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1.
《Applied Geochemistry》2002,17(5):569-581
This study examined the sorption of trace metals to precipitates formed by neutralization of 3 natural waters contaminated with acid mine drainage (AMD) in the former Ducktown Mining District, Tennessee. The 3 water samples were strongly acidic (pH 2.2 to 3.4) but had distinctively different chemical signatures based on the mole fractions of dissolved Fe, Al and Mn. One sample was Fe-rich (Fe=87.5%, Al=11.3%, and Mn=1.3%), another was Al-rich (Al=79.4%, Mn=18.0%, and Fe=2.5%), and the other was Mn-rich (Mn=51.4%, Al=25.7%, and Fe=22.9%). In addition, these waters had high concentrations of trace metals including Zn (37,700 to 17,400 μg/l), Cu (13,000 to 270 μg/l), Co (1,500 to 520 μg/l), Ni (360 to 75 μg/l), Pb (30 to 8 μg/l), and Cd (30 to 6 μg/l). Neutralization of the AMD-contaminated waters in the laboratory caused the formation of either schwertmannite at pH<4 or ferrihydrite at pH>4. Both phases were identified by XRD analyses of precipitates from the most Fe-rich water. At higher pH values (∼5) Al-rich precipitates were formed. Manganese compounds were precipitated at pH∼8. The removal of trace metals depended on the precipitation of these compounds, which acted as sorbents. Accordingly, the pH for 50% sorption (pH50) ranged from 5.6 to 7.5 for Zn, 4.6 to 6.1 for Cu, 5.4 to 7.7 for Ni, 5.9 to 7.9 for Co, 3.1 to 4.3 for Pb, and 5.5 to 7.7 for Cd. The pH dependence of sorption arose not only because of changes in the sorption coefficients of the trace metals but also because the formation and composition of the sorbent was controlled by the pH, the chemical composition of the water, and the solubilities of the oxyhydroxide-sulfate complexes of Fe, Al, and Mn.  相似文献   

2.
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   

3.
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   

4.
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   

5.
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   

6.
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   

7.
《Applied Geochemistry》1998,13(2):213-233
Porewater concentration profiles were determined for Fe, trace elements (As, Cd, Co, Cu, Mn, Ni, Pb, Zn), sulfide, SO4 and pH in two Canadian Shield lakes (Chevreuil and Clearwater). Profiles of pyrite, sedimentary trace elements associated with pyrite and AVS were also obtained at the same sites. Thermodynamic calculations are used, for the anoxic porewaters where sulfide was measured, to characterize diagenetic processes involving sulfide and trace elements and to illustrate the importance of sulfide, and possibly polysulfides and thiols, in binding trace elements. The ion activity products (IAP) of Fe sulfide agree with the solubility products (Ks) of greigite or mackinawite. For Co, Ni and Zn, IAP values are close to the KS values of their sulfide precipitates; for Cu and Pb, IAP/Ks indicate large oversaturations, which can be explained by the presence of other ligands (not measured) such as polysulfides (Cu) and thiols (Pb). Cobalt, Cu, Ni and Zn porewater profiles generally display a decrease in concentration with increasing ΣH2S, as expected for transition metals, whereas Cd, Pb and Zn show an increase (mobilisation). The results suggest that removal of trace elements from anoxic porewaters occurs by coprecipitation (As and Mn) with FeS(s) and/or adsorption (As and Mn) on FeS(s), and by formation of discrete solid sulfides (Cd, Cu, Ni, Pb, Zn and Co). Reactive Fe is extensively sulfidized (51–65%) in both lakes, mostly as pyrite, but also as AVS. Similarities between As, Co, Cu and Ni to Fe ratios in pyrite and their corresponding mean diffusive flux ratios suggest that pyrite is an important sink at depth for these trace elements. High molar ratios of trace elements to Fe in pyrite from Clearwater Lake correspond chronologically to the onset of smelting activities. AVS can be an important reservoir of reactive As, Cd and Ni and, to a lesser extent, of Co, Cu and Pb. Overall, the trace elements most extensively sulfidized were Ni, Cd and As (maximum of 100%, 81% and 49% of the reactive fraction, respectively), whereas Co, Cu, Mn, Pb and Zn were only moderately sulfidized (11–16%).  相似文献   

8.
M. Frei  U. Bielert  H. Heinrichs   《Chemical Geology》2000,170(1-4):221-242
Thirty-four springs were sampled on five different source rocks in the upper Ecker watershed of the Northern Harz Mountains (Germany) four times during the course of 1995. The analyses included 41 cations and the major anions. Approximately 90% of the rocks in the upper Ecker watershed are low in basic cations, which inhibit the neutralisation of hydrogen-ion loading. As a consequence, the concentrations of Al, Fe, Mn, Zn, Pb, Y, Ce, As, La, Nd, Cd, Be, Co, Sb, Pr, Gd, Dy, Yb, Er, Sm, U, Tl, Ho and Tb of the Ecker dam water (pH=5.1) exceed those of the nearby Söse Dam water (pH=6.5) by almost one order of magnitude or more. With the exception of the spring waters on gabbro (pH up to 7.7) all waters on the highly siliceous rocks (quartzite, granite and gneiss) are dominated by sulfate anions with a pH range of 4–6. The concentrations of major conservative ions show a progressive increase with decreasing catchment elevation and decreasing average precipitation. Trace elements such as Sr, Be, Zn, Cd, Ba, Y, La, lanthanides, U, Li, Ni, Al, Mn, Co, Cu, Pb, As, Sb and Tl are increased in the low acid neutralizing capacity (ANC(aq)) spring waters. The behaviours of Sr, Be, Zn, Cd, Ba, Y, La, lanthanides and U resemble that of the major cations. The highest concentrations of Li and Ni are found on quartzite. Al, Mn, Co and Cu exhibit no clear correlation with catchment elevation and one particular bedrock. The concentrations of V and Cr show a distinct increase in high ANC(aq) spring waters on gabbro. Pb, As, Sb and Tl are characterized by being found in relatively high concentrations on granite at higher altitudes. Pb, As and Sb are affected by contaminated soils. The extreme variability of trace element concentrations of low ANC(aq) spring waters cannot be explained by the rock data. It is mainly controlled by the topography-dependent weathering rates of the different rock-types and the decreasing dilution with decreasing catchment elevation.  相似文献   

9.
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   

10.
The Gulf of Mannar along the Tuticorin coast is a coral base of the southeast coast of India. To obtain a preliminary view of its environmental conditions, geochemical distribution of major elements (Si, Al, Fe, Ca, Mg, Na, K, P), trace elements (Mn, Cr, Cu, Ni, Co, Pb, Zn, Cd) and acid leachable elements (Fe, Mn, Cr, Cu, Ni, Co, Pb, Zn, Cd) were analyzed in surface sediment samples from two seasons. Geochemical fractionation confirmed the lithogenic origin of metals, which were mainly associated with the detrital phase. The sediments in the gulf are sandy with abundant calcareous debris, which controls the distribution of total and acid leachable elements. Enrichment factors relative to crust vary by a magnitude of two to three and the presence of trace metals indicates the input of Cr, Pb, Cd, Cu and Zn in both forms through industrial activities. Factor analysis supports the above observation with higher loadings on acid leachable elements and its association with CaCO3. The increase in concentration of trace metals (Cr, Pb, Cd, Cu, Co, Ni, Zn) along the Gulf of Mannar indicates that the area has been contaminated by the input from riverine sources and the industries nearby. The present study indicates that other sources should be evaluated in the long-term monitoring program.  相似文献   

11.
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12.
Thermodynamic calculations have been performed for cation hydrolysis, including temperatures from 2°C to the high values of significance near Mid-Oceanic Ridge Systems (MORS). Eighteen elements with wide range of residence times (t) in seawater (Mn, Th, Al, Bi, Ce, Co, Cr(III), Fe, Nd, Pb, Sc, Sm, Ag, Cd, Cu, Hg, Ni and Zn) have been considered. A model for the regulation of trace metal composition in seawater by cation hydrolytic processes, including those at MORS, is presented. Results show an increase in the abundance of neutral metal hydroxyl species with increase in temperature. During hydrothermal mixing, as the temperature increases, transformation from lower positive hydroxyl complexes to higher or neutral complexes would occur for Cd, Ce, Co, Cr(III), Cu, Mn, Nd, Ni, Pb, Sm and Zn. pH values for adsorption of the metal ion onto solid surfaces have direct relation with pH values of hydrolysis. Co, Mn and Pb could be oxidized to higher states (at Mn-oxide surfaces) that would occur even at MORS. Ce can also be oxidized at 25°C. Solubility calculations show that Al, Bi, Cr(III), Sc, Fe and Th are saturated while Ce, Nd and Sm are not with respect to their oxyhydroxide solids at their concentrations in seawater at 25°C. Cu, Hg, Ni and Zn reach saturation equilibrium at 250°C, whereas Co, Mn and Pb exhibit unsaturation. The results suggest an increase in scavenging capacity of a cation with rise in temperature.  相似文献   

13.
The paper presents data on the specifics of the distributions of chemical elements in natural waters of the Kola North depending on the landscape–geochemical characteristics of the water catchment areas and aerotechnogenic pollution. The territory is subdivided into seven zones with different dominant rock types and typical landscapes. Lakes in the Kola region generally contain elevated concentrations of Cu, Ni, Co, Cr, V, Mo, U, Sb, Bi, Al, Fe, Mn, Sr, Li, Rb, Pb, Zn, Cd, La, and Ce. The waters of lakes in the influence zones of Cu–Ni mines are enriched in La, Ce, Sm, Gd, Pr, and Nd. In waterlogged landscapes, waters are enriched in certain trace elements because of their migration with humic acids. Technogenic acidic precipitation is proved to result in leaching of several elements, first of all Cd, Zn, and As (as well as other elements contained in rocks composing the water catchment areas) and their transfer into the waters.  相似文献   

14.
《Applied Geochemistry》1998,13(3):359-368
Studies on the speciation (particulate, colloidal, anionic and cationic forms) of trace metals (Cd, Co, Cu, Fe, Mn, Mo, Ni, Pb, Zn) in the water column and in pore waters of the Gotland Deep following the 1993/94 salt-water inflows showed dramatic changes in the total “dissolved” metal concentrations and in the ratios between different metal species in the freshly re-oxygenated waters below 125 m. Changes in concentrations were greatest for those metals for which the solubility differs with the redox state (Fe, Mn, Co) but were also noted for those metals which form insoluble sulphides (Cd, Pb, Cu, Zn) and/or stable complexes with natural ligands (Cu). Pore water data from segmented surface muds (0–200 mm) indicated that significant redox and related metal speciation changes took place in the surface sediments only a few weeks after the inflow of the oxygenated sea water into the Gotland Deep.  相似文献   

15.

Sulfide‐rich materials comprising the waste at the abandoned Montalbion silver mine have undergone extensive oxidation prior to and after mining. Weathering has led to the development of an abundant and varied secondary mineral assemblage throughout the waste material. Post‐mining minerals are dominantly metal and/or alkali (hydrous) sulfates, and generally occur as earthy encrustations or floury dustings on the surface of other mineral grains. The variable solubility of these efflorescences combined with the irregular rainfall controls the chemistry of seepage waters emanating from the waste dumps. Irregular rainfall events dissolve the soluble efflorescences that have built up during dry periods, resulting in ‘first‐flush’ acid (pH 2.6–3.8) waters with elevated sulfate, Fe, Cu and Zn contents. Less‐soluble efflorescences, such as anglesite and plumbojarosite, retain Pb in the waste dump. Metal‐rich (Al, Cd, Co, Cu, Fe, Mn, Ni, Zn) acid mine drainage waters enter the local creek system. Oxygenation and hydrolysis of Fe lead to the formation of Fe‐rich precipitates (schwertmannite, goethite, amorphous Fe compounds) that, through adsorption and coprecipitation, preferentially incorporate As, Sb and In. Furthermore, during dry periods, evaporative precipitation of hydrous alkali and metal sulfate efflorescences occurs on the perimeter of stagnant pools. Flushing of the streambed by neutral pH waters during heavy rainfall events dissolves the efflorescences resulting in remobilisation and transport of sulfate and metals (particularly Cd, Zn) downstream. Thus, in areas of seasonal or irregular rainfall, secondary efflorescent minerals present in waste materials or drainage channels have an important influence on the chemistry of surface waters.  相似文献   

16.
Black shale is often rich in sulfides and trace elements, and is thus a potential environmental threat in a manner similar to acid sulfate soils and active or abandoned sulfide mines. This study aims at characterising how exposed and processed (mined and burnt) black shale (alum shale) in Degerhamn, SE Sweden, affects the chemistry (Al, As, Ba, Cd, Ca, Cr, Co, Cu, Fe, Pb, Mg, Mn, Mo, Ni, K, Si, Na, Sr, S, U, V and Zn) of the groundwater. There were large variations in groundwater chemistry between nearby sampling points, while the temporal variations generally were small. Acidic groundwater (around pH 4), found in deposits of burnt and carbonate-poor shale where the conditions for sulfide oxidation were favourable, was strongly elevated in Al, U and several chalcophilic metals (Cd, Co, Cu, Ni and Zn). Cadmium and U were also, together with Mo, abundant in many of the near-neutral waters, both in the non-mined black shale bedrock and in the deposits of burnt shale. An extrapolation to a national level suggests that the dispersion of Ni from naturally occurring black shale is similar to that from anthropogenic point sources, while for Cd and As it is assessed to be approximately one tenth of that from point sources. The processed shale was, however, a much larger source of metals than the black shale bedrock itself, showing this material’s potential as a massive supplier of metals to the aquatic environment. A comparison of waters in contact with the processed Cambrian–Ordovician black shale in Degerhamn and acid sulfate soils of the region shows that these two sulfide-bearing materials, in many respects very different, delivers basically the same suite of trace elements to the aquatic environment. This has implications for environmental planning and protection in areas where these types of materials exist.  相似文献   

17.
《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   

18.
Water, sediment, and mine spoil samples were collected within the vicinity of the Okpara coal mine in Enugu, Southeastern Nigeria, and analyzed for trace elements using ICP-MS to assess the level of environmental contamination by these elements. The results obtained show that the mine spoils and sediments are relatively enriched in Fe, with mean values of 1,307.8(mg/kg) for mine spoils and 94.15% for sediments. As, Cd, Cr, Mn,Ni, Pb, and Zn in the sediments were found to be enriched relative to the mean values obtained from the study area, showing contamination by these elements. The mean values of Fe, Mn, Cu, and Cr in the mine spoils and mean values of Fe, Cu, Pb, Zn, Ni, Cr, and Mn in sediments, respectively, are above the background values obtained from coal and shale in the study area, indicating enrichment with these elements. The water and sediments are moderately acidic, with mean pH values of 4.22?±?1.06 and 4.66?±?1.35, respectively. With the exception of Fe, Mn, and Ni, all other elements are within the Nigerian water quality standard and WHO limits for drinking water and other domestic purposes. The strong to moderate positive correlation between Fe and Cu (r?=?0.72), Fe and Zn (r?=?0.88), and Fe and As (r?=?0.60) at p?<?0.05 as obtained for the sediments depict the scavenging effect of Fe on these mobile elements. As also shows a strong positive correlation with Mn (r?=?≥ 0.70, p?<?0.05), indicating that Mn plays a major role in scavenging elements that are not co-precipitated with Fe. In water, the strong positive correlation observed between Cr and Cd (r?=?1.00), Cu and Ni (r?=?0.94), Pb and Cu (r?=?0.87) and Zn and Cu (r?=?0.99); Ni and Pb (r?=?0.83) and Zn and Ni (r?=?0.97); and between Pb and Zn (0.84) at p?<?0.05 may indicate similar element–water reaction control on the system due to similarities in chemical properties as well as a common source. Elevated levels of heavy metals in sediments relative to surface water probably imply that sorption and co-precipitation on Al and Fe oxides are more effective in the mobilization and attenuation of heavy metals in the mine area than acid-induced dissolution. The level of concentration of trace elements for the mine spoils will serve as baseline data for future reference in the study area.  相似文献   

19.
《Applied Geochemistry》2005,20(7):1391-1408
Surface water samples from the St. Lawrence River were collected in order to study the processes controlling minor and trace elements concentrations (Al, Fe, Mn, Cd, Co, Cu, Ni and Zn), and to construct mass balances allowing estimates of the relative importance of their natural and anthropogenic sources. The two major water inputs, the upper St. Lawrence River, which drains waters originating from the Lake Ontario, and the Ottawa River were collected fortnightly over 18 months. In addition, other tributaries were sampled during the spring floods. The output was monitored near Quebec City at the river mouth weekly between 1995 and 1999. Dissolved metal concentrations in the upper St. Lawrence River carbonated waters were lower than in the acidic waters of the tributaries draining the crystalline rocks of the Canadian shield and the forest cover. Biogeochemical and hydrodynamic processes occurring in Lake Ontario drive the seasonal variations observed in the upper St. Lawrence River. Biogeochemical processes relate to biological uptake, regeneration of organic matter (for Cd and Zn) and oxyhydroxide formation (for Mn and Fe), while hydrodynamic processes mainly concern the seasonal change in vertical stratification (for Cd, Mn, and Zn). In the Ottawa River, the main tributary, oxyhydroxide formation in summer governs seasonal patterns of Al, Fe, Mn, Cd, Co and Zn. The downstream section of the St. Lawrence River is a transit zone in which seasonal variations are mainly driven by the mixing of the different water masses and the large input of suspended particulate matter from erosion. The budget of all dissolved elements, except Fe and Zn, was balanced, as the budget of particulate elements (except Cd and Zn). The main sources of metals to the St. Lawrence River are erosion and inputs from tributaries and Lake Ontario. Direct anthropogenic discharges into the river accounted for less than 5% of the load, except for Cd (10%) and Zn (21%). The fluxes in transfer of dissolved Cd, Co, Cu and Zn species from the river to the lower St. Lawrence estuary were equal to corresponding fluxes calculated for Quebec City since the distributions of dissolved concentrations of these metals versus salinity were conservative. For Fe, the curvature of the dilution line obtained suggests that dissolved species were removed during early mixing.  相似文献   

20.
The distribution and controls of trace elements (Cd, Cr, Cu, Ni, Pb, Zn and U) in shallow groundwater in discharge and recharge zones were analysed at two sites on the Baltic coast of Sweden; one granite-dominated and one with a significant addition of calcite. Although the study sites differ in overburden geochemistry and groundwater trace metal concentrations, which were well reflected in the general groundwater composition, the relative hydrochemical differences between recharge and discharge ground waters were similar at both sites, and temporally stable. The concentrations of Cd, Cu, Ni and U were higher in soil tubes in recharge areas, but Cr was higher in discharge zones. Also concentrations of HS, Fe, Mn and NH4 were higher in discharge samples, which in combination with increased 34S values provide strong evidence of a transition from oxidizing to more reducing conditions along the groundwater flow gradient. In terms of trace metals, this might mean either mobilisation due to dissolution of trace-metal carrying Fe(III) and Mn(IV) phases, or immobilisation caused by precipitation of discrete trace-metal sulfides or co-precipitation with Fe sulfides. The results from this study show that the latter is dominant in both the carbonate and granite environments for the metals Cd, Cu and Ni. Chromium concentrations were likely coupled to organic complexation and were higher in discharge groundwater, where DOC was also more abundant. As the concentration of several potentially toxic trace metals were found to differ between recharge and discharge areas, a climate driven change in hydrology might have a substantial impact on the distribution of these metals.  相似文献   

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