Applied Geochemistry (v.48, #C)
Obtaining isochrones from pollution signals in a fluvial sediment record: A case study in a uranium-polluted floodplain of the Ploučnice River, Czech Republic by T. Matys Grygar; J. Elznicová; O. Bábek; M. Hošek; Z. Engel; T. Kiss (1-15).
Uranium mining and processing in the watershed of the Ploučnice River in the Czech Republic during a well-defined time interval (1969–1989) allowed for a study of pollutant fates in sediments of a meandering river that is otherwise in a nearly natural state. A considerable part of the primary pollution is present in hotspots in the floodplain 10–15 km downstream from the mining district. One of the hotspots was characterised using geoinformatic, geophysical and geochemical means. The floodplain geomorphology and architecture and river channel dynamics were studied to develop an understanding of the formation of the hotspot and evaluate further movement of pollutants in the river system. Local background functions (with Rb or Ti as a predictor) and local enrichment factors (LEFs) were obtained for Ba, Ni, Pb, U and Zn concentrations in unpolluted sediments from the deeper strata of the active floodplain, an abandoned floodplain and an ancient terrace. The most recent (2013) overbank fines in the study area are still considerably enriched in Ni, U and Zn (LEF 3, 6 and 8, respectively), and thus pollution by heavy metals several km downstream of the hotspots continuously increases even though the primary source of pollution was terminated more than 20 years ago. The onset of the primary pollution (the base of the polluted strata) is hence clearly identified in the distal floodplain sediments as persistent and a potentially isochronous pollution signal in the fluvial record, whereas a secondary pollution signal overwrites the expected “primary pollution climax” and “pollution improvement” signals. That inertia of the fluvial system can also be expected in other river systems with both laterally and vertically deposited sediments. The Ploučnice case study allowed for further elaboration of the concept of local enrichment factors in pollution assessment of fluvial sediments, which efficiently reduces the grain-size effects (the impact of hydraulic sorting) and hence allows for reconstruction of the pollution history.
Mobilization of selenium from the Mancos Shale and associated soils in the lower Uncompahgre River Basin, Colorado by M. Alisa Mast; Taylor J. Mills; Suzanne S. Paschke; Gabrielle Keith; Joshua I. Linard (16-27).
This study investigates processes controlling mobilization of selenium in the lower part of the Uncompahgre River Basin in western Colorado. Selenium occurs naturally in the underlying Mancos Shale and is leached to groundwater and surface water by limited natural runoff, agricultural and domestic irrigation, and leakage from irrigation canals. Soil and sediment samples from the study area were tested using sequential extractions to identify the forms of selenium present in solid phases. Selenium speciation was characterized for nonirrigated and irrigated soils from an agricultural site and sediments from a wetland formed by a leaking canal. In nonirrigated areas, selenium was present in highly soluble sodium salts and gypsum. In irrigated soils, soluble forms of selenium were depleted and most selenium was associated with organic matter that was stable under near-surface weathering conditions. Laboratory leaching experiments and geochemical modeling confirm that selenium primarily is released to groundwater and surface water by dissolution of highly soluble selenium-bearing salts and gypsum present in soils and bedrock. Rates of selenium dissolution determined from column leachate experiments indicate that selenium is released most rapidly when water is applied to previously nonirrigated soils and sediment. High concentrations of extractable nitrate also were found in nonirrigated soils and bedrock that appear to be partially derived from weathered organic matter from the shale rather than from agricultural sources. Once selenium is mobilized, dissolved nitrate derived from natural sources appears to inhibit the reduction of dissolved selenium leading to elevated concentrations of selenium in groundwater. A conceptual model of selenium weathering is presented and used to explain seasonal variations in the surface-water chemistry of Loutzenhizer Arroyo, a major tributary contributor of selenium to the lower Uncompahgre River.
Enhancement of in situ biodegradation of organic compounds in groundwater by targeted pump and treat intervention by S.F. Thornton; K.M. Baker; S.H. Bottrell; S.A. Rolfe; P. McNamee; F. Forrest; P. Duffield; R.D. Wilson; A.W. Fairburn; L.A. Cieslak (28-40).
This study demonstrates the value of targeted pump and treatment (PAT) to enhance the in situ biodegradation of organic contaminants in groundwater for improved restoration. The approach is illustrated for a plume of phenolic compounds in a sandstone aquifer, where PAT is used for hydraulic containment and removal of dissolved phase contaminants from specific depth intervals. Time-series analysis of the plume hydrochemistry and stable isotope composition of dissolved species (δ34S-SO4, δ13C-CH4, δ13C-TDIC (TDIC = Total Dissolved Inorganic Carbon)) in groundwater samples from high-resolution multilevel samplers were used to deduce changes in the relative significance of biodegradation processes and microbial activity in the plume, induced by the PAT system over 3 years. The PAT system has reduced the maximum contaminant concentrations (up to 6800 mg L−1 total phenols) in the plume by 50% to ∼70% at different locations. This intervention has (i) stimulated in situ biodegradation in general, with an approximate doubling of contaminant turnover based on TDIC concentration, which has increased from <200 mg L−1 to >350 mg L−1, (ii) enhanced the activity of SO4-reducing microorganisms (marked by a declining SO4 concentration with corresponding increase in SO4-δ34S to values >7–14‰V-CDT relative to background values of 1.9–6.5‰V-CDT), and (iii) where the TDIC increase is greatest, has changed TDIC-δ13C from values of −10 to −15‰V-PDB to ∼−20‰V-PDB. This indicates an increase in the relative importance of respiration processes (including denitrification and anaerobic methane oxidation, AMO) that yield 13C-depleted TDIC over fermentation and acetoclastic methanogenesis that yield 13C-enriched TDIC in the plume, leading to higher contaminant turnover. The plume fringe was found to be a zone of enhanced biodegradation by SO4-reduction and methanogenesis. Isotopically heavy methane compositions (up to −47.8‰V-PDB) and trends between δ13C-TDIC and δ13C-CH4 suggest that AMO occurs at the plume fringe where the contaminant concentrations have been reduced by the PAT system. Mass and isotope balances for inorganic carbon in the plume confirm the shift in spatial dominance of different biodegradation processes and significant increase in contribution of anaerobic respiration for contaminant biodegradation in zones targeted by the PAT system. The enhanced in situ biodegradation results from a reduction in organic contaminant concentrations in the plume to levels below those that formerly suppressed microbial activity, combined with increased supply of soluble electron acceptors (e.g. nitrate) into the plume by dispersion. An interruption of the PAT system and recovery of the dissolved organic contaminant concentrations towards former values highlights the dynamic nature of this enhancement on restoration and relatively rapid response of the aquifer microorganisms to changing conditions induced by the PAT system. In situ restoration using this combined engineered and passive approach has the potential to manage plumes of biodegradable contaminants over shorter timescales than would be possible using these methods independently. The application of PAT in this way strongly depends on the ability to ensure an adequate flux of dissolved electron acceptors into the plume by advection and dispersion, particularly in heterogeneous aquifers.
Assessing the solubility controls on vanadium in groundwater, northeastern San Joaquin Valley, CA by Michael T. Wright; Kenneth G. Stollenwerk; Kenneth Belitz (41-52).
The solubility controls on vanadium (V) in groundwater were studied due to concerns over possible harmful health effects of ingesting V in drinking water. Vanadium concentrations in the northeastern San Joaquin Valley ranged from <3 μg/L to 70 μg/L with a median of 21 μg/L. Concentrations of V were highest in samples collected from oxic groundwater (49% > 25 μg/L) and lowest in samples collected from anoxic groundwater (70% < 0.8 μg/L). In oxic groundwater, speciation modeling (SM) using PHREEQC predicted that V exists primarily as the oxyanion H2VO4 −. Adsorption/desorption reactions with mineral surfaces and associated oxide coatings were indicated as the primary solubility control of V5+ oxyanions in groundwater. Environmental data showed that V concentrations in oxic groundwater generally increased with increasing groundwater pH. However, data from adsorption isotherm experiments indicated that small variations in pH (7.4–8.2) were not likely as an important a factor as the inherent adsorption capacity of oxide assemblages coating the surface of mineral grains. In suboxic groundwater, accurate SM modeling was difficult since Eh measurements of source water were not measured in this study. Vanadium concentrations in suboxic groundwater decreased with increasing pH indicating that V may exist as an oxycationic species [e.g. V(OH)3 +]. Vanadium may complex with dissolved inorganic and organic ligands under suboxic conditions, which could alter the adsorption behavior of V in groundwater. Speciation modeling did not predict the existence of V-inorganic ligand complexes and organic ligands were not collected as part of this study. More work is needed to determine processes governing V solubility under suboxic groundwater conditions. Under anoxic groundwater conditions, SM predicts that aqueous V exists as the uncharged V(OH)3 molecule. However, exceedingly low V concentrations show that V is sparingly soluble in anoxic conditions. Results indicated that V may be precipitating as V3+- or mixed V3+/Fe3+-oxides in anoxic groundwater, which is consistent with results of a previous study. The fact that V appears insoluble in anoxic (Fe reducing) redox conditions indicates that the behavior of V is different than arsenic (As) in aquifer systems where the reductive dissolution of Fe-oxides with As adsorbed to the surface is a well-documented mechanism for increasing As concentrations in groundwater. This hypothesis is supported by the relation of V to As concentrations in oxic versus anoxic redox conditions.Sequential extraction procedures (SEP) applied to aquifer material showed that the greatest amount of V was recovered by the nitric acid (HNO3) extract (37–71%), followed by the oxalate-ascorbic acid extract (19–60%) and the oxalate extract (3–14%). These results indicate that V was not associated with the solid phase as an easily exchangeable fraction. Although the total amount of V recovered was greatest for the HNO3 extract that targets V adsorbed to sorption sites of crystalline Al, Fe and Mn oxides, the greatest V saturation of sorption sites appeared to occur on the amorphous and poorly crystalline oxide solid phases targeted by the oxalate and oxalate-ascorbic acid extracts respectively. Adsorption isotherm experiments showed no correlation between V sorption and any of the fractions identified by the SEP. This lack of correlation indicates the application of an SEP alone is not adequate to estimate the sorption characteristics of V in an aquifer system.
The zinc stable isotope signature of waste rock drainage in the Canadian permafrost region by Romy Matthies; Sean A Sinclair; David W Blowes (53-57).
Leachate from a well-instrumented experimental-scale waste-rock pile (test pile) at the Diavik Diamond mine, Northwest Territories, was monitored. The well-characterized waste rock consists of granite, pegmatitic granite and biotite schist with an average total sulfur and carbonate carbon concentration of 0.053 and 0.027 wt.%, respectively. The leachate emerging from the southern basal drain of the waste rock pile has been monitored since 2007. The zinc stable isotope footprint was characterized alongside standard monitoring parameters during two field seasons, May to November 2011 and 2012. The pH ranged between 4.3 and 6.8 and carbonate alkalinity was low or undetectable (<35 mg L−1 CaCO3). The pH was governed by the oxidation of sulfide minerals and the dissolution of primary carbonate minerals and secondary Al and Fe oxyhydroxysulfates and hydroxides. Dissolved Al and Fe concentrations averaged 6.78 mg L−1 and 175 μg L−1, respectively. The main processes controlling Zn concentrations in the range of 0.4 and 4.7 mg L−1 (average = 2.2 mg L−1) were the oxidative dissolution of sphalerite (ZnS) and the attenuation by secondary Fe and Al hydroxides. Zinc isotopes were fractionated mass dependently. Zinc isotope ratios, ranging between −0.16 and +0.18‰ (average = +0.05‰, n = 43) were consistent with values reported for sphalerite from other deposits. The deviations in isotope ratios (Δ = 0.36‰) were significant in comparison to analytical uncertainties (0.06‰). Zinc isotope ratios and concentrations were largely uncorrelated, suggesting that the processes affecting Zn mobility had little or no impact on the Zn isotope signature. These data suggest that the Zn isotope ratios of the waste-rock leachate may be used as a fingerprint to track anthropogenic, mine-derived Zn sources in an environment under fluctuating pH, temperature and ionic strength.
Biogeochemical processes in infiltration basins and their impact on the recharging effluent, the soil aquifer treatment (SAT) system of the Shafdan plant, Israel by O. Goren; A. Burg; I. Gavrieli; I. Negev; J. Guttman; T. Kraitzer; W. Kloppmann; B. Lazar (58-69).
Soil aquifer treatment (SAT) systems utilize infiltration basins for recharging pre-treated effluent into the aquifer for water quality improvement. The present research focuses on the diurnal and seasonal variations of oxygen, carbon and nitrogen species in the infiltration basins and in the uppermost vadose zone for determining the impact of different environmental conditions on the composition of the infiltrating effluent. The study was conducted in one of the infiltration basins of the Dan Region Sewage Reclamation Project (Shafdan), Israel. Solar radiation and aeration were recognized to be the two main factors controlling the chemical composition of the effluent within the basin and the uppermost vadose zone. The effluent entering the basin show initial enrichment with dissolved oxygen (DO) due to gas exchange caused by “injection” through the inlet fountain and turbulence during basin filling. The DO, pH and dissolved inorganic carbon (DIC) fluctuate diurnally as a result of intense in-basin daylight photosynthesis and nighttime respiration. DO and pH increase during day and decrease during night and the DIC shows an opposite behavior. The daylight net primary production was ∼240 μmol L−1 d−1 and the diurnal respiration rate was ∼430 μmol L−1 d−1 (assuming that the nighttime respiration rate is constant over a whole diurnal cycle). The gross primary production during daylight was ∼450 μmol L−1 d−1. Dissolved organic carbon (DOC) and inorganic nitrogen species (NH4 + + NO3 −) varied significantly in the uppermost vadose zone, however, neither the vadose zone nor the basin showed diurnal fluctuations. It appears that chemical variations between three sampling campaigns conducted in different seasons stemmed mainly from the efficiency of basin aeration that resulted from changes in basin’s operation regime and local environmental conditions. The results of this study lead to the following basin management recommendations: (1) keeping short flooding and drying cycles and allowing complete basin desiccation before the next flooding; and (2) flooding the basin during daytime, starting at dawn to maximize oxygen production and minimize infiltration during nighttime. Following these routines would result in higher redox potential of the infiltrating effluent.
Tracking selenium in the Chalk aquifer of northern France: Sr isotope constraints by L. Cary; H. Benabderraziq; J. Elkhattabi; L. Gourcy; M. Parmentier; J. Picot; M. Khaska; A. Laurent; Ph. Négrel (70-82).
Groundwater at the southern and eastern edges of France’s Paris Basin has a selenium content that at times exceeds the European Framework Directive’s drinking-water limit value of 10 μg/L. To better understand the dynamics of the Chalk groundwater being tapped to supply the city of Lille and the Se origins, we used a combination of geochemical and isotopic tools. Strontium isotopes, coupled with Ca/Sr, Mg/Sr and Se/Sr ratios, were used to identify the main groundwater bodies and their mixings, with the Mg/Sr and Se/Sr ratios constraining a ternary system. Groundwater in the agricultural aquifer-recharge zone represents a first end-member and displays the youngest water ages of the catchment along with the highest Sr isotopic signature (0.70842) and low Se contents. Anaerobic groundwater constitutes a second major end-member affected by water-rock interactions over a long residence time, with the lowest Sr isotopic signature (0.70789) and the lowest Se content, its low SF6 content confirming the contribution of old water. Se-rich groundwater containing up to 30 μg/L of Se represents a third major end-member, with an intermediate Sr isotopic ratio (0.70826), and is mainly constrained by the clayey Se-rich formation overlying the Chalk aquifer. The spatial and temporal Se variability in the groundwater is clearly linked to the presence of this formation identified as Tertiary and also to the hydrological conditions; saturation of the Se-rich clays by oxygenated groundwater enhances Se mobility and also Sr adsorption onto the clays. This multi-tool study including Sr isotopes successfully identified the Se origins in the aquifer and has led to a better understanding of the regional mixing and processes affecting the Chalk groundwater.
Impact of water diversion on the hydrogeochemical characterization of surface water and groundwater in the Yellow River Delta by Qiang Liu; Fadong Li; Qiuying Zhang; Jing Li; Yan Zhang; Chun Tu; Zhu Ouyang (83-92).
The Yellow River Delta is undergoing severe ecosystem degradation through salinization caused mainly by seawater intrusion. The Yellow River diversion project, in operation since 2008, aims to mitigate a projected ecosystem disaster. We conducted field investigations across three ecosystems (Farmland, Wetland and Coast) in the delta to assess the effectiveness of the annual water pulse and determine the relationships between surface water and groundwater. The chemical characteristics of the groundwater in Farmland exclude the possibility of seawater intrusion. The Wetland is vulnerable to pollution by groundwater discharge from Farmland and to secondary salinization caused by rising water tables. The salinity values of groundwater at Coast sites likely reflect the presence of seawater trapped in the clay sediments, a premise corroborated through measurements of groundwater levels, stable isotopes and major ion signatures. Our δD–δ18O two-dimensional graphic plot demonstrated that groundwaters of Farmland and Wetland changed toward more depleted isotopic compositions following water diversion, but this was not the case in the Coast sites, where the water table varied little year-round. A hydrochemical facies evolution diagram (HFE-D) demonstrated that freshening is taking place in the largest portions of the aquifers and that, without sustained water diversion recharge, these underground water bodies may switch from freshening to salinization on a seasonal time scale. Thus, the qualities of waters in coastal aquifers in the Yellow River Delta are substantially influenced by the process of ecological water diversion, and also by land use practices and by the lithological properties of the drainage landscape.
Factors controlling radiocesium distribution in river sediments: Field and laboratory studies after the Fukushima Dai-ichi Nuclear Power Plant accident by Qiaohui Fan; Kazuya Tanaka; Aya Sakaguchi; Hiroaki Kondo; Naoko Watanabe; Yoshio Takahashi (93-103).
This study used laboratorial estimations and determined the distribution coefficient (K d) of 137Cs in river sediments sampled from the Abukuma River and the Kuchibuto River to investigate the particle size dependence of RCs distribution. Results show that the K d patterns of 137Cs (particle size-dependence of K d) were not only related to the particle size of large particles (low clay mineral content) but also to the clay mineral content of small particles (high clay mineral content) and particularly cation concentration in aqueous phase. By contrast, the K d patterns of stable Cs (133Cs) exhibited no obvious particle size dependence. Adsorption species of Cs that was added to the river sediments at various particle sizes was almost the same at the molecular scale as determined by the extended X-ray absorption fine structure.Our findings indicate that river sediments have high fixation ability to 137Cs. Nevertheless, adsorbed 137Cs can be extracted from sediments in the water phase when salinity becomes high, such as that in seawater. The distribution patterns of 137Cs at various particle sizes can slowly down the equilibrium of the adsorption of 137Cs during the transportation of river sediments, and then the behavior of 137Cs should eventually be similar to that of stable Cs in the river system. Therefore, the particle size of sediments is an important factor in the distribution of RCs at the early stage of its deposition. In the end, RCs adsorbed on the sediments will be equilibrated with the stable Cs during its transportation in the river system. Controlling factors such as the mineralogy of sediments could possibly make the distribution patterns of RCs similar to that of stable Cs in the long run.
Uraninite chemistry as forensic tool for provenance analysis by Hartwig E. Frimmel; Sibylle Schedel; Helene Brätz (104-121).
Electron microprobe and laser ablation-inductively coupled plasma mass spectrometric (LA-ICPMS) analyses were carried out on individual uraninite grains from several localities worldwide, representing a variety of different U-deposit types ranging in age from Mesoarchaean to the Mesozoic. For the first time, concentration data on a comprehensive set of minor/trace elements in uraninite are presented, i.e. LA-ICPMS concentration data for Th, Si, Al, Fe, Mn, Ca, Mg, P, Ti, V, Cr, Co, Ni, Pb, Zn, As, rare earth elements (REE), Y, Zr, Nb, Mo, Ag, Ta, W, Bi, and Au. Most of these elements could be detected in significant quantities in many of the studied examples. The results obtained in this study, supplemented by previously published data on major element and REE concentrations, reveal systematic differences in uraninite composition between genetically different deposit types and also, for a given genetic type, between different locations.Low-temperature hydrothermal uraninite is marked by U/Th >1000, whereas high-temperature metamorphic and magmatic (granitic, pegmatitic) uraninite has U/Th <100. Our new data also confirm previous observations that low-temperature, hydrothermal uraninite has low total REE contents (<1 wt%) whereas higher temperature uraninite can contain as much as several percent total REE. Genetically different uraninite types can be further identified by means of different REE fractionation patterns. Systematic differences between primary uraninite from different localities could be also noted with respect to the abundances of especially Y, V, W, Zr, Nb, Ta, and to a lesser extent Mo, P, Bi, and As. Our findings open up the possibility of using uraninite chemistry as provenance tool, both for geological applications, as exemplified in this study by the application to uraninite in the Mesoarchean Witwatersrand Basin (South Africa), as well as for forensic purposes to track down the likely source of illegally mined uraninite. Uraninite chemistry provides strong support for a palaeoplacer model for the U-mineralisation in the auriferous and uraniferous conglomerates of the Witwatersrand, in which individual uraninite particles display chemical characteristics typical of high-temperature (magmatic) uraninite and a great variation in trace element concentrations that point to a variety of (magmatic) source rocks.
Impact of air pollution in deterioration of carbonate building materials in Italian urban environments by Donatella Barca; Valeria Comite; Cristina M. Belfiore; Alessandra Bonazza; Mauro F. La Russa; Silvestro A. Ruffolo; Gino M. Crisci; Antonino Pezzino; Cristina Sabbioni (122-131).
This work presents results from a petrographic, morphological and chemical study of the black crusts developing on monuments in three Italian cities, the Cathedral of Milan, the Cathedral of St. Maria del Fiore in Florence, and the Vittoriano Monument in Rome.Black crusts (BCs) were studied with traditional techniques such as optical microscopy (OM), scanning electron microscopy coupled with energy-dispersive X-ray spectrometry (SEM-EDS) and infrared spectroscopic techniques (FT-IR), in combination with laser ablation inductively coupled mass spectrometry (LA-ICP-MS), which has shown itself to be particularly useful in determining concentrations of heavy metals in BCs.Although the BCs of the three monuments show general enrichment in heavy metals with respect to the substrate (S), interesting differences were observed among them. The BCs from Milan are the richest in heavy metals, particularly Pb and Zn, reflecting the severe air pollution of this very large city, which, in addition to its intense traffic, is located in the most highly industrialized area of Northern Italy. The BCs from the south-eastern side of the Cathedral of St. Maria del Fiore in Florence, facing a pedestrian area, show little enrichment in heavy metals, and those from the Vittoriano Monument in Rome, which is exposed to intense road traffic, display variable enrichment, attributable to mobile emission sources.Results show that the various enrichment trends in heavy metals observed in the BCs of these three monuments are due to many factors: various sources of anthropogenic pollution, sampling height, exposure, orientation, and the shape of the deposition surface.
Solubility of chromate in a hydrated OPC by Sabine M. Leisinger; Amit Bhatnagar; Barbara Lothenbach; C. Annette Johnson (132-140).
The knowledge of the chromate binding mechanisms is essential for the prediction of the long-term leachability of cement-based solidified waste containing increased chromate concentrations because of its toxicity and high mobility. In this paper pore water concentrations from OPC doped with varying CaCrO4 concentrations (0.01–0.8 mol/kg), equilibrated for 28 days were reported. It could be shown that the cementitious matrix can bind chromate concentrations up to 0.1 mol/kg and that the chromate solubility limiting phase was CrO4-ettringite, while chromate containing AFm (monochromate) was unstable. Comparison with thermodynamic modelling indicated that at lower chromate dosages chromate was mainly bound by CrO4-ettringite while at very high dosages also a mixed CaCrO4–CaSO4·2H2O phase precipitated. Additional experiments indicated a solubility product of 10− 3.66 for CaCrO4 and verified the solid solution formation with CaSO4·2H2O.Leaching tests indicated a strong chromate binding mainly in the pH range 10.5–13.5, while at pH < 10 very little chromate was bound as ettringite, monocarbonate and C–S–H phases were destabilized.Generally the thermodynamic modeling underestimated chromate uptake indicating that an additional chromate binding possibly on C–S–H or on mixed chromate–carbonate–hydroxide AFm phases.
Mineralogical and anthropogenic controls of stream water chemistry in salted watersheds by Hongbing Sun; John Alexander; Brita Gove; Eric Pezzi; Nicole Chakowski; Jonathan Husch (141-154).
The relatively stable concentrations of calcium (42.2–122.3 mg/l) and magnesium (48.9–88.1 mg/l) between 2012 and 2013 and their possible weathering paths identified by mass balance models for both soil solutions and stream water from a small salted (regular applications of winter road deicing salt) watershed in New Jersey, USA indicate that the weathering of feldspars and dissolution of carbonates are the primary sources for these cations. However, the relatively stable and lower concentrations of sodium and chloride in soil solutions (19.6–46.1 mg/l for Na and 12.7–88.3 mg/l for Cl) and their fluctuating and higher concentrations in stream water (14.6–103.1 mg/l for Na and 15.2–260.4 mg/l)) from the same watershed during the same period also indicate that road deicing salt is the primary source for sodium and chloride in stream water. Furthermore, positive correlations between calcium and sulfur concentrations (correlation coefficient r = 0.77) and magnesium and sulfur concentrations (r = 0.73) in stream water between 2009 and 2013, as well as positive correlations between sulfur and iron concentrations in soil compositions (r = 0.27), indicate that both the dissolution of gypsum and the oxidation of pyrite into hematite might be the primary sources of sulfate in the watershed. Analyses of water chemistry from the related and much larger Delaware River Watershed (DRW) show that sodium and chloride concentrations have increased steadily (2.7 times for Na and 4.56 times for Cl for 10-year average) due to the regular application of winter deicing salt from 1944 to 2011 for which data are available. The greater increase of stream water chloride concentrations compared with sodium concentrations also results in the steady decline of Na+/Cl− molar ratios from 1.51 to 0.92 for the 10-year average during that time in the DRW and approximately 78% of the chloride in the DRW now being anthropogenic. In addition, the decline of sulfate concentration from 22.08 to 14.59 mg/l (∼34%) for the 10-year average from 1980 to 2011 in the DRW stream water may be attributed to the decline of sulfate levels in atmospheric deposition resulting from enhanced national and state environmental regulations and a shift in local economic activities. There also are more periods of low silica stream water concentrations in the DRW than in the past, perhaps as a result of recent increases in summer stream temperatures combined with an increase of impervious surface area in the region. Warmer stream water might cause the temporary bloom of biota requiring silica, particularly plankton, increasing its uptake from stream water, while an expanded impervious surface area increases the contribution of low-silica runoff water to total stream discharge, thereby lowering the silica concentration in stream water. The combined results of this study illustrate the possible changing anthropogenic factors that can control stream water chemistry in salted watersheds and that these factors need to be taken into account when future water quality regulations and policy are considered.
Dawsonite formation in the Beier Sag, Hailar Basin, NE China tuff: A natural analog for mineral carbon storage by Bing Zhou; Li Liu; Shuang Zhao; Xiao-Ran Ming; Eric H. Oelkers; Zhi-Chao Yu; De-Feng Zhu (155-167).
We determined the rock types, the authigenic minerals, the paragenetic sequence, and the origin of dawsonite in pyroclastic rocks from the Yimin Formation of Beier Sag in the Hailar Basin, China. Dawsonite, a diagenetic mineral, is thought to result from a large influx of CO2 and, therefore, this system represents a natural analogue for in-situ mineral carbon storage. The studied host rocks are mainly tuffs/tuffaceous sandstones which now contain up to 70 vol% authigenic carbonates, including dawsonite, ankerite, and siderite. The initial alteration of the tuffs yielded minor siderite. Kaolinite, illite and mixed illite/smectite then formed as product phases. Dawsonite and quartz subsequently precipitated in response to CO2 influx apparently coupled to feldspar and perhaps kaolinte dissolution. Dawsonite reaches a maximum 25 vol% of the bulk rock. Mass balance suggests that this CO2 influx was coupled to the external import of sodium and export of SiO2. Ankerite and additional siderite precipitated during the late-stage alkaline diagenesis. The carbon isotope values of the dawsonite are in the range −4.1‰ to −2.2‰, indicating the magmatic origin of the CO2. Vitrinite reflectance and thermal gradient constraints suggest that the dawsonite at this location formed at a temperature of ∼75 °C.
Lead migration in smelter-impacted deciduous and coniferous organic soil horizons based on a long-term in-situ implantation and laboratory column experiments by Vladislav Chrastný; Aleš Vaněk; Eva Čadková; Alice Růžičková; Ivana Galušková; Dagmar Faturíková; Michael Komárek (168-175).
Lead (Pb) contamination of forest soils constitute a serious threat against soil organisms and wildlife and the transport of previously deposited Pb from surface soils is of high environmental relevance. We studied the migration of Pb in highly contaminated deciduous and coniferous soils in a smelting area. A mixture of fermented/humified (F + H) deciduous and coniferous soil horizons highly contaminated by Pb smelting operations were implanted to the same horizon types in an area of low Pb atmospheric input for 6 months. The implantation was accompanied with mechanical turbation, which caused changes in the soil parameters, i.e., CEC (cation exchange capacity), C org. (organic carbon) or pH. The target soil horizons F + H (and partly A) were enriched with Pb, compared to background concentrations. The retention of Pb in smelter-impacted coniferous forest soil horizons L (raw litter), F + H, A (organo-mineral) and C (mineral) was studied using a column experiment.As a result of the Pb addition with a specific isotope composition (American galena) it was found that with the exception of the L horizon, all of the added Pb was completely retained in soil horizons. The isotope composition of Pb in eluate from the L horizon was represented by linear mixing between the original and added Pb sources. The majority of Pb would be eluted from the L horizon after less than 5 years (using linear approximation).
Influence of ion exchange processes on salt transport and distribution in historic sandstone buildings by Satish C. Pandey; A.M. Pollard; H.A. Viles; J.H. Tellam (176-183).
Crystallisation of salts in the pores of stone is a major concern in the preservation of heritage buildings, monuments and sculptures, but the mechanism of transport and distribution of salts is still not properly understood. The fractionation and distribution of salts in the porous matrix has, in building material research, conventionally been attributed to the solubility and concentration of salts present in the groundwater. We propose another mechanism contributing to the control of the salt distribution based on the interaction of ions in the salt solution with the charged mineral phases within the stone. The transport of mixed salt solutions was studied in laboratory simulated flow-through experiments on two fluvial sandstones – a Permo-Triassic red bed sandstone and a Carboniferous sandstone, both from the UK. The experiments were carried out under non-evaporative conditions, eliminating the possibility of solubility-dependent crystallisation. The results indicate that the process of ion exchange significantly controls the transport of ions in the pores and leads to fractionation of solutes in the course of transport even in the absence of evaporation and crystallisation. The sandstones behave like a chromatographic column and retention of various ionic species is significantly controlled by ion exchange processes. A quantitative estimation of cation exchange capacity (CEC) indicates that sandstones with higher CEC have greater influence on retention and fractionation of salts in the course of capillary transport than those with lower CEC. Simple scoping calculations using a geochemical modelling code and the ion exchange properties based on those determined in the laboratory experiments, demonstrate that ion exchange can have a significant effect on mineral precipitation during evaporation.
Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite: Characterization and behaviors by Kai Zhao; Huaming Guo; Xiaoqian Zhou (184-192).
Although natural siderite has been investigated to remove both As(III) and As(V), it has relatively low adsorption rate and capacity. It is crucial to enhance its adsorption characteristics for As removal prior to being used in practical application. Modified granular natural siderite (MGNS) was fabricated through addition of organic binder, extrusion granulation and calcination, and evaluated for adsorption characteristics by means of batch and column tests. Results showed that MGNS had higher adsorption rate and capacity for As(III) in comparison with natural siderite. Arsenic(III) adsorption achieved equilibrium at 24 h, with adsorption capacity of 9.43 mg/g estimated from Langmuir isotherm at 25 °C. Column tests showed that there was less difference in total As loads in MGNS-packed filters for As(III)-spiked deionized water, As(III)-spiked tap water, and real-world high-As groundwater. The coexistence of anions had no significant effect on As adsorption in both batch and column experiments. Results of XRD, SEM and BET analysis indicated that MGNS, as an Fe(II)/(III) hybrid system, had a much larger specific surface area relative to the pristine natural siderite due to massive spherical aggregates attaching to the siderite matrix. XANES spectra showed that As(V) was the major species in the adsorbent after As(III) adsorption. Its proportion in total As slightly increased with the increase in contact time. Adsorption and heterogeneous oxidation of As(III) were believed to be the main mechanisms of As(III) removal by MGNS. This study suggested that MGNS is a potential adsorbent for effectively removing As from As-contaminated groundwater in filter application.
Determination of regional soil geochemical baselines for trace metals with principal component regression: A case study in the Jianghan plain, China by Shuang Zhang; Dong Yang; Fanglin Li; Huayong Chen; Zhengyu Bao; Bin Huang; Dongfeng Zou; Jun Yang (193-206).
The soil geochemical baseline is an important index in environmental assessment. Detailed baseline studies are necessary in large areas with complex geological settings, landforms and soil types. The Jianghan plain, a major industrial and agricultural region located in central China, has a soil geochemical baseline that has yet to be fully defined. The objective of this paper is to study the baseline of Cd, Pb and Zn in the topsoil of the Jianghan plain in a subarea using principal component regression (PCR). A total of 9030 samples were collected from the surface layer, and 2 soil profiles and 2 sedimentary columns were sampled near the Yangtze and Han rivers. Fifty-two elements and two parameters were analyzed. Data processing and the creation of spatial distribution maps of the elements were performed using MapGIS, R and SPSS software. The results show that the distributions of Cd, Pb and Zn are mainly controlled by parent material, drainage system and soil type. The study area is divided into 3 subareas, with factors reflecting the physico-chemical characteristics of the soil using factor analysis (FA). The geochemical baseline model is established in every subarea to predict the Cd, Pb and Zn values using principal component regression analysis (PCR); the exceptional values (as a result of anthropogenic input or mineralization) are distinguished by residuals (γ); and the natural background values and anthropogenic contributions are clearly distinguished. Therefore, the PCR method in these subareas is objective and reasonable, and the conclusion provides effective evidence of exceptional high values for further environmental assessment.
GEMAS: Spatial distribution of the pH of European agricultural and grazing land soil by Clea Fabian; Clemens Reimann; Karl Fabian; Manfred Birke; Rainer Baritz; Edith Haslinger (207-216).
During 2008 the GEochemical Mapping of Agricultural Soils (GEMAS) project collected 2108 agricultural (ploughed soil, Ap horizon, 0–20 cm) and 2023 grazing land soil samples (Gr, 0–10 cm) evenly spread over 33 European countries and covering an area of 5.6 million km2. The pH of all samples was determined by one single laboratory applying a 0.01 M CaCl2 extraction, and following a strict quality-control procedure. The resulting pH-value distributions for European Ap and Gr soil are both bimodal. Broad acidic modes, with pH between 4 and 6, and sharp alkaline modes, with pH between 7 and 8 due to the Ca2+ buffer system, are clearly separated. The European median pH is 5.8 for the GEMAS Ap soil samples and 5.5 for the GEMAS Gr soil samples. According to the pH distribution maps, Europe is separated into two main zones: northern Europe with generally lower pH values (Ap: 5.2, Gr: 4.8), dominated by acidic soils occurring in Fennoscandia, and southern Europe with higher pH values (Ap: 6.3, Gr: 5.9), dominated by carbonate rich soils. The separation line coincides with the southern border of the sediments of the last glaciation. The dominant factors controlling pH at the European scale are thus geology (crystalline bedrock) in combination with climate (temperature and precipitation). The GEMAS pH maps mainly reflect the natural site conditions on the European scale, whilst anthropogenic impact is hardly detectable. The GEMAS results provide a unique set of homogenous and spatially representative soil pH data for the continent. The data set defines a dependable continental-scale background, and offers the possibility to calibrate studies on more detailed scales.
Corrigendum to “Evaluation of the influence of urbanization processes using mangrove and fecal markers in recent organic matter in a tropical tidal flat estuary” [Appl. Geochem. 38 (2013) 82–91] by C.F. Grilo; R.R. Neto; M.A. Vicente; E.V.R. de Castro; R.C.L. Figueira; R.S. Carreira (217).