The origin of high sulfate concentrations in a coastal plain aquifer,Long Island,New York     

《Applied Geochemistry》2004,19(3):343-358

Ion-exchange batch experiments were run on Cretaceous (Magothy aquifer) clay cores from a nearshore borehole and an inland borehole on Long Island, NY, to determine the origin of high SO₄²⁻ concentrations in ground water. Desorption batch tests indicate that the amounts of SO₄²⁻ released from the core samples are much greater (980–4700 μg/g of sediment) than the concentrations in ground-water samples. The locally high SO₄²⁻ concentrations in pore water extracted from cores are consistent with the overall increase in SO₄²⁻ concentrations in ground water along Magothy flow paths. Results of the sorption batch tests indicate that SO₄²⁻ sorption onto clay is small but significant (40–120 μg/g of sediment) in the low-pH (<5) pore water of clays, and a significant part of the SO₄²⁻ in Magothy pore water may result from the oxidation of FeS₂ by dissolved Fe(III). The acidic conditions that result from FeS₂ oxidation in acidic pore water should result in greater sorption of SO₄²⁻ and other anions onto protonated surfaces than in neutral-pH pore water. Comparison of the amounts of Cl⁻ released from a clay core sample in desorption batch tests (4 μg/g of sediment) with the amounts of Cl⁻ sorbed to the same clay in sorption tests (3.7–5 μg/g) indicates that the high concentrations of Cl⁻ in pore water did not originate from connate seawater but were desorbed from sediment that was previously in contact with seawater. Furthermore, a hypothetical seawater transgression in the past is consistent with the observed pattern of sorbed cation complexes in the Magothy cores and could be a significant source of high SO₄²⁻ concentrations in Magothy ground water.  相似文献   

On the model of Mn,Fe, Ni,Co ore formation in recent basins: Experiments with the synthesis of Me-hydroxide phases on Mn3O4     

I. M. Varentsov  N. V. Bakova  Yu. P. Dikov  T. S. Gendler  R. Giovanoli 《Mineralium Deposita》1979,14(3):281-296

Experiments on the sorption of dissolved Ni, Co, Mn, Fe from seawater by Mn₃O₄ reveal a sequence of reactions taking place: Ion exchange, hydrolysis, then autocatalytic oxidation and layer formation on the interface. The composition of the new compounds depends on the kinetics of i) sorption, and ii) interface oxidation. The highest oxidized Me ions accumulate at low sorption rates, i. e. when sorption does not inhibit interface oxidation: 60% Mn⁴⁺, 30% Ni³⁺ & 30% Co³⁺ are a representative example for that layer type. Iron is present in this layer as amorphous FeOOH·xH₂O according to Mössbauer spectra. Specific for the Me sorption by Mn₃O₄ is the interaction of Ni & Co with Mn²⁺ and Mn³⁺ of the sorbent lattice. Mn is found in the solute phase equivalent to 16, 14% of the adsorbed Co or 17, 96% of the adsorbed Ni. These results confirm the earlier presented model on the transition metal accumulation in recent basins as taking place in distinct stages with interface autocatalysis for the Me oxidation playing the main role.  相似文献   

Fractionation of oxygen isotopes in phosphate during its interactions with iron oxides     

Deb P. Jaisi  Ruth E. Blake 《Geochimica et cosmochimica acta》2010,74(4):1309-4227

Iron (III) oxides are ubiquitous in near-surface soils and sediments and interact strongly with dissolved phosphates via sorption, co-precipitation, mineral transformation and redox-cycling reactions. Iron oxide phases are thus, an important reservoir for dissolved phosphate, and phosphate bound to iron oxides may reflect dissolved phosphate sources as well as carry a history of the biogeochemical cycling of phosphorus (P). It has recently been demonstrated that dissolved inorganic phosphate (DIP) in rivers, lakes, estuaries and the open ocean can be used to distinguish different P sources and biological reaction pathways in the ratio of ¹⁸O/¹⁶O (δ¹⁸O_P) in PO₄³⁻. Here we present results of experimental studies aimed at determining whether non-biological interactions between dissolved inorganic phosphate and solid iron oxides involve fractionation of oxygen isotopes in PO₄. Determination of such fractionations is critical to any interpretation of δ¹⁸O_P values of modern (e.g., hydrothermal iron oxide deposits, marine sediments, soils, groundwater systems) to ancient and extraterrestrial samples (e.g., BIF’s, Martian soils). Batch sorption experiments were performed using varied concentrations of synthetic ferrihydrite and isotopically-labeled dissolved ortho-phosphate at temperatures ranging from 4 to 95 °C. Mineral transformations and morphological changes were determined by X-Ray, Mössbauer spectroscopy and SEM image analyses.Our results show that isotopic fractionation between sorbed and aqueous phosphate occurs during the early phase of sorption with isotopically-light phosphate (P¹⁶O₄) preferentially incorporated into sorbed/solid phases. This fractionation showed negligible temperature-dependence and gradually decreased as a result of O-isotope exchange between sorbed and aqueous-phase phosphate, to become insignificant at greater than ∼100 h of reaction. In high-temperature experiments, this exchange was very rapid resulting in negligible fractionation between sorbed and aqueous-phase phosphate at much shorter reaction times. Mineral transformation resulted in initial preferential desorption/loss of light phosphate (P¹⁶O₄) to solution. However, the continual exchange between sorbed and aqueous PO₄, concomitant with this mineralogical transformation resulted again in negligible fractionation between aqueous and sorbed PO₄ at long reaction times (>2000 h). This finding is consistent with results obtained from natural marine samples. Therefore, ¹⁸O values of dissolved phosphate (DIP) in sea water may be preserved during its sorption to iron-oxide minerals such as hydrothermal plume particles, making marine iron oxides a potential new proxy for dissolved phosphate in the oceans.  相似文献   

Effect of fulvic acids on sorption of U(VI), Zn,Yb, I and Se(IV) onto oxides of aluminum,iron and silicon     

《Applied Geochemistry》2000,15(2):133-139

The sorption of Yb³⁺, UO²⁺₂, Zn²⁺, I⁻ and SeO²⁻₃ onto Al₂O₃, Fe₂O₃ and SiO₂ were determined by a batch technique in the presence and absence of fulvic acids. The effects of fulvic acid on sorption were compared. The existing general consensus, that humic substances tend to enhance metal cation sorption at low pH, reduce metal cation sorption at high pH and reduce inorganic anion sorption between pH values 3 to 10, was generally shown to be true. However, in this work many exceptions to the general consensus were found. The study indicated that the effect of humic substances on sorption of inorganic cations or anions depends not only on pH, but also on the nature of the oxide, the nature of humic substance, fractionation of the humic substance by sorption, the relative strength of complexes of both soluble and sorbed humic substances, the extent of surface coverage by humic substance, the initial concentration of humic substance and the inorganic electrolyte composition.  相似文献   

Deposition of deep-sea manganese nodules     

David A Crerar  H.L Barnes 《Geochimica et cosmochimica acta》1974,38(2):279-300

Manganese at equilibrium in seawater occurs dominantly as Mn²⁺ and inorganic complexes at a concentration ratio of about 1:0.72; solubility decreases exponentially with increasing pH or Eh. However, the nodule oxides birnessite and todorokite are at least four orders of magnitude undersaturated relative to the Mn concentrations of seawater, and are metastable relative to hausmannite and manganite. This apparent lack of equilibrium is explicable by the mechanism of precipitation.Surfaces assist Mn precipitation by catalyzing equilibration between dissolved and reactive O₂ and simultaneously also by adsorbing ionic Mn species. The effective Eh at the surface becomes 200–400 mV above that of seawater; the oxidation rate of Mn increases about 10⁸ ×, and the activation energies for Mn oxidation decrease ~ 11.5 kcal/mole. Consequently, marine Mn nodules and crusts form by adsorption and catalytic oxidation of Mn²⁺ and ferrous ions at nucleating surfaces such as sea-floor silicates, oxyhydroxides, carbonates, phosphates and biogenic debris. The resulting ferromanganese surfaces autocatalyze further growth. In addition, Mn-fixing bacteria may also significantly accelerate accretion rates on these surfaces.Mn which accumulates in submarine sediments may be diagenetically recycled in response to steep solubility gradients causing upward migration from more acidic and reducing horizons toward the sea floor. In contrast, the concentrations of the predominant ferric complexes, Fe(OH)₃⁰ and Fe(OH)₄^?, are relatively less sensitive to the Eh's and pH's found in this environment; Fe is therefore not as readily recycled within buried sediments. Consequently, Fe is not so effectively enriched on the sea floor, although it precipitates more readily than Mn because seawater is saturated in amorphous Fe(OH)₃.The metastable, perhaps kinetically-related, Mn oxides of nodules have a characteristic distribution: birnessite predominates in oxidizing environments of low sedimentation rate and todorokite where sedimentation rates and diagenetic Mn mobility are higher. Surface adsorption and cation substitution within the disordered birnessite-todorokite structure account for the high trace element content of Mn nodules.  相似文献   

Sorption of inorganic mercury and monomethyl mercury in an iron–humus podzol soil of southern Norway studied by batch experiments     

K. Schlüter 《Environmental Geology》1997,30(3-4):266-279

Considerable fractions of the Hg content of lake and river systems in Scandinavia are discharged from the soil of the catchments. An important soil type in Scandinavia is the iron–humus podzol. The sorption characteristics of this soil type for inorganic Hg(II) and monomethyl mercury were investigated by batch experiments. The solubility of Hg²⁺ and CH₃Hg⁺ in the soil horizons containing organic matter increases with increasing pH of the soil solution by favoring the formation of solute organic matter–mercury complexes. While the solubility of Hg²⁺ is strongly dependent on complexation to dissolved organic matter, the solubility of CH₃Hg⁺ is more dependent on ion exchange. The concentration of solute inorganic Hg(II) increased with increasing temperature probably because of an increase in the concentration of dissolved organic carbon. There was no effect of temperature on the concentration of solute CH₃Hg⁺. At pH values where inorganic mercury–hydroxo complexes are formed, inorganic Hg(II) is efficiently sorbed to the metal oxides of the mineral soil. The soil–water distributions of inorganic Hg(II) in the different soil horizons were described by Freundlich isotherms or linear isotherms for common and contaminated mercury contents in the soils.  相似文献   

Potential Influence of Ocean Acidification on Deep-Sea Fe–Mn Nodules and Pelagic Clays: An Improved Assessment by Using Artificial Seawater     

Quan Wang  Hodaka Kawahata  Kyoko Yamaoka  Atsushi Suzuki 《Aquatic Geochemistry》2018,24(4):307-322

In order to assess the potential risk of metal release from deep-sea sediments in response to pH decrease in seawater, the mobility of elements from ferromanganese (Fe–Mn) nodules and pelagic clays was examined. Two geochemical reference samples (JMn-1 and JMS-2) were reacted with the pH-controlled artificial seawater (ASW) using a CO₂-induced pH regulation system. Our experiments demonstrated that deep-sea sediments have weak buffer capacities by acid–base dissociation of surface hydroxyl groups on metal oxides/oxyhydroxides and silicate minerals. Element concentrations in the ASW were mainly controlled by elemental speciation in the solid phase and sorption–desorption reaction between the charged solid surface and ion species in the ASW. These results indicated that the release of heavy metals such as Mn, Cu, Zn and Cd should be taken into consideration when assessing the influence of ocean acidification on deep-sea environment.  相似文献   

Nature of Co-bearing ferromanganese crusts of the Magellan Seamounts (Pacific Ocean): Communication 2. Ion exchange properties of ore minerals     

G. V. Novikov  S. V. Yashina  M. E. Mel’nikov  I. V. Vikent’ev  O. Yu. Bogdanova 《Lithology and Mineral Resources》2014,49(2):138-164

The results of experimental studies of ion exchange properties of Co-bearing ferromanganese crusts in the Magellan Seamounts (Pacific Ocean) are discussed. Maximum reactivity in reactions with the participation of manganese minerals (Fe-vernadite, vernadite) is typical of Na⁺, K⁺, and Ca²⁺ cations, whereas minimum activity is recorded for cations Pb²⁺ and Co²⁺. The exchange complex of ore minerals in crusts is composed of Na⁺, K⁺, Ca²⁺, Mg²⁺, and Mn²⁺ cations. The exchange capacity of manganese minerals increases from the alkali metal cations to rare and heavy metal cations. Peculiarities of the affiliation of Co²⁺, Mn²⁺, and Mg²⁺ cations in manganese minerals of crusts are discussed. In manganese minerals, Co occurs as Co²⁺ and Co³⁺ cations. Metal cations in manganese minerals occur in different chemical forms: sorbed (Na⁺, K⁺, Ca²⁺, Mn²⁺, Co²⁺, Cu²⁺, Zn²⁺, Cd²⁺, and Pb²⁺); sorbed and chemically bound (Mg²⁺, Ni²⁺, Y³⁺, La³⁺, and Mo⁶⁺); and only chemically bound (Co³⁺). It is shown that the age of crust, its preservation time in the air-dry state, and type of host substrate do not affect the ion exchange indicators of manganese minerals. It has been established that alkali metal cations are characterized by completely reversible equivalent sorption, whereas heavy metal cations are sorbed by a complex mechanism: equivalent ion exchange for all metal cations; superequivalent, partly reversible sorption for Ba²⁺, Pb²⁺, Co²⁺, and Cu²⁺ cations, relative to exchange cations of manganese minerals. The obtained results refine the role of ion exchange processes during the hydrogenic formation of Co-bearing ferromanganese crusts.  相似文献   

Impacts of hydrous manganese oxide on the retention and lability of dissolved organic matter     

Jason W. Stuckey  Christopher Goodwin  Jian Wang  Louis A. Kaplan  Prian Vidal-Esquivel  Thomas P. BeebeJr.  Donald L. Sparks 《Geochemical transactions》2018,19(1):6

Minerals constitute a primary ecosystem control on organic C decomposition in soils, and therefore on greenhouse gas fluxes to the atmosphere. Secondary minerals, in particular, Fe and Al (oxyhydr)oxides—collectively referred to as “oxides” hereafter—are prominent protectors of organic C against microbial decomposition through sorption and complexation reactions. However, the impacts of Mn oxides on organic C retention and lability in soils are poorly understood. Here we show that hydrous Mn oxide (HMO), a poorly crystalline δ-MnO₂, has a greater maximum sorption capacity for dissolved organic matter (DOM) derived from a deciduous forest composite O_i, O_e, and O_a horizon leachate (“O horizon leachate” hereafter) than does goethite under acidic (pH 5) conditions. Nonetheless, goethite has a stronger sorption capacity for DOM at low initial C:(Mn or Fe) molar ratios compared to HMO, probably due to ligand exchange with carboxylate groups as revealed by attenuated total reflectance-Fourier transform infrared spectroscopy. X-ray photoelectron spectroscopy and scanning transmission X-ray microscopy–near-edge X-ray absorption fine structure spectroscopy coupled with Mn mass balance calculations reveal that DOM sorption onto HMO induces partial Mn reductive dissolution and Mn reduction of the residual HMO. X-ray photoelectron spectroscopy further shows increasing Mn(II) concentrations are correlated with increasing oxidized C (C=O) content (r = 0.78, P < 0.0006) on the DOM–HMO complexes. We posit that DOM is the more probable reductant of HMO, as Mn(II)-induced HMO dissolution does not alter the Mn speciation of the residual HMO at pH 5. At a lower C loading (2 × 10² μg C m^?2), DOM desorption—assessed by 0.1 M NaH₂PO₄ extraction—is lower for HMO than for goethite, whereas the extent of desorption is the same at a higher C loading (4 × 10² μg C m^?2). No significant differences are observed in the impacts of HMO and goethite on the biodegradability of the DOM remaining in solution after DOM sorption reaches steady state. Overall, HMO shows a relatively strong capacity to sorb DOM and resist phosphate-induced desorption, but DOM–HMO complexes may be more vulnerable to reductive dissolution than DOM–goethite complexes.  相似文献   

The Removal of Dissolved Metals by Hydroxysulphate Precipitates during Oxidation and Neutralization of Acid Mine Waters, Iberian Pyrite Belt   总被引：4，自引：0，他引：4  

J. Sánchez España  E. López Pamo  E. Santofimia Pastor  J. Reyes Andrés  J. A. Martín Rubí 《Aquatic Geochemistry》2006,12(3):269-298

This study examines the removal of dissolved metals during the oxidation and neutralization of five acid mine drainage (AMD) waters from La Zarza, Lomero, Esperanza, Corta Atalaya and Poderosa mines (Iberian Pyrite Belt, Huelva, Spain). These waters were selected to cover the spectrum of pH (2.2–3.5) and chemical composition (e.g., 319–2,103 mg/L Fe; 2.85–33.3 g/L SO₄⁼) of the IPB mine waters. The experiments were conducted in the laboratory to simulate the geochemical evolution previously recognized in the field. This evolution includes two stages: (1) oxidation of dissolved Fe(II) followed by hydrolysis and precipitation of Fe(III), and (2) progressive pH increase during mixing with fresh waters. Fe(III) precipitates at pH < 3.5 (stages 1 and 2) in the form of schwertmannite, whereas Al precipitates during stage 2 at pH 5.0 in the form of several hydroxysulphates of variable composition (hydrobasaluminite, basaluminite, aluminite). During these stages, trace elements are totally or partially sorbed and/or coprecipitated at different rates depending basically on pH, as well as on the activity of the SO₄⁼ anion (which determines the speciation of metals). The general trend for the metals which are chiefly present as aqueous free cations (Pb²⁺, Zn²⁺, Cu²⁺, Cd²⁺, Mn²⁺, Co²⁺, Ni²⁺) is a progressive sorption at increasing pH. On the other hand, As and V (mainly present as anionic species) are completely scavenged during the oxidation stage at pH < 3.5. In waters with high activities (> 10⁻¹) of the SO ₄⁼ ion, some elements like Al, Zn, Cd, Pb and U can also form anionic bisulphate complexes and be significantly sorbed at pH < 5. The removal rates at pH 7.0 range from around 100% for As, V, Cu and U, and 60–80% for Pb, to less than 20% for Zn, Co, Ni and Mn. These processes of metal removal represent a significant mechanism of natural attenuation in the IPB.  相似文献   

Speciation of the rare earth element neodymium in groundwaters of the Nevada Test Site and Yucca Mountain and implications for actinide solubility     

《Applied Geochemistry》1995,10(5):565-572

  相似文献   

Fe(II)-Na(I)-Ca(II) Cation Exchange on Montmorillonite in Chloride Medium: Evidence for Preferential Clay Adsorption of Chloride – Metal Ion Pairs in Seawater     

Laurent?Charlet  Christophe?TournassatEmail author 《Aquatic Geochemistry》2005,11(2):115-137

Fe(II)–Ca(II), Fe(II)–Na(I), and Fe(II)–Ca(II)–Na(I) exchange experiments on montmorillonite were performed in chloride background. These experiments show the possible sorption of Fe²⁺ and FeCl⁺ ion pairs in exchange site positions, a result confirmed with 77 K ⁵⁷Fe Mössbauer experiments. The sorption data were modeled and the cation exchange selectivity for Fe(II) were found to be nearly equal to that of Ca(II). Vanselow selectivity coefficients, for Na–Fe²⁺ and Na–FeCl⁺ reactions, were found to be equal to 0.4 (0.5 for Ca²⁺) and 2.3 (2.5 for CaCl⁺) respectively. High affinity of montmorillonite for chloride ion pairs seems to be a common mechanism as first stated by Sposito et al., (Soil Sci. Soc. Am. J. 47, 51–56, 1983a), and should have implications e.g., on the chemistry of suspended particles in seawater. Exchange selectivity coefficients derived from this study and others were used to model experimental data on river water and seawater equilibrated particles. The agreement between simulations and experimental data is very good. The simulation shows the predominance of monovalent ion (Na⁺ and chloride ion pairs) sorption on clay particles in seawater. This sorption of monovalent ions leads to the dispersion of particles in seawater and to the extension of a plume of particles spreading away from river deltas, such as that of the River Amazon.  相似文献   

Iron control by equilibria between hydroxy-Green Rusts and solutions in hydromorphic soils     

《Geochimica et cosmochimica acta》1999,63(19-20):3417-3427

In order to verify Fe control by solution - mineral equilibria, soil solutions were sampled in hydromorphic soils on granites and shales, where the occurrence of Green Rusts had been demonstrated by Mössbauer and Raman spectroscopies. Eh and pH were measured in situ, and Fe(II) analyzed by colorimetry. Ionic Activity Products were computed from aqueous Fe(II) rather than total Fe in an attempt to avoid overestimation by including colloidal particles. Solid phases considered are Fe(II) and Fe(III) hydroxides and oxides, and the Green Rusts whose general formula is [Fe^II_1−xFe^III_x(OH)₂]^+x· [x/z A^−z]^−x, where compensating interlayer anions, A⁻, can be Cl⁻, SO₄²⁻, CO₃²⁻ or OH⁻, and where x ranges a priori from 0 to 1. In large ranges of variation of pH, pe and Fe(II) concentration, soil solutions are (i) oversaturated with respect to Fe(III) oxides; (ii) undersaturated with respect to Fe(II) oxides, chloride-, sulphate- and carbonate-Green Rusts; (iii) in equilibrium with hydroxy-Green Rusts, i.e., Fe(II)-Fe(III) mixed hydroxides. The ratios, x = Fe(III)/Fe_t, derived from the best fits for equilibrium between minerals and soil solutions are 1/3, 1/2 and 2/3, depending on the sampling site, and are in every case identical to the same ratios directly measured by Mössbauer spectroscopy. This implies reversible equilibrium between Green Rust and solution. Solubility products are proposed for the various hydroxy-Green Rusts as follows: log K_sp = 28.2 ± 0.8 for the reaction Fe₃(OH)₇ + e⁻ + 7 H⁺ = 3 Fe²⁺ + 7 H₂O; log K_sp = 25.4 ± 0.7 for the reaction Fe₂(OH)₅ + e⁻ + 5 H⁺ = 2 Fe²⁺ + 5 H₂O; log K_sp = 45.8 ± 0.9 for the reaction Fe₃(OH)₈ + 2e⁻ + 8 H⁺ = 3 Fe²⁺ + 8 H₂O at an average temperature of 9 ± 1°C, and 1 atm. pressure. Tentative values for the Gibbs free energies of formation of hydroxy-Green Rusts obtained are: Δ_fG° (Fe₃(OH)₇, cr, 282.15 K) = −1799.7 ± 6 kJ mol⁻¹, Δ_fG° (Fe₂(OH)₅, cr, 282.15 K) = −1244.1 ± 6 kJ mol⁻¹ and Δ_fG° (Fe₃(OH)₈, cr, 282.15 K) = −1944.3 ± 6 kJ mol⁻¹.  相似文献   

The synergistic effect of calcium on organic carbon sequestration to ferrihydrite   总被引：1，自引：0，他引：1  

Tyler D. Sowers  Jason W. Stuckey  Donald L. Sparks 《Geochemical transactions》2018,19(1):4

Sequestration of organic carbon (OC) in environmental systems is critical to mitigating climate change. Organo-mineral associations, especially those with iron (Fe) oxides, drive the chemistry of OC sequestration and stability in soils. Short-range-ordered Fe oxides, such as ferrihydrite, demonstrate a high affinity for OC in binary systems. Calcium commonly co-associates with OC and Fe oxides in soils, though the bonding mechanism (e.g., cation bridging) and implications of the co-association for OC sequestration remain unresolved. We explored the effect of calcium (Ca²⁺) on the sorption of dissolved OC to 2-line ferrihydrite. Sorption experiments were conducted between leaf litter-extractable OC and ferrihydrite at pH 4 to 9 with different initial C/Fe molar ratios and Ca²⁺ concentrations. The extent of OC sorption to ferrihydrite in the presence of Ca²⁺ increased across all tested pH values, especially at pH ≥ 7. Sorbed OC concentration at pH 9 increased from 8.72 ± 0.16 to 13.3 ± 0.20 mmol OC g^?1 ferrihydrite between treatments of no added Ca²⁺ and 30 mM Ca²⁺ addition. Batch experiments were paired with spectroscopic studies to probe the speciation of sorbed OC and elucidate the sorption mechanism. ATR-FTIR spectroscopy analysis revealed that carboxylic functional moieties were the primary sorbed OC species that were preferentially bound to ferrihydrite and suggested an increase in Fe-carboxylate ligand exchange in the presence of Ca at pH 9. Results from batch to spectroscopic experiments provide significant evidence for the enhancement of dissolved OC sequestration to 2-line ferrihydrite and suggest the formation of Fe–Ca-OC ternary complexes. Findings of this research will inform modeling of environmental C cycling and have the potential to influence strategies for managing land to minimize OM stabilization.  相似文献   

Sorption of heavy metal cations by low-temperature deposits of Pacific hydrothermal fields     

G. V. Novikov  I. V. Vikent’ev  O. Yu. Bogdanova 《Geology of Ore Deposits》2006,48(4):304-325

Cation exchange reactions with participation of heavy metals Mn, Co, Ni, Cu, Zn, Cd, Ba, and Pb were studed in oceanic low-temperature hydrothermal deposits of various mineral compositions and in hydrogenic Fe-Mn crusts. Individual minerals and their assemblages differ significantly in absorptive capacity, which increases in the following order: hematite ? Si-protoferrihydrite < protoferrihydrite < geothite < nontronite ? Fe-vernadite + Mn-feroxyhyte < Fe-free vernadite < bernessite + Fe-free vernadite < bernessite; i.e., it successively increases from the mineral with a coordination type of lattice to minerals with a layer-type structure. The exchange complex of all minerals includes Na⁺, K⁺, Ca²⁺, and Mg²⁺, i.e., the main cations of seawater. In Mn minerals, Mn²⁺ is the main exchange component. The contribution of all the mentioned cations to the exchange capacity of minerals is as high as 90–98%. The highest absorptive capacity among the examined low-temperature oceanic deposits is characteristic of hydrothermal Mn minerals. Their capacity exceeds substantially that of hydrothermal oxides, hydroxides, Fe-aluminosilicates, and hydrogenic Fe-Mn minerals. The absorptive capacity of all examined Mn minerals relative to heavy metals increases in the same order: Ni < Zn < Cd < Mn < Co < Pb < Cu.  相似文献   

The post-depositional reactivity of iron and managanese in the sediments of a macrotidal estuarine system     

B. Ouddane  D. Boust  E. Martin  J. C. Fischer  M. Wartel 《Estuaries and Coasts》2001,24(6):1015-1028

Four cores of anoxic sediments were collected from the Seine estuary to assess the early diagenesis pathways leading to the formation of previously reactive phase. Pore waters were analyzed for dissolved iron (Fe) and manganese (Mn) and different ligands (e.g., sulfate, chloride, total inorganic carbon). The anoxic zone is present up to the first centimeter depth, in these conditions the reduction of Mn and Fe oxides and SO₄ ²⁻ was verified. The sulfate reduction was well established with a subsequent carbon mineralization in the NORMAI94 core. The chemical speciation of Mn and Fe in the dissolved and solid phases was determined. For the dissolved phase, thermodynamic calculations were used to characterize and illustrate the importance of carbonate and phosphate phases as sinks for Fe and Mn. The ion activity product (IAP) of Fe and Mn species was compared to the solubility products (Ks) of these species. In the solid phase, the presence of higher concentration of calcium carbonate in the Seine sediments is an important factor controlling Mn cycle. The carbonate-bound Mn can reach more than 75% of the total concentration. This result is confirmed by the use of electron spin resonance (ESR) spectroscopy. The reduction of Fe is closely coupled to the sulfate reduction by the formation of new solid phases such as FeS and FeS₂, which can be regarded as temporal sinks for sulfides. These forms were quantified in all cores as acid volatile sulfide (AVS: FeS+ free sulfide) and chromium reducible sulfide (CRS: FeS₂+elemental sulfur S⁰).  相似文献   

Sorption behavior of the sandy residual unconsolidated materials from the sandstones of the Botucatu Formation,the main aquifer of Brazil     

Junio René Toledo Fagundes  Lázaro Valentin Zuquette 《Environmental Earth Sciences》2011,62(4):831-845

Pollutant transport through porous geological materials depends on the intrinsic characteristics of the materials that define the sorption behavior. This is the main environmental aspect that must be evaluated in terms of natural attenuation and retardation factor of the pollutants. Sorption is directly related to the electrostatic charge of the mineral, the organic matter, and the oxide and hydroxide contents. We assessed the sorption characteristics of the sandy residual unconsolidated material of the Botucatu Formation, which is part of the main aquifer of Brazil, using Batch Equilibrium Tests. The tests used multicomponent solutions of NaCl, KCl, ZnCl₂, and CuCl₂·H₂O with a total concentration that varied from 20 to 1,000 ppm. Different plotting systems were applied so that the isotherms better reflected the sorption behavior of the studied cations onto the unconsolidated materials. The cation Na⁺ was not sorbed. The Langmuir I and Freundlich equations adequately represent the behavior of Cu⁺⁺, the Langmuir II approximation better represented K⁺, and the Langmuir I and Freundlich equations were reasonably fitted Zn⁺⁺.  相似文献   

Interaction of organic compounds with calcium carbonate—III. Amino acid composition of sorbed layers     

Peter J. Müller  Erwin Suess 《Geochimica et cosmochimica acta》1977,41(7):941-949

Nitrogenous organic compounds in sorbed surface layers and in calcified organic matter associated with calcium carbonate sediment particles consist of 40–50% amino acids, 2% amino sugars and 25% ammonia. In grain size classes > 20 μm these compounds are mainly contained in the calcified protein of carbonate secreting organisms but with smaller grain sizes—and consequently increased specific surface area—they are contained in sorbed layers at the mineral surface. The composition of the sorbed layer is characterized by a predominance of neutral amino acids, a relative enrichment of basic and weakly polar amino acids, and a deficiency of acidic amino acids in comparison with the proteinaceous matter of calcifying organisms. The respective abundances for sorbed and calcified matter are: 505 and 380 Res./ of neutral amino acids, 262 and 450 Res./1000 of acidic amino acids, 92 and 51 Res./l000 of basic amino acids, and 141 and 129 Res./1000 of weakly polar amino acids.The composition of the sorbed layer appears to be the result of sorption of proteinaceous matter from solution since it reflects the free and peptide-bound amino acid composition of seawater. The characteristic amino acid assemblage could also be the result of preferential decomposition of protein and subsequent enrichment of neutral and basic amino acids; however, sorption from solution appears more likely since the total amount of amino acids sorbed to calcium carbonate (0.58 mg m ^?2) corresponds closely to the amount of protein known to cover one m² of aqueous substrate in monolayer arrangement. Sorption from solution is further supported by the low arginine/ornithine ratios in both the sorbed layer and the natural dissolved organic matter. This process might lead to a characteristic amino acid spectrum in fine grained calcareous sediments that reflects the composition of the dissolved organic matter in seawater rather than that of the carbonate secreting proteinaceous matter.  相似文献   

Sorptive stabilization of organic matter by amorphous Al hydroxide   总被引：3，自引：0，他引：3  

M.P.W. Schneider  T. Scheel  P. van Hees  K. Kalbitz 《Geochimica et cosmochimica acta》2010,74(5):1606-3154

Amorphous Al hydroxides (am-Al(OH)₃) strongly sorb and by this means likely protect dissolved organic matter (OM) against microbial decay in soils. We carried out batch sorption experiments (pH 4.5; 40 mg organic C L⁻¹) with OM extracted from organic horizons under a Norway spruce and a European beech forest. The stabilization of OM by sorption was analyzed by comparing the CO₂ mineralized during the incubation of sorbed and non-sorbed OM. The mineralization of OM was evaluated based in terms of (i) the availability of the am-Al(OH)₃, thus surface OM loadings, (ii) spectral properties of OM, and (iii) the presence of phosphate as a competitor for OM. This was done by varying the solid-to-solution ratio (SSR = 0.02-1.2 g L⁻¹) during sorption. At low SSRs, hence limited am-Al(OH)₃ availability, only small portions of dissolved OM were sorbed; for OM from Oa horizons, the mineralization of the sorbed fraction exceeded that of the original dissolved OM. The likely reason is competition with phosphate for sorption sites favouring the formation of weak mineral-organic bindings and the surface accumulation of N-rich, less aromatic and less complex OM. This small fraction controlled the mineralization of sorbed OM even at higher SSRs. At higher SSRs, i.e., with am-Al(OH)₃ more available, competition of phosphate decreased and aromatic compounds were sorbed selectively, which resulted in pronounced resistance of sorbed OM against decay. The combined OC mineralization of sorbed and non-sorbed OM was 12-65% less than that of the original DOM. Sorbed OM contributed only little to the overall OC mineralization. Stabilization of OC increased in direct proportion to am-Al(OH)₃ availability, despite constant aromatic C (∼30%). The strong stabilization at higher mineral availability is primarily governed by strong Al-OM bonds formed under less competitive conditions. Due to these strong bonds and the resulting strong stabilization, the surface loading, a proxy for the mineral’s occupation by OM, was not a factor in the mineralization of sorbed OM over a wide range of C sorption (0.2-1.1 mg C m⁻²). This study demonstrates that sorption to am-Al(OH)₃ results in stabilization of OM. The mineral availability as well as the inorganic solution chemistry control sorptive interactions, thereby the properties of sorbed OM, and the stability of OM against microbial decay.  相似文献   

Limestone drains to increase pH and remove dissolved metals from acidic mine drainage     

《Applied Geochemistry》1999,14(5):581-606

Despite encrustation by Fe and Al hydroxides, limestone can be effective for remediation of acidic mine drainage (AMD). Samples of water and limestone (CaCO₃) were collected periodically for 1 a at 3 identical limestone-filled drains in Pennsylvania to evaluate the attenuation of dissolved metals and the effects of pH and Fe- and Al-hydrolysis products on the rate of CaCO₃ dissolution. The influent was acidic and relatively dilute (pH<4; acidity <90 mg) but contained 1–4 mg·L⁻¹ of O₂, Fe³⁺, Al³⁺ and Mn²⁺. The total retention time in the oxic limestone drains (OLDs) ranged from 1.0 to 3.1 hr. Effluent remained oxic (O₂>1 mg·L⁻¹) but was near neutral (pH=6.2–7.0); Fe and Al decreased to less than 5% of influent concentrations. As pH increased near the inflow, hydrous Fe and Al oxides precipitated in the OLDs. The hydrous oxides, nominally Fe(OH)₃ and Al(OH)₃, were visible as loosely bound, orange-yellow coatings on limestone near the inflow. As time elapsed, Fe(OH)₃ and Al(OH)₃ particles were transported downflow. The accumulation of hydrous oxides and elevated pH (>5) in the downflow part of the OLDs promoted sorption and coprecipitation of dissolved Mn, Cu, Co, Ni and Zn as indicated by decreased UK concentrations of the metals in effluent and their enrichment relative to Fe in hydrous-oxide particles and coatings on limestone. Despite thick (∼1 mm) hydrous-oxide coatings on limestone near the inflow, CaCO₃ dissolution was more rapid near the inflow than at downflow points within and the OLD where the limestone was not coated. The high rates of CaCO₃ dissolution and Fe(OH₃) precipitation were associated with the relatively low pH and high Fe³⁺ concentration near the inflow. The rate of CaCO₃ dissolution decreased with increased pH and concentrations of Ca²⁺ and HCO₃⁻ and decreased Pco₂. Because overall efficiency is increased by combining neutralization and hydrolysis reactions, an OLD followed by a settling pond requires less land area than needed for a two-stage treatment system consisting of an anoxic limestone drain an oxidation-settling pond or wetland. To facilitate removal of hydrous-oxide sludge, a perforated-pipe subdrain can be installed within an OLD.  相似文献