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1.
Total concentrations of chemical elements in soils may not be enough to understand the mobility and bioavailability of the elements. It is important to characterise the degree of association of chemical elements in different physical and chemical phases of soil. Another geochemical characterisation methodology is to apply sequential selective chemical extraction techniques. A seven-step sequential extraction procedure was used to investigate the mobility and retention behaviour of Al, Fe, Mn, Cu, Zn, Pb, Cr, Co, Ni, Mo, Cd, Bi, Sn, W, Ag, As and U in specific physical–chemical and mineral phases in mine tailings and soils in the surroundings of the abandoned Ervedosa mine. The soil geochemical data show anomalies associated with mineralised veins or influenced by mining. Beyond the tailings, the highest recorded concentrations for most elements are in soils situated in mineralised areas or under the influence of tailings. The application of principal components analysis allowed recognition of (a) element associations according to their geochemical behaviour and (b) distinction between samples representing local geochemical background and samples representing contamination. Some metal cations (Mn, Cd, Cu, Zn, Co, Cr, Ni) showed important enrichment in the most mobilisable and bioavailable (i.e., water-soluble and exchangeable) fractions due likely to the acidic conditions in the area. In contrast, oxy-anions such as Mo and As showed lower mobility because of adsorption to Fe oxy-hydroxides. The residual fraction comprised largest proportions of Sn and Al and to a lesser extent Zn, Pb, Ni, Cr, Bi, W, and Ag, which are also present at low concentrations in the bioavailable fractions. The elements in secondary mineral phases (mainly Fe, Mn, Cu, Zn, Cd, Pb, W, Bi, Mo, Cr, Ni, Co, As and U) as well as in organic matter and sulphides are temporarily withheld, suggesting that they may be released to the environment by changes in physico-chemical conditions.  相似文献   

2.
Twelve soil profiles and 62 soil cores were described from two neighboring landscapes in the northwest of Iran to understand whether long-term wastewater irrigation has caused variations in morphological, physicochemical, and DTPA-heavy metals contents in soils. Along a gradual slope, different positions reflected heterogeneous response to flooding wastewater irrigation. Upper slope and mainly midslope were subject to gradual soil loss as characterized by thin Ap-horizons and shallow soil depth, whereas periodic cycles of soil accumulation and sediment along with local reducing condition were highlighted in lower slope. Compared to different positions of control land, wastewater irrigation increased significantly (P????0.05) soil fertility attributes (N, P, K, and organic matter) along with electrical conductivity. Significant correlations were observed between soil fine particles fraction and available P and also with available K, indicating that spatial distribution pattern of these elements is mainly dependent on distribution of the <0.002?mm fractions along the landscape as it is affected by wastewater irrigation. Midslope position was found to be more degraded compared to the other position regarding soil loss and available nutrients (N, P, and K) as a result of the processes of soil redistribution and soil transport in wastewater irrigation system. Mean concentrations of DTPA-extractable Zn, Cu, Cd, and Pb in the different geomorphological positions were 3.8?C7.8, 2.5?C3, 3?C4, and 1.7?C3.5 times greater, respectively, when compared to the adjacent control soil. With the exception of lower slope position, which indicated a remarkable increasing pattern of smectite in response to wastewater irrigation and unfavorable drainage condition, the relative abundances of clay minerals in view of the peak position and intensity followed almost the same pattern in both wastewater-irrigated and control landscape.  相似文献   

3.
Irrigation by treated wastewater (TWW) can pollute the soil by different organic and inorganic compounds. The pollution level can depend on the irrigation period, soil nature, and wastewater characteristics. Since 1989, the Zaouit Sousse area (central Tunisian) has been irrigated by treated wastewater. The irrigation period and the mineralogy of soil composition change from one locality to another in Zaouit Sousse area. In this work, we are interested in organic compounds, polycyclic aromatic hydrocarbons (PAHs), and heavy metals (HMs) evolution. One control soil (S1) and four irrigated areas soil (S2, S3, S4, and S5) were chosen. The soil samples differ by the irrigation period and soil characteristics. Total PAHs content in control soil was 66.2 ng?g?1 and in irrigated areas were between 46.23 and 129.51 ng?g?1. The PAHs content in irrigated soil, except S5 which has been irrigated with wastewater for 20 years and contains the highest clay fraction percent, decreased with the irrigation period (from 0 to 20 years). The microbial degradation may decrease the PAHs concentrations in the soil thanks to bacterium brought by TWW and the important soil permeability. Concentration of heavy metals ranged from 24 to 1,320 μg?L?1. The HMs (Cu, Cr, Zn, Fe, Ni, Pb, and Cd) contents decreased with the irrigation period (from 10 to 20 years). So, following the PAHs aerobic bio-degradation, this organic compound discharges their absorbed heavy metals which leached to deeper levels. The Cr, Cu, Al, Zn, and Cd mobility depend on the clay yield too. However, the PAHs and Pb mobility are also related to humic substance quantities. Cr and Cu have affinities both to clay and humic substance quantities.  相似文献   

4.
Sequential core sediments from northwestern Taihu Lake in China were analyzed for grain size, organic carbon and heavy metal content. The sediments are composed of organic-poor clayey-fine silts. The chemical speciations of Cu, Fe, Mn, Ni, Pb, and Zn were also analyzed using the BCR sequential extraction procedure. Cu, Fe, Ni, and Zn are mainly associated with the residue fraction; Mn is concentrated mainly in exchangeable/carbonate fraction and residue fraction; and Pb mainly in Fe/Mn oxide fraction and organic/sulfide fraction. The exchangeable/carbonate fractions of Cu, Fe, Ni, Zn and Pb are lower. The fractions of Ni, Pb and Zn bound to the Fe/Mn oxide have significant correlations with reducible Mn; the organic/sulfide fractions of Cu, Mn, Ni, Pb, and Zn have significant correlations with TOC. The extractable fractions of Cu, Mn, Ni, Pb, and Zn are high at the top 4 cm of the core sediments as compared to those in the deeper layers, showing the anthropogenic input of heavy metals is due to rapid industrial development. The heavy metal pollution history of the sediments has been recorded since the late 1970s, determined by the result of ^137Cs dating.  相似文献   

5.
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   

6.
The long-term impact of irrigation on a Mediterranean sandy soil irrigated with treated wastewater (TWW) since 1980 was evaluated. The main soil properties (CEC, pH, size distribution, exchangeable cations and chloride, hydraulic conductivity) as well as the organic matter and Cu, Cr and Pb speciation in an irrigated soil and a non-irrigated control soil at various soil depths were monitored and compared during a 2 year experiment. In this second part, we focused on Cu, Cr and Pb behaviour in relation with soil organic carbon (SOC). Soil samples were collected every 3 months during 2 years at the depths 0–20, 20–40 and 40–60 cm and were analysed for exchangeable and total metals, organic carbon content, metal sequential extraction and humic substances – Humic Acids (HA), Fulvic Acids (FA) and Non-Humified Fraction (NHF). Long-term irrigation with a domestic treated wastewater (TWW) may be considered safe with regard to trace metal accumulation in soil. Irrigation lowered the HA and NHF fractions of SOC and made the FA fraction more mobile. Cu bound preferentially to the SOC fraction, Cr was found mainly in the reducible fraction and Pb was bound to all fractions indiscriminately. Cu exhibited a high affinity for the HA fraction, while Pb and Cr had a high affinity for the FA fraction, which indicates a greater mobility of the organically-bound Pb and Cr than of the organically-bound Cu. Evaluation of the potential metal mobility has to take into account not only the usual speciation between labile, reducible and oxidisable fractions, but also the nature of the SOC responsible for the oxidisable fraction.  相似文献   

7.
The impact of waste disposal on trace metal contamination was investigated in eleven wetlands in the Lake Victoria Basin. Samples of soil, water and plants were analysed for total Zn, Cu, Pb and Ni concentrations using flame atomic absorption spectrophotometry. The trace metal concentrations in soil were the highest in Katanga wetland with the highest mean concentrations of 387.5±86.5 mg/kg Zn, 171.5±36.2 mg/kg Pb, 51.20±6.69 mg/kg Cu and 21.33±2.23 mg/kg Ni compared to the lowest levels observed at Butabika (30.7±3.2 mg/kg Zn, 15.3±1.7 mg/kg Pb, 12.77±1.35 mg/kg Cu and 6.97±1.49 mg/kg Ni). Katanga receives waste from multiple industrial sources including a major referral city hospital while Butabika is a former solid waste dumpsite. Wetland soil near a copper smelter had a Cu concentration of 5936.3±56.2 mg/kg. Trace metal concentrations in industrial effluents were above international limits for irrigation water with the highest concentrations of 357,000 μg/L Cu and 1480 μg/L Zn at a Cu smelter and 5600 μg/L Pb at a battery assembling facility compared to the lowest of 50 μg/L Cu and 50 μg/L Zn in water discharged from Wakaliga dumpsite. Uptake of trace metals from soil differed from plant to plant and site to site. Higher levels of trace metals accumulated in the root rather than in the rhizome and the least amount was in the leaf. The study identifies industry as a potential source of trace metal contamination of water and the environment pent-up need for policy intervention in industrial waste management.  相似文献   

8.
The influence of metals, Cd, Cr, Cu, Ni, Pb and Zn, on the microbial biomass and enzyme activities of an amended acid lateritic soil were investigated under field conditions receiving a one-time application of 52 t ha–1 of sludge, coal ash and their mixtures at 1:3, 1:1 and 3:1 proportions, and including control and chemical fertilizer treatment at crop-specific recommended doses. Paddies and peanuts were grown in the experimental plots and soil was sampled twice after 6 months and 1 year after amendment application. The heavy metals in the soil were fractionated using sequential extraction and the increments in their concentrations in amended soil with respect to the control were determined. Concentrations of Cd, Ni and Zn were determined to have increased in their mobile fractions and were more pronounced in soil collected during the second sampling, which was associated with a decrease in soil organic carbon. The size of the microbial biomass carbon and the soil enzyme activities increased with the addition of an amendment and was highest at equal proportions of coal ash and sludge. Further increase in the proportion of sludge resulted in a significant decrease in biomass carbon. Simple correlation revealed significant and strong negative relations of mobile fractions of Cd and Ni with the ratio between microbial biomass C and organic carbon in soil, while the organic carbon content and the pH were positively correlated. The microbial activities were determined to be sensitive to the concentrations of some heavy metals in mobile fractions and therefore indicated possibilities of being useful as indicators for evaluation of toxic effects of sludge-borne metals on soil organisms.  相似文献   

9.
This study investigated the organic carbon, reduced inorganic sulfur, and heavy metal distribution in superficial sediments at an estuary, a wastewater discharge area, and a mariculture area, as compared with an unpolluted distal site, in the north Yellow Sea, China. Sediment grain size, acid volatile sulfur (AVS), chromium (II)-reducible sulfur, elemental sulfur, total sulfur, total organic carbon (TOC), total nitrogen and trace metal content were determined for each site. These results indicate that pollution leads to increased TOC at all affected sites, which in turn leads to elevated AVS. The resultant change in diagenetic environment leads to changes in the mineralogical fate of Mn. Pb, Zn, Cu, and Cd: all are present at elevated concentrations, and with more metal in the non-residual fractions. Cd shows by far the most elevated concentrations and most significant increase in non-residual fractions and consequently poses the most significant pollution risk.  相似文献   

10.
The objectives of the current study were to determine the chemical partitioning of Pb, Ni, Zn, Co, Cr, Mn, Fe and Cd using sequential extraction procedure and to assess the environmental risk associated with these metals in the farming soils along Zerqa River. Metal concentrations were measured by atomic absorption spectrophotometer. The study area demonstrated a wide range for pH, organic matter, carbonate contents, and cation exchange capacity, and is polluted with Pb, Cd, Mn, and Cu. The extensive use of fertilizers and pesticides in the agricultural activities, and discharge of treated and untreated wastewater are the major sources of pollution in the study area. Principal component analysis coupled with Pearson’s correlation analysis between the heavy metals revealed strong and positive correlation between these metals in the study area. According to the Risk Assessment Code (RAC), major portions of Cd and Mn are contained in exchangeable and carbonates fractions and therefore can easily enter the food chain. These metals pose a high to very high risk to the environment. Cu, Ni, Pb, and Zn pose medium risk, while Cr poses a low environment risk.  相似文献   

11.
Several samples of groundwater and soils and plants have been collected from Sohar (Batina region, NE Oman), which is affected by various activities such as mining, agriculture, and sewage. To characterize quality of groundwater, As and Cu concentrations have been investigated in waters collected from different wells. Comparison of data with local and international standard values revealed that groundwater in Sohar region is characterized by lower concentrations in Cu and As compared with standards. In soils collected from the same area, concentrations of heavy metals have been measured in different fractions in order to investigate the mobility of such elements and risk of vulnerability in this area. A sequential extraction procedure has been applied to surface sediments to determine the partitioning of Zn, Cu, Co, Mn, Fe, Pb, Cr, Cd and Ni among (1) exchangeable and acid-soluble phases, (2) Fe–Mn oxides, (3) organic matter and sulphides and (4) resistant phases. The results showed that the mobile fraction in the sewage area accounts only for 10 % of the total concentration in sediments while in the Cu mining area, the contribution of the mobile fraction may exceed 10 %, especially for Pb, Mn, Cd, Cu and Co. Investigation of concentrations in As and Cu in plants collected from mining and sewage areas revealed an important accumulation of these elements in leaves and may explain enrichment of As in shallow groundwater relative to deep groundwater. This investigation also showed that Cu is more available in sewage area than in mining zone, as opposed to As.  相似文献   

12.
对拜仁达坝铅锌矿矿集区3个多金属矿区的3个土壤粒级样品中Zn、Pb、Cu、Ag 4种主要成矿元素的7种赋存形式(水溶态、离子交换态、碳酸盐结合态、有机质结合态、铁锰氧化物结合态、硫化物结合态和残渣态)进行了测定。研究结果表明:1银都矿区土壤中Zn、Pb和Ag浓度最高,而道伦达坝矿区土壤中Cu的浓度最高;2拜仁达坝矿集区土壤中Zn、Pb和Cu主要以残渣态形式赋存,而Ag主要以铁锰氧化物结合态和硫化物结合态形式赋存;3拜仁达坝矿集区Zn、Pb和Cu元素在3个土壤粒级中的各个赋存形式所占的比例略有差别,但总体上大致相同,而Ag元素的赋存状态在3个土壤粒级的差异较大;4 3个矿区土壤中水溶态、离子交换态、碳酸盐结合态和有机质结合态的Zn和Pb差别不大;铁锰氧化物结合态、硫化物结合态和残渣态的Zn和Pb,以及Cu和Ag的7个赋存状态在3个矿区的差别较大。  相似文献   

13.
Soils and selected edible plants of the Noun river catchment basin of western Cameroon were sampled to investigate the distribution of trace elements, based on the preliminary idea of unusual anomalies. Analytical techniques for trace elements included ICP-AES, GF-AAS, and ICP-MS. Further soil analyses comprised the mineralogy and contents of the biogenic elements carbon, nitrogen and sulphur (CNS). The trace element concentrations in the soils reflect those of the lithogeochemical background of the pluto-volcanic rocks of the region. This is consistent with the results from the mineralogical analyses and physicochemical parameters such as pH, taken in the field, which also do not suggest any geochemical anomaly. Most trace elements analyzed in the plants showed concentrations that reflect those of the soils (Al, Fe, Ti, and Rb). However, some trace elements were enriched in the plants as compared to the soils, such as Zn, Cu, Cd, Mo (excluding yam), Ni (peanut), Ba (peanut), Sr (peanut, bean), and B. Trace elements such as As, Cr, V, and Se were not bioavailable for all the analyzed plants. Besides, trace elements such as Cu, Zn, Mo, Fe, Al, Ni, B, Ti, Rb, Cs, and Ba were in the range of phytotoxicity and reached or exceeded human food tolerance level (Cu). The plants with seeds showed a higher absorption of trace elements compared to plants with tubercles.  相似文献   

14.
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   

15.
The seasonal variation in the trace metals’ concentrations (Cd, Co, Cu, Fe, Mn, Ni, Pb, and Zn) were investigated in surface sediments of the Pandoh Lake. The horizontal distribution of TC, TN, and TP reflects spatial and temporal differences in sedimentary organic production. The chemical sequential extraction of heavy metals was carried out by seven-step fractionation scheme (Leleyter and Probst in Int J Environ Chem 73:109–128, 1999). The significant concentrations of Ni and Cd were associated with “water soluble (Eua)” fraction in the monsoon and winter, respectively, while “exchangeable (Exch)” and “carbonate-bound (Carb)” fractions for Ni and Cd were abundant in winter and summer. The Cd, Cu, and Pb associated with “Exch” fraction in the summer season support their availability on exchange sites due to oxidized nature of surface sediments. Enrichment of Co, Fe, Mn, and Zn in “AFeO” fraction showed poor bioavailability, while Cd, Cu, and Mn in the monsoon, Co in the winter and summer, and Zn in the winter season showed significant “organically bound (Org)” fraction. The ANOVA was significant for chemical fractions of trace elements except “Carb” fraction of Pb and Zn and “CFeO” fraction of Pb. Factor analysis revealed that the “Eua”, “Exch”, and “Carb” fractions together control the metal enrichment of “MnO”, “AFeO”, and “CFeO” fractions in the summer season.  相似文献   

16.
以广东省揭阳市揭东区表层土壤B、Cu、Mn、Zn、Mo 5种元素为研究对象,在分析微量元素含量状况和分布特征的基础上,从成土母质、土地利用方式、pH值和有机质含量4个方面来分析其对土壤微量元素含量的影响。利用GIS空间分析法、SPSS数理统计法和相关分析法对揭东区土壤微量元素含量、空间分布特征和影响因素进行分析。结果显示：揭东区表层土壤B、Cu、Mn元素的平均含量分别为18.0 mg/kg、14.5 mg/kg、313 mg/kg,含量均处于缺乏水平;Zn元素的平均含量为77.3 mg/kg,总体处于较丰富水平;Mo元素的平均含量为1.31 mg/kg,含量丰富。相关分析表明B、Cu、Mn、Zn、Mo均受到成土母质和土地利用方式的影响,在粉砂岩成土母质区土壤中B和Mn含量最高,凝灰岩成土母质区土壤中Cu和Mo含量最高,Zn在第四纪沉积物中含量最高;比较各种利用方式的土壤,B、Cu在农用地中含量最高,Mn、Zn和Mo在建设用地中含量最高;土壤pH值与B、Cu、Mn、Zn含量呈极显著的正相关关系(P<0.01);土壤有机质与B、Cu、Zn含量呈极显著的正相关关系(P<0.001...  相似文献   

17.
The heavy metal contents of Mn, Ni, Cu, Zn, Cr, Co, Pb, Cd, Fe, and V in the surface sediments from five selected sites of El Temsah Lake was determined by graphite furnace atomic absorption spectrophotometer. Geochemical forms of elements were investigated using four-step sequential chemical extraction procedure in order to identify and evaluate the mobility and the availability of trace metals on lake sediments, in comparison with the total element content. The operationally defined host fractions were: (1) exchangeable/bound to carbonate, (2) bound to Fe/Mn oxide, (3) bound to organic matter/sulfides, and (4) acid-soluble residue. The speciation data reveals that metals Zn, Cd, Pb, Ni, Mn, Cu, Cr, Fe, and V are sink primarily in organic and Fe–Mn oxyhydroxides phases. Co is mainly concentrated in the active phase. This is alarming because the element is enriched in Al Sayadin Lagoon which is still the main site of open fishing in Ismailia. Average concentration of the elements is mostly above the geochemical background and pristine values of the present study. There is a difference on the elemental composition of the sediment collected at the western lagoon (Al Sayadin Lagoon), junction, the shoreline shipyard workshops, and eastern beach of the lake. Depending upon the nature of elements and local pollution source, high concentration of Zn, Pb, and Cu are emitted by industrial wastewater flow (shoreline workshops), while sanitary and agricultural wastewater (El Bahtini and El Mahsama Drains) emit Co and Cd in Al Sayadin Lagoon. On the other hand, there is a marked decrease in potentially toxic heavy metal concentrations in the sediments at the most eastern side of the lake, probably due to the successive sediment dredging and improvements in water purification systems for navigation objective. These result show that El Temsah receives concentrations in anthropogenic metals that risk provoking more or less important disruptions, which are harmful and irreversible on the fauna and flora of this lake and on the whole ecobiological equilibrium.  相似文献   

18.
The Pliocene aquifer receives inflow of Miocene and Pleistocene aquifer waters in Wadi El Natrun depression. The aquifer also receives inflow from the agricultural activity and septic tanks. Nine sediment samples were collected from the Pliocene aquifer in Wadi E1 Natrun. Heavy metal (Cu, Sr, Zn, Mn, Fe, Al, Ba, Cr, Ni, V, Cd, Co, Mo, and Pb) concentrations of Pliocene aquifer sediments were investigated in bulk, sand, and mud fractions. The determination of extractable trace metals (Cu, Zn, Fe, Mn, and Pb) in Pliocene aquifer sediments using sequential extraction procedure (four steps) has been performed in order to study environmental pathways (e.g., mobility of metals, bounding states). These employ a series of successively stronger chemical leaching reagents which nominally target the different compositional fractions. By analyzing the liquid leachates and the residual solid components, it is possible to determine not only the type and concentration of metals retained in each phase but also their potential ecological significance. Cu, Sr, Zn, Mn, Fe, and Al concentrations are higher in finer sediments than in coarser sediments, while Ba, Cr, Ni, V, Cd, Co, Mo, and Pb are enriched in the coarser fraction. The differences in relative concentrations are attributed to intense anthropogenic inputs from different sources. Heavy metal concentrations are higher than global average concentrations in sandstone, USEPA guidelines, and other local and international aquifer sediments. The order of trace elements in the bulk Pliocene aquifer sediments, from high to low concentrations, is Fe?>?Al?>?Mn?>?Cr?>?Zn?>?Cu?>?Ni?>?V?>?Sr?>?Ba?>?Pb?>?Mo?>?Cd?>?Co. The Pliocene aquifer sediments are highly contaminated for most toxic metals, except Pb and Co which have moderate contamination. The active soluble (F0) and exchangeable (F1) phases are represented by high concentrations of Cu, Zn, Fe, and Mn and relatively higher concentrations of Pb and Cd. This may be due to the increase of silt and clay fractions (mud) in sediments, which act as an adsorbent, retaining metals through ion exchange and other processes. The order of mobility of heavy metals in this phase is found to be Pb?>?Cd?>?Zn?>?Cu?>?Fe?>?Mn. The values of the active phase of most heavy metals are relatively high, indicating that Pliocene sediments are potentially a major sink for heavy metals characterized by high mobility and bioavailability. Fe–Mn oxyhydroxide phase is the most important fraction among labile fractions and represents 22% for Cd, 20% for Fe, 11% for Zn, 8% for Cu, 5% for Pb, and 3% for Mn. The organic matter-bound fraction contains 80% of Mn, 72% of Cu, 68% of Zn, 60% of Fe, 35% of Pb, and 30% of Cd (as mean). Summarizing the sequential extraction, a very good immobilization of the heavy metals by the organic matter-bound fraction is followed by the carbonate-exchangeable-bound fraction. The mobility of the Cd metal in the active and Fe–Mn oxyhydroxide phases is the highest, while the Mn metal had the lowest mobility.  相似文献   

19.
Urban roadside soils are important environmental media for assessing heavy metal concentrations in urban environment. However, among other things, heavy metal concentrations are controlled by soil particle grain size fractions. In this study, two roadside sites were chosen within the city of Xuzhou (China) to reflect differences in land use. Bulk soil samples were collected and then divided by particle diameter into five physical size fractions, 500–250, 250–125, 125–74, 74–45, < 45 μm. Concentrations of metals (Ti, Cr, Al, Ga, Pb, Ba, Cd, Co, Cu, Mn, Ni, V, Zn, Mo, As, Sb, Se, Hg, Bi, Ag) were determined for each individual fraction. These metals could be roughly classified into two groups: anthropogenic element (Pb, Ba, Cd, Cu, Zn, Mo, As, Sb, Se, Hg, Bi, Ag) and lithophile element (Ti, Cr, Al, Ga, Co, Mn, Ni, V) in terms of values of enrichment factor. As expected, higher concentrations of anthropogenic heavy metals (Cu, Zn, Mo, As, Hg, Bi, Ag) are observed in the finest particle grain size fraction (i.e. < 45 μm). However, heavy metals Se, Sb and Ba behave independently of selected grain size fractions. From the viewpoint of mass loading, more than 30% of the concentrations for all anthropogenic heavy metals are contributed by the particle grain size fractions of 45–74 μm at site 1 and more than 70% of the concentrations for all heavy metals are contributed by the particle grain size fractions of 45–74 and 74–125 μm at site 2. These results are important for transport of soil-bound heavy metals and pollution control by various remedial options.  相似文献   

20.
Due to the explosive industrialization and rapid expansion of the population in many parts of the world, heavy metals are released into the environment continuously and pose a great risk on human health. Street dust and surface soil samples from very heavy, heavy, medium and low traffic areas and a natural site in Tehran, Iran, were analyzed for some physicochemical features, total and chemical fractionating of selected metals (Zn, Al, Sr, Pb, Cu, Cr, Cd, Co, Ni and V) to investigate the influence of traffic on their mobility and accumulation in the environment. The pH, electrical conductivity (EC), carbonates and organic carbon contents were similar in soil and dust samples from the areas with same traffic. The traffic increases EC contents in dust/soil matrixes, but has no effect on concentrations of metals in soil samples. Rises in metal levels with traffic were found in dust samples. Moreover, the traffic increases the percentage of both acid-soluble and reducible fractions, which are related to Pb and Zn. The mobilization of Cu, Zn, Pb, Cr in dust samples was easier than in soil. The speciation of metals except Cd is mainly affected by physicochemical features in soil, though total metals affected the speciation in dust samples (except chromium and nickel).  相似文献   

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