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1.
A study of the San Pedro River (SPR), which is located in a semi-arid region in Sonora, Mexico, was conducted to evaluate the chemical, spatial and temporal (mobilization) trends of potentially harmful metals in its sediment in the rainy and dry seasons. High total concentrations of metals were detected in the following order: Fe > Cu > Mn > Zn > Pb > Cd. All studied metals except for Pb were increased during the dry season showing the effect of climate on the metal distribution in sediments. The results of sequential extraction indicated that the residual and Fe/Mn oxide fractions were the most important with regard to retaining potentially harmful metals in the sediments. In the exchangeable carbonate and Fe oxide fractions, high concentrations of metals were detected, representing high environmental risk. The geoaccumulation index shows slight to moderate contamination in most samples, and sampling point E4 (related to cattle activity) shows strong contamination for Cd, Cu, Pb and Zn. Enrichment factors (EFs) demonstrate anthropogenic origins for Pb (EF: 3–57), Cd (EF: 6–73) and Cu (EF: 1.5–224). This study shows that sediments are impacted by anthropogenic activities related to the mining industry, untreated wastewater discharges from the city of Cananea and cattle activities. Metal mobility in the SPR can disrupt the development of aquatic species in the river.  相似文献   

2.
Ion chemistry of mine pit lake water reveals dominance of alkaline earths (Ca2+ and Mg2+) over total cation strength, while SO4 2? and Cl? constitute the majority of total anion load. Higher value of Ca2+?+?Mg2+/Na+?+?K+ (pre-monsoon 5.986, monsoon 8.866, post-monsoon 7.09) and Ca2+?+?Mg2+/HCO3 ??+?SO 4 2 (pre-monsoon 7.14, monsoon 9.57, post-monsoon 8.29) is explained by weathering of Ca?CMg silicates and dissolution of Ca2+-bearing minerals present in parent rocks and overburden materials. Silicate weathering supposed to be the major geological contributor, in contrast to bicarbonate weathering does a little. Distribution coefficient for dissolved metals and sorbed to surface sediments is in the order of Cd?>?Pb?>?Fe?>?Zn?>?Cu?>?Cr?>?Mn. Speciation study of monitored metals in surface sediments shows that Fe and Mn are dominantly fractionated in exchangeable-acid reducible form, whereas rest of the metals (Cr, Pb, Cd, Zn, and Cu) mostly in residual form. Cd, Pb, and Zn show relatively higher recalcitrant factor that indicates their higher retention in lake sediments. Factor loading of monitored physico-chemical parameters resembles contribution/influences from geological weathering, anthropogenic inputs as well as natural temporal factors. Ionic load/strength of lake water accounted for geochemical process and natural factors, while pollutant load (viz BOD, COD and metals, etc.) is associated with anthropogenic inputs through industrial discharge.  相似文献   

3.
In the old mining area of Rodalquilar, mine wastes, soil and sediments were characterized and the results revealed high concentration of Au, Ag, As, Bi, Cu, Fe, Mn, Pb, Se, Sb and Zn in tailings and sediments. The contaminant of greatest environmental concern is As. The mean concentration in the tailings was 679.9, and 345 mg/kg in the sediments of Playazo creek. The groundwater samples from the alluvial aquifer showed high concentration of Al, As, Cd, Fe, Hg, Mn, Ni, Pb, Se, Sb and Zn and very high concentration of chloride and sulfate, which were above the concentration defined in the European standards for drinking water. The presence of As in groundwater may be caused by the oxidation of arsenian pyrite, the possible As desorption from goethite and ferrihydrite and the jarosite dissolution. Groundwater concentrations of Cd, Fe, Mn, and possibly Cu, were associated with low values of Eh, indicating the possible dissolution of oxy-hydroxides of Fe and Mn. The mobility of metals in the column experiments show the release of Al, Fe, Mn, Cr, Cu, Ni, V and Zn in significant concentrations but below the detected values in groundwater. However, As, Cd, Sb, Se Pb and Au, are generally mobilized in concentrations above the detected values in groundwater. The possible mass transfer processes that could explain the presence of the contaminants in the aquifer and the leachates was simulated with the PHREEQC numerical code and revealed the possible dissolution of the following mineral phases: jarosite, natrojarosite, arsenian pyrite, alunite, chlorite, kaolinite and calcite.  相似文献   

4.
A 24-cm long sediment core from an oxic fjord basin in Ranafjord, Northern Norway, was sliced in 2 cm sections and analysed for As, Co, Cu, Ni, Hg, Pb, Zn, Mn, Fe, ignition loss and Pb-210. Partitioning of metals between silicate, non-silicate and non-detrital phases was assessed by leaching experiments, in an attempt to understand the mechanisms of surface metal enrichment in sediments. Relative to metal concentrations in sediments deposited in the 19th century, metals in near surface sediments were enriched in the following order: Pb > Mn > Hg > Zn > Cu > As > Fe. Cobalt and Ni showed no enrichment. The non-detrital fraction of Cu, Pb, Mn and Zn was significantly higher in the upper 10 cm than at greater depth in the core. This corresponds to sediments deposited since 1900, when mining activities started in the area. The enrichment of Cu, Pb and Zn is assumed to be mainly a result of mining, while Mn is apparently enriched in the surface due to migration of dissolved Mn and precipitation in the oxic surface layer. Elevated concentrations of As and Fe in the upper 4 cm are presumably due to discharges from a coke plant and an iron works respectively. The excess Hg present in the near surface sediments is tightly bound, either in coal particles or ore dust introduced by local industry, or via long distance transport of atmospheric particles. Calculations of metal flux to the sediments indicate an anthropogenic flux of Zn equal to its natural flux, while the flux of Pb shows a threefold increase above natural input.  相似文献   

5.
 The concentrations of various metals (Cr, Cu, Co, Fe, Mn, Ni, Pb, Zn, and Cd) were determined in recently deposited surface sediments of the Gomati River in the Lucknow urban area. Markedly elevated concentrations (milligrams per kilogram) of some of the metals, Cd (0.26–3.62), Cu (33–147), Ni (45–86), Pb (25–77), and Zn (90–389) were observed. Profiles of these metals across the Lucknow urban stretch show a progressive downstream increase due to additions from 4 major drainage networks discharging the urban effluents into the river. The degree of metal contamination is compared with the local background and global standards. The geoaccumulation index order for the river sediments is Cd>Zn>Cu>Cr>Pb. Significant correlations were observed between Cr and Zn, Cr and Cu, Cu and Zn and total sediment carbon with Cr and Zn. This study reveals that the urbanization process is associated with higher concentrations of heavy metals such as Cd, Cu, Cr, Pb, and Zn in the Gomati River sediments. To keep the river clean for the future, it is strongly recommended that urban effluents should not be overlooked before their discharge into the river. Received: 16 February 1996 · Accepted: 29 February 1996  相似文献   

6.
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   

7.
The technique of diffusive gradients in thin films (DGT) was applied to obtain high-resolution vertical profiles of trace metals in sediment porewater of a eutrophic lake, Lake Chaohu. All sampling sediments were under anaerobic conditions with Eh values below 0, the redox potential profile in M4 was relatively stable, and higher Eh values in M4 than that in M1 were observed due to hydrodynamic effects. Fe, Mn and As exhibited closely corresponding profiles due to the co-release of Fe and Mn oxides and the reduction of As. Higher Fe and Mn concentrations and lower As concentrations were observed in M1 of the western half-lake than those in M4 of the eastern half-lake due to different sources and metal contamination levels in the two regions. Cu and Zn showed increasing concentrations similar to Mn and Fe at 1–2 cm depth of sediments, while DGT measured Co, Ni, Cd and Pb concentrations decreased down to 3–4 cm in the profiles. Co, Ni, Cu, Zn, Cd and Pb showed insignificant regional concentration variances in the western and eastern half-lakes. According to the R(C DGT/C centrifugation) values, the rank order of metal labilities decrease as follows: Fe (>1) > Cu, Pb, Zn (>0.9) > Co, Ni, Cd (>0.3) > Mn, As (>0.1).  相似文献   

8.
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   

9.
In order to assess the pollution levels of selected heavy metals, 45 bottom sediment samples were collected from Al-Kharrar lagoon in central western Saudi Arabia. The concentrations of the heavy metals were recorded using inductively coupled plasma-mass spectrometer (ICP-MS). The results showed that the concentrations of Pb and Cd exceeded the environmental background values. However, the heavy metal contents were less than the threshold effect level (TEL) limit. The concentrations of heavy metals in lagoon bottom sediments varied spatially, but their variations showed similar trends. Elevated levels of metals were observed in the northern and southern parts of the lagoon. Evaluation of contamination levels by the sediment quality guidelines (SQG) of the US-EPA revealed that sediments were non-polluted-moderately to heavily polluted with Pb; non-polluted to moderately polluted with Cu; and non-polluted with Mn, Zn, Cd, and Cr. The geoaccumulation index showed that lagoon sediments were unpolluted with Cd, Mn, Fe, Hg, Mo, and Se; unpolluted to moderately polluted with Zn and Co; and moderately polluted with Pb, Cr, Cu, and As. The high enrichment factor values for Pb, As, Cu, Cr, Co, and Zn (>2) indicate their anthropogenic sources, whereas the remaining elements were of natural origins consistent with their low enrichment levels. The values of CF indicate that the bottom sediments of Al-Kharrar lagoon are moderately contaminated with Mn and Pb.  相似文献   

10.
A sediment core collected from coastal zone near the Qiao Island in the Pearl River Estuary was analyzed for total metal concentrations, chemical partitioning, and physico-chemical properties. Three vertical distribution patterns of the heavy metals in the sediment core were identified, respectively. The dominant binding phases for Cu, Pb, Cr, and Zn were the residual and Fe/Mn oxides fractions. Cd in all sediments was mainly associated with exchangeable fraction. Influences of total organic carbon content and cation exchange capacity on the total concentrations and fractions of almost all the metals were not evident, whereas sand content might play an important role in the distributions of residual phases of Cr, Cu, Pb, and Zn. In addition, sediment pH had also an important influence on the Fe/Mn oxides, organic/sulfide and residual fractions of Cr, Cu, and Zn. Contamination assessment on the heavy metals in the sediment core adopting Index of Geoaccumulation showed that Cr, V, Be, Se, Sn, and Tl were unpolluted, while Cu, Ni, Pb, Zn, Cd, and Co were polluted in different degrees throughout the core. It was remarkable that the various pollution levels of the metals from moderate (for Cu, Pb, and Zn) to strong (for Cd) were observed in the top 45 cm of the profiles. The relative decrease of the residual fraction in the upper 45 cm of the core is striking, especially for Zn and Cu, and, also for Pb, and Cr. The change in fraction distribution in the upper 45 cm, which is very much contrasting to the one at larger depths, confirms that the residual fraction is related to the natural origin of these metals, whereas in the upper part, the non-residual fractions (mainly the Fe/Mn oxides fraction) are increased due to pollution in the last decade. The possible sources for Cu, Pb, Zn, and Cd contaminations were attributed to the increasing municipal and industrial wastewater discharges, agricultural runoff, atmospheric inputs, and runoff from upstream mining or smelting activities, which may be associated with an accelerating growth of economy in the Pearl River Delta region in the past decade.  相似文献   

11.
In this research, we have worked on the evaluation of heavy metal contamination in the sediments taken from the intertidal zone of Asaluyeh region using Modified Community Bureau of Reference sequential extraction method (mBCR), the simplified bioaccessibility extraction test (SBET), and calculated enrichment factor (EF). Also, potential influencing factors including sediment characteristics that may affect the heavy metals bioavailability and bioaccessibility were investigated. mBCR extraction analysis indicated that among the metals, Mn, Zn, V, Cu, and Cd exhibit relatively higher mobility, while Ti, Pb, Cr, and Ni occur mainly in the residual fractions. Based on the mean values, the bioaccessibility of metals decreased in the order: Mn (50.01%)>Cd (46.26%)>Zn (14.61%)>V (13.97%)>Pb (10.88%)>Ni (9.2%)>Ti (8.43%)>Cr (6.66%)>Cu (6.23%). The obtained results from the principal component analysis (PCA), EF and mBCR extraction showed that most anthropogenic-derived metals with higher solubility are more bioaccessible compared to those of natural origin. Multiple linear regression analysis demonstrated that the main physicochemical variables of the sediment influencing the bioaccessibility of metals include cation exchange capacity (CEC), pH, and particle size fraction.  相似文献   

12.
The concentration of trace metals like Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn were studied in beach and estuarine sediments of the Velanganni Coast, South East coast of India to understand metal pollution due to urbanization/industrialization. This area was affected by the urbanization activity like untreated effluent discharge, transportation and incineration of solid waste, etc. In this context, quality of the sediments was evaluated based on the enrichment factor, geo-accumulation index (Igeo), pollution load index, and sediment quality guidelines. Furthermore, correlation matrix and principal compound analyses have been performed with SPSS 7.5 statistical software. The result illustrated that the metal enrichment is in the following order: Cd > Cr > Ni > Zn > Pb > Mn > Cu. The level of Igeo suggests that Cd has moderately polluted the sediment class. Similarly, principal component analysis showed that Cd and Pb accounted for the anthropogenic pollution, but Pb inferred as its tracers level. The results strongly indicate anthropogenic sources for moderate input of Cd contamination in to Velanganni coastal sediments.  相似文献   

13.
A sequential extraction method was employed to extract the metals Al, Ag, Cd, Co, Cr, Cu, Pb, Fe, Li, Mn, Ni, and Zn from a 10-m sediment core taken from the Tilbury Basin on the Thames Estuary. Characteristics of the observed metal partitioning distributions were attributed primarily to the composition of the estuarine waters at the time of deposition. For some metals, a decrease in the bulk sediment metal concentrations from a depth of ?6.59 m ODN to the surface was also observed in one of the solid phases. This was the case for Cr, Cu, and Pb extracted from the organic phase and for Zn extracted from the carbonate phase. This decrease in sediment concentrations is thought to reflect reported improvements to water quality in this region of the Thames Estuary in the early 1960s, following updating of major sewage treatment works (STW) approximately 20 km upstream. These findings give an indication of the influence of estuarine inputs from STW on metal partitioning distributions. The order of mobility for the metals of environmental concern was Cd>Ag>Cr>Ni, Zn>Co, Cu, Pb. for Cd and Ag there was a tendency to partition towards the exchangeable phase, both at the surface and at depth, which indicates the potential for long-term leaching of these metals from the sediments.  相似文献   

14.
The concentrations of Cd, Cu, Mn, Ni, Pb, Fe and Zn were determined in superficial sediments extracted from nine zones of Budi Lagoon, located in the Araucanía Region (Chile). The concentrations of these metals were determined by flame atomic absorption spectroscopy and the method was validated using certified reference material (marine sediment). The concentration ranges found for the trace elements were: Pb < 0.5; Cd < 0.2–3.9; Cu 21.8–61.9; Ni 31.2–59.4; Zn 54.5–94.8 mgkg?1 (dry weight). The elements that registered the highest concentrations were Mn 285.4–989.8 mgkg?1 and Fe 4.8–10.6 %. The lagoon cluster analysis of the stations was divided into three groups (Temo station with high Cu and low Mn concentrations, Bolleco, Comué, Allipén and Deume 3 stations presented highest Cd concentration, and another group Botapulli, Río Budi, Deume 2 and Deume 1 stations presented low levels of Cd). The textural characteristics of the sediment were determined (gravel, sand and mud) and the results were correlated with the concentrations of the metals in the various study zones. The sediments of Budi Lagoon presented high levels of Fe and Mn, which are of natural origin and exceed the maximum values recorded by many authors. With respect to the recorded concentrations for Cd, Cu, Ni and Zn, are within the ranges published by other authors in similar works. The Pb element was not detected. The results were subjected to statistical analysis to evaluate the correlations between the content of the elements and obtain the site of sediment.  相似文献   

15.
Assessment of heavy metal pollution in surface water   总被引：4，自引：3，他引：1  
A total of 96 surface water samples collected from river Ganga in West Bengal during 2004–05 was analyzed for pH, EC, Fe, Mn, Zn, Cu, Cd, Cr, Pb and Ni. The pH was found in the alkaline range (7.21–8.32), while conductance was obtained in the range of 0.225–0.615 mmhos/cm. Fe, Mn, Zn, Ni, Cr and Pb were detected in more than 92% of the samples in the range of 0.025–5.49, 0.025–2.72, 0.012–0.370, 0.012–0.375, 0.001–0.044 and 0.001–0.250 mg/L, respectively, whereas Cd and Cu were detected only in 20 and 36 samples (0.001–0.003 and 0.003–0.032 mg/L). Overall seasonal variation was significant for Fe, Mn, Cd and Cr. The maximum mean concentration of Fe (1.520 mg/L) was observed in summer, Mn (0.423 mg/L) in monsoon but Cd (0.003 mg/L) and Cr (0.020 mg/L) exhibited their maximum during the winter season. Fe, Mn and Cd concentration also varied with the change of sampling locations. The highest mean concentrations (mg/L) of Fe (1.485), Zn (0.085) and Cu (0.006) were observed at Palta, those for Mn (0.420) and Ni (0.054) at Berhampore, whereas the maximum of Pb (0.024 mg/L) and Cr (0.018 mg/L) was obtained at the downstream station, Uluberia. All in all, the dominance of various heavy metals in the surface water of the river Ganga followed the sequence: Fe > Mn > Ni > Cr > Pb > Zn > Cu > Cd. A significant positive correlation was exhibited for conductivity with Cd and Cr of water but Mn exhibited a negative correlation with conductivity.  相似文献   

16.
The concentrations and speciation of heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) in the sediments of the nearshore area, river channel and coastal zones of the Yangtze estuary, China, were systematically investigated in this study. The concentrations of all heavy metals except Ni in the sediments of the nearshore area were higher than those of the river channel and coastal zones. In the nearshore area, the concentrations of most heavy metals except Hg in the sediments of the southern branch were higher than those of the northern branch because of the import of pollutants from the urban and industrial activities around. When compared with the threshold effect level (TEL) and geochemical background levels, Cr, Ni and As accumulated and posed potential adverse biological effects. The speciation analysis suggested that Cd, Pb and Zn in the sediments of the three zones showed higher bioavailability than the other heavy metals, and thus posed ecological risk. Significant correlations were observed among Cr, Cu, Ni and Zn (r > 0.77) in the nearshore area, Ni, Cu, Zn and Pb (r > 0.85) in the river channel and Ni, Cu, Cr, Pb and Zn (r > 0.75) in the coastal zone. Principal component analysis (PCA) indicated that the discharge of unban and industrial sewage, shipping pollution and the properties of the sediments (contents of Fe, Mn, Al, TOC, clay and silt) dominated the distribution of heavy metal in the nearshore area, river channel and coastal zones of the Yangtze estuary.  相似文献   

17.
《Applied Geochemistry》2000,15(6):807-817
The concentrations of major and trace elements were determined (aqua regia leach and ICP-AES analyses) in stream, lake and dredged sediments downstream of the historical Antskog iron- and copperworks, S.Finland. The levels of Ag, Cd, Cu, Pb and Zn are highly elevated in all studied sediment types: roughly half of the studied lake-sediment samples contain >5 ppm Ag, >15 ppm Cd, >0.1% Cu, >0.1% Pb and >0.3% Zn. In the dredged sediment material located onshore, the concentrations of Ag, Cu and Pb are comparable to those in the polluted lake-sediment samples, while in stream sediments elevated metal concentrations are found especially in samples characterised by high concentrations of organic material. The source of the elevated metal concentrations is the historical metalworks at Antskog, mainly the copperworks of the 19th century. Compared to the limit values for contaminated soils in Finland, the concentrations of Cu, Pb and Zn are on average elevated by factors >10 in the polluted horizons of lake sediments, >5 in the dredged sediment located onshore and >2 at the most heavily contaminated site in the stream. Since the surface waters in the area are used for agricultural purposes and for various leisure activities, it is necessary to make further detailed investigations into the extent of the metal pollution and to determine species, mobility and bioavailability of the metals.  相似文献   

18.
The interaction between heavy metals and river sediment is very important because river sediment is the sink for heavy metals introduced into a river and it can be a potential source of pollutants when environmental conditions change. The Kumho River, the main tributaries of the Nakdong River in Korea, can be one of the interesting research targets in this respect, because it runs through different geologic terrains with different land use characteristics in spite of its short length. Various approaches were used, including mineralogical, geochemical, and statistical analyses to investigate the distribution and behavior of heavy metals in the sediments and their sources. The effect of geological factor on the distribution of these metals was also studied. No noticeable changes in the species or relative amounts of minerals were observed by quantitative X-ray diffraction in the sediments at different stations along the river. Only illite showed a significant correlation with concentrations of heavy metals in the sediments. Based on an average heavy metal concentration (the average concentrations of Cd, Co, Cr, Cu, Ni, Pb, and Zn were 1.67, 20.9, 99.7, 125, 97.6, 149, 298 ppm, respectively), the sediments of the Kumho River were classified as heavily polluted according to EPA guidelines. The concentrations of heavy metals in the sediments were as follows: Zn > Pb > Cu > Ni > Cr > Co > Cd. In contrast, contamination levels based on the average I geo (index of geoaccumulation) values were as follows: Pb > Cd > Zn > Cu > Co = Cr > Ni. The concentrations of heavy metals increased downstream (with the exception of Cd and Pb) and were highest near the industrial area, indicating that industrial activity is the main factor in increasing the concentrations of most heavy metals at downstream stations. Sequential extraction results, which showed increased heavy metal fractions bound to Fe/Mn oxides at the downstream stations, confirmed anthropogenic pollution. The toxicity of heavy metals such as Ni, Cu, and Zn, represented by the exchangeable fraction and the fraction bound to carbonate, also increased at the downstream stations near the industrial complexes. Statistical analysis showed that Pb and Cd, the concentrations of which were relatively high at upstream stations, were not correlated with other heavy metals, indicating other possible sources such as mining activity.  相似文献   

19.
This study concerns the mineralogy, spatial distribution and sources of nine heavy metals in surface sediments of the Maharlou saline lake, close to the Shiraz metropolis in southern Iran. The sources for these sediments were studied by comparing the mineralogy and the distribution of heavy metals, using multivariate statistical analysis (correlation analysis and principal component analysis). The geochemical indices, including geo-accumulation index (Igeo), contamination factor (CF) and pollution load index (PLI), were used to assess the degree of heavy metal contamination in surface sediments. Sediment quality guidelines (SQGs) have also been applied to assess its toxicity. The XRD analysis shows that the main minerals of the surface sediments are aragonite, calcite, halite and quartz, with small amounts of montmorillonite, dolomite and sepiolite. The total heavy metal contents in surface sediments decrease in order of Sr?>?Ni?>?Cr?>?Zn?>?Cu?>?Co?>?Pb?>?As >?Cd and the average concentrations of Sr, Ni and As exceeded more than 10, 5 and 3 times, respectively, by comparing with the normalized upper continental crust (UCC) values. The results of pollution indices (Igeo, CF and PLI) revealed that strontium (Sr), nickel (Ni) and arsenic (As) were significantly enriched in those sediments. Based on the sediment quality guidelines (SQGs), Ni would infrequently cause toxicity. Multivariate statistical analysis indicated that the Ni, Co and Cr came mainly from natural geological background sources, while Cd, Cu, Pb, and Zn were derived from urban effluents (especially traffic emissions) and As originated from agriculture activities. Significant relationships of Sr with S, CaO and MgO in sediments suggest that Sr was derived from carbonate- and gypsum-bearing catchment source host rocks.  相似文献   

20.
Thirty-three bottom sediments were collected from the Potomac and Anacostia rivers, Tidal Basin, and Washington Ship Channel in June 1991 to define the extent of trace metal contamination and to elucidate source areas of sediment contaminants. In addition, twenty-three sediment samples were collected directly in front of and within major storm and combined sewers that discharge directly to these areas. Trace metals (e.g., Cu, Cr, Cd, Hg, Pb, and Zn) exhibited a wide range in values throughout the study area. Sediment concentrations of Pb ranged from 32.0 μg Pb g?1 to 3,630 μg Pb g?1, Cd from 0.24 μg Cd g?1 to 4.1 μg Cd g?1, and Hg from 0.13 μg Hg g?1 to 9.2 μg Hg g?1, with generally higher concentrations in either outfall or sewer sediments compared to river bottom-sediments. In the Anacostia River, concentration differences among sewer, outfall, and river sediments, along with downriver spatial trends in trace metals suggest that numerous storm and combined swers are major sources of trace metals. Similar results were observed in both the Tidal Basin and Washington Ship Channel. Cadminum and Pb concentrations are higher in specific sewers and outfalls, whereas the distribution of other metals suggests a more diffuse source to the rivers and basins of the area. Cadmium and Pb also exhibited the greatest enrichment throughout the study area, with peak values located in the Anacostia River, near the Washington Navy Yard. Enrichment factors decrease in the order: Cd>Pb>Zn>Hg>Cu>Cr. Between 70% and 96% of sediment-bound Pb and Cd was released from a N2-purged IN HCl leach. On average, ≤40% of total sedimentary Cu was liberated, possibly due to the partial attack of organic components of the sediment. Sediments of the tidal freshwater portion of the Potomac estuary reflect a moderate to highly components area with substantial enrichments of sedimentary Pb, Cd, and Zn. The sediment phase that contains these metals indicates the potential mobility of the sediment-bound metals if they are reworked during either storm events or dredging.  相似文献   

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