Mobile and bound forms of trace metals in sediments of the lower ganges

Mobile and bound trace metals associated with sediment components (viz. exchangeable, carbonate, organic, Fe/Mn oxide and residual fractions) were determined at five locations on the River Ganges in the lower reaches. In the exchangeable phase, 5–22% of Pb, 5–14.4% of Cr, 3–16.4% of Cd, 3–16% of Zn and 1–13.5% of Cu were found, and in the carbonate phase 73–87% of Zn, 38–41% of Cd, 13–27% of Ni and 3–10.1% of Pb were found. The Fe/Mn oxide phase retained about 79–83% of Mn, 30–40% of Cr and Fe, 22–25% of Cu, 14–16% of Ni and 9–11% of Pb. In the organic phase about 36–47% of Cd, 22–28% of Cu and 10–15% of Pb were found. The order of release of metals was Cd > Cr > Pb > Cu > Zn > Ni > Mn > Fe, and the order of adsorption characteristics of most of the mobile metal fractions was Fe/Mn oxide > organic > clay. Correlations of the physico-chemical parameters with adsorption characteristics were also determined and a good correlation (r = 0.7) of cation exchange capacity with the clay fraction was found. I_geo (geoaccumulation indices) of metals in the sediments were also evaluated. Results showed a considerable enrichment of trace metals in the sediment phase at almost all the sites.     

Species of dissolved metals derived from oligotrophic hard water

By fractioning of dissolved organic carbon (DOC) and of associated metals Na, K, Mg, Ca, Al, Fe, Mn, Ni, Cr, Cu, Pb, Cd, and Zn according to the molecular sizes by means of gel chromatography in several stages, it could be shown that all metals, even the alkaline and alkaline earth metals, are, to a measurable degree, present in chelated form. This type of association covers 97.3% with Pb, 94.6% with Al, 91.5% with Cr, 82.2% with Fe of the total concentrations of each metal mentioned. About 69% of all metal chelates are represented by Mg-compounds. This may be caused by pre-treatment procedures, nevertheless the Mg-concentrations of the different DOC-fractions indicating to be one regulating factor for the uptake of other metals in the studied hard water. The chelated form was also obtained with Mn, Cd, Zn, and Mg, while with Cu, Ni, Na, Ca, and K there is an abundance of ionic forms.The metal distribution within the different molecular size fractions of the DOC proves the existence of specific distribution pattern for Pb and Mn: Pb is preferably chelated by macromolecular substances, whereas Mn combines mainly with minor ones. Cr seems to behave similar as Pb. Regulation' mechanisms for the different metal distribution patterns within the DOC-fractions as well as ecophysiological aspects of the results are discussed.     

Concentrations of heavy metals and plant nutrients in water, sediments and aquatic macrophytes of anthropogenic lakes (former open cut brown coal mines) differing in stage of acidification.

Concentration of heavy metals (Al, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sr, V and Zn) as well as macronutrients (N, P, K, Ca, Mg, S) were measured in water, bottom sediments and plants from anthropogenic lakes in West Poland. The collected plants were: Phragmites australis, Potamogeton natans, Iris pseudoacorus, Juncus effusus, Drepanocladus aduncus, Juncus bulbosus, Phalaris arundinacea, Carex remota and Calamagrostis epigeios. Two reference lakes were sampled for Nymphaea alba, Phragmites australis, Schoenoplectus lacustris, Typha angustifolia and Polygonum hydropiper. These plants contained elevated levels of Cd, Co, Cr, Cu and Mn, and part of the plants contained in addition elevated levels of Mn, Fe, Pb, Ni and Zn. Analyses of water indicated pollution with sulfates, Cd, Co, Ni. Zn, Pb and Cu, and bottom sediments indicated that some of the examined lakes were polluted with Cd, Co and Cr. Strong positive correlations were found between concentrations of Co in water and in plants and between Zn in sediments and plants, indicating the potential of plants for pollution monitoring for this metal. Heavy metal accumulation seemed to be directly associated with the exclusion of Ca and Mg.     

Trace metals in Shatt al-Arab River,Iraq

The distribution of 10 trace metals Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, V and Zn have been determined along the northern section of the Shatt al-Arab River, Iraq. Analyses were carried out, employing a flameless AAS instrument. The mean concentrations of the dissolved species were as follows (expressed in μg l^?1): 0.25 Cd, 0.9 Cu, 716 Fe, 1.3 Mn, 0.3 Pb, 0.2 V and 1.8 Zn. Mean concentrations of Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, V and Zn in the particulate matter were 55.2, 6.0, 188, 77, 31 472, 1731, 3807, 93, 207 and 77 μg g^?1 respectively. In the exchangeable fraction of the sediment were 0.15, 5.5, 11.1, 11.9, 1625, 482, 42, 30.5, 25.7 and 6 μg g^?1, whereas in the residual were 0.025, 11.5, 96.1, 22, 5176, 258, 613, 3.9, 162 and 56.8 μg g^?1 respectively. Thus, the exchangeable trace metals represent the following mean percentage of the total; 75% Cd, 33% Co, 10% Cr, 34% Cu, 24% Fe, 63% Mn, 7% Ni, 74% Pb, 14% V and 23% Zn. The concentration of Ni and V were relatively high, this was attributed to the petroleum-rich deposits of the region. The concentrations observed for other metals were lower or equal to those reported for control sites except for Pb which was slightly higher. The data obtained were subjected to simple linear regression analysis and expressed in the form of correlation coefficients. It was found that the inter-elemental relationships are rather complex.     

Transformation of metals speciation in a combined landfill leachate treatment

Landfill leachate was treated by a combined sequential batch reactor (SBR), coagulation, Fenton oxidation and biological aerated filter (BAF) technology. The metals in treatment process were fractionated into three fractions: particulate and colloidal (size charge filtration), free ion/labile (cation exchange) and non-labile fractions. Fifty percent to 66% Cu, Ni, Zn, Mn, Pb and Cd were present as particulate/colloidal matter in raw leachate, whereas Cr was present 94.9% as non-labile complexes. The free ion/labile fractions of Ni, Zn, Mg, Mn, Pb and Cd increased significantly after treatment except Cr. Fifty-nine percent to 100% of Al was present mainly as particulate/colloidal matter > 0.45 μm and the remaining portions were predicted as non-labile complexes except in coagulation effluent. The speciation of Fe varied significantly in various individual processes. Visual MINTEQ simulation showed that 95-100% colloidal species for Cu, Cd and Pb were present as metal-humic complexes even with the lower dissolved organic carbon. Optimum agreements for the free ion/labile species were within acidic solution, whereas under-estimated in alkaline effluents. Overestimated particulate/colloidal fraction consisted with the hypothesis that a portion of colloids in fraction < 0.45 μm were considered as dissolved.     

Accumulation of heavy metals in a lake ecosystem

The concentrations of Cu, Zn, Fe, Mn, Ni, Cd, Pb and Co have been determined in water, bottom sediments, plankton, zoobenthos and ichthyofauna of mesotropic Lake Piaseczno located in eastern Poland. In water, sediments, plankton and benthos the most abundant heavy metals were Fe, Zn and Mn, whereas in fish Zn, Cu, and Mn were most abundant. The amount of heavy metals in the biotic components was dependent upon their concentration in water and partly upon the concentration in bottom sediments. A considerably less important role in the translocation of heavy metals is probably played by trophic interactions.     

Anthropogenic contamination and risk assessment of heavy metals in stream sediments influenced by acid mine drainage from a northeast coalfield,India

The total concentrations and chemical partitioning of heavy metals in streambed sediments, collected around the Jaintia Hills coal deposit of northeast India, were studied using pollution indices and multivariate techniques to evaluate the risk and contamination levels from heavy metals and their possible origins. Results show that sediments close to mining sites have low pH (<4), high organic carbon, and contain significant amounts of Fe-oxyhydroxide phases (mainly, goethite and schwertmannite), which implies direct impact of coal mine drainage. The average concentrations of Fe, Cu, Co, Cd, Cr, and Zn exceeded the World average, and in some cases, Cd, Cu, Ni, and Cr concentrations exceeded the threshold effects level, which suggests they will be toxic to aquatic biota. Contamination factors (CF) show that the sediments are low to highly contaminated with Cd, Cu, Mn, Pb, Fe, and Zn and low to moderately contaminated with Co, Cr and Ni. The pollution load index (PLI), degree of contamination index (C _deg) and Nemerow integrated pollution index (NIPI) show that the sediments are moderately to highly contaminated, with the extent of pollution greatest nearest to the collieries. The potential ecological risk index (RI) shows low to considerable ecological risk from heavy metals in the sediments, with Cd having the high potential of risk, which also agrees with the risk assessment code (RAC). Multivariate statistical analysis suggests that the concentrations of the heavy metals in stream sediments are strongly influenced by Fe-oxyhydroxide phases and organic carbon derived from anthropogenic sources, mainly coal mining activities. Although a significant proportion of the Cd, Mn, and Ni in the sediments are partitioned into exchangeable and organic fractions, a sizable amount of metals are also found in the Fe–Mn fraction, suggesting that Fe-oxyhydroxides play a dominant role in controlling metal mobility in these stream sediments.     

Concentrations of selected metals in honey consumed in Nigeria

The concentration of metals, cadmium (Cd), lead (Pb), nickel (Ni), chromium (Cr), copper (Cu), cobalt (Co), iron (Fe), manganese (Mn), and zinc (Zn) was measured in selected samples of honey in Nigeria with a view to providing information on the regional concentration profile of metals in these honeys. The honey samples were digested with a mixture of acids and analysed for metal concentrations using atomic absorption spectrophotometry. The concentrations of metals (mg kg^?1) in these honeys ranged from < 0.3 for Cd,<0.50–39.75 for Pb,<0.25–6.98 for Ni,<0.25–55.25 for Cr,<0.25–71.25 for Cu,<0.25–3.50 for Co,<5.0–163.15 for Fe,<11.0–31.75 for Mn and 1.0–31.0 for Zn. The concentrations of metals were relatively high but lower than their respective permissible limits in food except for Pb and Cu in some samples. The regional distribution patterns of metals indicated that honey samples from the Niger Delta region of Nigeria had higher mean concentrations of Ni, Cr, Co, Fe and Zn than honey samples from other regions. The honey samples from the northern region had higher mean concentrations of Pb and Cu.     

Geochemistry of trace metals in a fresh water sediment: field results and diagenetic modeling

Concentrations of Fe, Mn, Cd, Co, Ni, Pb, and Zn were determined in pore water and sediment of a coastal fresh water lake (Haringvliet Lake, The Netherlands). Elevated sediment trace metal concentrations reflect anthropogenic inputs from the Rhine and Meuse Rivers. Pore water and sediment analyses, together with thermodynamic calculations, indicate a shift in trace metal speciation from oxide-bound to sulfide-bound over the upper 20 cm of the sediment. Concentrations of reducible Fe and Mn decline with increasing depth, but do not reach zero values at 20 cm depth. The reducible phases are relatively more important for the binding of Co, Ni, and Zn than for Pb and Cd. Pore waters exhibit supersaturation with respect to Zn, Pb, Co, and Cd monosulfides, while significant fractions of Ni and Co are bound to pyrite. A multi-component, diagenetic model developed for organic matter degradation was expanded to include Zn and Ni dynamics. Pore water transport of trace metals is primarily diffusive, with a lesser contribution of bioirrigation. Reactions affecting trace metal mobility near the sediment-water interface, especially sulfide oxidation and sorption to newly formed oxides, strongly influence the modeled estimates of the diffusive effluxes to the overlying water. Model results imply less efficient sediment retention of Ni than Zn. Sensitivity analyses show that increased bioturbation and sulfate availability, which are expected upon restoration of estuarine conditions in the lake, should increase the sulfide bound fractions of Zn and Ni in the sediments.     

Correlation analyses on binding behavior of heavy metals with sediment matrices

This article presents the amounts of heavy metals bound to the sediment matrices (carbonates, Fe-oxides, Mn-oxides, and organic matter), the correlations between any two heavy-metal binding fractions, and the correlations between sediment matrices and their heavy-metal binding fractions. Data consisted of 313 sets obtained from five main rivers (located in southern Taiwan) were analyzed by statistical methods. Among six heavy metals analyzed (Zn, Cu. Pb, Ni, Cr, and Co), the statistical results show that Zn is primarily bound to organic matter, and Cr is primarily bound to Fe-oxides. Principal component analysis (PCA) and correlation analysis (CA) result in significant correlations between carbonates bound Ni and carbonates bound Cr, Fe-oxides bound Ni and Fe-oxides bound Cr, and Mn-oxides bound Cu and Mn-oxides bound Cr. From linear regression results, the levels of the six heavy metals bound to either organic matter or Fe-oxides is moderately dependent on the contents of organic matter or Fe-oxides, especially true for Cr and Pb. According to slope values of linear regression, Cu and Cr have the highest specific binding amounts (SBA) to organic matter and Fe-oxides, respectively. A significant correlation between organic matter and organically bound heavy metals implied that organic matter contained in the sediments of the Potzu river and the Yenshui river can be adequately used as a normalizing agent. However, the six heavy metals bound to either carbonates or Mn-oxides do not correlate with carbonates or Mn-oxides. The obtained results also imply that competitions of various sediment phases in association with heavy metals occur, and organic matter and Fe-oxides are more accessible to heavy metals than other sediment phases.     

Metal Accumulation In Sediments Of The Exclusive Economic Zone Of Qatar,Persian Gulf

The EEZ of Qatar is subjected to different landbased sources and marine activities. Twenty-three sediment samples were collected from the EEZ of Qatar, Persian Gulf and analyzed to determine the effect of increasing man-made activities on the structure and chemical composition of seabed. Grain size analysis support the predominance of sand sized sediments with patches of sandy silt at the northeastern and southeastern areas. Coarse grained sand was characterized by elevated carbonate content reaching >95%. Off the capital Doha and opposite to industrial parks, the organic matter reached >7.4%. Cu (0.8-30.3 r w g/g), Pb (2.2-22.6 r w g/g), Co (2.4-9.1 r w g/g) and Mn (36.8-746 r w g/g) levels were high compared to other Gulf values. Stations were clustered on the basis of sediment texture rather than metal accumulation. The high organic content of northeastern sediments, derived from planktonic origin is coupled by low metals concentrations. Except for Cr, Cu and Fe, the non-residual fraction of metals contributed between 56 and 92% of the total metals concentrations. Stations sampled closer to potential metal sources are characterized by increased non-residual fractions. Negligible or very low amount (<5%) of the non-residual fraction of metals appeared in the exchangeable phase. Metals are mostly associated with the easily and moderately reducible fraction (23% Fe, 17% Cr, 24% Co, 34% Mn, 14% Ni and 18% Cu) due to strong scavenging capabilities of Fe-Mn oxides. Pb is partitioned equally among easily/moderately reducible and carbonate fractions, dominating in the latter. Co (38%) and Ni (35%) are mostly associated with organic matter/sulphide phase, while Zn (27-29%) is equally partitioned between easily/moderately reducible, carbonate and organic matter phases. Cr (73%), Cu (62%) and Fe (58%) appeared mainly in the residual form. The concentrations of bioavailable metal fractions (exchangeable and easily/moderately reducible) do not put at risk the economically important living resources.     

A comparison of native and transplanted Fontinalis antipyretica Hedw. as biomonitors of water polluted with heavy metals

Native and transplanted mosses of the species Fontinalis antipyretica were studied to assess their capacity as biomonitors of heavy metals. Assays were carried out with transplanted mosses (sampled from an unpolluted control stream) exposed for 60 days to five streams polluted with heavy metals. At the same time, native mosses were collected from the exposure sites. Concentrations of N, P, K, Ca, Mg, S, Fe, Al, Ba, Cd, Co, Cr, Cu, Mn, Ni, Pb, V, and Zn were determined in the mosses (native and transplants), stream waters, and sediments of both exposure and control sites. The results showed that the transplanted mosses accumulated significantly more Al, Cr, Cu, Pb, V, and Zn than the native mosses. The concentrations of Co and Mn in all streams were significantly higher in the native mosses.     

Potential kinetic availability of metals in sulphidic freshwater sediments

The insolubility of metal sulphides is believed to limit the bioavailability of trace metals in sulphidic sediments. However, if non-equilibrium conditions are important, metals may be more available than simple thermodynamic calculations suggest. To investigate the possible dynamic supply of Cu, Ni and Zn in a sulphidic freshwater sediment, they were measured, along with iron, manganese and sulphide, by the technique of diffusive gradients in thin-films (DGT). DGT measures the supply of solute from sediment to solution in response to a local solute sink. Release of Mn, Cu, Zn and Ni was observed at the sediment surface and attributed to the supply from reductive dissolution of manganese oxides. The depth profile of simultaneously extractable metals (SEM) for Cu and Ni followed the shape of the Mn profile more closely than the profiles of either acid volatile sulphur (AVS) or Fe, again consistent with supply from Mn oxides. Solubility calculations for a mesocosm of homogenised sediment indicated supersaturation with respect to the sulphides of Fe, Cu, Ni and Zn, yet DGT measurements demonstrated a substantial supply of both trace metals and sulphide from the solid phase to the pore waters. Ratios of metals measured in pore waters by DGT were consistent with their release from iron and manganese oxides, indicating that supply, as much as removal processes, determines the pseudo-steady state concentrations in the pore waters. The observations suggest that trace metals are not immediately bound in an insoluble, inert form when they are in contact with sulphide. This has consequences for modelling metal processes in sediment, as well as for uptake by some biota.     

Solid state partitioning of trace metals in suspended particulate matter from a river system affected by smelting-waste drainage

The partitioning of particulate trace metals was investigated during one year of monthly sampling of suspended particulate matter (SPM) at eight sites along the Lot-Garonne fluvial system, known for its polymetallic pollution. The chemical partitioning in five operationally defined fractions (exchangeable/carbonate, Fe/Mn oxides, organic matter/sulfides, acid soluble, residual) was determined using a multiple single extraction approach. This approach showed that Cd, Zn, Pb and Cu were mainly associated with acid soluble phases (84-95%, 65-88%, 61-82% and 55-80% of the respective total metal content), and therefore showed a high mean potential of mobilization and bioavailability. In the Riou-Mort River, draining the smelting-wastes, Zn, Cd and Mn showed high mobility as they were little associated with the residual fraction (1-2%) and mainly bound to the 'exchangeable' fraction of SPM (60-80%), probably weakly adsorbed on amorphous freshly-precipitated sulfide and/or oxide phases. Upstream and downstream of the anthropogenic source of metallic pollution, Mn and Cd, and Zn to a lesser extent, remained highly reactive. The other trace metals were mainly associated with the residual fraction and thus less mobile. However, the multiple single extraction scheme revealed that the most reactive transport phases were non-selectively extracted by the conventional extractants used here. These selectivity problems could not have been observed if sequential extraction was used.     

Short-term effects of biosolid and municipal solid waste applications on heavy metals distribution in a degraded soil under a semi-arid environment

Digested biosolid (SS) and municipal solid waste (MSW) were surface-applied to a degraded carbonated soil, under semi-arid environment, at rates of 0 and 80 Mg/ha, to determine the changes in organic matter and in the distribution of heavy metals in the topsoil, 1 year after its application. Waste application slightly increased the organic matter content and improved the composition of humic fractions in the treated soils, mainly in the MSW amended plots. A sequential extraction method (Tessier et al., 1979) was used to determine the distribution of Cd, Cr, Cu, Ni, Pb and Zn in both the waste and the amended.soils. Waste application had little effect on the total concentration of Ni and Cr in the treated soils as a consequence of the low availability of these metals in the wastes. A considerable increase of Cd, Cu, Pb and Zn was observed as a consequence of the high content and/or high availability of these metals in the wastes. The more labile fraction (exchangeable fraction) of all metals studied increased slightly (< 1.5 mg/kg) when SS and MSW were added. However, a remarkable increase in the Fe/Mn oxide fraction of Cd, Cu and Pb and in the organic fraction of Zn were noted in treated plots, this increase being higher in the MSW treated soils.     

Estuarine capacity in removal of trace metals from contaminated river water, Southern Caspian Sea

In the present investigation, the flocculation of dissolved Cd, Cu, Ni, Pb, Mn and Zn with initial concentrations of 1, 2.5 and 5 mg/L in Tadjan River water during mixing with the Caspian Sea water has been studied in order to determine estuarine capacity to remove dissolved metals in the accidental contamination of the river. The flocculation process was investigated on a series of mixtures with salinities ranging from 0.1 to 11 p.p.t. The flocculation rates were indicative of the nonconservative behaviour of Cd, Cu, Ni, Pb, Mn and Zn during estuarine mixing. The order of the final flocculation rate of dissolved metals at 1, 2.5 and 5 mg/L of initial metal concentrations in the river water is as follows:Cu (99%)>Cd (95%)>Zn (88%)>Mn (85%)>Pb (83%)>Ni (73%), Cu(95.6%)>Pb(92.4%)>Cd (90%)>Zn(88.4%)>Mn (81.6%)>Ni(78.8%) and Cd (100%)>Cu(88%)>Ni (85.2%)>Pb (84%)>Zn (83.2%)>Mn (81.2%), respectively. The results also revealed that removal of dissolved metals is not influenced by pH changes and precipitation processes. The flocculation rates revealed that the overall dissolved metal pollution loads may be reduced to about 70% up to about more than 90% during estuarine mixing of Tadjan River with the Caspian Sea water.     

Heavy metal behaviour during the activated sludge process I. Extent of soluble and insoluble metal removal

The extent of removal of Ag, Bi, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Tl and Zn and their distribution between the soluble and insoluble phases in the influent, and effluent of the activated sludge process has been studied using a pilot-scale plant operated at sludge ages of 3, 6, 9 and 12 days. Molybdenum, Tl, Co, Mn and Ni were >50% soluble in the influent settled sewage. The mean removals of the former two metals were <3% and the latter three were 35 and 50%. Silver, Bi, Cd, Cr, Cu, Pb and Zn were all <35% soluble in the influent and had substantial removals of >75%. Solubilities were greater in the effluent than the influent with the exception of Mn. The observed overall removals of Ag, Bi, Co, Ni, Pb, Tl and Zn were almost entirely due to insoluble metal removal; Cd, Cr and Cu removals had a significant contribution from soluble metal removal. Overall Mn removal appeared to be solely due to soluble metal removal.     

Behavior of Mn, Fe, Cu, Zn, Cd and Pb discharged from a wastewater treatment plant into an estuarine environment

To obtain information on the fate of trace metals discharged to an estuarine environment, analyses have been made on water and sediment samples from Back River, MD., and on effluent from the large wastewater treatment plant that discharges there. Within 2–3 km of the outfall, the concentration (in μg 1⁻¹) of all metals decreases as follows: Mn, > 120-90; Fe, > 570-300; Cu, 53-7; Zn, 280-9; Cd, 3.5-0.5 and Pb, 31-<4. Except possibly for Mn and Fe, these decreases are much greater than can be ascribed to simple dilution, so physical, chemical or biological processes must be removing metals to the sediments. Correspondingly, sediment concentrations of Cu, Zn, Cd and Pb are approximately one order of magnitude higher than normally found in uncontaminated areas. After the initial decrease, concentrations of Mn and Cd in the water begin to rise again, suggesting remobilization from the sediments. Comparison of the estimated annual discharge of 8 trace metals to the Chesapeake Bay from wastewater treatment plants and from rivers suggests that the wastewater input may be within one order of magnitude of the fluvial input for Cr, Cu, Zn, Cd and Pb. Of the metals studied, Cd presents the greatest potential for serious pollution because its input from wastewater probably exceeds fluvial input, it appears to be readily remobilized from sediments, and it is known to be toxic to many organisms.     

Seasonal and time variability of heavy metal content and of its chemical forms in sewage sludges from different wastewater treatment plants

Sewage sludges obtained from seven wastewater treatment plants from the province of Salamanca, Spain, were periodically sampled to determine seasonal and time variation of their elemental composition over 2000 to 2002. The aim of this paper was to provide additional insight to evaluate the potential environmental impact following soil incorporation of these materials as amendments. Aqua regia extractable metals (pseudo total content) of Cd, Cr, Cu, Ni, Pb and Zn were determined and furthermore, the main chemical forms of metals within the sludge were evaluated using a five-step fractionation procedure. All the studied sludges displayed high fertility properties due to their richness of OC, P and K. Total mean concentrations of Cd, Cr, Cu, Ni, Pb and Zn in the sludges were within the regulation of the Spanish legislation. Using an multifactor analysis of variance, significant differences between Cr, Cu, Ni, Pb and Zn pseudo total contents (p<0.01) of sludges at different sites were found while the Cd content was statistically similar. Also significant differences were found between these pseudo total contents of heavy metals in samples collected along the time after three years (0.001相似文献   

Heavy metals in the dump of an abandoned mine in Galicia (NW Spain) and in the spontaneously occurring vegetation

The concentrations of different forms of heavy metals (Fe, Mn, Zn, Cu, Cr, Ni, Cd and Pb) were determined in a mine dump material rich in chalcopyrite. The concentrations were compared with those of the natural vegetation colonising the dump. Samples taken from the dump are acid (pH(H(2)O) between 3.0 and 5.0), have carbon contents lower than 0.5%, N lower than 0.2%, effective cation exchange capacity between 0.74 and 4.96 cmol(+)kg(-1) and percent Al saturation in the exchange complex higher than 20% in 85% of the samples. Iron was the most abundant heavy metal, in both total and bioavailable forms, and the relative abundance of metals was: Fe>Cu>Mn>Zn>Cr. The total Fe concentrations ranged between 4315 and 31578 mg x kg(-1), the total Cu between 273 and 5241 mg x kg(-1), the total Mn between 294 and 2105 mg x kg(-1), the total Zn between 73 and 894 mg x kg(-1) and total Cr between 0.01 and 30 mg x kg(-1). Ni, Cd and Pb were below the analytical detection limits. The concentration of bioavailable Fe ranged between 40 and 1550 mg x kg(-1); Zn was the least abundant metal in this fraction (between 2 and 100 mg x kg(-1)). Copper was the most abundant heavy metal in the exchange complex and in the aqueous extracts, followed by Zn, Mn and Fe. Exchangeable Cu ranged between 17.7 and 1866 mg x kg(-1), whereas the maximum concentrations of exchangeable Zn, Mn and Fe did not exceed 140 mg x kg(-1). The Cu concentration in the aqueous extracts varied between 0.1 and 8.3 mg x l(-1) and the concentration of Fe was always less than 0.52 mg x l(-1). The heavy metal contents in the spontaneously occurring vegetation in the dump ranged between: 150 and 900 mg Fe x kg(-1), 84 and 2069 mg Mn x kg(-1), 20.5 and 106 mg Cu x kg(-1) and between 35 and 717 mg Zn x kg(-1), when considering all the plant samples analysed. Festuca sp. accumulated Fe, Salix atrocinerea accumulated Zn and Mn, and Frangula alnus and Quercus robur accumulated Mn. These native plant species may contribute to decrease the heavy metal contents in the dump material.