Environmental contamination of trace elements in the vicinity of Okpara coal mine, Enugu, Southeastern Nigeria

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.     

Integrated mass balance of some heavy metals fluxes in Yaakob village,south Sohag,Egypt

The pollution of soil with heavy metals has direct or indirect adverse effect on human health. The present work was conducted to identify all the expected sources and sinks for heavy metals by applying mass balance model to identify the retention rate of metals by soils in Yaakob village, south Sohag Governorate, Egypt. The studied inputs (sources) include P-fertilizers, irrigation water and dustfall, while the main outputs (sinks) are drainage water and harvested plants. The measurements indicate that soil, clover, dustfall and P-fertilizers contain considerable concentration of Cd, Cr, Co, Cu and Pb. The mass balance measurements indicate that the accumulation rate of Cd, Cr and Co in soil was 5.4, 54.6 and 16.3 g ha^?1 year^?1, respectively. However, depletion trend of Pb and Cu was about 1.4 and 5.2 g ha^?1 year^?1, respectively. The main source of Cd, Pb, Cr and Co in the study area is P-fertilizers with input flux 14.9, 89.9, 198.6 and 18.5 g ha^?1 year^?1, while Cu source was dustfall with 19.33 g ha^?1 year^?1. The index of geoaccumulation calculations indicates different degrees of contamination with Cd, Cr, Co and Cu. On the other hand, the main sink for the studied heavy metals was the Egyptian clover (Trifolium alexandrinum) which can be considered a good bioaccumulator of heavy metals.     

Comparison of extractability of Cd, Cu, Pb and Zn with sequential extraction in contaminated and non-contaminated soils

Various extraction procedures were employed for measuring extractable concentrations of potential toxic elements in soil. The extractability of Cd, Cu, Pb and Zn in four contaminated and four non-contaminated soils of Japan, was compared by single extraction (CaCl₂, DTPA, NH₄Cl, 0.1 M HCl and 1 M HCl ) and sequential extraction procedures [(six operationally defined chemical phases, viz. water soluble (Fl), exchangeable (F2), carbonate (F3), oxide (F4), organic (F5) and residual (F6) fractions)]. Extractability of metals from soils samples varied depending on metals and/or extradants used. Among the extradants, 1 M HCl extracted the largest proportion of Cd (79 to 96% of total), Cu (61 to 83%), Pb (51 to 99%) and Zn (23 to 52%) from soils followed by 0.1 M HCl, NH₄Cl, DTPA and CaCl₂. In all the extradants, the proportion of extractability of metals was higher in the contaminated soils than the non-contaminated soils. Regardless of soils and extradants, relative extractability was higher for Cd as compared to other three metals. The use of 1 M HCl may be recommended for first-level screening of soil contamination with heavy metals. The other four weak extradants are believed to provide a better assessment of bioavailable/mobile metals content in soils than 1 M HCl extradant. However, 0.1 M HCl mobilized all four metals irrespective of soil types, therefore, might be the best choice if only one extradant is to be used. The sequential extraction procedures showed 22 to 64% of total Cd was in the mobile fraction (sum of Fl to F3), while the corresponding values for Cu, Pb and Zn in this fractions were 2 to 23% suggesting higher mobility of Cd than other three metals. The single extraction procedures are simple and easy to perform and obtained results are comparable with sequential extraction procedure.     

Multivariate statistics and hydrogeochemical modeling for source identification of major elements and heavy metals in the groundwater of Qareh-Ziaeddin plain,NW Iran

The present study aims to evaluate the possible source of major and some minor elements and heavy metals in the groundwater of Qareh-Ziaeddin plain, NW Iran with respect to chemical elements, saturation index, and multivariate statistics including correlation coefficient, cluster analysis, and factor analysis. Groundwater samples were collected in Jun 2016 and measured with respect to EC, pH, major and some minor elements and heavy metals including Fe, Mn, Zn, Cr, Pb, Cd, Al, and As. Among all the measured parameters, some of the samples exceed the World Health Organization (WHO) guideline value for EC, Na, Mg, HCO₃, SO₄, Cl, NO₃, F, As, Zn, and Pb. The results of correlation analysis show that weathering and dissolution of minerals especially evaporites and silicates, water-rock interaction, and cation exchange are dominant occurred processes in the groundwater of the study area. Also, denitrification process is occurred in the groundwater system. Cluster analysis categorizes the samples into three distinct groups which are different based on their EC and dependent variables, e.g., Na, Ca, Cl, SO₄ and pH, Pb, Cd, and As. It can be found that volcanic, evaporite, and clay formations have the least impact on the chemistry of the cluster 1 samples while clay and evaporite formations have the highest impact on the cluster 3 and also calcareous formations on cluster 2. Factor analysis shows that five factors, with total variance of 83%, are effective in the release of heavy metals and groundwater chemistry which are mostly geogenic.     

Mapping potential risks of long-term wastewater irrigation in alluvial soils,Egypt

In Egypt, wastewater has been used for irrigation in areas with fresh water scarcity; however, continuous applications may cause potential risks. Thus, the current study aims to map the spatial distribution of soil contamination and human risks of long-term wastewater irrigation due to the exposure of heavy metals. Soils from nine sites in Al-Qalyubia Governorate, Egypt, were sampled and analyzed. Wastewater irrigation resulted in a buildup of heavy metals in soils compared to Nile fresh water-irrigated soil. The pollution index (PI) showed the decreasing order of Cd?>?Zn?>?Ni?>?Cu?>?Co?>?Pb?>?Cr. The soils were out of the safe domain, as the integrated pollution index of Nemero’s (IPIN) exceeded the safe limit of 0.7. The enrichment factor (EF) exceeded 1.0, proving anthropogenic effects. The geo-accumulation index (I_geo) indicated high threats associated with Cd. The calculated hazard index (HI) indicated that humans exposed to such contaminated soils would have a potential health risk, particularly children. It is recommended to perform a treatment to the wastewater used in irrigation to avoid such threats.     

珠江三角洲污灌区地下水重金属含量及其相互关系

为了解污灌区地下水重金属含量特征,采集地表水样5组、地下水样14组进行化学组分定量分析。结果表明：污灌区地下水8种重金属元素中,仅有Ni和As两种元素超标,超标率分别为14.3％和42.9％。8种重金属含量在污灌区地表水、工厂废水以及地下水中存在明显的对应关系。Ni、Zn、Se、Cd这4种元素间存在显著或极显著的正相关关系,Cu与Pb和Cd分别呈极显著和显著的正相关关系,Cr仅与Ni呈显著的正相关关系,As与其它7种元素的相关性均不明显。聚类分析结果显示8种重金属可分为4类：Pb和Cu一类,Se、Cd、Ni、Zn一类,Cr和As均单独一类。Pb和Cu与Fe的相似性最好,Se、Cd、Ni、Zn与Mg²⁺存在较好的相似性,Cr与HCO^－₃的相似性最好,As与SO^2－₄存在一定的相似性。     

A GIS-based approach for detecting pollution sources and bioavailability of metals in coastal and marine sediments of Chabahar Bay,SE Iran

Chabahar Bay in SE of Iran is a shallow semi-enclosed environment affected by anthropogenic activities. In this paper, 19 sediment samples were collected and concentration of selected metals (Cu, Pb, Zn, Cd, Ni, Cr, Co, V and Fe) was determined using ICP-MS analytical method. Sediment samples from five stations were also selected for sequential extraction analysis and concentration of metals in each fraction was determined using ICP-OES. In order to investigate the environmental quality of Chabahar Bay, geographic information system (GIS) along with geochemical data, environmental indices and statistical analyses were used. Calculated contamination degree (C_d) revealed that most contaminated stations (Ch3, S1 and S3) are located SE of Chabahar Bay and contamination decreases in a NW direction. The S9 station, west of the bay, is also contaminated. High organic matter (OM) content in the sediments is most likely the result of fuel and sewage discharge from fishing vessels along with discharge of fishing leftovers. Significant correlation coefficient among OM, Fe, Cu, Pb, Zn and Cd seemingly reflects the importance of the role that OM and Fe oxy-hydroxides play in the metals mobility. The results of hierarchical cluster analysis (HCA), computed correlation coefficient and sequential extraction analysis suggest that Cu, Pb, Zn and Cd probably come from antifouling and sea vessel paints, while Ni, Cr, Co, V and Fe are most likely contributed by ophiolitic formations located north of the bay and/or deep sea sediments. Average individual contamination factors (ICFs) indicated that the highest health hazard from the bay is posed by Cu, Pb and Zn.     

Bioaccumulation of heavy metals in <Emphasis Type="Italic">Limnobium laevigatum</Emphasis> and <Emphasis Type="Italic">Ludwigia peploides</Emphasis>: their phytoremediation potential in water contaminated with heavy metals

Contamination with heavy metals in surface and groundwater is a threat to human health and ecosystems. Due to this, the need arises to remediate water polluted through ecological and profitable technologies, such as phytoremediation. The objective of the work was to evaluate the concentration of lead (Pb) and zinc (Zn) in the floating macrophytes Limnobium laevigatum and Ludwigia peploides, after being exposed to contaminated water experimentally. In this way to be able to determine if these plants have mechanisms that allow them to accumulate the metals in the roots and to perform the translocation of these to different vegetative organs, L. laevigatum and L. peploides were placed in solutions contaminated with Pb ([Pb]?=?5 mg/l) and Zn ([Zn]?=?20 mg/l). The concentrations of metals in water, root and leaf samples were evaluated as a function of time (0, 1, 2 and 4 days). The determination of the metals was performed by the atomic absorption spectrophotometry technique. After 4 days of exposure to Pb and Zn, the plants showed high metal removal efficiencies of water, more to 70% in all cases. Pb was accumulated fundamentally by roots, while Zn was accumulated more in the leaves. In addition, the bioconcentration and translocation factors for each metal were calculated.     

Using multivariate statistical analyses to evaluate groundwater contamination in the northwestern part of Saudi Arabia

Chemical characteristics of groundwater in the Midyan Basin (northwestern Saudi Arabia) were investigated and evaluated. A total of 72 water samples were collected from existing shallow wells and analyzed for different elements. Two multivariate statistical methods, hierarchical cluster analysis (HCA) and principal components analysis (PCA), were applied to a subgroup of the data set in terms of their usefulness for groundwater classification, and to identify the processes controlling groundwater geochemistry. The subgroup consisted of 46 water samples out of 72 samples and 24 variables included major elements (Ca²⁺, Na⁺, Mg²⁺, K⁺, Cl^?, HCO₃ ^?, NO₃ ^?, SO₄ ^2?), minor and trace element (SiO₂, Al, As, B, Ba, Cd, Cr, F, Fe, Mo, P, Pb, Sb, Sn, Ti, and V). For water samples, four geochemically distinct clusters (i.e., C1, C2, C3 and C4) have been observed by hierarchical cluster analysis. Cr, F and Pb are the dominant ions in cluster C2. Al, As, Cd, Mo, Sb and Ti are the dominant ions in cluster C3, while B, Ca, Cl, HCO₃, K, Mg, Na, SO₄ and V are identified as dominant ions in the cluster C4. In the PCA, a total of five components are extracted form the data set, which explained 73.37 % of the total data variability. Among them the first component reveals strong associations between As, B, Cd, Cr, F, Mo, Pb, Sb and Ti. The second component reveals the associations between Ca, Cl, HCO₃, Mg, Na, SO₄ and V.     

Carcinogenic and Non-carcinogenic Risk Assessment of Metals in Groundwater via Ingestion and Dermal Absorption Pathways for Children and Adults in Malwa Region of Punjab

The concentration of trace metals was measured in groundwater samples collected from Malwa region of Punjab, India. The samples were analyzed by using high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS). The results were compared with permissible limits prescribed by various health and environmental protection agencies. The concentrations of trace metals such as Mn, Se, Mo, Cd, Sb and Pb were higher than their respective permissible limits at some sampling sites. The total hazard index (HI_total) (summing the hazard index through ingestion and dermal routes) at all the sampling sites exceeded or nearing unity, indicating the presence of non-carcinogenic health effects from ingestion of groundwater and dermal contact with groundwater. The results reveal that the total excess lifetime cancer risk (ELCR_total) of metals exposure was in accordance with the acceptable lifetime risks for carcinogens in drinking water.     

Contamination and ecological risk assessment of heavy metals in street dust of Tehran,Iran

Heavy metals are introduced in human tissue through breathing air, food chain and human skin. They can cause damage to the nervous system and internal organs. In the present study, sixty street dust samples were collected from the central area of Tehran and were digested in the laboratory to determine the content of Zn, Ni, Cd, Cr, Cu and Pb, using inductively coupled plasma optical emission spectrometry (ICP-OES). The level of contamination with the analyzed metals was determined according to the following indices: geo-accumulation index (I _geo), enrichment factor (EF), pollution index (PI), integrated pollution index (IPI) and potential ecological risk index (RI). The average concentration of heavy metals found was in the order of Zn > Cu > Pb > Ni > Cr > Cd. The average I _geo values for Cd, Cr, Cu, Ni, Pb and Zn were 1.53, ?1.88, 2.68, ?0.67, 1.62 and 2.70, respectively. Among the investigated heavy metals, zinc and copper had the maximum average EF values and were placed into the “very severe enrichment” class. Potential ecological risk factor (E _r) also indicated that Cd had the highest risk, and it was classified as of considerable potential ecological risk. Therefore, it is necessary to pay more attention to the appearance of Cd in the human environment. The calculated potential ecological risk index values also illustrated that the street dust samples presented a “moderate ecological risk.” The calculated IPI values showed that the pollution levels of the street dust samples ranged from high to extremely high.     

Competitive sorption and desorption of cadmium and lead in paddy soils of eastern China

To assess the competitive sorption and desorption of cadmium (Cd) and lead (Pb), batch equilibrium experiments were performed using single- and binary-metal solutions in surface samples of three paddy soils from eastern China. Sorption isotherms were well fitted with one-metal and competitive Langmuir equation for single- and binary-metal system, respectively. The distribution coefficient (K _d) values were K _{d single} (Pb) > K _{d binary} (Pb) > K _{d single} (Cd) > K _{d binary} (Cd), indicating that Pb was stronger sorbed by these soils than Cd in binary metal system. Soils with high pH and clay content had the greatest sorption capacity as estimated by the maximum sorption parameter (Q). The co-existence of both metals reduces their tendency of sorption, whereas Cd sorption was affected to a greater extent than that of Pb. The Langmuir binding strength parameter (b) in binary sorption system was greater than that in single sorption system for all soils (b < b ₁), indicating that competition for sorption sites promote the retention of both metals into more specific sorption sites. Sorption of Cd and Pb decreased soil pH by 1.61 U for YRS, 1.39 U for PCS, and 0.91 U for SLS. The decreases of pH in binary metal system were greater than in single-metal system for three soils. Cadmium and Pb desorption increased with increasing Cd and Pb sorption saturation for all soils; however, Cd desorption ratio in binary metal system (d _Cd*) was much greater than Pb (d _Pb*), indicating that under the competitive sorption conditions, the sorbed Cd was more readily desorbed from the soils than the sorbed Pb.     

Tracing recharge to aquifers beneath an Asian megacity with Cl/Br and stable isotopes: the example of Dhaka,Bangladesh

Dhaka, the capital of Bangladesh, is home to a population of 15 million people, whose water supply is 85% drawn from groundwater in aquifers that underlie the city. Values of Cl/Br >500 are common in groundwater beneath western Dhaka in areas <3 km from the river, and in rivers and sewers around and within the city. The study shows that groundwater beneath western Dhaka is strongly influenced by infiltration of effluent from leaking sewers and unsewered sanitation, and by river-bank infiltration from the Turag-Buriganga river system which bounds the western limit of the city. River-bank infiltration from other rivers around Dhaka is minor. Values of Cl/Br and Cl concentrations reveal that 23 % of wells sampled in Dhaka are influenced by saline connate water in amounts up to 1%. This residual natural salinity compromises the use of electrical conductivity of groundwater as a method for defining pathways of recharge by contaminated surface waters. Concentrations of As, B, Ba, Cd, Cu, F, Ni, NO₃, Pb, Sb, Se and U in groundwater samples are less than WHO health-based guideline values for drinking water.     

Comparison of different methods for assessing heavy metal contamination in street dust of Xianyang City, NW China

Street dust is one of the important indicators that reflect the status of urban environmental pollution. There are many studies of heavy metals contamination of street dust in capital cities; however, little attention has been paid to this kind of study in medium cities, including China. The dust samples were collected in the district of traffic crossroads in Xianyang city, Shaanxi Province. Pb, Cd, Cu, Ni, Zn, Cr and Mn concentrations were determined using atomic absorption spectrometry (AAS). The results indicate that the concentrations of heavy metals are higher than the background values of soils in Shaanxi Province. The contamination level of heavy metals is assessed by potential ecological risk index (E _r), geoaccumulation index (I _geo), enrichment factor (EF) and pollution index (Pi). The low I _geo, EF, E _r, Pi and PI_n (integrated pollution index) for Mn in street dusts indicate an absence of distinct Mn pollution. The high EF, Pi and PI_n of Cu and Zn indicate that there is considerable Cu and Zn pollution. It is suggested that more attention should be paid to heavy metals contamination of Cu and Zn. The assessment results of Pi and PI_n suggest that Pb, Ni and Cr present strong pollution; however, their EFs indicate that they cause moderate pollution and their I _geo indicates that they are unpolluted to moderately polluted. The contamination class value with different assessing methods is of the order: Pi ≈ PI_n > EF > I _geo > E _r.     

The transport and fate of Fe,Mn, Cu,Zn, Cd,Pb and SO4 in a groundwater plume and in downstream surface waters in the Coeur d'Alene Mining District,Idaho, U.S.A.

The controls on metal concentrations in a plume of acidic (pH 3.29–5.55) groundwater in the Moon Creek watershed in Idaho, U.S.A., were investigated with the use of property-property plots. A plot of Ca vs S demonstrated that a plume of contaminated groundwater was being diluted by infiltration of rain and creek water at shallow depths and by ambient groundwater near bedrock. The small amount of dissolved Fe (2.1 mg/l) was removed while dissolved Pb was added, reaching a maximum concentration of 0.37 mg/l. The other metals (Zn ≤ 16, Al ≤ 6.2, Cu ≤ 2.1 and Cd ≤ 0.077 mg/l) in the shallow groundwater were essentially conserved until they emerged as a seep along the creek bank. Upon mixing with the creek water, groundwater was diluted by factors between 11 and 50, and the pH of the mixture became neutral. Metals originating from the contaminated groundwater were removed in the creek in the following order: Fe > Al > Pb ≫ Cu > Mn > Zn = Cd.Pb and Cu continued to be removed from solution even as the creek passed adjacent to a tailings pile. In contrast, Zn concentrations in the creek increased adjacent to the tailings area, presumably as a result of the reemergence of the upgradient plume as the creek lost elevation.Below the tailings dam, contaminated creek water (400–800 μg Zn/l) was diluted by both smaller side streams and a creek of equal flow. The presence of 3 distinctive water masses required the use of two tracers (dissolved Si and S) to distinguish between mixing and geochemical reactions. The removal of metals was greater during low flow conditions. Pb was removed to the greatest extent, falling below detection limits (0.5 μ/l) at the first sampling location. Copper and Mn were removed to a lesser extent during low flow conditions and approached conservative behavior during high flow conditions. During a 5-km journey through two hydrological regimes, less than 10% of the dissolved Zn and Cd was lost.     

Migration and contamination of major and trace elements in groundwater of Madras city,India

Groundwater samples collected from both open and bore wells in an area of about 270 km² from Madras City, India, have been analyzed for major ions (HCO₃, Cl, Si, Na, Ca, and Mg) and trace elements (As, Se, B, V, Cr, Fe, Co, Pb, Cu, Zn, Cd, Mn, Ni, Mo, and Ba). The study reveals that the quality of potable water has deteriorated to a large extent. Seawater intrusion into the aquifer has been observed in nearly 50 percent of the study area. The toxic elements (As and Se) have already exceeded the maximum permissible limits of drinking water in almost the entire city. A positive correlation of As and Se with other toxic metals such as V, Cr, Fe, B, etc., indicates that all these elements are anthropogenic in origin. Applying multivariate analysis, the source for trace elements in groundwater has been grouped into two major factors: pollution and mobilization factors. The groundwater in the study area is largely contaminated by organic effluents and reflects the intensity of pollution caused by the overlying soil sediment and rapid infiltration of the pollutants.     

Spatial distribution,pollution characterization and health risk assessment of selected metals in groundwater of Lahore,Pakistan

Groundwater pollution is a major global environmental issue especially in the large cities and trace metals are considered as most important aquatic pollutants. The present study is based on the measurement and characterization of various physicochemical parameters (pH, EC, TDS, DO, alkalinity, hardness, and chloride), major cations (Ca, Mg, Na and K) and selected trace metals (Sr, Li, Fe, Zn, Cu, Co, Mn, Ag, Cd, Cr, Ni, and Pb) in the groundwater of Lahore, Pakistan during summer and winter (2017–18) seasons. Groundwater is the main source of drinking water in urban areas of Lahore. Seasonal comparison of the data indicated that majority of the metals showed relatively higher concentrations during winter than summer. Most of the metals exhibited significant spatial variability during both seasons; relatively higher metal levels were found in the old settlements and thickly populated areas of the city. Average concentrations of Pb, Ni, Cd and Co in the groundwater were found to be higher than the national and international guideline values. Factor analysis and cluster analysis revealed major anthropogenic contributions of Ni, Co, Cd, Cu, Cr and Pb in the groundwater while rest of the metals showed mixed and/or natural contributions. Evaluation of human health risks for the metal contents in groundwater revealed that Pb, Co, Ni and Cd were associated with significantly higher non-carcinogenic risks (HQ_ing > 1); the calculated risk for children was considerably higher than the adults. Moreover, the carcinogenic risk associated with Ni, Cr, Cd and Pb exceeded the safe limits. The present study revealed significantly higher anthropic pollutants in the groundwater which imposed considerable risks to human; therefore, it is recommended to implement immediate remedial measures to ensure safe drinking water.     

<Emphasis Type="Italic">Robinia pseudoacacia</Emphasis> and <Emphasis Type="Italic">Melandrium album</Emphasis> in trace elements biomonitoring and air pollution tolerance index study

The accumulation efficiency of selected trace elements in the leaves of Melandrium album and Robinia pseudoacacia grown on heavy metal contaminated sites in comparison with a non-contaminated one was evaluated. The study was undertaken to calculate air pollution tolerance index and to determine the contents of selected metabolites: glutathione, non-protein thiols, ascorbic acid, chlorophyll and the activity of antioxidant enzymes: guaiacol peroxidase and superoxide dismutase. Such estimations can be useful in better understanding of plants defense strategies and potential to grow in contaminated environments. The results in the most contaminated site revealed higher contents of metals in M. album leaves, especially Zn, Cd and Pb (3.4, 6 and 2.3 times higher, respectively) in comparison with the R. pseudoacacia. Better accumulation capacity found in M. album was shown by metal accumulation index values. The plants could be used as indicators of Zn, Cd (both species) and Pb (M. album) in the soil. Glutathione content (in both species) and peroxidase activity (in M. album), general markers of heavy metals contamination, were increased in contaminated sites. In most cases in contaminated areas R. pseudoacacia had decreased ascorbic acid and chlorophyll levels. Opposite tendency was recorded in M. album leaves, where similar or higher contents of the above-mentioned metabolites were found. In our study, M. album and R. pseudoacacia proved to be sensitive species with the air pollution tolerance index lower than 11 and can be recommended as bioindicators.     

多壁碳纳米管固相萃取快速检测水样中铅镉铜铁

传统的固相萃取填料应用于环境样品的重金属处理过程中,存在pH不稳定和不同极性萃取物共同萃取较为困难等方面的不足,因此寻找新型固相萃取填料显得尤为重要。本文采用多壁碳纳米管填充固相萃取柱,萃取水中金属元素铅、镉、铜和铁,采用石墨炉原子吸收光谱法测定铅和镉,电感耦合等离子体发射光谱法测定铜和铁。实验考察了多壁碳纳米管的性质、溶液pH值、洗脱溶液、样品流速以及基体效应对测定结果的影响。结果显示:溶液pH=9,1 mol/L硝酸为洗脱溶液,样品流速为2 mL/min时,外径8 nm未修饰的多壁碳纳米管有较好的萃取效率,对溶液中铅、镉、铜和铁的最大吸附容量分别为44.91、42.31、54.68和49.07 mg/g,四种元素的吸附容量均衡;钾、钠、钙、镁离子以及苯和甲苯等基质对四种金属元素的萃取影响不大。方法回收率为95.3%~99.5%,精密度(RSD,n=7)为1.2%~3.2%。本方法采用外径8 nm的多壁碳纳米管固相萃取,与传统萃取方法相比,富集效果好、回收率较高,而且操作简便、准确度高;与前人采用外径20~30 nm的多壁碳纳米管的性能相比,镉和铜的吸附容量更高,还可实现对铁的吸附,且铅、镉、铜和铁四种元素的吸附容量均衡,更适合用于检测水样中的金属元素。     

Phytoremediation potential and morphological changes of plants growing in the vicinity of lead smelter plant

With the increasing industrialization, heavy metals concentration in soils has greatly increased. Phytoremediation is a low-cost, non-intrusive and aesthetically harmonious technology that uses plants to remediate contaminated sites by heavy metals. The aim of the study was to determine Cd, Pb and Zn concentration in the biomass of plant species growing on a multi-metal-contaminated site of lead smelter processing, to assess the workability of using these plants for phytoremediation purposes and highlight possible damage in morphological leaf changes. Two plant species, i.e., Ipomoea asarifolia and Urochloa decumbens and the associated soil samples were collected and analyzed Cd, Pb and Zn concentrations and then calculating the bioconcentration factor and translocation factor parameters for each element. Leaves and roots samples were observed by light microscopy. Metal concentrations varied greatly and majorly depend on site sampled, plant species and tissue. Cd, Pb and Zn in tissue ranged from 0 to 102.48, 0 to 381.04 and 12.84 to 295.02 mg Kg^?1. However, none of the plant showed potential for hyperaccumulation. Both plants showed bioaccumulation factor more than one, where it was 7.66 and 6.82 for Pb and Zn in U. decumbens, respectively. Translocation factor was calculated below one for both plants and all metals. Morphological studies revealed development of adaptive features that strengthen the U. decumbens to grow in contaminated soil. Our study suggests that I. asarifolia and U. decumbens have potential for phytostabilization at multi-metal-contaminated site.