Elevated Sulfate Concentrations Research Articles

English

Water-quality data for discharges from 140 abandoned mines in the Bituminous and Anthracite Coalfields of Pennsylvania illustrate relations among pH, sulfate, and dissolved metal concentrations. The pH for the 140 samples ranged from 2.7 to 7.3, with two modes at pH 2.5 to 4 (acidic) and 6 to 7 (near neutral). Generally, flow rates were smaller and solute concentrations were greater for low-pH samples; flow rates increased with pH. Although the pH distribution was similar for the bituminous and anthracite subsets, the bituminous discharges had smaller median flow rates, greater concentrations of sulfate, iron, and aluminum, and smaller concentrations of barium and lead than anthracite discharges with the same pH values. The observed relations between the pH and constituent concentrations can be attributed to (1) dilution of acidic water by alkaline ground water; (2) solubility control of aluminum, iron, manganese, barium, and lead by hydroxide, sulfate, and/or carbonate minerals; and (3) aqueous sulfate-complex formation. The formation of AlSO4 + and AlHSO4 +2 complexes adds to the total dissolved aluminum concentration at pH of equilibrium with aluminum hydroxide or hydroxysulfate minerals and can account for 10 to 20 times greater concentrations of dissolved aluminum in bituminous discharges compared to anthracite discharges at similar pH. Sulfate complexation also can account for 10 to 30 times greater concentrations of dissolved ferric iron concentrations at equilibrium with ferrihydrite (Fe(OH)3) and/or schwertmannite (Fe8O8(OH)4.5(SO4)1.75) at pH of 3 to 5. In contrast, lower barium and lead concentrations in bituminous than anthracite discharges indicates elevated sulfate concentration could decrease mobility of these metals by the formation of insoluble minerals such as barite (BaSO4) or anglesite (PbSO4). Most samples were saturated with barite, but none were saturated with anglesite. Hence, lead concentrations could be controlled by coprecipitation with barite and/or by adsorption to schwertmannite or another sulfate-bearing oxide. Additional

Deep groundwater flow and geochemical processes in limestone aquifers: evidence from thermal waters in Derbyshire, England, UK

Thermal waters potentially provide information on geochemical processes acting deep within aquifers. New isotopic data on groundwater sulphate, inorganic carbon and strontium in thermal and non-thermal waters of a major limestone aquifer system in Derbyshire, England, UK, are used to constrain sulphate sources and groundwater evolution. Shallow groundwaters gain sulphate from oxidation of sulphide minerals and have relatively 13C-depleted dissolved inorganic carbon (DIC). Thermal waters have relatively high Sr/Ca and more 13C-enriched DIC as a result of increased water–rock interaction. In other respects, the thermal waters define two distinct groups. Thermal waters rising at Buxton have higher Mg, Mn and 87Sr/86Sr and lower Ca and SO4, indicating flow from deep sandstone aquifers via a high permeability pathway in the limestone. By contrast, Matlock-type waters (97% of the thermal flux) have elevated sulphate concentrations derived from interaction with buried evaporites, with no chemical evidence for flow below the limestone. About 5% of the limestone area's groundwater flows to the Matlock group springs via deep regional flow and the remainder flows via local shallow paths to many non-thermal springs. Gypsum dissolution has produced significant tertiary porosity and tertiary permeability in the carbonate aquifer and this is an essential precursor to the development of karstic drainage.

Speciation of adsorbed arsenate on the surface of hydrous iron oxide

effluent is complex and is characterized by elevated concentrations of iron and sulfate, low pH, and high concentrations of a wide variety of metals depending on the host rock geology. Massive inadvertent discharges from acid mines have given rise to dramatic cases of ecological damage. These events indicate an improved understanding of the mechanism controlling metal transport to the river is irr~portant, since the aquatic ecology will be affected, to some degree, dependent on the phase (dissolved or particulate) in which the metal is transported. In this study, polluted water samples were collected along the Hengshi River near the Dabaoshan mine, Guangdong, China, in April 2005. The concentrations of dissolved Cu, Zn, Cd and Pb have been determined using ICP-MS and the chemical speciation of those metals in suspended particles was examined using BCR methods and SEM/EDX mineralogical analysis. Combining these two sets of data, the intention was to develop geochemical concepts, which explain the behavior of Cu, Zn, Cd and Pb in particle-water interactions of heavy metals in AMD. The results show that the dissolved heavy metals exhibited non-conservative behavior in the Hengshi River. The dissolved and particulate Cu, Zn, Cd and Pb have the similar spatial distribution, which decreased gradually along the fiver except in the lower reaches because of the absorption-desorption between dissolved and particulate phases. Although the metal concentrations in both phases were elevated, dissolved metals were dominant and had the maximum concentrations in the low pH region. The maximum concentrations of dissolved Cu, Zn, Cd and Pb were as high as 13.82, 50.83, 0.103 and 2.91 mg/L, respectively. These four metals displayed similar evolution trends along the river, while some different behaviors do exist. Pb decreased sharply with the rise of pH, however, Cd appeared to decrease much slower. Studies on suspended particles with chemical speciation analysis and SEM/EDX indicate that the residual speciation was the major species for those four metals in suspensions. And the reductable speciation was also high, especially Cd, which indicated that they all have potential risk to the environment.

DNA damage in bone marrow and blood cells of mice exposed to municipal sludge leachates

Leachates of municipal solid waste from unsecured disposal sites contaminate sources of potable water and affect human health. In the present study, we have used the Comet assay to evaluate the DNA damage in mice exposed to municipal sludge leachates. Ten percent leachates were prepared from municipal sludge obtained from two different disposal drains. Male Swiss albino mice were treated daily with 0.1-0.4 ml of the leachates by oral gavage for 15 days, and the DNA damage was evaluated in bone marrow and blood using Olive tail moment, % tail DNA, and tail length as measures of DNA damage. Physicochemical and metal analysis of the leachates detected the presence of cadmium, chromium, copper, nickel, lead, and zinc, as well as elevated concentrations of sulfate and nitrate. Both of the leachates produced significant dose-responsive increases in DNA damage in both mouse tissues. There were no significant differences in the responses for any of the Comet endpoints between tissues (for the same leachate sample) or between leachate samples (for the same tissue). The results of this study indicate that municipal waste leachates produce DNA damage in vivo.

Source identification of groundwater pollution with the aid of multivariate statistical analysis

With the aid of multivariate statistical analysis, this study attempted to predict possible underlying processes, attribute their influence, and isolate the distribution of sources that might threaten groundwater quality. Tainan County, Taiwan was employed as a case study, and 34 monitoring wells were sampled for routine lab analysis. Lab data of groundwater quality including pH, EC, hardness, chloride, sulfate, ammonia, nitrate, Fe, Mn, As, Zn, TOC and TDS were subjected to factor and cluster analysis. Principal component analysis (PCA) was utilized to reflect those chemical data with the greatest correlation, whereas cluster analysis (CA) was used to evaluate the similarities of water quality in groundwater samples. By utilizing PCA, the identified four major principal components (PCs) representing 78.8% of cumulative variance were able to interpret the most information contained in the data. PC 1 reflects the dominance of salinization, which was characterized by the elevated concentrations of EC, hardness, chloride and sulfate in groundwater. PC 2 with the positive loadings of TOC and pH but negative loading of nitrate is thought to be representative of organic pollution within the aquifer. PC 3 is regarded as mineralization factor on the basis of the loadings of manganese and zinc. PC 4 shows a strong monotonic relationship with ammonia concentration in the groundwater revealing the linkage with agricultural activity. CA results illustrated that coastal area was partially salinized as a result of seawater intrusion and part of salinization zone was also subjected to the impact of mineral dissolution.

Sulfate-Reducing Bacteria in Gypsum Karst Lakes of Northern Lithuania

Microbiological studies were performed in three small gypsum karst lakes in northern Lithuania, most typical of the region. Samples were taken in different seasons of 2001. The conditions for microbial growth in the lakes are determined by elevated content of salts (from 0.5 to 2.0 g/l), dominated by SO(2-)4 and Ca2+ ions (up to 1.4 and 0.6 g/l, respectively). The elevated sulfate concentration is favorable for sulfate-reducing bacteria (SRBs). Summer and winter stratification gives rise to anaerobic water layers enriched in products of anaerobic degradation: H2S and CH4. The lakes under study contain abundant SRBs not only in bottom sediments (from 10(3) to 10(7) cells/dm3) but also in the water column (from 10(2) to 10(6) cells/ml). The characteristic spatial and temporal variations in the rate of sulfate reduction were noted. The highest rates of this process were recorded in summer: 0.95-2.60 mg S(2-)/dm3 per day in bottom sediments and up to 0.49 mg S(2-)/l per day in the water column. The maximum values (up to 11.36 mg S(2-)/dm3) were noted in areas where bottom sediments were enriched in plankton debris. Molecular analysis of conservative sequences of the gene for 16S RNA in sulfate-reducing microorganisms grown on lactate allowed them to be identified as Desulfovibrio desulfuricans.

Sulphur cycling in the drinking water catchment area of Torgau–Mockritz (Germany): insights from hydrochemical and stable isotope investigations

AbstractThe hydrochemical composition of groundwater and the isotopic composition of sulphur compounds in sediments (δ34S of sulphide, inorganic sulphate) and groundwater (δ34S, δ18O of dissolved sulphate) have been investigated to reveal the reasons for elevated concentrations of dissolved groundwater sulphate in the drinking water catchment area of Torgau–Mockritz (Germany).The three most important anthropogenic sources of sulphate identified in this study are historic atmospheric sulphate deposition, predominantly of anthropogenic origin, inorganic fertilization, and dissolution of gypsum from waste dumps. Owing to their overlapping isotopic range, no clear differentiation between the individual anthropogenic sources is possible. Sulphate from the oxidation of sedimentary sulphides, however, was recognized by its negative sulphur isotope signature (δ34S < − 5‰).The mobilization of sulphate from different soil sulphur species is closely connected with variable isotopic fractionations, resulting in a wide isotopic variation range for the sulphate entering the saturated zone. Generally, sulphur and oxygen isotope ratios of the dissolved groundwater sulphate range from −19 to +37‰ (Vienna Cañon Diablo troilite) and from −2 to +19‰ (Vienna standard mean ocean water), respectively. Sulphate from the majority of groundwater samples can be assigned to anthropogenic sources. Sulphate from sulphide oxidation is especially present in samples from the upper sampling level and the groundwater surface. Sulphate concentrations above 700 mg l−1 are mostly caused by the oxidation of sulphide. Sulphate that occurs in low and moderate concentrations dominantly originates from anthropogenic sources.δ34S distribution patterns were used to locate the sources for the elevated sulphate concentrations in the raw water. It was shown that the sulphate is not mobilized in the immediate vicinity of the production wells. Rather, it originates in an area ∼1·5 km west of the intake. The main mobilization mechanism there is the oxidation of reduced sedimentary sulphur species.Beyond its local significance, this study presents a general example how changes in the sulphur cycle indicate major, anthropogenically induced alterations of the hydrochemical situation in catchment areas. Copyright © 2005 John Wiley & Sons, Ltd.

The effect of emergent macrophytes on the dynamics of sulfur species and trace metals in wetland sediments

This study focuses on the effect of plants on the biogeochemistry of sulfur species and the mobility of heavy metals in wetland sediments. Results showed that, in the presence of plants, sediments had elevated sulfate concentrations in the rhizosphere during the growing season, ranging from 0.2 to 6.20 mmol L −1, whereas only a small difference in the sulfate profiles between vegetated and non-vegetated sediments was observed during senescence. Based on the sulfate concentration increase, the oxygen release rate from the roots to achieve the corresponding oxidation of sulfide was estimated as 0.85 g m −2 day −1. Evapotranspiration-induced advection is a major contributor to the transport of sulfate from the water column into the sediments, and also allows dissolved trace metals (i.e. Cd, Pb, and Zn) to be transported into the sediments and react with the acid volatile sulfide pool, resulting in the immobilization of trace metals in these sediments.

Sodium sulphate and sodium chloride effects on batch culture of iron oxidising bacteria

The effect of specific inhibitors on the growth and activity of chemolithotrophic cells has been studied by a number of workers using a comparative batch culture technique. In this study, the comparison method has been quantified and the test period extended to provide information about the ability of mixed cultures to adapt or become habituated to elevated concentrations of sodium sulphate and sodium chloride. A bio-oxidation culture showed the ability to rapidly adapt to concentrations of sodium sulphate up to 20 g L − 1 within 20–30 generations. Higher concentrations of 40 g L − 1 imposed a permanent inhibitive effect that reduced the maximum cell reproduction rate by ca. 50%. Since sulphate is rarely present in process water at these concentrations, this electrolyte does not present significant problems to operational processes. The bio-oxidation culture proved capable of adapting only to low concentrations of sodium chloride. Concentrations of 7 g L − 1 or greater provoked an inhibitive effect that reduced the cell replication rate by more than 50%. Prolonged exposure to sodium chloride at these concentrations demonstrated that no significant culture adaptation or habituation occurred.

Schmücke hill cap cloud and valley stations aerosol characterisation during FEBUKO (I): Particle size distribution, mass, and main components

Hill cap cloud field experiments were performed during autumn 2001 and 2002 in the Thüringer Wald (Germany). Gas phase trace compounds were determined at an upwind, summit, and downwind sites and major particulate components at an upwind and downwind site. Cloud water and total cloud components (drop residuals and interstitial particles) were determined at a summit site. Three events were fulfilling the criteria for the best conditions defined by during a connected flow upwind–summit–downwind sites and further detailed analysis was performed on these events. Cloud water components were compared with particle concentration at upwind and downwind site. The concentrations of non-volatile components in cloud water were found to be in good agreement with corresponding particle phase concentrations at the upwind site. Downwind site particulate component concentrations of non-volatile compounds were lower than in cloud water indicating loss processes during transport such as deposition. The concentrations of volatile components were found to be higher in cloud water than in the particle phase concentrations at up- and downwind site samples probably due to a loss from impactor sampling technique as well as a transport loss. Indications for changes of aerosol composition by cloud processes were found from a limited number of cases. Elevated sulphate and ammonium concentrations from upwind to downwind site in the smallest particle size range (PM0.05–0.14) were found during event I (20% and 17%) and event III (70% and 150%), respectively. In the particle size range of PM0.14–0.42 an increase of OC by about 20% for event I was observed. Considering the relative contributions of components to the single size range mass (avoiding physical sink processes), comparatively higher increases for sulphate, nitrate, ammonium, OC, and EC could be observed. Indications of an increase of aerosol mass can be derived in some cases from the aerosol number and volume size distributions. Results from a complex multiphase model (SPACCIM) are consistent showing an increase in concentrations of some compounds for some cases.

Use of pyrite for pH control during hydrogenotrophic denitrification using metallic iron as the ultimate electron donor

Maintenance of stable pH through provision of adequate buffering is of importance to many pollutant removal processes where either acid or base is produced as a reaction product. The objective of this study was to evaluate the suitability of pyrite (FeS 2) as an in situ buffering agent for arresting pH increase during metallic iron assisted hydrogenotrophic denitrification. Pyrite is considered promising for this purpose because it is a mineral which is unstable under moderately reducing, i.e., anoxic conditions, where such denitrification takes place, and therefore expected to consume hydroxide ions produced due to hydrogenotrophic denitrification reactions and get oxidized to ferrous hydroxide Fe(OH) 2. The theoretical basis for this buffering action was established through chemical speciation studies using the chemical speciation software, MINEQL+. Experimental evaluation of the buffering efficiency of pyrite showed that it was effective in arresting pH increase associated with denitrification in both batch systems and during flow through reactive porous media. Further, addition of pyrite had no demonstrable toxic effect on the denitrifying microorganisms, though elevated sulfate concentration was seen in the effluent after denitrification.

Sources of Hydrogen Sulfide in Groundwater on Reclaimed Land

Fisherman Islands is an area of reclaimed land at the mouth of the Brisbane River in Queensland, Australia. Ongoing groundwater monitoring has found elevated concentrations of hydrogen sulfide (H 2 S) in the groundwater on the island. The presence of H 2 S on Fisherman Islands is of concern because of its toxic nature, the potential for acid sulfate soil formation, and its noxious odor. The aim of this study was to identify the sources of H 2 S within the groundwater on Fisherman Islands. It was hypothesized that the H 2 S is being formed by sulfate reducing bacteria acting on sulfate from seawater, rather than the introduction of sulfide with the dredge sediments. Groundwater and soil samples were collected and analyzed for sulfide, sulfate, and organic carbon contents. Elevated concentrations of sulfides coincide with elevated concentrations of sulfate in the groundwater and elevated concentrations of organic carbon in the sediments, supporting the hypothesis that sulfide formation is the result of heterotrophic, sulfate reducing organisms.

Three-dimensional geologic modeling and groundwater flow modeling of the Töllinperä aquifer in the Hitura nickel mine area, Finland - Providing the framework for restoration and protection of the aquifer

Elevated concentrations of sulphate, chloride, and nickel were discovered in water samples taken from the Tollinpera aquifer in western Finland. The area is located adjacent to the tailings area of the Hitura nickel mine. Earlier studies revealed that the groundwater contamination resulted from tailings-derived mine waters leaking from a tailings impoundment area. The tailings area directly overlies the Weichselian esker system, part of which is the Tollinpera classifi ed groundwater area. The observed groundwater and surface water contamination resulted in a need to characterize the subsurface geology in the whole area of the contaminated esker aquifer. The primary sedimentary units were introduced into a three-dimensional (3-D) geologic model of the aquifer made with EarthVision  geologic modeling software. The information obtained from the 3-D geological model was then introduced into a numerical groundwater flmodel made with MODFLOW code, which was calibrated with MODFLOWP code. The results of this study were used to guide the sealing of the tailings impoundment in order to prevent the further contamination of the Tollinpera aquifer. The groundwater flmodel was used to interpret and simulate the fl ow system, and to provide a plan to safely continue water supply to local inhabitants from the unpolluted parts of the aquifer.

The kinetics of 75[Se]-selenite uptake by Saccharomyces cerevisiae and the vacuolization response to high concentrations

Uptake of 75[Se]-selenite by Saccharomyces cerevisiae has been characterized. At a 0.5 mM selenite, approximately 0.14 nmol Se (10(6) cells)-1 was rapidly accumulated by the cells at a rate of approximately 56 pmol x min-1 (10(6) cells)-1 which was independent of temperature and glucose. This rapid phase was followed by a slower uptake phase which was sensitive to glucose, temperature and metabolic inhibitors [2,4-dinitrophenol (DNP), carbonyl cyanide m-chlorophenyl hydrazone (CCCP), potassium cyanide (KCN) and sodium azide (NaN3)] and therefore presumed to be metabolism-dependent. Two transport systems appeared to be involved in selenite uptake. At the low range of selenite concentrations used (0.025-0.1 mM), a high affinity transport system occurred with apparent Km and Vmax values of 54.0 microM and 3.14 pmol x min(-1) (10(6) cells)(-1) respectively. A low affinity system was present at higher concentrations (0.1-1.0 mM) with apparent kinetic parameters of Km = 435 microM and Vmax = 11.6 pmol x min(-1) (10(6) cells)(-1). Elevated sulphate concentrations (up to 2.5 mM) did not affect the accumulation of selenite. However, the transport rate from 0.5 mM selenite was stimulated by sulphite, with the maximum effect occurring at 0.5 mM sulphite. Methionine had a detectable inhibitory action on selenite uptake whereas cystine and cysteine completely inhibited active transport of selenite. Transmission electron microscopy of 5 mM selenite-grown cells revealed the presence of abundant small cytoplasmic vesicles containing electron-dense granules which could represent an intracellular selenium-detoxification mechanism.

Modeling the response of soil and surface waters in the Adirondack and Catskill regions of New York to changes in atmospheric deposition and historical land disturbance

Abstract In this study, an integrated biogeochemical model (PnET-BGC) was used to evaluate the response of five forest ecosystems in the Adirondack and Catskill regions of New York to changes in atmospheric deposition and land disturbance. Model simulations showed that over the past 150 years, acidic deposition caused depletion of nutrient base cations (i.e., Ca 2+ , Mg 2+ ), enhanced mobilization of aluminum (Al) and accumulation of sulfur (S) within the soil. Model simulations also showed that acidic deposition resulted in elevated concentrations of inorganic monomeric Al, sulfate (SO 4 2− ) and nitrate (NO 3 − ), and low values of pH and acid neutralizing capacity (ANC) in surface waters. Model results also indicated that forest harvests resulted in enhanced leaching of base cations and NO 3 − over the short term (∼5 yr). Over the long term, forest harvesting influences surface water NO 3 − and base cation concentrations, and pH and ANC. The model was also used to predict the responses of these forest ecosystems to three emission control scenarios. Model simulations indicated that under the 1990 Clean Air Act Amendment, these ecosystems showed little recovery after 2010. Additional reductions in strong acid inputs will result in significant benefits in terms of recovery from acidification. Under an aggressive control scenario, surface water ANC of these ecosystems was predicted to recover at rates ranging from 0.28 to 0.58 μeq l −1 yr −1 .

Groundwater recharge in a sedimentary basin in semi-arid Mexico

Recharge mechanisms and the hydrochemical evolution of groundwater in a semi-arid, 6,840-km2, intermountain basin in central Mexico were investigated using stable isotopes and major chemical constituents. Ionic ratio analysis helped to conceptualize and quantify in part the subsequent geochemical evolution in the aquifer system. Mass balance models (PHREEQC) were used to interpret and rectify the geochemical properties of the aquifer. The recharge conditions have not changed noticeably during the last several thousands of years. The recharge mechanisms are accompanied by leaching of meteoric salts on and near the ground surface during major rain events, which previously accumulated after minor rain events. Rapid and diffuse infiltration can be excluded. Indirect infiltration from wadis (arroyos) and depressions (playas) with little mixing in shallow groundwater contrasts with a high degree of mixing for water with deep circulation. The prevailing source of major cations (Ca2+, Mg2+, Na+, K+) is weathering of carbonates and albite, followed by exchange reactions on clays and hydroxides. Ca2+/Na+ exchange may interchange along the flow path with reverse (Na+/Ca2+) exchange, although the Ca2+/Na+ option is prevalent. Meteoric Ca and Mg inputs are relatively small; however, meteoric Na is insignificant. Irrigation return flow plays an important role in the western part of the study area, giving rise to elevated sulfate and chloride concentrations.

FACTORS AFFECTING THE INCORPORATION OF COBALT AND NICKEL IN JAROSITE-TYPE COMPOUNDS

Laboratory studies have shown that minor amounts of cobalt and nickel are structurally incorporated in sodium jarosite, potassium jarosite and ammonium jarosite and that the extent of incorporation increases as the concentration of dissolved cobalt or nickel increases. Potassium jarosite incorporates more cobalt or nickel (∼1% Co or Ni) than does sodium jarosite or ammonium jarosite (∼0.4% Co or Ni). Elevated temperatures increase the incorporation of Co or Ni in the jarosite precipitates, but the increase is modest. Increasing concentrations of Na2SO4, K2SO4 or (NH4)2SO4 result in an increase in the Co and Ni contents of the jarosite precipitates. The extent of Co or Ni incorporation also increases as the pH of the synthesis solution increases. In contrast, elevated concentrations of ferric sulphate reduce the extent of Co or Ni incorporation in the jarosite precipitates. The above parametric dependencies suggest that Co(II) and Ni(II) substitute to a limited extent for Fe(III) in the jarosite structure and the X-ray diffraction analyses of the precipitates support this hypothesis. Efforts to extend the level of incorporation by the coupled substitution of Co(II) + Cu(II) for K(I) + Fe(III) or by the precipitation of lead jarosite were not successful. The oxidation of Co(II) to Co(III) resulted in a modest increase in the Co content of the jarosite precipitates, but the presence of poorly crystalline Co(III) oxyhydroxide (heterogenite) sometimes accounts for part of the increase.Une étude de laboratoire a montré que des quantités mineures de cobalt et de nickel étaient incorporées structurellement dans la jarosite de sodium, la jarosite de potassium et la jarosite d’ammonium et que le degré d’incorporation augmentait à mesure que la concentration de cobalt et de nickel dissous augmentait. La jarosite de potassium incorpore plus de cobalt ou de nickel (∼1% Co ou Ni) que ne le fait la jarosite de sodium ou la jarosite d’ammonium (∼0.4% Co ou Ni). Les températures élevées augmentent l’incorporation du Co ou du Ni dans les précipités de jarosite, mais l’augmentation est modeste. L’augmentation des concentrations de Na2SO4, K2SO4 ou (NH4)2SO4 résulte en une augmentation du contenu en Co et en Ni des précipités de jarosite. Le degré d’incorporation de Co ou de Ni augmente également à mesure que le pH de la solution de synthèse augmente. Par contre, des concentrations élevées de sulfate ferrique réduisent le degré d’incorporation du Co ou du Ni dans les précipités de jarosite. Les dépendances paramétriques mentionnées ci-dessus suggèrent que le Co(II) et le Ni(II) se substituent de façon limitée au Fe(III) dans la structure de la jarosite et les analyses de diffraction des rayons x des précipités supportent cette hypothèse. Les efforts pour étendre le niveau d’incorporation par la substitution couplée de Co(II) + Cu(II) pour le K(I) + Fe(III) ou par la précipitation de la jarosite de plomb n’ont pas eu de succès. L’oxydation du Co(II) en Co(III) a résulté en une augmentation modeste de la teneur en Co dans les précipités de jarosite, mais la présence de l’oxyhydroxyde Co(III) (hétérogénite) faiblement cristallin tient parfois compte d’une partie de l’augmentation

The significance of the North Atlantic Oscillation (NAO) for sea-salt episodes and acidification-related effects in Norwegian rivers.

Acidification of Norwegian surface waters, as indicated by elevated concentrations of sulfate and a corresponding reduction in acid neutralizing capacity and pH, is a result of emission and subsequent deposition of sulfur and nitrogen compounds. Episodic sea-salt deposition during severe weather conditions may increase the effects of acidification by mobilizing more toxic aluminum during such episodes. Changes in climatic conditions may increase the frequency and strength of storms along the coast thus interacting with acidification effects on chemistry and biota. We found that the North Atlantic Oscillation (NAO) is linked to sea-salt deposition and sea-salt induced water chemistry effects in five rivers. Particularly, toxic levels of aluminum in all rivers were significantly correlated with higher NAO index values. Further, temporal trends were studied by comparing tendencies for selected statistical indices (i.e. frequency distributions) with time. The selected indices exhibited strong correlations between the NAO index, sea-salt deposition and river data such as chloride, pH and inorganic monomeric aluminum, pointing at the influence of North Atlantic climate variability on water chemistry and water toxicity. The potentially toxic effects of sea-salt deposition in rivers seem to be reduced as the acidification is reduced. This suggests that sea-salt episodes have to increase in strength in order to give the same potential negative biological effects in the future, if acid deposition is further reduced. More extreme winter precipitation events have been predicted in the northwest of Europe as a result of climate change. If this change will be associated with more severe sea-salt episodes is yet unknown.

Irrigation Method Affects Selenium Accumulation in Forage Brassica Species

A greenhouse study was conducted in sand cultures to compare the effects of saline irrigation waters applied by two different methods, flooding and above‐canopy sprinkling, on selenium (Se) accumulation by the forage brassicas, kale (Brassica oleracea L., cv. “Premier”) and turnip (B. rapa L., cv. “Forage Star”). The composition of the irrigation water was designed to simulate saline (7 dS m−1) drainage effluent commonly encountered in the San Joaquin Valley of California, and being evaluated for reuse by irrigation of salt tolerant crops. The experimental design was a randomized complete block with two irrigation methods, two plant species (kale and turnip), four Se concentrations (0.25, 0.50, 1.0, and 2.0 mg L−1 Se–SeO4 2−), and three replications. Kale was generally a more efficient Se accumulator than turnip. Shoot Se concentrations in kale and turnip increased with increasing Se in the irrigation waters regardless of irrigation method. Selenium was readily taken up by the leaves of the sprinkled plants to give shoot‐Se concentrations that were two‐ to three‐fold higher than in plants of the same cultivar grown under flood irrigation. Both kale and turnip can accumulate Se to concentrations that would be toxic to animals if exclusively fed this material. These Se‐enriched forages may be useful as an additive to Se‐deficient fodders in order to meet the nutritional requirements of livestock. The potential for phytoremediation of Se contaminated soils or waters is greatly enhanced by sprinkler irrigation via the mechanism of foliar absorption of Se. This enhanced uptake is especially important in the presence of elevated sulfate concentrations, which normally reduce Se uptake by plants.

Carbonate Speleothems in the Dry, Inneralpine Vinschgau Valley, Northernmost Italy: Witnesses of Changes in Climate and Hydrology Since the Last Glacial Maximum

ABSTRACT An interesting association of slope breccia, inactive and active tufa deposits, and speleothems is present in the central Vinschgau Valley, Italy. The occurrence of abundant carbonate cements in fractures and voids of crystalline basement rocks is unexpected considering the fact that this valley is among the driest spots in the entire Alps. Low annual precipitation of 440-530 mm coupled with frequent wind give rise to a semiarid climate and steppe vegetation along the south-facing slopes of the valley. Springs in this area are mostly supersaturated with respect to calcite, and carbonate precipitation occurs locally as tufas and, less well known because of lack of accessibility, as speleothems in the shallow subsurface. The majority of the tufa deposits and speleothems, however, are fossil. Speleothems are composed of low-Mg calcite and calcite-aragonite, respectively. Delicate growth textures including presumable annual lamination caused by pronounced changes in fluorescence intensity are preserved in both calcite and aragonite. Most calcite is a primary precipitate, but small amounts of secondary calcite replacing aragonite are common in most aragonite-bearing samples. The highly radiogenic Sr isotope composition, as well as high concentrations of U, Fe, Sr, and Mg, indicate that the groundwater from which these carbonates precipitated experienced intensive interaction with the host crystalline rocks. The very low tritium concentrations and the lack of a seasonal O isotope variation in modern spring waters, as well as their rather constant hydrochemical composition, also support this suggestion. S isotope data for dissolved sulfate and Ca and Mg sulfate precipitates indicate a sulfide source, i.e., oxidation of sulfide ore minerals in the aquifer, resulting in elevated sulfate and Fe concentrations. Th/U dating of speleothem samples using thermal ionization mass spectrometry yielded ages between 13,710 and 378 yr BP, with most ages falling in the early to middle Holocene. Although no isotopic dates are available for the tufa deposits, field evidence strongly suggests that speleothems, tufa deposits, and carbonate cements in the slope breccia were closely related. We therefore interpret the existence of these terrestrial carbonates as evidence of changes in climate since the middle Holocene. Their presence suggests a higher annual rainfall during the first half of the Holocene, possibly because of enhanced moisture transport from the Mediterranean.