首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 265 毫秒
1.
《Applied Geochemistry》2002,17(8):1081-1092
Different types of fine-grained chemical precipitates were characterized in the surroundings of the pyrite-chalcopyrite mine of Libiola (Northern Italy). Both water chemistry and sediment composition were used to investigate metal mobility near the mine area. Local drainage waters were very acidic (with a pH as low as 2.5) and were rich in dissolved metals (Fe, Al, Cu, Zn, Mn, Ni). Sediments associated with low pH water (pH <4.5) were ochreous mixtures of schwertmannite and goethite with traces of jarosite. Their chemistry was dominated by Fe and they had, compared to other sediments investigated, low concentrations of other metals. When the acidity decreased gradually, other precipitates formed. At a pH of approximately 5, a poorly crystalline, whitish, Al-rich precipitate occurred. At a pH between 6 and 7, a poorly crystalline, blue, Cu (Zn) rich phase was present. These “sequential” precipitation events progressively reduced the metal loading typical of the acidic mine water when there was a gradual mixing with normal water. When a sudden mixing between normal waters (pH ∼8, Ca–HCO3, low metal bearing) and acidic waters took place, a rapid flocculation occurred of mixed precipitates containing Fe, Al and trace elements.  相似文献   

2.
The geochemical evolution of two acid mine effluents in Tharsis and La Zarza-Perrunal mines (Iberian Pyrite Belt, Huelva, Spain) has been investigated. In origin, these waters present a low pH (2.2 and 3.1) and high concentrations of dissolved sulphate and metals (Fe, Al, Mn, Cu, Zn, As, Cd, Co, Cr, Ni). However, the natural evolution of these acidic waters (which includes the bacterial oxidation of Fe(II) and the subsequent precipitation of Fe(III) minerals) represents an efficient mechanism of attenuation. This self-mitigating process is evidenced by the formation of schwertmannite, which retains most of the iron load and, by sorption, toxic trace elements like As. The later mixing with pristine waters rises the pH and favours the total precipitation of Fe(III) at pH 3.5 and, subsequently, Al compounds at pH 4.5, along with the sorption of trace metals (Mn, Zn, Cu, Cd, Co, Ni) until chemical equilibrium at circumneutral conditions is achieved.  相似文献   

3.
《Applied Geochemistry》2000,15(7):1003-1018
Stream discharges and concentrations of dissolved and colloidal metals (Al, Ca, Cu, Fe, Mg, Mn, Pb, and Zn), SO4, and dissolved silica were measured to identify chemical transformations and determine mass transports through two mixing zones in the Animas River that receive the inflows from Cement and Mineral Creeks. The creeks were the dominant sources of Al, Cu, Fe, and Pb, whereas the upstream Animas River supplied about half of the Zn. With the exception of Fe, which was present in dissolved and colloidal forms, the metals were dissolved in the acidic, high-SO4 waters of Cement Creek (pH 3.8). Mixing of Cement Creek with the Animas River increased pH to near-neutral values and transformed Al and some additional Fe into colloids which also contained Cu and Pb. Aluminium and Fe colloids had already formed in the mildly acidic conditions in Mineral Creek (pH 6.6) upstream of the confluence with the Animas River. Colloidal Fe continued to form downstream of both mixing zones. The Fe- and Al-rich colloids were important for transport of Cu, Pb, and Zn, which appeared to have sorbed to them. Partitioning of Zn between dissolved and colloidal phases was dependent on pH and colloid concentration. Mass balances showed conservative transports for Ca, Mg, Mn, SO4, and dissolved silica through the two mixing zones and small losses (<10%) of colloidal Al, Fe and Zn from the water column.  相似文献   

4.
《Applied Geochemistry》2005,20(8):1445-1460
Changes in precipitate mineralogy, morphology, and major and trace element concentrations and associations throughout 5 coal mine drainage (CMD) remediation systems treating discharges of varying chemistries were investigated in order to determine the factors that influence the characteristics of precipitates formed in passive systems. The 5 passive treatment systems sampled in this study are located in the bituminous coal fields of western Pennsylvania and northern Maryland, and treat discharges from Pennsylvanian age coals. The precipitates are dominantly (>70%) goethite. Crystallinity varies throughout an individual system, and lower crystallinity is associated with enhanced sorption of trace metals. Degree of crystallinity (and subsequently morphology and trace metal associations) is a function of the treatment system and how rapidly Fe(II) is oxidized, forms precipitates, aggregates and settles. Precipitates formed earlier in the passive treatment systems tend to have the highest crystallinity and the lowest concentrations of trace metal cations. High surface area and cation vacancies within the goethite structure enable sorption and incorporation of metals from coal mine drainage-polluted waters. Sorption affinities follow the order of Zn > Co ≈ Ni > Mn. Cobalt and Ni are preferentially sorbed to Mn oxide phases when these phases are present. As pH increases in the individual CMD treatment systems toward the pHpzc of goethite, As sorption decreases and transition metal (Co, Mn, Ni and Zn) sorption increases. Sulfate, Na and Fe(II) concentrations may all influence the sorption of trace metals to the Fe hydroxide surface. Results of this study have implications not only for solids disposal and resource recovery but also for the optimization of passive CMD treatment systems.  相似文献   

5.
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   

6.
Soils of loamy sand on weathered, sandy dolomite were cored from six holes up to 70 ft beneath a municipal waste landfill in central Pennsylvania. Mn, Fe, Ni, Co, Cu, Zn, Cd, Pb, and Ag were determined in exchangeable and non-exchangeable forms in total and < 15 μm soil samples. Most of these metals were bound in Mn oxides, non-exchangeable with 0.5 M CaCl2. The Mn oxides (often X-ray amorphous) identified when crystalline as todorokite occurred chiefly as coatings on quartz grains.Somewhat higher amounts of acid leachable trace metals were found in the < 15 μm size fraction than in the total soil samples; however, trace metal/Mn ratios were similar in both. In general, the initial mild soil leaching, which dissolved chiefly Mn oxides, gave MnFeX>Co>Ni>Pb>Zn> Cu>Cd>Ag. The final leaching, which dissolved chiefly ferric oxides, gave Fe>Mn>Ni>Zn>Co> Cu>Pb>Cd>Ag. Samples taken from an unpolluted site and from the same soils affected for seven years by leachate from the refuse had similar metal contents.Soil extractable Co, Ni, Cu, and Zn could be predicted from the Mn extracted. Based in part on factor analysis of the data, Mn-rich oxides had at least tenfold higher heavy metal percentages than Fe-rich oxides (crystalline component goethite), reflecting their greater coprecipitation potential. Because of this potential and because of the generally higher solubility of Mn than Fe oxides, more heavy metals may be released from Mn-rich than from Fe-rich soils by disposal of organic-bearing wastes. However, leaching of the moisture-unsaturated soils in situ is rarely severe enough to completely dissolve both Mn and Fe oxides. Based on the Mn content, Cd, Cu, and Pb were depleted in soil moisture beneath the landfill relative to their amounts in the soil. This depletion may reflect factors including heterogeneity in metal content of the soil oxides; preferential resorption of these metals; and removal of the Cd, Cu, and Pb as organic precipitates or as inorganic precipitates such as carbonates.  相似文献   

7.
Sorption of metals on humic acid   总被引：1，自引：0，他引：1  
The sorption on humic acid (HA) of metals from an aqueous solution containing Hg(II). Fe(III), Pb, Cu, Al, Ni, Cr(III), Cd, Zn, Co and Mn, was investigated with special emphasis on effects of pH, metal concentration and HA concentration. The sorption efficiency tended to increase with rise in pH, decrease in metal concentration and increase in HA concentration of the equilibrating solution. At pH 2.4. the order of sorption was: Hg? Fe? Pb? CuAl ? Ni ? CrZnCdCoMn. At pH 3.7. the order was: Hg and Fe were always most readily removed, while Co and Mn were sorbed least readily. There were indications of competition for active sites (CO2H and phenolic OH groups) on the HA between the different metals. We were unable to find correlations between the affinities of the eleven metals to sorb on HA and their atomic weights, atomic numbers, valencies, and crystal and hydrated ionic radii. The sorption of the eleven metals on the HA could be described by the equation Y = 100[1 + exp ? (A + BX)], where Y = % metal removed by HA; X = mgHA; and A and B are empirical constants.  相似文献   

8.
The behaviour of trace elements (Al, As, Cd, Co, Cr,Cu, Fe, Mn, Ni, V, Zn) was studied in five humus-richstreams (dissolved organic carbon = 14–40 mg/L)impacted by acid sulphate soils developed in marinesulphide-bearing fine-grained sediments. During heavyrainfalls in autumn, on which the study focusses, themetals Al, Cd, Co, Cu, Mn, Ni and Zn are extensivelyleached from these acidic soils (pH = 2.5–4.5), whileAs, Cr, Fe and V are not leached more strongly fromthis soil type than from areas of till and peat. Aspeciation experiment, based on anion and cationexchange of the stream waters in the field, showedthat (1) the metals Al, Cd, Co, Mn, Ni and Zn aretransported in the streams mainly as inorganiccations, (2) Cu exists mainly in cationic form but isalso to a significant extent associated with dissolvedhumic substances, (3) Fe occurs mainly in the anionicfraction explained by organic coating on colloidal Feoxyhydoxides and (4) the hydrochemistry of As, Cr andV is complex as these elements may exist in severalunquantified anionic fractions and to a minor extentin cationic species/forms. Whereas the proportion ofacid sulphate soils in the catchments had a largeimpact on concentrations levels of several elements inthe stream waters, these soils did not have a largeaffect on the speciation of elements in water.  相似文献   

9.
《Applied Geochemistry》1995,10(2):237-250
The geochemistry of metal-rich mine waters and mineral precipitates from the Levant mine, Cornwall, has been examined. Sulphide oxidation at Levant mine has produced a wide range of secondary sulphides, oxides, chlorides, sulphates and carbonates in a gossan environment. The mine waters display a wide variation in alkalinity, pH, chloride, sulphate, sodium, potassium and heavy metal content which can be explained by variable degrees of mixing between acidic, metal-rich, rock drainage waters and neutral to alkaline sea waters. Transition metals are soluble in the acidic mine waters with concentrations up to 665 mg/l Cu, 41 mg/l Zn, 76 mg/l Mn, 6 mg/l Co and >2500 mg/l total Fe. The production of acid rock drainage and leaching of metals can be related to sulphide oxidation. Where these metal-rich acidic waters mix with infiltrated sea water, neutralization occurs and some metals are precipitated (principally Cu). Where pools of mine drainage are stagnant native copper and cuprite are precipitated, frequently observed replacing iron pipes and rail tracks and wooden shaft supports, due to electrode potential differences. In these solutions, dissolved copper species are also reduced by interaction with wood-derived organic species. Precipitation of iron oxyhydroxides, caused by a pH increase, also occurs and leads. to coprecipitation of other metals, including Cd, Co, Ph, Mn, Ag and Zn, thus limiting the release of dissolved metals in solution from the mine. However, the release of suspended metal-rich ochres in mine discharge waters (with high Ph, Zn, Cd, Mn, Ni, Sn, Sb, As, Bi, Cu, Co and Ag) will still present a potential environmental hazard.  相似文献   

10.
The oxidation of sulfide minerals generates acidic waters containing high levels of SO4 and Fe. The study area has active Pb?CZn?CCu mining. It is thought that the surface/subsurface/underground sulfide minerals in the region generally contribute to the acidification of groundwater. Low pH values are also responsible for dissolved metals (Al, Fe, Mn, SO4, Pb, Zn) in the groundwater and river. Furthermore, current mining wastes have affected concentrations of trace elements in the water. High Fe and Mn concentrations are generally found in the spring which has acidic and low Eh values, while Al, Fe and Mn concentrations in the acidic waters show notable increases with the maximum values reaching 8,829, 19,084 and 1,708?ppb, respectively. These values exceed the Turkish drinking water standard of 200, 200 and 50?ppb, respectively.  相似文献   

11.
《Applied Geochemistry》1997,12(4):447-464
The controls on metal concentrations in a plume of acidic (pH 3.29–5.55) groundwater in the Moon Creek watershed in Idaho, U.S.A., were investigated with the use of property-property plots. A plot of Ca vs S demonstrated that a plume of contaminated groundwater was being diluted by infiltration of rain and creek water at shallow depths and by ambient groundwater near bedrock. The small amount of dissolved Fe (2.1 mg/l) was removed while dissolved Pb was added, reaching a maximum concentration of 0.37 mg/l. The other metals (Zn ≤ 16, Al ≤ 6.2, Cu ≤ 2.1 and Cd ≤ 0.077 mg/l) in the shallow groundwater were essentially conserved until they emerged as a seep along the creek bank. Upon mixing with the creek water, groundwater was diluted by factors between 11 and 50, and the pH of the mixture became neutral. Metals originating from the contaminated groundwater were removed in the creek in the following order: Fe > Al > Pb ≫ Cu > Mn > Zn = Cd.Pb and Cu continued to be removed from solution even as the creek passed adjacent to a tailings pile. In contrast, Zn concentrations in the creek increased adjacent to the tailings area, presumably as a result of the reemergence of the upgradient plume as the creek lost elevation.Below the tailings dam, contaminated creek water (400–800 μg Zn/l) was diluted by both smaller side streams and a creek of equal flow. The presence of 3 distinctive water masses required the use of two tracers (dissolved Si and S) to distinguish between mixing and geochemical reactions. The removal of metals was greater during low flow conditions. Pb was removed to the greatest extent, falling below detection limits (0.5 μ/l) at the first sampling location. Copper and Mn were removed to a lesser extent during low flow conditions and approached conservative behavior during high flow conditions. During a 5-km journey through two hydrological regimes, less than 10% of the dissolved Zn and Cd was lost.  相似文献   

12.
Passive treatment systems are widely used for remediation of acid mine drainage (AMD), but existing designs are prone to clogging or loss of reactivity due to Al- and Fe-precipitates when treating water with high Al and heavy metal concentrations. Dispersed alkaline substrate (DAS) mixed from a fine-grained alkaline reagent (e.g. calcite sand) and a coarse inert matrix (e.g. wood chips) had shown high reactivity and good hydraulic properties in previous laboratory column tests. In the present study, DAS was tested at pilot field scale in the Iberian Pyrite Belt (SW Spain) on metal mine drainage with pH near 3.3, net acidity 1400–1650 mg/L as CaCO3, and mean concentrations of 317 mg/L Fe (95% Fe(II)), 311 mg/L Zn, 74 mg/L Al, 20 mg/L Mn, and 1.5–0.1 mg/L Cu, Co, Ni, Cd, As and Pb. The DAS-tank removed an average of 870 mg/L net acidity as CaCO3 (56% of inflow), 25% Fe, 93% Al, 5% Zn, 95% Cu, 99% As, 98% Pb, and 14% Cd, but no Mn, Ni or Co. Average gross drain pipe alkalinity was 181 mg/L as CaCO3, which increased total Fe removal to 153 mg/L (48%) in subsequent sedimentation ponds. Unfortunately, the tank suffered clogging problems due to the formation of a hardpan of Al-rich precipitates. DAS lifetime could probably be increased by lowering Al-loads.  相似文献   

13.
The distributions of particulate elements (Al, P, Mn, Fe, Co, Cu, Zn, Cd, and Pb), dissolved trace metals (Mn, Fe, Co, Cu, Zn, and Cd), and dissolved nutrients (nitrate, phosphate, and silicic acid) were investigated in the Gulf of the Farallones, a region of high productivity that is driven by the dynamic mixing of the San Francisco Bay plume, upwelled waters, and California coastal surface waters. Particulate metals were separated into >10 and 0.4-10 μm size-fractions and further fractionated into leachable (operationally defined with a 25% acetic acid leach) and refractory particulate concentrations. Dissolved metals (< 0.4 μm pore-size filtrate) were separated into colloidal (0.03-0.4 μm) and soluble (<0.03 μm) fractions. The percent leachable particulate fractions ranged from 2% to 99% of the total particulate concentration for these metals with Mn and Cd being predominantly leachable and Fe and Al being predominantly refractory. The leachable particulate Pb concentration was associated primarily with suspended sediments from San Francisco Bay and was a tracer of the plume in coastal waters. The particulate trace metal data suggest that the leachable fraction was an available source of trace metal micronutrients to the primary productivity in coastal waters. The dissolved trace metals in the San Francisco Bay plume and freshly upwelled surface waters were similar in concentration, with the exception of Cu and Co, which exhibited relatively high concentrations in plume waters and served as tracers of this water mass. The dissolved data and estimates of the plume dynamics suggest that the impact of anthropogenic inputs of nutrients and trace metals in the San Francisco Bay plume contributes substantially to the concentrations found in the Gulf of the Farallones (10-50% of estimated upwelled flux values), but does not greatly disrupt the natural stoichiometric balance of trace metal and nutrient elements within coastal waters given the similarity in concentrations to sources in upwelled water. In all, the data from this study demonstrate that the flux of dissolved nutrients and bioactive trace metals from the San Francisco Bay plume contribute to the high and relatively constant phytoplankton biomass observed in the Gulf of the Farallones.  相似文献   

14.
The mineralogy of natural ferromanganese coatings on quartz grains and the crystal chemistry of associated trace elements Ni, Zn, Ba, and As were characterized by X-ray microfluorescence, X-ray diffraction, and EXAFS spectroscopy. Fe is speciated as ferrihydrite and Mn as vernadite. The two oxides form alternating Fe- and Mn-rich layers that are irregularly distributed and not always continuous. Unlike naturally abundant Fe-vernadite, in which Fe and Mn are mixed at the nanoscale, the ferrihydrite and vernadite are physically segregated and the trace elements clearly partitioned at the microscopic scale. Vernadite consists of two populations of interstratified one-water layer (7 Å phyllomanganate) and two-water layer (10 Å phyllomanganate) crystallites. In one population, 7 Å layers dominate, and in the other 10 Å layers dominate. The three trace metals Ni, Zn, and Ba are associated with vernadite and the metalloid As with ferrihydrite. In vernadite, nickel is both substituted isomorphically for Mn in the manganese layer and sorbed at vacant Mn layer sites in the interlayer. The partitioning of Ni is pH-dependent, with a strong preference for the first site at circumneutral pH and for the second at acidic pH. Thus, the site occupancy of Ni in vernadite may be an indicator of marine vs. continental origin, and in the latter, of the acidity of streams, lakes, or soil pore waters in which the vernadite formed. Zinc is sorbed only in the interlayer at vacant Mn layer sites. It is fully tetrahedral at a Zn/Mn molar ratio of 0.0138, and partly octahedral at a Zn/Mn ratio of 0.1036 consistent with experimental studies showing that the VIZn/IVZn ratio increases with Zn loading. Barium is sorbed in a slightly offset position above empty tetrahedral cavities in the interlayer. Arsenic tetrahedra are retained at the ferrihydrite surface by a bidentate-binuclear attachment to two adjacent iron octahedra, as commonly observed. Trace elements in ferromanganese precipitates are partitioned at a few, well-defined, crystallographic sites that have some elemental specificity, and thus selectivity. The relative diversity of sorption sites contrasts with the simplicity of the layer structure of vernadite, in which charge deficit arises only from Mn4+ vacancies (i.e., no Mn3+ for Mn4+ substitution). Therefore, sorption mechanisms primarily depend on physical and chemical properties of the sorbate and competition with other ions in solution, such as protons at low pH for Ni sorption.  相似文献   

15.
Concentrations of Al, Mn, Fe, Ag, and Pb in dissolved and particulate phases of the surface water were determined at 15 stations along the coastline off western Taiwan in April of 2007. This study presents the first set of data for Al, Ag, and Pb in the nearshore waters. Latitudinal distribution of these metals showed that high values were present in the regions affected by high fluvial discharge from the Dan-Sui River and the Cho-Sui River. Using the particle fluxes from 210Po/210Pb disequilibria, the removal fluxes and the residence times of the trace metals were calculated. Based on the K d values, the sequence of particle affinity of trace metals, Fe ~ Al >> Pb > Mn > Ag, was found. The correlation of the residence times and of the partitioning coefficients of multiple metals in the nearshore waters implies that the affinities to the particles determine the geochemical cycling of metals in the coastal water.  相似文献   

16.
Transport and sediment–water partitioning of trace metals (Cr, Co, Fe, Pb, Cu, Ni, Zn, Cd) in acid mine drainage were studied in two creeks in the Kwangyang Au–Ag mine area, southern part of Korea. Chemical analysis of stream waters and the weak acid (0.1 N HCl) extraction, strong acid (HF–HNO3–HClO4) extraction, and sequential extraction of stream sediments were performed. Heavy metal pollution of sediments was higher in Chonam-ri creek than in Sagok-ri creek, because there is a larger source of base metal sulfides in the ores and waste dump upstream of Chonam-ri creek. The sediment–water distribution coefficients (K d) for metals in both creeks were dependent on the water pH and decreased in the order Pb ≈ Al > Cu > Mn > Zn > Co > Ni ≈ Cd. K d values for Al, Cu and Zn were very sensitive to changes in pH. The results of sequential extraction indicated that among non-residual fractions, Fe–Mn oxides are most important for retaining trace metals in the sediments. Therefore, the precipitation of Fe(–Mn) oxides due to pH increase in downstream sites plays an important role in regulating the concentrations of dissolved trace metals in both creeks. For Al, Co, Cu, Mn, Pb and Zn, the metal concentrations determined by 0.1 N HCl extraction (Korean Standard Method for Soil Pollution) were almost identical to the cumulative concentrations determined for the first three weakly-bound fractions (exchangeable + bound to carbonates + bound to Fe–Mn oxides) in the sequential extraction procedure. This suggests that 0.1 N HCl extraction can be effectively used to assess the environmentally available and/or bioavailable forms of trace metals in natural stream sediments.  相似文献   

17.
The acid mine drainage (AMD) discharged from the Hejiacun uranium mine in central Hunan (China) was sampled and analyzed using ICP-MS techniques. The analyzing results show that the AMD is characterized by the major ions FeTotal, Mn, Al and Si, and is concentrated with heavy metals and metalloids including Cd, Co, Ni, Zn, U, Cu, Pb, Tl, V, Cr, Se, As and Sb. During the AMD flowing downstream, the dissolved heavy metals were removed from the AMD waters through adsorption onto and co-precipitation with metal-oxhydroxides coated on the streambed. Among these metals, Cd, Co, Ni, Zn, U, Cu, Pb and Tl are negatively correlated to pH values, and positively correlated to major ions Fe, Al, Si, Mn, Mg, Ca and K. The metals/metalloids V, Cr, Se, As and Sb are conservative in the AMD solution, and negatively-correlated to major ions Na, Ca and Mg. Due to the above different behaviors of these chemical elements, the pH-negatively related metals (PM) and the conservative metals (CM) are identified; the PM metals include Cd, Co, Ni, Zn, U, Cu, Pb and Tl, and the CM metals V, Cr, Se, As and Sb. Based on understanding the geochemistry of PM and CM metals in the AMD waters, a new equation: EXT = (Acidity + PM)/pH + CM × pH, is proposed to estimate and evaluate extent of heavy-metal pollution (EXT) of AMD. The evaluation results show that the AMD and surface waters of the mine area have high EXT values, and they could be the potential source of heavy-metal contamination of the surrounding environment. Therefore, it is suggested that both the AMD and surface waters should be treated before they are drained out of the mine district, for which the traditional dilution and neutralization methods can be applied to remove the PM metals from the AMD waters, and new techniques through reducing the pH value of the downstream AMD waters should be developed for removal of the CM metals.  相似文献   

18.
Complete hydrochemical data are rarely reported for coal-mine discharges (CMD). This report summarizes major and trace-element concentrations and loadings for CMD at 140 abandoned mines in the Anthracite and Bituminous Coalfields of Pennsylvania. Clean-sampling and low-level analytical methods were used in 1999 to collect data that could be useful to determine potential environmental effects, remediation strategies, and quantities of valuable constituents. A subset of 10 sites was resampled in 2003 to analyze both the CMD and associated ochreous precipitates; the hydrochemical data were similar in 2003 and 1999. In 1999, the flow at the 140 CMD sites ranged from 0.028 to 2210 L s−1, with a median of 18.4 L s−1. The pH ranged from 2.7 to 7.3; concentrations (range in mg/L) of dissolved (0.45-μm pore-size filter) SO4 (34–2000), Fe (0.046–512), Mn (0.019–74), and Al (0.007–108) varied widely. Predominant metalloid elements were Si (2.7–31.3 mg L−1), B (<1–260 μg L−1), Ge (<0.01–0.57 μg L−1), and As (<0.03–64 μg L−1). The most abundant trace metals, in order of median concentrations (range in μg/L), were Zn (0.6–10,000), Ni (2.6–3200), Co (0.27–3100), Ti (0.65–28), Cu (0.4–190), Cr (<0.5–72), Pb (<0.05–11) and Cd (<0.01–16). Gold was detected at concentrations greater than 0.0005 μg L−1 in 97% of the samples, with a maximum of 0.0175 μg L−1. No samples had detectable concentrations of Hg, Os or Pt, and less than half of the samples had detectable Pd, Ag, Ru, Ta, Nb, Re or Sn. Predominant rare-earth elements, in order of median concentrations (range in μg/L), were Y (0.11–530), Ce (0.01–370), Sc (1.0–36), Nd (0.006–260), La (0.005–140), Gd (0.005–110), Dy (0.002–99) and Sm (<0.005–79). Although dissolved Fe was not correlated with pH, concentrations of Al, Mn, most trace metals, and rare earths were negatively correlated with pH, consistent with solubility or sorption controls. In contrast, As was positively correlated with pH.  相似文献   

19.
Field experiments were conducted over a 460-day period to assess the efficiency of different mixtures of organic substrates to remediate coalmine-generated acid mine drainage (AMD). Five pilot-scale, flow-through bioreactors containing mixtures of herbaceous and woody organic substrates along with one control reactor containing only limestone were constructed at the Tab-Simco site and exposed to AMD in situ. Tab-Simco is an abandoned coal mine near Carbondale, Illinois that produces AMD with pH ∼2.5 and notably high average concentrations of SO4 (5050 mg/L), Fe (950 mg/L), Al (200 mg/L), and Mn (44 mg/L). Results showed that the sequestration of SO4 and metals was achieved in all reactors; however, the presence and type of organic carbon matrix impacted the overall system dynamics and the AMD remediation efficiency. All organic substrate-based reactors established communities of sulfate reducing microorganisms that contributed to enhanced removal of SO4, Fe, and trace metals (i.e., Cu, Cd, Zn, Ni) via microbially-mediated reduction followed by precipitation of insoluble sulfides. Additional mechanisms of contaminant removal were active in all reactors and included Al- and Fe-rich phase precipitation and contaminant surface sorption on available organic and inorganic substrates. The organic substrate-based reactors removed more SO4, Fe, and Al than the limestone-only control reactor, which achieved an average removal of ∼19 mol% SO4, ∼49 mol% Fe, 36 mol% Al, and 2 mol% Mn. In the organic substrate-based reactors, increasing herbaceous content correlated with increased removal efficiency of SO4 (26–35 mol%), Fe (36–62 mol%), Al (78–83 mol%), Mn (2–6 mol%), Ni (64–81 mol%), Zn (88–95 mol%), Cu (72–85 mol%), and Cd (90–92 mol%), while the diversity of the intrinsic microbial community remained relatively unchanged. The extrapolation of these results to the full-scale Tab-Simco treatment system indicated that, over the course of a 460-day period, the predominantly herbaceous bioreactors could remove up to 92,500 kg SO4, 30,000 kg Fe, 8,950 kg Al, and 167 kg Mn, which represents a 18.3 wt%, 36.8 wt%, 4.1 wt% and 82.3 wt% increase in SO4, Fe, Al, and Mn, respectively, removal efficiency compared to the predominantly ligneous bioreactors.The results imply that anaerobic organic substrate bioreactors are promising technologies for remediation of coal-generated AMD and that increasing herbaceous content in the organic substrate matrix can enhance contaminant sequestration. However, in order to improve the remediation capacity, future designs must optimize not only the organic carbon substrate but also include a pretreatment phase in which the bulk of dissolved Fe/Al-species are removed from the influent AMD prior to entering the bioreactor because of 1) seasonal variations in temperature and redox gradients could induce dissolution of the previously formed redox sensitive compounds, and 2) microbially-mediated sulfate reduction activity may be inhibited by the excessive precipitation of Al- and Fe-rich phases.  相似文献   

20.
The Pliocene aquifer receives inflow of Miocene and Pleistocene aquifer waters in Wadi El Natrun depression. The aquifer also receives inflow from the agricultural activity and septic tanks. Nine sediment samples were collected from the Pliocene aquifer in Wadi E1 Natrun. Heavy metal (Cu, Sr, Zn, Mn, Fe, Al, Ba, Cr, Ni, V, Cd, Co, Mo, and Pb) concentrations of Pliocene aquifer sediments were investigated in bulk, sand, and mud fractions. The determination of extractable trace metals (Cu, Zn, Fe, Mn, and Pb) in Pliocene aquifer sediments using sequential extraction procedure (four steps) has been performed in order to study environmental pathways (e.g., mobility of metals, bounding states). These employ a series of successively stronger chemical leaching reagents which nominally target the different compositional fractions. By analyzing the liquid leachates and the residual solid components, it is possible to determine not only the type and concentration of metals retained in each phase but also their potential ecological significance. Cu, Sr, Zn, Mn, Fe, and Al concentrations are higher in finer sediments than in coarser sediments, while Ba, Cr, Ni, V, Cd, Co, Mo, and Pb are enriched in the coarser fraction. The differences in relative concentrations are attributed to intense anthropogenic inputs from different sources. Heavy metal concentrations are higher than global average concentrations in sandstone, USEPA guidelines, and other local and international aquifer sediments. The order of trace elements in the bulk Pliocene aquifer sediments, from high to low concentrations, is Fe?>?Al?>?Mn?>?Cr?>?Zn?>?Cu?>?Ni?>?V?>?Sr?>?Ba?>?Pb?>?Mo?>?Cd?>?Co. The Pliocene aquifer sediments are highly contaminated for most toxic metals, except Pb and Co which have moderate contamination. The active soluble (F0) and exchangeable (F1) phases are represented by high concentrations of Cu, Zn, Fe, and Mn and relatively higher concentrations of Pb and Cd. This may be due to the increase of silt and clay fractions (mud) in sediments, which act as an adsorbent, retaining metals through ion exchange and other processes. The order of mobility of heavy metals in this phase is found to be Pb?>?Cd?>?Zn?>?Cu?>?Fe?>?Mn. The values of the active phase of most heavy metals are relatively high, indicating that Pliocene sediments are potentially a major sink for heavy metals characterized by high mobility and bioavailability. Fe–Mn oxyhydroxide phase is the most important fraction among labile fractions and represents 22% for Cd, 20% for Fe, 11% for Zn, 8% for Cu, 5% for Pb, and 3% for Mn. The organic matter-bound fraction contains 80% of Mn, 72% of Cu, 68% of Zn, 60% of Fe, 35% of Pb, and 30% of Cd (as mean). Summarizing the sequential extraction, a very good immobilization of the heavy metals by the organic matter-bound fraction is followed by the carbonate-exchangeable-bound fraction. The mobility of the Cd metal in the active and Fe–Mn oxyhydroxide phases is the highest, while the Mn metal had the lowest mobility.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号