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 607 毫秒
1.
In the mining district of Plombières-La Calamine (East Belgium), extensive Pb–Zn mining activities resulted in an important contamination of overbank sediments along the Geul river. Moreover, a huge amount of heavy metals is stored in a dredged mine pond tailing, which is located along the river. In the dredged mine pond tailing sediments, Pb–Zn minerals control the solubility of Zn, Pb and Cd. Although Pb, Zn and Cd display a lower solubility in overbank sediments compared to the mine tailing pond sediments, elevated concentrations of Pb, Zn and Cd are still found in the porewater of the overbank sediments. The considerable ‘actual’ and ‘potential’ mobility of Zn, Pb and Cd indicates that the mine pond tailing sediments and the overbank sediments downstream from the mine pond tailing represent a considerable threat for the environment. Besides the chemical remobilisation of metals from the sediments, the erosion of overbank sediments and the reworking of riverbed sediments act as a secondary source of pollution.  相似文献   

2.
Macquarie Harbour in southwest Tasmania, Australia, has been affected severely by the establishment of mines in nearby Queenstown in the 1890s. As well as heavy metal-laden acid rock drainage from the Mount Lyell mine area, over 100 Mt of mine tailings and slag were discharged into the Queen and Ring Rivers, with an estimated 10 Mt of mine tailings building a delta of ca. 2.5 km2 and ca. 10 Mt of fine tailings in the harbour beyond the delta. Coring of sediments throughout Macquarie Harbour indicated that mine tailings accreted most rapidly close to the King River delta source with a significant reduction in thickness of tailings and heavy metal contamination with increasing distance from the King River source. Close to the King River delta the mine tailings are readily discriminated from the background estuarine sediments on the basis of visual logging of the core (laminations, colour), sediment grain size, sediment magnetic susceptibility and elemental geochemistry, especially concentrations of the heavy metals Cu, Zn and Pb. The high heavy metal concentrations are demonstrated by the very high contamination factors (CF > 6) for Cu and Zn, with CF values mostly >50 for Cu for the mine-impacted sediments. Although the addition of mine waste into the King River catchment has ceased, the catchment continues to be a source of these heavy metals due to acid rock drainage and remobilisation of mine waste in storage in the river banks, river bed and delta. The addition of heavy metals to the harbour sourced from the Mount Lyell mines preceded the advent of direct tailings disposal into the Queen River in 1915 with the metals probably provided by acid rock drainage from the Mount Lyell mining area.  相似文献   

3.
The given work focused on solving the problem of environmental geochemistry related to investigation of element speciation, their mobility, and migration in polluted areas. The purpose was to describe quantitatively migration, distribution, and redistribution of heavy metals by the example of the old tailings (Talmovaya sands) of the Lead Zinc Concentration Plant (Salair, Kemerovo region, Russia) and technogenic bottom sediments of the Malaya Talmovaya river. Contents of elements in the sulfide tailings range in the following limits: Zn: 1,100–27,000 ppm, Cd: 1.3–240 ppm, Pb: 0.01–0.81 ppm, Cu: 220–960 ppm, As: 15–970 ppm, Fe: 19,000–76,000 ppm, and Ba: 80,000–1,00,000 ppm. Element concentrations in the river sediment are proportional to the element contents in the sulfide tailings. Element speciations in the sulfide tailings and technogenic bottom sediments were investigated by the modified sequential extraction procedure. Chemical forms of heavy metals in pore water and surface water were calculated by WATEQ4F software. Principles of heavy metal migration in the sulfide tailings and technogenic bottom deposits were established. The obtained results about element species in the sulfide tailings and sediment explain the main principles of element migration and redeposition. In the mine waste and technogenic bottom deposits, there is vertical substance transformation with formation of geochemical barriers.  相似文献   

4.
Acid Mine Drainage (AMD) is a great concern in many abandoned mines because of its adverse effect on the environment. In mining processes, many kinds of wastes are produced. These wastes may become eventually sources of environmental degradation. The focus of this study is the geochemical characterization of the end-processed tailings generated by Akara Gold Mine, the biggest gold mine in Thailand. Tailing samples were systematically collected for analyses of chemical and mineralogical compositions. As a result, their quantitative chemical analyses are slightly different from place to place, but mineral components cannot be clearly differentiated. For instance, it may be assumed that the end-processed tailings, which were a mixture between high and low grade concentrates, would have similar mineral components. However, the little variation of chemical composition may be caused by the ore refining processes that are somehow varied in proportion to chemical additives, alkali cyanide and quick lime in particular. In addition, clay composition in ore-bearing layers may also influence alumina content of tailings, accordingly. Distribution of the tailings is not related to depth and distance of the tailing storage pond because the disposal has sped them over the pond during operation. Total heavy metals of the tailing samples were analyzed on the basis of the EPA 3052 method. Consequently, the most toxic elements (e.g., Co, Cu, Cd, Cr, Pb, Ni and Zn) were found falling within the standard of Thailand Soil Quality Standards for Habitat and Agriculture. Only Mn appears to have higher content than the standard. In addition, leaching tests proved that these tailings contain low metal concentrations. As a result, at pH 2, Mn can leach out exceeding the Thailand Surface Water Quality Standard for Agricultural (Mn <1 ppm) and the Thailand Industrial Effluent Standard (<5 ppm). Although leachate at pH 4 and neutral conditions contains lower Mn than the Industrial Effluent Standard it still exceeds the surface water quality standard. Interestingly, Pb can be leached out exceeding both standards (0.2 ppm for the industrial effluent standard and 0.05 ppm for the surface water quality standard). For Ni leaching, its concentration is lower than the Industrial Effluent Standard at all pH conditions but still exceeds the Surface Water Standard at pH 2 and 4. This information should be taken into consideration for further environmental monitoring. Acid generating potential of the tailings was estimated using acid–base accounting (ABA) and net acid generation (NAG) tests. The results of ABA and NAG tests show that the tailing samples contain a high amount of sulfur. However, they also contain high acid neutralization capacity. Consequently, these tailings may not have potential to generate acid drainage; in the other words, they can be classified as a non-acid forming (NAF) material. However, since these tailings contain some heavy metals (e.g., Ni, Mn and Pb) that are observed in leachates exceeding the standards at low pH, the AMD conditions may lead to heavy metal release. Therefore, prevention of oxidizing process and dissolution should be considered with great care. In addition, Mn and Pb can also be leached at neutral conditions. Barrier of air and water, clay layer for example, should be placed over the tailings pound before covering by topsoil for re-vegetation. Growing native grass is recommended for stabilization of the surface and reducing erosion rate. Monitoring of water quality should also be carried out annually.  相似文献   

5.
Mine tailings are ubiquitous in the landscapes of mined areas. Metal solubilities were compared in two chemically distinct mine tailings from the old Mining District of Cartagena-La Unión (SE Spain). One of the tailings was acidic (pH 3.0) with 5400 mg/kg Zn, 1900 mg/kg As and 7000 mg/kg Pb. The other was neutral (pH 7.4) with 9100 mg/kg Zn, 5200 mg/kg Pb and 350 mg/kg As. In samples from the acidic tailings, more than 15% of the Zn and 55% of the Cd were extractable with 0.1 M NaNO3, and distilled water. In the neutral tailings, using the same reagents, less than 1% of the metals were extractable. A sequential extraction procedure revealed that the sum of the residual and the Fe oxide fractions of Cu, Zn and Pb comprised 80–95% in the acidic tailings and 70–90% in the neutral tailings. The acidic mine tailings had a higher metal solubility, resulting in more metal leaching in the short-term, but also a higher fraction of inert metal. In contrast, in the neutral tailings, the metals were evenly distributed between, oxides and the residual fraction. This implies lower metal mobility in the short-term, but that metal mobility may increase in the long-term. When applied to mine tailings, sequential extractions may provide misleading results because the strong cation exchange capacity of some extractants may induce pH changes and thereby significantly change metal solubility.  相似文献   

6.
Contamination of soils with heavy metals is widespread and poses a long-term risk to ecosystem health. Abandoned and active mining sites contain residues from ore-processing operations that are characterised by high concentrations of heavy metals. The distribution and mobility characteristics of heavy metals (As, Cd, Cu, Pb, and Zn) in paddy soil samples from Kočani Field (Macedonia) using ICP-EAS and a sequential extraction procedure was evaluated. The results indicate that highly elevated concentrations of As, Cd, Cu, Pb, and Zn were detected in the paddy soil sample from location VII-2 in the vicinity of Zletovo mine and Zletovska river in the western part of Kočani Field, which drains the untreated acid mine waters and mine wastes from the active Zletovo mine. The degree of contamination based on index of geoaccumulation (I geo) from strong to weak in the paddy soils samples is Pb > As > Cd > Zn > Cu. The mobility potential of heavy metals in all paddy soil samples increases in the order As < Cu < Pb < Zn < Cd. According to the results of the anthropogenic impact on the paddy soils, a further study on the heavy metal concentrations in rice and other edible crops, the remediation process of the paddy soils and a dietary study of the local population are needed.  相似文献   

7.
陕西潼关金矿区太峪河底泥重金属元素的含量及污染评价   总被引：3，自引：1，他引：2  
徐友宁  张江华 《地质通报》2008,27(8):1263-1671
通过对潼关金矿区太峪河和太峪水库底泥中重金属元素总量的调查,探讨了金矿开发活动中重金属元素对河流底泥的污染程度。研究结果表明,除As外,河流底泥中重金属元素的含量与尾矿渣中重金属元素的含量变化一致,表明其主要来源于尾矿渣,但又明显高于尾矿渣。在同一地点河流底泥中重金属元素的含量平均高出河水中的1048.61～666030.08倍,呈显著富集。以邻近地区不受工矿活动影响的河流底泥重金属元素的含量均值作为评价参比值,太峪河底泥受到了Hg、Pb、Cd、Cu、Zn元素的极度污染,单项污染超标倍数及综合污染指数法评价结果表明,Hg、Pb、Cd平均污染超标倍数达366.90、217.42和149.97,是底泥中最主要的污染元素。河流底泥重金属元素的综合污染指数高达278.97,表明河流的复合污染亦呈极度状态。太峪河底泥受重金属元素极度污染的现实提示,矿区的环境防治工作已刻不容缓。  相似文献   

8.
Urbanisation and industrial development lead to contamination of estuaries and streams with dispersed loadings of heavy metals and metalloids. Contributions of these elements also occur from natural sources. This study provides baseline geochemical data on the respective natural and anthropogenic inputs of Cu, Pb, Zn, Cd, As, Sb, Cr, Ni, Mn and S to estuarine, fluvial and wetland sediments, and adjacent soils, in the Kooloonbung Creek catchment that drains the Port Macquarie urban area in north coastal New South Wales. There have been anthropogenic additions of Cu, Pb, Zn and As from dispersed urban sources at Port Macquarie, but they are restricted to the local catchment and do not impact on the adjacent Hastings River estuary. The most contaminated sediments display enrichment factors up to 20 × for Cu and Pb, 9 × for Zn and 5 × for As relative to local background values. However, only one value (for Pb) exceeds National Water Quality Management Strategy interim sediment quality guideline (high) values. On the other hand, sediments and local soils are commonly strongly enriched in Cr, Ni and Mn, reflecting adjacent ultramafic and mafic rock substrate and lateritic regolith. Concentrations of Cr and Ni are commonly well above interim sediment quality guideline (high) values for sediments, but are in mineralogical forms that are not readily bioavailable. Sediment and soil quality guideline values consequently need to recognise natural enrichments and the mineralogical siting of heavy metals. Although dissolved concentrations of heavy metals in stream waters are commonly low, there is evidence for mobility of Cu, Zn, Fe and Al. Parts of the Kooloonbung Creek wetland area lie on sulfidic estuarine sediments (potential acid sulfate soils). Experimental oxidation of uncontaminated and contaminated sulfidic sediments leads to substantial dissolution of heavy metals under acid conditions, with subsequent aquatic mobility. The results warn about disturbance and oxidation of potential acid sulfate soils that have been contaminated by urban and natural heavy-metal sources.  相似文献   

9.
Batch experiments were conducted to investigate As mobilization from mine tailings in the presence of a biosurfactant (JBR425, mixed rhamnolipids) and to evaluate the feasibility of using biosurfactant in remediating As contaminated mine tailings/soils. Introduction of the biosurfactant increased As mobilization greatly. When the mass ratio was 10 mg biosurfactant/g mine tailings at pH 11, As mobilization by the biosurfactant was greatest after 24 h, with a corresponding concentration ratio (the ratio of As mobilization by the biosurfactant to that by distilled water at same adjusted pH, wt/wt) of 21.6. Selective sequential extraction indicated that As was easily mobilized from the weakly bound and relatively more mobile fractions by washing with the biosurfactant. A mobilization isotherm was developed to predict As mobilization from the mine tailings in the presence of biosurfactant. It was shown that biosurfactant sorption to the mine tailings is essential for As mobilization. Arsenic mobilization was found to be positively correlated with the mobilization of Fe and other metals (i.e., Cu, Pb and Zn), which might further enhance As mobilization by helping incorporate it into soluble complexes or micelles. Capillary electrophoresis analyses indicated that As redox or methylation reactions had insignificant effect on As mobilization. Biosurfactants might be used potentially to remove bulk As from mine tailings or contaminated soils under alkaline conditions.  相似文献   

10.
Heavy metal contamination was the main environmental problem around the Jinchang Ni–Cu mine area of Gansu, Northwest China. The concentration of heavy metals (Cr, Cu, Ni, Pb, and Zn) in various environmental mediums around the Jinchang Ni–Cu mine area were analyzed using atomic absorption spectrometry (AAS). The different chemical speciation of heavy metals was extracted using BCR (European Community Bureau of Reference) sequential extraction procedure, and the concentration of chemical speciation of each heavy metal was measured by inductively coupled plasma-atomic emission spectrometry. The results showed that Cu and Ni were the most important heavy metal pollutants in various mediums including cultivated soils, dust on slagheap surfaces, tailings, and sediments in waste water drains. In the tailings and sediments, the concentrations of Ni were obviously higher than those of Cu, whereas, in the soil and dust, the concentrations of Cu were higher than those of Ni. Analysis of chemical speciation indicated that Cr and Zn were mainly in residual fraction; Cu was mainly in oxidizable fraction; Ni was mainly in reducible fraction and acid soluble fraction; and Pb was mainly in reducible fraction and residual fraction. The extent of contamination of various environmental mediums was different because the heavy metals were derived from different sources. Furthermore, the mobility of various heavy metals was different because of the different distribution of chemical speciation.  相似文献   

11.
长江上游是整个长江经济带的重要生态屏障。以长江上游攀西大梁子铅锌矿区水系沉积物为研究对象,查明了重金属元素含量的空间分布特征,分析了重金属来源,探讨了在不同pH条件下重金属的淋滤规律,并进行了生态风险评估。研究结果显示:攀西大桥河流域水系沉积物中重金属的空间分布极不均匀,其含量明显要高于长江水系沉积物中重金属的平均含量;重金属生态风险属于很强风险,Hg和Cd呈高度富集、严重污染;Pb和Zn呈中度富集、中等污染。淋滤实验结果表明Pb、Zn、Cd在酸性和中性条件下淋滤浓度先快速下降,后逐渐趋于平衡,而As在快速下降后又有缓慢升高的趋势。大桥河流域水系沉积物中As、Cd、Pb、Zn主要来源于大梁子铅锌矿的采选活动,Hg为岩石风化和土壤剥蚀来源,而Cu和Cr主要为农业和工业活动来源。综合对比发现,攀西成矿带铅锌矿周边土壤富Cd而贫Cr,此外Cd、Pb、Zn、Hg是主要潜在污染物,且生态风险程度较高。  相似文献   

12.
Nador lagoon sediments (East Morocco) are contaminated by industrial iron mine tailings, urban dumps and untreated wastewaters from surrounding cities. The lagoon is an ecosystem of biological, scientific and socio-economic interests but its balance is threatened by pollution already marked by biodiversity changes and a modification of foraminifera and ostracods shell structures. The aim of the study is to assess the heavy metal contamination level and mobility by identifying the trapping phases. The study includes analyses by ICP-AES and ICP-MS, of, respectively, major (Si, Al, Mg, Ca, Fe, Mn, Ti, Na, K, P) and trace elements (Sr, Ba, V, Ni, Co, Cr, Zn, Cu, As, Pb, Cd) in sediments and suspended matter, heavy metals enrichment factors calculations and sequential extractions. Results show that sediments contain Zn, Cu, Pb, V, Cr, Co, As, Ni with minimum and maximum concentrations, respectively, of 4–1190 μg/g, 4–466 μg/g, 11–297 μg/g, 11–194 μg/g, 9–139 μg/g, 1–120 μg/g, 4–76 μg/g, 2–62 μg/g. High concentrations in Zn are also present in suspended matter. The enrichment factors show contamination in Zn, Pb and As firstly induced by the mining industry and secondly by unauthorized dumps and untreated wastewaters. Cr and Ni are bound to clays, whereas V, Co, Cu and Zn are related to oxides. Thus, the risk in metal mobility is for the latter elements and lies in the oxidation–reduction-changing conditions of sediments.  相似文献   

13.
《Applied Geochemistry》2001,16(11-12):1377-1386
The heavy metal contamination and seasonal variation of the metals in soils, plants and waters in the vicinity of an abandoned metalliferous mine in Korea were studied. Elevated levels of Cd, Cu, Pb and Zn were found in tailings with averages of 8.57, 481, 4,450 and 753 mg/kg, respectively. These metals are continuously dispersed downstream and downslope from the tailings by clastic movement through wind and water. Thus, significant levels of the elements in waters and sediments were found up to 3.3 km downstream from the mining site, especially for Cd and Zn. Enriched concentrations of heavy metals were also found in various plants grown in the vicinity of the mining area, and the metal concentrations in plants increased with those in soils. In a study of seasonal variation on the heavy metals in paddy fields, relatively high concentrations of heavy metals were found in rice leaves and stalks grown under oxidizing conditions rather than a reducing environment (P<0.05).  相似文献   

14.
We studied the mobility of silver, heavy metals and europium in waste from the Las Herrerías mine in Almería (SE Spain). The most abundant primary mineral phases in the mine wastes are hematite, hydrohematite, barite, quartz, muscovite, anorthite, calcite and phillipsite. The minor phase consisted of primary minerals including ankerite, cinnabar, digenite, magnesite, stannite, siderite and jamesonite, and secondary minerals such as glauberite, szomolnokite, thenardite and uklonscovite. The soils show high concentrations of Ag (mean 21.6 mg kg–1), Ba (mean 2.5%), Fe (mean 114,000 mg kg–1), Sb (mean 342.5 mg kg–1), Pb (mean 1,229.8 mg kg–1), Zn (mean 493 mg kg–1), Mn (mean 4,321.1 mg kg–1), Cd (mean 1.2 mg kg–1) and Eu (mean 4.0 mg kg–1). The column experiments showed mobilization of Ag, Al, Ba, Cu, Cd, Eu, Fe, Mn, Ni, Sb, Pb and Zn, and the inverse modelling showed that the dissolution of hematite, hausmannite, pyrolusite and anglesite can largely account for the mobilization of Fe, Mn and Pb in the leaching experiment. The mobility of silver may be caused by the presence of kongsbergite and chlorargyrite in the waste, while the mobility of Eu seems to be determined by Eu(OH)3, which controls the solubility of Eu in the pH–Eh conditions of the experiments. The mineralogy, pH, Eh and geochemical composition of the mine wastes may explain the possible mobilization of heavy metals and metalloids. However, the absence of contaminants in the groundwater may be caused by the carbonate-rich environment of “host-rocks” that limits their mobility.  相似文献   

15.
Levels of the chalcophile metals Hg, Pb, Cd, Cu and Zn and the metalloid As in soils from rice paddy fields were assessed in two regions impacted by different industrial activities in Guizhou province, China. The two study areas (Wanshan and Qingzhen) have previously received attention in the international literature due to heavy Hg pollution, though levels of other potentially harmful elements have not previously been reported. The regions were selected as representing two important, but categorically different metal(loid) contaminated areas in China: Wanshan has been a major region for Hg production while Qingzhen is an important region for a large range of various heavy industries based on coal as an energy source.Within a limited distance of the Hg mine tailings in Wanshan the rice paddy fields are heavily contaminated by Hg (median concentration 25 μg g−1, maximum 119 μg g−1) and moderately contaminated by Zn and Cd (median concentrations of 86 and 0.9 μg g−1, respectively). Zinc and Cd levels correlate well with Hg contamination, which indicates a similar source and mechanism of transport and accumulation. Other studies have concluded that the main sources of Hg contamination in Wanshan are the numerous Hg mine tailings. This is likely as these metals are all geochemically associated with the mineral cinnabar (HgS). The other chalcophile elements (Pb, Cu and As) are nevertheless found at background levels only. In Qingzhen the soils were found to contain elevated levels of As and Hg (median concentrations of 38 and 0.3 μg g−1, respectively). These are elements that are known to be more associated with coal and released during coal combustion.  相似文献   

16.
Concentration and distribution of heavy metals (Cd, Cu, Pb and Zn) in urban soils of Hangzhou, China, were measured based on different land uses. The contamination degree of heavy metals was assessed on the basis of pollution index (PI), integrated pollution index (IPI) and geoaccumulation index (I geo). The 0.1 mol l−1 HCl extraction procedure and gastric juice simulation test (GJST) were used to evaluate the potential mobility and environmental risk of heavy metals in urban soils. The average concentration of Cd, Cu, Pb and Zn in urban soils was measured at 1.2 (with a range of 0.7–4.6), 52.0 (7.4–177.3), 88.2 (15.0–492.1) and 206.9 (19.3–1,249.2) mg kg−1, respectively. The degree of contamination increased in the order of industrial area (IA) > roadside (RS) > residential and commercial areas (RC) > public park and green areas (PG). The PIs for heavy metals indicated that there is a considerable Cd, Cu, Pb and Zn pollution, which originate from traffic and industrial activities. The IPI of these four metals ranged from 1.6 to 11.8 with a mean of 3.5, with the highest IPI in the industrial area. The assessment results of I geo also supported that urban soil were moderately contaminated with Cd and to a lesser extent also with Cu, Pb and Zn. The IP and I geo values reveal the pollution degree of heavy metal was the order of Cd > Pb > Zn ≈ Cu. It was shown that mobility and bioavailability of the heavy metals in urban soils increased in the order of Cd > Cu > Zn ≈ Pb. Owing to high mobility of Cd and Cu in the urban soils, further investigations are needed to understand their effect on the urban environment and human health. It is concluded that industrial activities and emissions from vehicles may be the major source of heavy metals in urban contamination. Results of this study present a rough guide about the distribution and potential environmental and health risk of heavy metals in the urban soils.  相似文献   

17.
In this study we investigated the sulphidic mine tailings from Frongoch and Grogwynion, two abandoned lead zinc mines in mid-Wales, UK. Despite falling within the same ore field the mine waste characterisation has identified differences in the tailings from the two sites. Bulk concentrations range from 10 to 52 g kg− 1 for Pb, 1.1 to 2.9 g kg− 1 for Zn in Grogwynion and from 1.0 to 130 g kg− 1 for Pb, 11 to 110 g kg− 1 for Zn in Frongoch. An experimental (European standard leaching tests TS 14429 and TS 14405) and geochemical modelling approach was used to study the leaching composition as a function of pH and liquid/solid ratio. There was little correlation between the tailings bulk metal concentrations and the leachate composition, but variations in Pb and Zn concentrations were found to be consistent with control of dissolved Pb and Zn by secondary minerals and the mechanisms of dissolution/precipitation/sorption involving them. Specifically, the Grogwynion mine tailings with near-neutral pH have predominantly lead and zinc carbonates controlling Pb and Zn solubility in the leachates, whereas the Pb and Zn concentrations in Frongoch leachates are best modelled with a surface complexation model for metal sorption to oxyhydroxides. The different speciation results in a greater sensitivity of Grogwynion tailings to acidification with a potential release of Pb in solution up to 10 times higher than in Frongoch, despite similar bulk Pb concentrations. At acid pH, Zn is similarly dissolved to a greater extent in Grogwynion than in Frongoch tailings. There was no evidence of sulphide oxidation during the batch and column leaching tests and the suitability of using these European leaching standards for the characterisation of sulphidic mine waste materials for waste management purposes has been considered.  相似文献   

18.
H. Leenaers 《GeoJournal》1989,19(1):37-43
The floodplain soils in the Guel basin have unacceptably high levels of pollution,v brought about by metal mining and related industrial activities in the past. Spoil heaps still exist along the Geul river and these are susceptible to erosion and leaching processes. An additional source of metals is formed by erosion of older, locally highly contaminated streambank deposits. These older sediments are polluted as a result of solid waste disposal containing metalliferous ore and tailings in the sand fraction. At present, these sediments function as a major source of heavy metals during high flow stages when streambanks are undermined and suspended sediments are deposited on the floodplains. The flood deposits have a relatively coarse texture, i.e. 70% dry weight in the fraction > 63 um.In order to obtain an indication about the potential mobility of the heavy metals in these deposits, 16 samples (8 samples < 63 um and 8 samples > 63 um) out of a set of 122 were subjected to a sequential extraction scheme as proposed by Calmano & Förstner (1983). It was found that up to 80% of the metals may be present in the first three leaching stages (exchangeable cations, carbonate fraction and easily reducible fraction) and that hardly any difference exists between the chemical partitioning of metals in the size fractions < 63 um and > 63 um. Moreover, as the total metal concentrations exponentially decrease along the 40 km distance away from the source area, the percentage of metals in these 3 potentially mobile fractions steadily increases. It is concluded that despite the rapid decay of total metal concentrations, Large amounts of potentially mobile metals are probably stored in the floodplain sediments even at a large distance from the source area.  相似文献   

19.
The San Pedro River (SPR) is located in northern Sonora (Mexico) and southeastern Arizona (USA). SPR is a transboundary river that develops along the Sonora (Mexico) and Arizona (USA) border, and is considered the main source of water for a variety of users (human settlements, agriculture, livestock, and industry). The SPR originates in the historic Cananea mining area, which hosts some of the most important copper mineralizations in Mexico. Acid mine drainage derived from mine tailings is currently reaching a tributary of the SPR near Cananea City, resulting in the contamination of the SPR with heavy metals and sulfates in water and sediments. This study documents the accumulation and distribution of heavy metals in surface water along a segment of the SPR from 1993 to 2005. Total concentrations of Cd, Cu, Fe, Mn, Pb, and Zn in surface waters are above maximum permissible levels in sampling sites near mine tailing deposits. Nevertheless, a significant decrease in the Fe and SO4 2− in surface water (SO4 2−: 7,180–460.39 mg/L; Fe: 1,600–9.51 mg/L) as well as a gradual decrease in the heavy and transition metal content were observed during the period from 1994 to 2005. Approximately 2.3 km downstream of the mine tailings, the heavy metal content of the water drops quickly following an increase in pH values due to the discharging of wastewater into the river. The attenuation of the heavy metal content in surface waters is related to stream sediment precipitation (accompanied by metal coprecipitation and sorption) and water dilution. Determining the heavy metal concentration led to the conclusion that the Cananea mining area and the San Pedro River are ecosystems that are impacted by the mining industry and by untreated wastewater discharges arising from the city of Cananea (Sonora, Mexico).  相似文献   

20.
粤北大宝山是华南金属成矿带的大型铁铜、铅、锌、钼等多金属综合性矿床,富含硫化物,位于北江支流横石河的上游分水岭,流域封闭性很好。矿山开发引起横石河下游的上坝村成为远近闻名的"癌症"村,部分村民出现"痛痛病"疑似症状。由于其特殊的地理位置和对下游引发的严重污染,该矿山成为研究湿热地区含硫化物金属矿山重金属元素生态-环境地球化学迁移的理想场所。以Zn为例,该矿山重金属元素从矿体中向生物体迁移过程经过尾砂/水反应界面、水/沉积物反应界面、土壤/间隙水溶液界面和土壤/植物界面4个重要的反应界面。其中,尾砂/水反应界面控制重金属从源头尾砂中的释放;水/沉积物反应界面控制重金属在水体中与河流沉积物的沉淀与释放的平衡;土壤/间隙水溶液界面控制土壤生物有效性;土壤/植物界面控制生物对重金属的吸收与利用。4个界面的介质间相互作用较好地刻画大宝山矿山因为开采,重金属元素从内生环境中曝露出来,然后在表生环境中释放、迁移、转化、归宿的迁移模式。上述认识对矿山重金属污染治理具有重要的指导意义。通过改变重金属迁移反应界面的条件,可以阻断矿山元素的迁移,达到污染治理的目的。  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