Distribution of heavy metals in sediments of Igbede, Ojo and Ojora rivers of Lagos, Nigeria

The distribution of some heavy metals, namely Cd, Pb, Zn, Fe, Cu, Cr and Mn in epipellic sediments of Igbede, Ojo and Ojora rivers of Lagos was studied weekly in the early summer (November) of 2003. The levels of selected trace metals were determined using Atomic Absorption Spectrophotometer (UNICAM 969 AAS SOLAR). Trends in heavy metal burdens in the sediments revealed weekly variations in all the rivers assessed. Statistical analyses also showed different mean levels of trace metals in the aquatic environments, the distribution of which followed the sequence Fe > Zn > Mn > Pb > Cu > Cr > Cd, Fe > Zn > Cu > Mn > Pb > Cr > Cd and Fe > Zn > Mn > Cu > Cr > Pb > Cd in Igbede, Ojo and Ojora rivers respectively. Fe recorded the highest concentration levels (1,582.95 ± 96.57 μ g/g–1,910.34 ± 723.19 μ g/g) in all the sediments investigated while the Cd levels (0.06 ± 0.10 μ g/g–0.47 ± 0.36 μ g/g) were the lowest. Expectedly, trace metal concentrations in fine grain muddy sediments of the Igbede and Ojo coastline were much higher than those of Ojora which consist of coarse and sandy deposits covering the near shore area. Generally, the results obtained fell within tolerable limits stipulated by World Health Organization (WHO).     

Characteristic levels of heavy metals in soil profiles of automobile mechanic waste dumps in Nigeria

The characteristic levels of heavy metals (Cd, Cr, Cu, Pb, Ni and Zn) of soil profiles of automobile mechanic waste dumps were studied. The concentration of heavy metals decreased with the depth of the profile and lateral distance from the dumpsites. The levels found in this study exceeded background concentrations and limits for agricultural and residential purposes. The distribution pattern of heavy metals in the soil profiles were in the following order Pb > Zn > Cu > Cd > Ni > Cr. The mechanic waste dumps represent potential sources of heavy metal pollution to environment. The elevated levels of heavy metals in these soil profiles constitute a serious threat to both surface and groundwater.     

Assessment of tropical suburban surface soils contamination from Jengka,Malaysia

Heavy metals in suburban soils pose both indirect and direct health risks. This study assessed the concentrations of Cr, Zn, Pb, and Cd in Jengka (Malaysia) suburban soil and estimated the human health risk. Health risk assessment (HRA) was utilized to assess non-cancer and cancer risks. The concentrations of heavy metals increased in the following order: Cd < Zn < Cr < Pb. The heavy metals were found to be divided into two components using principal component analysis (PCA), with PC1 comprising Pb and Cd and PC2 containing Zn and Cr. PC1 originates from anthropogenic sources, while PC2 is often from mixed anthropogenic and natural sources. Despite having the lowest mean concentration, Cd was enriched based on the geo-accumulation index (Igeo) and enrichment factor (EF). Average hazard index values were below the acceptable threshold (HI < 1) for dermal and inhalation pathways suggesting a low non-cancer risk. Jengka suburban soil had total lifetime cancer risk values slightly higher than the acceptable threshold (1 × 10⁻⁵). Skin contact was the most prominent contributing exposure pathway for both non-carcinogenic and carcinogenic risks. This study suggests that heavy metal bioactivity levels be used to make a plausible HRA of heavy metal pollution in suburban soils.     

Total Contents and Sequential Extraction of Heavy Metals in Soils Irrigated with Wastewater,Akaki, Ethiopia

The Akaki River, laden with untreated wastes from domestic, industrial, and commercial sources, serves as a source of water for irrigating vegetable farms. The purpose of this study is to identify the impact of waste-water irrigation on the level of heavy metals and to predict their potential mobility and bioavailability. Zn and V had the highest, whereas Hg the lowest, concentrations observed in the soils. The average contents of As, Co, Cr, Cu, Ni, Zn, V, and Hg of both soils; and Pb and Se from Fluvisol surpassed the mean + 2 SD of the corresponding levels reported for their uncontaminated counterparts. Apparently, irrigation with waste water for the last few decades has contributed to the observed higher concentrations of the above elements in the study soils (Vertisol and Fluvisol) when compared to uncontaminated Vertisol and Fluvisol. On the other hand, Vertisol accommodated comparatively higher average levels of Cr, Cu, Ni, Zn, etc V, and Cd, whereas high contents of Pb and Se were observed in Fluvisol. Alternatively, comparable levels of Co and Hg were found in either soil. Except for Ni, Cr, and Cd in contaminated Vertisol, heavy metals in the soils were not significantly affected by the depth (0–20 and 30–50 cm). When the same element from the two soils was compared, the levels of Cr, Cu, Ni, Pb, Se, Zn, V, Cd at 0–20 cm; and Cr, Ni, Cu, Cd, and Zn at 30–50 cm were significantly different. Organic carbon (in both soils), CEC (Fluvisol), and clay (Vertisol) exhibited significant positive correspondences with the total heavy metal levels. Conversely, Se and Hg contents revealed perceptible associations with carbonate and pH. The exchangeable fraction was dominated by Hg and Cd, whereas the carbonate fraction was abounded with Cd, Pb, and Co. conversely, V and Pb displayed strong affinity to reducible fraction, where as Cr, Cu, Zn, and Ni dominated the oxidizable fraction. Cr, Hg, Se, and Zn (in both soils) showed preference to the residual fraction. Generally, a considerable proportion of the total levels of many of the heavy metals resided in non residual fractions. The enhanced lability is generally expected to follow the order: Cd > Co > Pb > Cu > Ni > Se > V and Pb > Cd > Co > Cu > Ni > Zn in Vertisol and Fluvisol, respectively. For the similar wastewater application, the soil variables influence the status and the distribution of the associated heavy metals among the different soil fractions in the study soils. Among heavy metals that presented relatively elevated levels and with potential mobility, Co, Cu, Ni (either soil), V (Vertisol), Pb, and Zn (Fluvisol) could pose health threat through their introduction into the food chain in the wastewater irrigated soils.     

基于地积累指数法和潜在生态风险指数法评价广西某蔗田土壤重金属污染

采用地积累指数法和潜在生态风险指数法对广西某蔗田土壤中重金属污染进行评价。结果表明：4种重金属元素的地积累指数污染程度由强到弱依次为：Cd〉Zn〉Pb〉Cu,潜在生态危害指数污染程度由强到弱依次为：Cd〉Pb〉Cu〉Zn,其中zn的影响程度发生了变化。2种评价方法的结果存在差异,蔗田土壤的地积累指数污染程度处于无污染情况,而潜在生态危害指数污染程度处于低度危害程度。潜在生态危害指数考虑外源重金属的富集程度和不同重金属的生物毒性的影响,使其评价结果更准确。     

Heavy metal content and distribution in surface sediments of the Seyhan River, Turkey

Chemical fractionation of seven heavy metals (Cd, Cr, Cu, Mn, Ni, Pb and Zn) was studied using a modified three-step sequential procedure to assess their impacts in the sediments of the Seyhan River, Turkey. Samples were collected from six representative stations in two campaigns in October 2009 and June 2010, which correspond to the wet and dry seasons, respectively. The total metal concentrations in the sediments demonstrated different distribution patterns at the various stations. Cadmium was the only metal that was below detection at all stations during both sampling periods. Metal fractionation showed that, except for Mn and Pb, the majority of metals were found in the residual fraction regardless of sampling time, indicating that these metals were strongly bound to the sediments. The potential mobility of the metals (non-residual fractions) is reflected in the following ranking: Pb > Mn > Zn > Cu > Ni > Cr in October 2009 and Mn > Pb > Zn > Cu > Ni > Cr in June 2010. The second highest proportion of metals was bound to organic matter/sulfides, originating primarily from anthropogenic activities. Non-residual metal fractions for all stations were highest in June 2010, which may be linked to higher organic matter concentrations in the sediment samples with 1.40% and 15.1% in October 2009 and June 2010, respectively. Potential sediment toxicity was evaluated using the Risk Assessment Code (RAC). Based on RAC classification, Cd and Cr pose no risk, Cu and Ni pose low risk, Pb and Zn were classified as medium risk metals, while the environmental risk from Mn was high. In addition, based on the sediment quality guidelines (SQG), the Seyhan River can be classified as a river with no, to moderate, toxicological risks, based on total metal concentrations.     

Phytoremediation of heavy metals by <Emphasis Type="Italic">Eichhornia crassipes</Emphasis>

Eichhornia crassipes was tested for its ability to bioconcentrate 8 toxic metals (Ag, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) commonly found in wastewater from industries. Young plants of equal size were grown hydroponically and amended with 0, 0.1, 0.3, 0.5, 1.0, 3.0, and 5.0 mM of each heavy metal individually for 21 days. The test plant had the lowest and the highest tolerance indices for Hg and Zn, respectively. A significant (P ≤ .05) reduction in biomass production was observed in metal treated plants compared with the control. All strace elements accumulated to higher concentrations in roots than in shoots. Trace element concentrations in tissues and the bioconcentration factors (BCF) were proportional to the initial concentration of individual metal in the growth medium and the duration of exposure. From a phytoremediation perspective, E. crassipes is a promising plant species for remediation of natural water bodies and/or wastewater polluted with low levels of Zn, Cr, Cu, Cd, Pb, Ag and Ni.     

柴窝堡湖表层底泥重金属污染评价

研究了乌鲁木齐市柴窝堡湖表层底泥的重金属含量,并采用Hakanson潜在生态危害指数法对底泥中的重金属潜在生态风险进行评价。结果表明:底泥中Cu、Zn、Pb、Cd含量均超出乌鲁木齐市土壤背景值。除湖心区外,Cd在5个监测区域中的潜在生态危害均为中等;其它重金属在5个采样点的潜在生态危害均为轻微。各重金属间的相关性分析表明,Zn与Cu,Pb与Cd、Cu呈显著正相关,说明这4种元素污染源可能相同。柴窝堡湖表层底泥受到Cu、Zn、Pb、Cd污染,需采取相应措施防止重金属由底泥进入水相。     

Metal contamination of surface water,sediment and <Emphasis Type="Italic">Tympanotonus fuscatus</Emphasis> var. <Emphasis Type="Italic">radula</Emphasis> of Iko River and environmental impact due to Utapete gas flare station,Nigeria

Inter-seasonal studies on the trace metal load of surface water, sediment and Tympanotonus fuscatus var. radula of Iko River were conducted between 2003 and 2004. The impact of anthropogenic activities especially industrial effluent, petroleum related wastes, gas flare and episodic oil spills on the ecosystem are remarkable. Trace metals analyzed included cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), lead (Pb), manganese (Mn), nickel (Ni), vanadium (V) and zinc (Zn). Sediment particle size analysis revealed that they were characteristically psammitic and were predominantly of medium to fine grained sand (>73%), less of silt (<15%) and clay (<10%). These results correlated with low levels of trace elements such as Pb (0.03 ± 0.02 mg kg⁻¹), Cr (0.22 ± 0.12 mg kg⁻¹), Cd (0.05 ± 0.03 mg kg⁻¹), Cu (0.04 ± 0.02 mg kg⁻¹) and Mn (0.23 ± 0.22 mg kg⁻¹) in the sediment samples. This observation is consistent with the scarcity of clayey materials known to be good scavengers for metallic and organic contaminants. Sediments indicated enhanced concentration of Fe, Ni and V, while other metal levels were relatively low. The concentrations of all the metals except Pb in surface water were within the permissible levels, suggesting that the petroleum contaminants had minimal effect on the state of pollution by trace metals in Iko River. Notably, the pollutant concentrations in the sediments were markedly higher than the corresponding concentrations in surface water and T. fuscatus tissues, and decreased with distance from point sources of pollution.     

杭州城区河道底泥重金属污染及潜在生态风险评价

对杭州城区34条河道45个点位河道底泥进行采样,分析了pH及汞、砷、铅、铬、镉、铜、锌、镍等重金属含量,并进行污染及潜在生态风险评价。结果表明,监测点位的底泥为中性偏碱性,重金属含量分布不均,且范围波动很大,部分河道底泥重金属中汞、铅、镉、铬、锌、镍等有不同程度的超标,少数河道镉、铬、锌污染严重;按《农用污泥中污染物控...     

Accretion of heavy metals in the catfish <Emphasis Type="Italic">Bagrus bayad</Emphasis> from Taylor Creek,southern Nigeria

Heavy metals in the aquatic environment have, to date, come essentially from naturally occurring geochemical resources. However, this has been enhanced by anthropogenic activities such as crude oil exploration and exploitation activities, resulting in pollution in the Taylor Creek aquatic ecosystem. The catfish species Bagrus bayad and other environmental segments were collected from five selected sites along Taylor Creek, southern Nigeria, and total metal concentration determined. The concentration levels of the metals in B. bayad were higher than the values reported in the literature for fresh fish and may lead to a higher risk of harmful effects. The bivariate regression models relating metals in B. bayad and metals in the surface waters were significant (R ² ≥ 0.9002). The log (bio-concentration factor; BCF) values of Cr and Zn in B. bayad were the highest, whereas the lowest was found for Ni. The ecological distribution of the log (BCF) values was, for all the heavy metals, moderately stable over the creek. All log-transformed bio-magnification factors (BMF) in the creek were positive, which indicates that the metal concentration was greater in B. bayad than in suspended particulate matter (SPM). The absolute log (BMF) values of heavy metals can, therefore, be ranked in order of decreasing magnitude: Cr (3.26) > Zn (2.99) > Cd (2.93) > Fe (2.76) > Pb (2.66) > Mn (2.36) > Ni (2.24). This sequence indicates that toxic metals such as Cd, Cr and Pb are undergoing significant bio-reduction from SPM to B. bayad. The degree of correlation between the metals was different in B. bayad, which suggests that the sources of the metals polluting Taylor Creek were diverse.     

超声波去除农用污泥中重金属的试验研究

污水处理厂污泥中的重金属浓度高是污泥农用的主要障碍。为了降低农用污泥中的重金属含量,以Cu、Zn、Ni、Pb为对象,研究了超声波对其的影响。结果表明:超声对污泥中重金属有一定的溶出作用。当超声时间为30min时,溶解状态Cu、Zn、Ni、Pb的析出率分别为42.1%、37.5%、12.7%、14.7%;总的析出率分别为52.7%、44.7%、23.6%、71%。其中析出的Pb大部分以胶体状态存在,而溶解状态只占很少一部分。其他几种金属则以溶解状态为主。     

Optimization of the removal of chromium and lead by Penicillium chrysogenum using 2k factorial experiments

This study aims to prepare a low-cost, environmentally friendly, and alternative, biosorbent to remove chromium Cr (III) and lead Pb (II) from polluted water and to find out the highest removal efficiencies using 2^k factorial experiments. The Cr (III) and Pb (II) tolerant fungal strain identified as Penicillium chrysogenum was isolated from ceramic industrial sludge. The impact of process variables on biosorption of Cr (III) and Pb (II) by P. chrysogenum was first evaluated with the Taguchi screening design. Factors and levels were determined to optimize Cr (III) and Pb (II) removal efficiency. According to this, five factors; initial concentration, pH, biosorbent dose, temperature, and inactivation methods were determined for both metals, each factor defined as a fixed factor with two levels. Optimization of the parameters affecting the removal process was determined by the Taguchi method and the signal-to-noise (S/N) ratios are calculated. The maximum removal efficiency (99.92%) was observed at pH 7, biosorbent 1 mg L^–1, inactivation with autoclaving, and at 20°C with an initial metal concentration of 50 mg L^–1 Cr (III). On the other hand, the maximum removal efficiency (98.99%) was observed at pH 4, biosorbent 5 mg L^–1, inactivation with autoclaving, and at 20°C with an initial metal concentration of 50 mg L^–1 Pb (II). Furthermore, metal ions removal by P. chrysogenum was also confirmed by scanning electron microscopy (SEM) combined with an energy dispersive X-ray spectrometer (EDS). The presence of functional groups on fungal cells of metal binding was investigated by Fourier transform infrared (FT-IR).     

The fate of heavy metals in green waste composting

It has long been known that heavy metals, when in high enough concentration, have the potential to be both phytotoxic and zootoxic. Heavy metals are frequently found as contaminants in green waste. Any such waste that is subsequently segregated for composting theoretically has the potential to retain that possible contamination. To date, there have been a limited number of publications addressing this issue. Most reports have concentrated on the types of heavy metals found in compost and their acceptable levels, rather than the fate of heavy metal contaminants throughout the composting process. This investigation was aimed to identify the fate of cadmium (Cd), copper (Cu), chromium (Cr), lead (Pb) and zinc (Zn) concentrations throughout a fourteen week composting cycle. The results of this study showed a general increase in the removal of Pb, Cu, Cr, and to a much smaller extent Zn, manifested by a decrease in their overall concentrations within the solid fraction of the final product, by 93, 49, 43, and 20 percent respectively. By contrast, there was no decrease in the overall concentration of Cd.     

A review and experimental verification of using chitosan and its derivatives as adsorbents for selected heavy metals

A literature survey on liquid-phase adsorption of selected heavy metals including Cu(II), Zn(II), Ni(II), Cd(II), Pb(II), Hg(II), and Cr(VI) on chitosan (CTS) and its derivatives was made from the viewpoint of adsorption capacity. This parameter was obtained from the Langmuir fit of isotherm data. The magnitude of adsorption capacity of heavy metals on pristine CTS was also used to discuss the mechanism of adsorption; that is, how many amino groups in CTS chains would coordinate with one heavy metal ion. Furthermore, a newly defined parameter, the approaching equilibrium factor R_L, was proposed to quantitatively indicate the favorability of the related adsorption process and to judge the correctness of adsorption capacity determined by the Langmuir equation.     

不同酸消解方法在土壤重金属测定中的比较研究

分别用三种不同的酸消解方法进行土壤标准样品的前处理,用原子吸收分光光度法测定其中铜、铅、锌、镉、镍、锰、总铬元素的含量。结果表明,电热板/硝酸-过氧化氢-氢氟酸消解方法耗酸量少,消解时间短,适用于土壤中铜、铅、锌、镉、镍、锰元素的前处理,相对标准偏差为1.0%～5.0%;而使用电热板/硝酸-硫酸-氢氟酸方法针对土壤中总铬元素进行消解前处理,准确度更高,相对标准偏差为2.7%～5.1%。     

Assessment of the Effectiveness of Environmental Dredging in South Lake,China

Environmental dredging is a primary remedial option for removal of the contaminated material from aquatic environment. Of primary concern in environmental dredging is the effectiveness of the intended sediment removal. A 5-year field monitoring study was conducted to assess the effectiveness of the environmental dredging in South Lake, China. The concentrations of total nitrogen (TN), total phosphors, and heavy metals (Zn, Pb, Cd, Cu, Cr, Ni, Hg, and As) before and after dredging in sediment were determined and compared. Multiple ecological risk indices were employed to assess the contamination of heavy metals before and after dredging. Our results showed that the total phosphorus levels reduced 42% after dredging. Similar changes for Hg, Zn, As Pb, Cd, Cu, Cr, and Ni were observed, with reduction percentages of 97.0, 93.1, 82.6, 63.9, 52.7, 50.1, 32.0, and 23.6, respectively, and the quality of sediment improved based on the criterion of Sediment Quality Guidelines by USEPA and contamination degree values (C_d) decreased significantly (paired t-test, p < 0.05). Unexpectedly, the TN increased 49% after dredging compared to before dredging. Findings from the study demonstrated that the environmental dredging was an effective mechanism for removal of total phosphorus and heavy metals from South Lake. Nevertheless, the dredging was ineffective to remove total nitrogen from sediment. We conclude that the reason for the observed increase in TN after dredging was likely ammonia release from the sediment impairing the dredging effectiveness.     

Effect of liming on the distribution of heavy metals in untreated industrial sewage sludge produced in Pakistan for the cultivation of <Emphasis Type="Italic">Sorghum bicolor</Emphasis> (L.)

The recycling of sewage sludge on agriculture land represents an alternative, advantageous, disposal of this waste material. The aim of the present study was to evaluate the feasibility of using industrial sewage sludge, produced in Pakistan, as a fertiliser. Agricultural soil amended with 25% (w/w) sewage sludge with or without lime treatment was used for growing a variety of sorghum (PARC-SS-1). The mobility of the heavy metals (HMs) (Cd, Cu, Cr, Ni, Pb and Zn) and metalloid (As) in the untreated industrial waste water sewage sludge (UIWS) samples were assessed by applying a modified BCR (Community Bureau of Reference) sequential extraction procedure. The single extraction procedure comprised of the application of mild extractant (CaCl₂) and water for the estimation of the proportion of easily soluble metal fractions. The precision and accuracy of BCR was evaluated by using a certified reference material of soil amended with sewage sludge BCR 483. The plant available metal contents, as extracted by the deionised water and 0.01 M CaCl₂ solution and exchangeable fraction of BCR sequential, decreased with lime application in the range of 10–44% for As, Cr, Ni, Pb and Zn, except in the cases of Cd and Cu, where their mobility was increased by 10% and 24%, respectively. Sludge amendment enhanced the dry weight yield of sorghum and the increase was more obvious after liming up to 25%. The uptake of HMs were lower in test samples (3.2–21.8%), except for Cu and Cd, which was higher (4%), while they were below the permissible limit of these metals. The present experiment demonstrates that liming was important in factors facilitating the growth of sorghum in sludge-amended soil.     

西湖和东苕溪沉积物重金属化学形态分析

不同赋存形态重金属的环境行为和生态效应不同,水体沉积物中重金属的迁移转化及其潜在环境危害更大程度上取决于其赋存形态。本研究在西湖和东苕溪设置12个采样点采集沉积物样品,采用改进BCR分步提取法,提取了重金属污染物的4种化学形态,分别为弱酸提取态、可还原态、可氧化态及残渣态。结果表明:沉积物中Cd以弱酸提取态为主,对外界环境的变化极其敏感,并易于发生迁移转化,生态风险较高。Cu离子对有机质表现出极强的亲和力导致Cu的可氧化态含量较高也有一定的生态风险。Pb会被Fe-Mn氧化物所吸附导致Pb的可还原态含量较高,存在较高的潜在生态危害。Mn的弱酸提取态、可还原态和残渣态含量都较高,在迁移的过程中变化地较快,能够逐渐降低Mn对自然环境的危害。其他各重金属(As、Cr、Zn)则都以残渣态为主,潜在危害较低。     

Understanding heavy metal and suspended solids relationships in urban stormwater using simulated rainfall

Urban stormwater from simulated rainfall on three different landuses in Queensland State, Australia (residential, industrial, commercial) was analysed for heavy metals and physico-chemical parameters such as Dissolved Organic Carbon (DOC) and Total Suspended Solids (TSS). Rainfall events were simulated using a specially designed rainfall simulator for paved surfaces. Event mean concentration samples were separated into five different particle sizes and analysed individually for eight metal elements (Zn, Fe, Cr, Cd, Cu, Al, Mn and Pb). Multivariate data analysis was carried out for the data thus generated. It was found that DOC and TSS influence the distribution of the metals in the different particle size classes. Zn was correlated with DOC at all three sites. Similarly, Pb, Fe and Al were correlated with TSS at all sites. The distribution of Cu was found to vary between the three sites, whilst Cd concentrations were too low to assess any relationships with other parameters. No correlation between Electrical Conductivity (EC), pH and heavy metals was found at the three sites. The identification of physico-chemical parameters influencing the distribution process kinetics of heavy metals in urban stormwater will significantly enhance the efficiency of urban stormwater management systems.