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1.
The Sb speciation in soil samples from Swiss shooting ranges was determined using Sb K-edge X-ray absorption spectroscopy (XAS) and advanced statistical data analysis methods (iterative transformation factor analysis, ITFA). The XAS analysis was supported by a spectral data set of 13 Sb minerals and 4 sorption complexes. In spite of a high variability in geology, soil pH (3.1-7.5), Sb concentrations (1000-17,000 mg/kg) and shooting-range history, only two Sb species were identified. In the first species, Sb is surrounded solely by other Sb atoms at radial distances of 2.90, 3.35, 4.30 and 4.51 Å, indicative of metallic Sb(0). While part of this Sb(0) may be hosted by unweathered bullet fragments consisting of PbSb alloy, Pb LIII-edge XAS of the soil with the highest fraction (0.75) of Sb(0) showed no metallic Pb, but only Pb2+ bound to soil organic matter. This suggests a preferential oxidation of Pb in the alloy, driven by the higher standard reduction potential of Sb. In the second species, Sb is coordinated to 6 O-atoms at a distance of 1.98 Å, indicative of Sb(V). This oxidation state is further supported by an edge energy of 30,496-30,497 eV for the soil samples with <10% Sb(0). Iron atoms at radial distances of 3.10 and 3.56 Å from Sb atoms are in line with edge-sharing and bidentate corner-sharing linkages between Sb(O,OH)6 and Fe(O,OH)6 octahedra. While similar structural units exist in tripuhyite, the absence of Sb neighbors contradicts formation of this Fe antimonate. Hence the second species most likely consists of inner-sphere sorption complexes on Fe oxides, with edge and corner-sharing configuration occurring simultaneously. This pentavalent Sb species was present in all samples, suggesting that it is the prevailing species after weathering of metallic Sb(0) in oxic soils. No indication of Sb(III) was found.  相似文献   

2.
The Mokrsko Stream in the central Czech Republic is an oxic and slightly alkaline stream that drains a natural As geochemical anomaly. Although long-term monitoring has characterized the general seasonal trends in trace element concentrations (i.e., As, Mo, Cu, Zn) in this stream, little is known about solubility controls and sorption processes that influence diel cycles in trace element concentrations. Trace elements (including As species, Cu, Mn, Mo, Pb and Sb) and other parameters were monitored over two 24-h periods in unfiltered and filtered (0.1 μm) samples collected in August 2010 and June 2011. Copper and Pb were predominantly (>92% of the mass) associated with the particulate fraction (>0.1 μm). Arsenic, Mo and Sb were predominantly (>88% of the mass) in the “dissolved” (<0.1 μm) form. Particulate-associated elements displayed up to a factor of 13 differences between minimum and maximum concentrations, most likely due to increased streamflow related to rainfall events. Dissolved concentrations of the trace metal cations (Cu, Fe, Mn and Pb) were consistently low and displayed no diel trends. Dissolved As(V), Mo and Sb varied on a diel cycle, with increased concentrations (up to 36%) during the late afternoon and decreased concentrations during the nighttime. Diel trends in trace anionic elements are explained by temperature-dependent sorption, as the diel changes in pH during base flow were very small (0.07 std. units). Very low concentrations of As(III), which have been shown to vary in a diel cycle, were attributed to enhanced hydraulic exchange with As(III)-rich hyporheic water during rainfall events.  相似文献   

3.
Arsenic and Antimony in Groundwater Flow Systems: A Comparative Study   总被引：3，自引：0，他引：3  
Arsenic (As) and antimony (Sb) concentrations and speciation were determined along flow paths in three groundwater flow systems, the Carrizo Sand aquifer in southeastern Texas, the Upper Floridan aquifer in south-central Florida, and the Aquia aquifer of coastal Maryland, and subsequently compared and contrasted. Previously reported hydrogeochemical parameters for all three aquifer were used to demonstrate how changes in oxidation–reduction conditions and solution chemistry along the flow paths in each of the aquifers affected the concentrations of As and Sb. Total Sb concentrations (SbT) of groundwaters from the Carrizo Sand aquifer range from 16 to 198 pmol kg−1; in the Upper Floridan aquifer, SbT concentrations range from 8.1 to 1,462 pmol kg−1; and for the Aquia aquifer, SbT concentrations range between 23 and 512 pmol kg−1. In each aquifer, As and Sb (except for the Carrizo Sand aquifer) concentrations are highest in the regions where Fe(III) reduction predominates and lower where SO4 reduction buffers redox conditions. Groundwater data and sequential analysis of the aquifer sediments indicate that reductive dissolution of Fe(III) oxides/oxyhydroxides and subsequent release of sorbed As and Sb are the principal mechanism by which these metalloids are mobilized. Increases in pH along the flow path in the Carrizo Sand and Aquia aquifer also likely promote desorption of As and Sb from mineral surfaces, whereas pyrite oxidation mobilizes As and Sb within oxic groundwaters from the recharge zone of the Upper Floridan aquifer. Both metalloids are subsequently removed from solution by readsorption and/or coprecipitation onto Fe(III) oxides/oxyhydroxides and mixed Fe(II)/Fe(III) oxides, clay minerals, and pyrite. Speciation modeling using measured and computed Eh values predicts that Sb(III) predominate in Carrizo Sand and Upper Floridan aquifer groundwaters, occurring as the Sb(OH)30 species in solution. In oxic groundwaters from the recharge zones of these aquifers, the speciation model suggests that Sb(V) occurs as the negatively charged Sb(OH)6− species, whereas in sufidic groundwaters from both aquifers, the thioantimonite species, HSb2S4 − and Sb2S4 2−, are predicted to be important dissolved forms of Sb. The measured As and Sb speciation in the Aquia aquifer indicates that As(III) and Sb(III) predominate. Comparison of the speciation model results based on measured Eh values, and those computed with the Fe(II)/Fe(III), S(-II)/SO4, As(III)/As(V), and Sb(III)/Sb(V) couples, to the analytically determined As and Sb speciation suggests that the Fe(II)/Fe(III), S(-II)/SO4 couples exert more control on the in situ redox condition of these groundwaters than either metalloid redox couple.  相似文献   

4.
High levels of antimony have been frequently detected in some industrial sites. This study evaluated the adverse effects of antimony (Sb) on the surface-casting activity of earthworm and the early growths of some important crop plants. Asian earthworm (Perionyx excavates) and four crop plant species (Chinese cabbage, Brassica campestris; wheat, Triticum aestivum; cucumber, Cucumis sativus; and mung bean, Phaseolus radiatus) were exposed to soil antimony in laboratory. Survival, abnormality and the surface-casting activity of earthworm were monitored. Negative effects of the survival and the morphological abnormalities were observed in the P. excavates exposed to Sb. The earthworm activity, expressed as surface cast production, was significantly inhibited with elevated Sb levels. In terms of plant assay, the growth of all test plants was adversely affected in Sb-contaminated soils, and the content of Sb in plant tissues increased with increasing Sb concentration in soil. The results demonstrate that elevated Sb concentrations in soil would inhibit the early growth of crop plants, and the earthworm casting activity that is a key function of earthworm to increase soil fertility. This is the first report on the negative effect of Sb on the casting activity of earthworm as well as the growth of test plant species selected.  相似文献   

5.
This study investigates Sb speciation in sediments along the drainage of the Upper Peter adit at the Bralorne Au mine in southern British Columbia, Canada, and compares the behavior of Sb with that of As. The Upper Peter mineralization consists of native Au in quartz-carbonate veins with 1 wt.% sulfides dominated by pyrite and arsenopyrite although stibnite, the primary Sb-bearing sulfide mineral, can be locally significant. Dissolved Sb concentrations can reach up to 349 μg L−1 in the mine pool. Sediments were collected for detailed geochemical and mineralogical characterization at locations along the 350-m flow path, which includes a 100-m shallow channel within the adit, a sediment settling pond about 45 m beyond the adit portal and an open wetland another 120 m farther downstream. From the mine pool to the wetland outlet, dissolved Sb in the drainage drops from 199 μg L−1 to below the detection limit due to the combined effect of dilution and removal from solution. Speciation analyses using X-ray absorption near-edge structure (XANES) spectroscopy indicate that Sb(III)–S accounts for around 70% of total Sb in the sediments in the main pool at the far end of the adit. At a short distance (24 m) downstream of the main adit pool, however, Sb(III)–O and Sb(V)–O species represent ?50% of total Sb in the bulk sediments, indicating significant oxidation of the primary sulfides inside the adit. Although Sb appears largely oxidized in the bulk samples collected near the portal, Sb(III)–S species are nevertheless present in the <53-μm fraction, suggesting a higher oxidation rate for stibnite in the coarser grains, possibly due to galvanic interaction with pyrite. Secondary Sb species released from the sulfide oxidation are most likely sorbed/co-precipitated with Fe-, Mn-, and Al-oxyhydroxides along the flow channel in the adit and in the sediment settling pond, with the Fe phase being the dominant sink for Sb.  相似文献   

6.
Antimony (Sb) emissions to the environment are increasing, and there is a dearth of knowledge regarding Sb fate and behavior in natural systems. In natural systems, the presence of competitive anions may compete with Sb for adsorption sites on mineral surfaces, hence increasing its potential bioavailability. Accordingly, the adsorption of Sb(III) on kaolinite was investigated in the presence of competitive anions. Kinetic studies suggest that adsorption reaction of Sb(III) on kaolinite is rapid initially and becoming slow after 12 h both in binary Sb(III)–kaolinite system and in ternary Sb(III)-competitive anion–kaolinite system. The presence of PO4 3? has a much stronger and more obvious promotive effect on the adsorption of Sb(III) on kaolinite compared with the other two anions. The adsorption data of Sb(III) on kaolinite in the absence and presence of competitive anions at three temperatures were successfully modeled using Langmuir (r 2 > 0.95) and Freundlich (r 2 > 0.95) isotherms. Accompanied the adsorption of Sb(III) on kaolinite, significant oxidation of Sb(III) to Sb(V) had occurred under the experimental conditions used in this study. The presence of kaolinite which has a larger specific surface area could increase the contact area between the adsorbed Sb(III) and oxygen in the bulk solution, which promoted the oxidation rate of Sb(III) to Sb(V).  相似文献   

7.
This paper investigates the mechanisms controlling Sb-leaching from fresh Municipal Solid Waste Incinerator (MSWI) bottom ash, as well as the possibilities of controlling the extent of Sb-leaching by the addition of sorbent minerals to the bottom ash. In alkaline MSWI bottom ash Sb is possibly incorporated in ettringite-like minerals. When weathering/carbonation continues the ettringite dissolves resulting in a mobilisation of Sb. At neutral pH values the leaching of Sb is likely to be controlled by sorption to amorphous Fe/Al-(hydr)oxides. It has been shown that Sb can effectively be removed from solution if salts of Fe(III) or Al(III) are added to the bottom ash. This addition of Fe(III)/Al(III)-salts leads to (1) the in-situ precipitation of Fe/Al-hydroxides and sorption/coprecipitation of contaminants such as Sb, and (2) a lower bottom ash pH and thus an increased affinity of oxyanions for sorption to Fe/Al-(hydr)oxides.  相似文献   

8.
《Earth》2002,57(1-2):125-176
Antimony is ubiquitously present in the environment as a result of natural processes and human activities. It exists mainly as Sb(III) and Sb(V) in environmental, biological and geochemical samples. Antimony and its compounds are considered to be priority pollutants interest by the USEPA and the EU. In this first review paper on antimony occurrence in natural waters, 420 papers on freshwaters, marine waters, estuaries, soils, and sediments have been reviewed. All data are quoted from the original sources. Typical concentrations of total dissolved antimony are usually less than 1.0 μg/l in non-polluted waters. When redox speciation determinations are performed, most studies report the dominance of Sb(V) under oxic conditions. However, the presence of significant proportions of Sb(III) is sometimes detected. This is in contrast with thermodynamic equilibrium predictions and discrepancies are often attributed to biological activity or kinetic effects but proofs are lacking. Similarly, the existence of Sb(V), although not thermodynamically predicted, is often reported under anoxic conditions. Low concentrations of methylated antimony species are mentioned in a few studies. Antimony is not considered to be a highly reactive element in oceans, with concentrations of the order of 200 ng/l. In estuarine waters, both conservative and non-conservative behaviours are reported depending on the estuaries' characteristics. Elevated concentrations of antimony in soils and sediments are either related to anthropogenic sources or associated with high arsenic concentrations in sulfidic ores. Antimony appears to be highly unreactive in soils. Low accumulation factors are reported in algae. Airborne supply of antimony to aquatic and terrestrial systems seems to be important in systems far from direct pollution sources. However, the limited available data do not allow firm conclusions to be drawn on the reactivity and cycling of the element in natural systems and a list of research priorities is given.  相似文献   

9.
《Applied Geochemistry》2000,15(6):879-889
Direct evidence of the structure of thioantimonide species in alkaline aqueous solutions is provided by X-ray absorption spectroscopy. Twenty solutions containing thioantimonide species were prepared by dissolving stibnite (Sb2S3) in deoxygenated aqueous NaHS solutions; the solution pH range was 8–14, the [Sbtot] 1–100 mM and the [HS−] 0.009–2.5 M. The structural environment of the dissolved Sb was determined by EXAFS analysis of the Sb K-edge over the temperature range 80–473 K.Many of the solutions contain a species with Sb bonded to four S atoms at 2.34 Å, consistent with the presence of a [Sb(V)S43−] species, demonstrating that oxidation of Sb(III) to Sb(V) has occurred on dissolution. There is evidence that the complementary reduced phase is H2. In three solutions, the Sb has three nearest neighbor S atoms and two of these solutions have an additional S shell of two atoms at 2.9Å, with one showing evidence of an Sb shell at 4.15 Å. This provides evidence of the presence of multimeric Sb(V) thioantimonide species. Analysis of several solutions reveals the presence of a species with three Sb–S interactions of 2.41–2.42 Å, supporting the presence of a Sb(III) species such as Sb2S2(SH)2. Six solutions have S coordination numbers from 2.7–4 Å and Sb–S distances of 2.37–2.39 Å, and are likely to contain mixtures of at least two species in concentrations such that each make a significant contribution to the EXAFS. There was no clear relationship between either [Sbtot] or [HS−] and the type of species present, but Sb(III) species were only present in the solutions with high pH. The effect of temperature was most significant in one solution, where at 423 K partial hydrolysis occurred and the presence of a species such as Sb2S2(OH)2, with an Sb–O distance of 1.91 Å, is indicated.The study provides new information on the coordination environment of thioantimonide species, complementary to previous studies and provides a basis for a better understanding of Sb speciation in aqueous solutions found in hydrothermal systems, anoxic basins and man-made, high pH environments. In particular it demonstrates the need for Sb(V) to be considered in theoretical and experimental studies of such systems. However, more definitive interpretation of some of the data is inhibited by the presence of mixtures of species and the lack of information on the outer coordination shells that would confirm the presence of multimeric species.  相似文献   

10.
锑属亲铜元素,易与硫结合。锑在地核(0. 14×10~(-6))、地幔(0. 006×10~(-6))和地壳(0. 02×10~(-6))中的丰度均很低,而在黑色页岩(5. 0×10~(-6))中明显富集。锑是一种典型的低温成矿元素。我国华南地区低温成矿域拥有世界60%的锑探明储量。研究结果显示锑的成矿主要经历两阶段富集过程:一是与风化和沉积作用有关的表生过程;二是地球内部热驱动过程。寒武纪时华南位于赤道附近,受冈瓦纳大陆的造山带的影响,是全球地表风化最强烈的地区之一。在新元古代氧化事件的驱动下,锑在表生风化过程中被氧化为更易迁移的水溶性的SbO_3~-。因埃迪卡拉生物群所产生的有机质,有利于萃取水体中的锑并沉淀在还原性沉积物(黑色页岩)中。华南中生代岩浆活动烘烤表层富锑的寒武纪黑色页岩,产生的成矿流体向上迁移,淋滤黑色页岩中的Sb或与黑色页岩变质脱水或熔融产生成矿流体混合;而后搬运至远离岩体的有利位置沉淀,最终形成大规模的华南锑矿带。  相似文献   

11.
The present work investigated the adsorption and mobility (desorption) of Sb(V) on kaolinite using batch experiments. The adsorption of Sb(V) on kaolinite was studied as a function of contact time, pH, ionic strength, humic acid (HA), initial Sb(V) concentration and temperature. Kinetic studies suggest that the equilibrium is achieved within 24 h. The adsorption of Sb(V) was strongly affected by changes in I at low ionic strength and unaffected at high ionic strength. The adsorption is weakly dependent on the presence of humic acid, but is strongly dependent on pH. Within the range tested, the optimal pH for Sb(V) adsorption is 3.6, and close to 75% removal can be achieved. Desorption is dependent on the original suspension pH. The addition sequence of Sb(V)/HA do not influence the adsorption of Sb(V) on kaolinite. The adsorption data fit both the Freundlich and Langmuir isotherm. The thermodynamic parameters (ΔH 0, ΔS 0 and ΔG 0) were calculated from the temperature dependence, and the results suggest the endothermic and spontaneous nature of the process.  相似文献   

12.
Previous studies in our laboratory have demonstrated that drinking-water treatment residuals are effective sorbents of arsenic V. However, the effect of soil solution chemistry on arsenic V sorption by drinking-water treatment residuals-amended soils remains to be explored. The current study uses a batch incubation experimental set up to evaluate the effect of soil solution pH, competing ligands, and complexing metal on arsenic V sorption by a sandy soil (Immokalee series) amended with two rates (25 and 50 g kg?1) of aluminum and iron-based drinking-water treatment residuals. Experiments were conducted at three initial arsenic loads (125, 1,875, 3,750 mg kg?1) and a constant solid: solution ratio of 200 g L?1. An optimum equilibration time of 8 days, obtained from kinetic studies, was utilized for sorption experiments with both aluminum and iron drinking-water treatment residual-amended soil. Presence of phosphate decreased arsenic V sorption by both aluminum and iron drinking-water treatment residual amended soils, with a strong dependence on pH, drinking-water treatment residual types, drinking-water treatment residual application rates, and phosphate concentrations. Addition of sulfate had no effect on arsenic V sorption by aluminum or iron drinking-water treatment residual-amended soil. A complementing effect of calcium on arsenic V sorption was observed at higher pH. Results elucidating the effect of soil solution chemistry on the arsenic V sorption will be helpful in calibrating drinking-water treatment residual as a sorbent for remediation of arsenic-contaminated soils.  相似文献   

13.
Batch and column experiments were conducted on As adsorption from aqueous solution by natural solids to test the feasibility of these materials to act as adsorbents for As removal from groundwater and drinking water. The solids considered are natural hematite and natural siderite. The As species studied are As(V), As(III) and dimethylarsinic acid (DMA). Arsenic(III), As(V) and DMA were removed to different extents by the solids studied from water solutions containing these three As species, with the highest efficiency for As(V). In aqueous solutions with a mixture of As species, adsorption kinetics depend on the species. On both materials, As(V) was preferentially adsorbed in the batches and first reached equilibrium, followed by DMA and As(III). The As adsorption took place more slowly on natural hematite and natural siderite compared with ferrihydrite. The results demonstrate that the amount of As removed from As(III) batches was greater than that from As(V) batches due to a surface alteration of the solids caused by As(III) oxidation. Although the highest efficiency for As retention was observed on hematite HIO1 in the batch experiments, siderite used as column filling was more efficient in removing As from water containing the As species studied in comparison with hematite. The coating of fresh Fe(III)-oxides was much more intensive in the siderite-packed column than in the hematite-packed column. The combination of siderite and hematite would promote the column filling performance in removing As from aqueous solution.  相似文献   

14.
Oxidation of As(III) by natural manganese (hydr)oxides is an important geochemical reaction mediating the transformation of highly concentrated As(III) in the acidic environment such as acid mine drainage (AMD) and industrial As-contaminated wastewater, however, little is known regarding the presence of dissolved Fe(II) on the oxidation process. In this study, oxidation of As(III) in the absence and presence of Fe(II) by MnO2 under acidic conditions was investigated. Kinetic results showed that the presence of Fe(II) significantly inhibited the removal of As(III) (including oxidation and sorption) by MnO2 in As(III)-Fe(II) simultaneous oxidation system even at the molar ratio of Fe(II):As(III) = 1/64:1, and the inhibitory effects increased with the increasing ratios of Fe(II):As(III). Such an inhibition could be attributed to the formation of Fe(III) compounds covering the surface of MnO2 and thus preventing the oxidizing sites available to As(III). On the other hand, the produced Fe(III) compounds adsorbed more As(III) and the oxidized As(V) on the MnO2 surface with an increasing ratio of Fe(II):As(III) as demonstrated in kinetic and XPS results. TEM and EDX results confirmed the formation of Fe compounds around MnO2 particles or separated in solution in Fe(II) individual oxidation system, Fe(II) pre-treated and simultaneous oxidation processes, and schwertmannite was detected in Fe(II) individual and Fe pre-treated oxidation processes, while a new kind of mineral, probably amorphous FeOHAs or FeAsO4 particles were detected in Fe(II)-As(III) simultaneous oxidation process. This suggests that the mechanisms are different in Fe pre-treated and simultaneous oxidation processes. In the Fe pre-treated and MnO2-mediated oxidation pathway, As(III) diffused through a schwertmannite coating formed around MnO2 particles to be oxidized. The newly formed As(V) was adsorbed onto the schwertmannite coating until its sorption capacity was exceeded. Arsenic(V) then diffused out of the coating and was released into the bulk solution. The diffusion into the schwertmannite coating and the oxidation of As(III) and sorption of both As(V) and As(III) onto the coating contributed to the removal of total As from the solution phase. In the simultaneous oxidation pathway, the competitive oxidation of Fe(II) and As(III) on MnO2 occurred first, followed by the formation of FeOHAs or FeAsO4 around MnO2 particles, and these poorly crystalline particles of FeOHAs and FeAsO4 remained suspended in the bulk solution to adsorb As(III) and As(V). The present study reveals that the formation of Fe(III) compounds on mineral surfaces play an important role in the sorption and oxidation of As(III) by MnO2 under acidic conditions in natural environments, and the mechanisms involved in the oxidation of As(III) depend upon how Fe(II) is introduced into the As(III)-MnO2 system.  相似文献   

15.
为探讨岩浆蚀变作用对煤层中锑赋存特征的影响,系统采集安徽淮北煤田卧龙湖煤矿岩浆侵入煤层侵入岩和全煤层样品共12个,利用原子荧光光谱法（AFS）测定样品中Sb含量,并对煤质参数进行分析。结果表明:卧龙湖煤矿岩浆侵入区煤表现为超低挥发分,中等灰分,特低硫的特点,煤中的硫主要以有机硫和黄铁矿硫存在。受岩浆热液影响,煤中灰分增加,挥发分减少;岩浆蚀变煤层中锑明显富集,算术平均值达到10.48 mg/kg,且侵入岩上方煤中Sb的平均含量明显增高,煤岩接触带位置Sb的含量达到最高值（13.93 mg/kg）;岩浆蚀变煤中的锑主要以无机结合态形式存在（相关系数r为0.74）,有机硫与煤中Sb呈显著负相关（相关系数r为-0.60）。岩浆侵入作用导致卧龙湖煤矿煤的煤质特征及煤层中锑的赋存方式受到不同程度的影响,研究结果可为特殊地质作用下煤中锑的环境地球化学特征提供参考。   相似文献   

16.
Historic antimony mining at Endeavour Inlet, New Zealand, was developed in a stibnite-rich mesothermal vein system hosted in a km scale shear zone in metasedimentary schist. The schist contains calcite, and all waters have pH between 7 and 8. Underground tunnels (adits) have largely collapsed, but two adits provided access to waters which have interacted chemically with mineralised rock. Natural groundwater entering an adit at the top of the mineralised catchment had 190 μg/l Sb and 10 μg/l As. The amount of arsenic increased along the adit as the water interacted with arsenopyrite-bearing rocks and debris (up to 2000 mg/kg As, 500 mg/kg Sb) on the adit floor. Sb(III) was below 14 μg/l, and there was no detectable As(III). Antimony content remained near constant in the adit but increased outside the adit because of interaction with stibnite-rich debris. Negligible attenuation of metalloids occurred via adsorption outside the adit, as iron oxyhydroxide is rare. Metalloid attenuation was by dilution in a nearby natural stream, which carried <30 μg/s Sb and <10 μg/s As away from the site. An adit 500 m downstream was developed in a lower, more arsenopyrite-rich portion of the mineralised system with debris containing up to 15,000 mg/kg As and 5000 mg/kg Sb. Water from this adit had up to 200 μg/l Sb and 1650 μg/l As. Arsenic was attenuated by adsorption outside this adit, and by dilution by the natural stream. Antimony was not attenuated by adsorption, nor by dilution as the natural stream contained up to 200 μg/l Sb. Metalloid flux away from this site was ca. 200 μg/s Sb and 40 μg/s As, and the adit contributed negligible amounts of metalloids to this flux. Total metalloid flux from the catchment is 14,000 μg/s antimony and 5000 μg/s arsenic, which is around three orders of magnitude greater than observed mine inputs to the catchment. Highest flux occurred in September as water tables rose in the winter. Nearly all the metalloid flux is derived by natural groundwater and surface water interaction with mineralised rock. This interaction between water and mineralised rock is enhanced in this area because the catchment runs subparallel to the shear zone which controls the mineralised veins.  相似文献   

17.
Antimony‐rich gold deposits represent a subclass of orogenic hydrothermal systems. The study of the Lapa gold deposit in the Abitibi greenstone belt shows that antimony occurs during two different stages: (1) as early prograde Sb–Ni disseminated sulphides in talc schists, associated with CO2‐bearing fluids, and (2) as a late native antimony association, associated with methane‐bearing fluids indicating a reducing environment. Methane could be related to the serpentinization of the ultramafic rocks of the Piché Group hosting the Lapa deposit. Several deposits display the same methane antimony association along fault zones.  相似文献   

18.
This paper present the possible alternative removal options for the development of safe drinking water supply in the chromium-affected areas. The Cr (VI) state is of particular concern because of its toxicity. The mordenite has suitable mineralogical properties that enable them to be used for ion-exchange processes. This includes total cation exchange capacity. However, in the present work, the modified-natural zeolite was used as an adsorbent for the removal of Cr (VI) from aqueous solution. The ability of modified natural zeolite (mordenite) to remove inorganic anion was investigated. Laboratory experiments were conducted examining the effect of the sorption of cationic surfactants. On the basis of the results of this study, the HDTMA-HSO4 modified zeolite appears suitable as a sorbent for hexavalent chromium whereas EHDDMA-modified zeolite were not removed with the same efficiency. The sorption of chromate on HDTMA-zeolite results from a combination of entropic, coulombic, hydrophobic effects, and HDTMA counterion.  相似文献   

19.
Arsenic and antimony contamination is found at the Pezinok mining site in the southwest of the Slovak Republic. Investigation of this site included sampling and analysis of water, mineralogical analyses, sequential extraction, in addition to flow and geochemical modeling. The highest dissolved arsenic concentrations correspond to mine tailings (up to 90,000 μg/L) and the arsenic is present predominately as As(V). The primary source of the arsenic is the dissolution of arsenopyrite. Concentration of antimony reaches 7,500 μg/L and its primary source is the dissolution of stibnite. Pore water in mine tailings is well-buffered by the dissolution of carbonates (pH values between 6.6 and 7.0) and arsenopyrite grains are surrounded by reaction rims composed of ferric iron minerals. Based on sequential extraction results, most solid phase arsenic is in the reducible fraction (i.e. ferric oxyhydroxides), sulfidic fraction, and residual fraction. Distribution of antimony in the solid phase is similar, but contents are lower. The principal attenuation mechanism for As(V) is adsorption to ferric oxide and hydroxides, but the adsorption seems to be limited by the competition with Sb(V) produced by the oxidation of stibnite for adsorption sites. Water in mine tailings is at equilibrium with gypsum and calcite, but far from equilibrium with any arsenic and antimony minerals. The concentrations of arsenic and antimony in the surrounding aquifer are much lower, with maximum values of 215 and 426 μg/L, respectively. Arsenic and antimony are transported by ground water flow towards the Blatina Creek, but their loading from ground water to the creek is much lower compared with the input from the mine adits. In the Blatina Creek, arsenic and antimony are attenuated by dilution and by adsorption on ferric iron minerals in stream sediments with resulting respective concentrations of 93 and 45 μg/L at the site boundary south of mine tailing ponds.  相似文献   

20.
Recent experimental studies have reported the existence of two new Sb sulfide species, Sb2S52− and Sb2S62−, in alkaline sulfidic solutions in equilibrium with stibnite, Sb2S3, and orthorhombic S. These species contain Sb(V), which has also recently been identified in similar solutions using EXAFS by other researchers. This represents a significant change from the consensus a decade ago that sulfidic solutions of Sb contained only Sb(III) species. I have calculated from first principles of quantum mechanics the energetics for the oxidation of the Sb(III) sulfide dimer Sb2S42− to the mixed Sb(III,V) dimer Sb2S52− and then to the all Sb(V) dimer, Sb2S62−. Gas-phase reaction energies have been evaluated using polarized valence double zeta effective core potential basis sets and Moller-Plesset second order treatments of electron correlation. All translational, rotational and vibrational contributions to the gas-phase reaction free energy have been calculated. Hydration energies have been obtained using the COSMO version of the self-consistent reaction field polarizable continuum method. Negative free energy changes are calculated for the oxidation of the dianion of the III,III dimer to the III,V dimer by both small polysulfides, like S4H−, and elemental S, modeled as S8. For the further oxidation of the III,V dimer to the V,V dimer the reaction free energies are calculated to be close to zero. The partially protonated Sb III,III dimer monoanion HSb2S4− can also be oxidized, but the reaction is not so favorable as for the dianion. Comparison of the calculated aqueous deprotonation energies of H2Sb2S4, H2Sb2S5 and H2Sb2S6 and their dianions with values calculated for various oxyacids indicates that the III,V and V,V dimers will have pKa2 values <5, so that their dianions will be the dominant species in alkaline solutions. These results are thus consistent with the recent identification of Sb2S52− and Sb2S62− species. I have also calculated the Raman spectra of Sb2S52− and Sb2S62− to assist in their identification. The calculated vibrational frequencies of the III,V and V,V dimers are characteristically higher than those of the III,III dimer I previously studied. The III,V dimer may contribute shoulders to the Raman spectrum.  相似文献   

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