels of anthropogenic Gd in tap water, which are not confined to Berlin but have also been observed in London, U.K., and in German cities in the Ruhr area and along the Rhine River, reveal that high-technology metals have become emerging contaminants. While non-toxic at the observed concentrations, the anthropogenic Gd is a microcontaminant that may be used as a conservative pseudo-natural tracer for wastewater-derived xenobiotics such as pharmaceuticals, food additives and personal care products. Our results suggest that monitoring the concentrations of such substances in Berlin’s drinking water can be restricted to a few central and western districts of the city, demonstrating that implementation of anthropogenic Gd as a tracer in monitoring programs can contribute to significant cost savings.