Effects of heavy metals on some soil biological parameters

The soils most polluted by heavy metals are probably alluvial soils. One of them is the alluvium of the Litavka River. The heavy metal content was much higher in some cases than the threshold values, allowed by the Czech standards. The effect of soil contamination on enzyme activity is presented. Generally, the values of enzymatic activities were highest in the soil above the source of contamination and they decrease as they approach the source of contamination. All measured parameters were affected by heavy metal concentrations. Our results demonstrate that several parameters of microbial activity could be used as good indicators of increasing concentrations of Cd, Pb and Zn in soil.     

Adsorption of heavy metals in glacial till soil

The charged sites on soil particles are important for the retention/adsorption of metals. Metallic counterions can neutralize the intrinsic charges on the surfaces of soil particles by forming complexes. In this study, efforts have been made to determine the effect of surface potential, pH, and ionic strength on the adsorption of four metal ions, hexavalent chromium Cr(VI), trivalent chromium Cr(III), nickel Ni(II) and cadmium Cd(II), in glacial till soil. Batch tests were performed to determine the effect of pH (2–12) and ionic strength (0.001–0.1 M KCl) on zeta potential of the glacial till soil. The point of zero charge (pH _PZC ) of glacial till was found to be 7.0±2.5. Surface charge experiments revealed the high buffering capacity of the glacial till. Batch adsorption experiments were conducted at natural pH (8.2) using various concentrations of selected metals. The adsorption data was described by the Freundlich adsorption model. Overall glacial till shows lower adsorption affinity to Cr(VI) as compared to cationic metals, Cr(III), Ni(II) and Cd(II).     

Changes in mobility and speciation of heavy metals in clay-amended incinerator fly ash

The generation of municipal solid waste incinerator fly ash (MSWIF) has been increasing significantly over the recent past, and its disposal is problematic and costly due to high concentration of leachable heavy metals present in the material. This study explored a potential stabilization of MSWIF by blending with a natural sorbent material with low permeability, clay, and assessed the potential release of heavy metals from the stabilized mixtures under various simulated subsurface environments. The leachability of heavy metals such as Pb, Cd, Cr, Zn and Cu in the MSWIF-clay mixtures cured for 1 to 360 days was investigated by performing leaching tests and sequential chemical extractions (SCE). Leaching tests were performed at acidic, neutral and alkaline pH values. The leaching test results suggested that the natural clay could turn the MSWIF into non-hazardous material. All the MSWIF-clay mixtures demonstrated leaching behavior different from that of the original MSWIF. SCE results revealed that the acidic and reducing conditions were the most unfavorable to the immobilization of the heavy metals in the stabilized MSWIF-clay matrix. Conversely, the oxidizing and alkaline conditions were not critical to the stabilized MSWIF-clay mixtures. Apparently, clay in the mixtures could function as an adsorptive micro-barrier to retain the heavy metals within the MSWIF-clay matrices.     

Competitive sorption of intermixed heavy metals in water repellent soil in Southern Australia

In water repellent soil, Cr, Pb and Cu showed higher adsorption intensities than Zn, Cd and Ni did. Soil water repellency is much more widespread than formerly thought. In order to promote fertility and productivity, the irrigation of recycled water onto water repellent soil may be an applied technology to be used in some areas of Southern Australia. Therefore, heavy metals in recycled water potentially enter into the soil. The competitive sorption and retention capacity of heavy metals in soil are important to be determined, especially considering the special geochemical origin of water repellent soil that was caused by waxes on or between the soil particles. Batch equilibrium sorption experiments on Cd, Cr, Cu, Ni, Pb and Zn in their typical proportion in recycled water were conducted in water repellent soil. The sorption intensity, sorption isotherm in the experiments together showed that Cr, Pb and Cu have higher sorption intensity than those of Zn, Ni and Cd in the competitive system. The risk assessment for the application of recycled water onto water repellent soil is definitely necessary, especially for the metal cations with relatively weak sorption.     

承德市土壤重金属空间结构与分布特征

基于地统计学和GIS相结合的方法,对承德全域表层土壤重金属As、Cd、Cr、Cu、Hg、Ni、Pb、Zn、微量元素Se正态分布特征、主导分布趋势及相互作用规律进行了分析,确定了不同元素最适宜的地统计插值模型并厘定出其空间分布规律。结果表明：As、Cd、Cr、Cu、Hg、Ni、Pb、Zn的质量含量平均值分别为8.28,0.200,60.85,24.37,0.034,27.76,26.65,77.10 mg/kg,Cd、Cu、Hg和Pb变异系数分别为385%、143%、350%、118%,分异性强。Zn含量均值受土壤类型影响显著,Cr、Cu、Ni含量均值则受土地利用类型影响显著。经过不同趋势阶数元素插值误差的综合对比,确定As、Cr、Pb、Zn、Ni、Se适宜选择无趋势参数,Hg和Cu适宜选择一阶趋势参数,而Cd适宜选择二阶趋势参数。As的理论模型为指数模型,主要受到结构性因素的影响;Cd、Cr、Cu、Hg、Ni、Pb、Zn、Se的理论模型为线性模型,主要受到随机性因素的影响。通过普通克里格插值图可见区内9种元素具有北低南高的特点,中部地区形成了一条较宽的Pb高值带,与Cd相似。按照含量分布特点,土壤中Cr和Ni、Cu和Hg、Zn和Pb、Se和Cd之间的高值空间展布区具有相似性且来源相同,仅As具有个性,分析结果与传统统计学结果数据保持部分一致性。     

吉林中部黑土区重金属元素生态地球化学特征

基于吉林省中部黑土区地球化学调查数据,分析统计As、Cd、Cr、Cu、Ni、Zn 6种可造成重金属污染的元素在土壤--作物系统中的生态地球化学特征。通过吉林省部分地区土壤样品与玉米籽实样品采样,采用元素有效系数与元素累积系数的方法,计算出采样点的土壤重金属元素全量、有效量和玉米籽实含量特征,从而研究重金属元素生态地球化学特征。结果表明:(1)研究区土壤重金属元素全量虽然较吉林省土壤元素背景值增加明显,但土壤与玉米籽实均未达到污染状态。(2)重金属元素有效系数均值由小到大依次为As Cr Zn Cu Ni Cd,在研究区的空间分布差异性较大;玉米籽实积累系数均值由小到大依次为Cr As Ni Cd Cu Zn,在的空间分布差异性相对较小。(3)吉林省中部黑土区的玉米籽实重金属元素积累程度均较低,在未发生土壤重金属元素污染的清洁土壤中,Cu与Zn对于玉米植株来说,属于必需营养元素范畴;重金属元素中Cd的有效系数大,作物可食部分积累程度较高,应注意其预防与治理工作; As与Cr的有效系数较小,可能是导致其在玉米籽实中积累程度较低的主要影响因素之一; Ni在土壤中有效态转化程度较高,玉米籽实Ni吸收量相对较低。(4)多数重金属元素在玉米籽实中的累积程度与其在土壤中的有效系数呈正相关关系。     

Removal of selected heavy metals from aqueous solutions using a solid by-product from the Jordanian oil shale refining

 The potential use of treated solid by-product of oil shale to treat aqueous solutions containing several heavy metals, i.e., Cd(II), Cu(II), Cr(III), Ni(III), Pb(II) and Zn(II), was explored. Different experimental approaches including equilibrium batch mode experiments and X-ray fluorescence (XRF) were used to explore the feasibility of this material as a cheap adsorbent for the removal of these heavy metals from predetermined solutions. Results indicate that the solid by-product of oil shale removes Cd(II), Cu(II), Ni(II), and Pb(II), from aqueous solutions by adsorption, but did not remove the other heavy metals investigated in this study. Received: 20 April 1998 · Accepted: 20 November 1998     

Mobility of heavy metals from coal fly ash

The mobility of Cd, Co, Cu, Ni, Pb, Sb, and Zn from six different coal-fired power plant fly ashes that show a wide compositional range was examined using a sequential extraction procedure in order to assess their mobility when these wastes are ponded or landfilled. The extraction sequence was as follows: (1) water extractable, (2) cation exchangeable (CH₃COONH₄ at pH 7), (3) surface oxide-bound cations (CH₃COONH₄ at pH 5), (4) Fe oxide-bound cations (HONH₃Cl), and (5) residual (HF, HCl, HNO₃, 211). The heavy metal contents in the extraction solutions were determined by anodic (Cd, Cu, Pb, Sb, and Zn) and cathodic (Ni and Co) stripping voltammetry. The results reveal differences in the total contents of the selected trace elements among the fly ash samples, which must be related to differences in coal composition and combustion technology. The extractable fraction under natural conditions ranges from 1.5 to 36.4 percent of the total element content. Cadmium, Co, Cu, and Zn show the highest extractable fraction (10.8–18.9 percent on average). Cadmium is the most easily water-extractable element, while Co, Cu, and Zn increase their mobility as the severity of the extraction increases. Cobalt, Ni, Pb, and Zn are mainly associated with the surface oxide-bound and Fe oxide-bound fractions. Nickel, Pb, and Sb have low mobility potentials (5.3–6.6 percent as extractable fraction), but Sb presents a relatively high water-extractable fraction.     

Sources of major ions and heavy metals in rainwater associated with typhoon events in southwestern Taiwan

Dissolved chemical compositions in rainwater have provided valuable information on pollutant sources in the atmosphere and short-term environmental changes. However, baseline chemical data associated with typhoon is rather limited. In this study, a suite of time-series rain specimens including four typhoon events are collected from Tainan city, southern Taiwan and analyzed for major ions, heavy metals and Pb isotopes to elucidate mechanisms causing dissolved components variation in rainwater and to understand how heavy metals are transported by air-mass along typhoon pathways.     

Statistical characteristics of heavy metals content in groundwater and their interrelationships in a certain antimony mine area

In recent years, most of domestic and foreign researches about heavy metal pollutions of metal mine mainly focus on water, soil and plants on the surface. There is lack of researches about heavy metal pollution in groundwater of metal mine. In this research, a certain antimony mine area is selected as a typical study area. Also, the study about statistical characteristics of heavy metals in groundwater has been carried out. Furthermore, the interrelationships have been preliminarily discussed through related analysis, such as relevant analysis, cluster analysis and principle component analysis. The results show that: the excessive elements in groundwater of study area are Sb, As, Pb, Se, and Ni. The average mass concentration of Sb, As, and Pb is higher than that of drinking water standards (GB5749-2006). The concentration of most heavy metals in dry season is lower than or equal to that in wet season for groundwater. Zn is the only metal in groundwater showing a different pattern, the concentration of which in dry season is higher than that in wet season. Under the impacts of stratum leaching and absorption effect, the concentration of heavy metals (except Pb and Ba) in groundwater are lower than or equal to that in surface water. As and Se, the two heavy metals have a significant positive correlation, which shows the two elements might have gone through similar environmental geochemical effect. Also, the connection among Zn, Hg, Pb, and Mn is not obvious; therefore, the sources of those elements are quite different. In addition, the elements of Se and As have obvious positive interrelationship with elements of CO32- and F-. Also, the Pb has significant positive correlation with PO43-, H2SiO3 and oxygen consumption. The results of cluster analysis show that 9 different heavy metals in the study area can be divided into 3 categories: Zn, Cd, Mn, Hg, Cu, and Cr belong to the first category, Se and As belong to the second one, and the last category is Pb. Also, the principle component analysis divides 6 heavy metals (Zn, As, Hg, Pb, Mn, and Se) into 4 different principle components, which can be utilized to assess heavy metals pollution situations in groundwater. The reliability of this method is higher than 91%. Moreover, the research provides theory basis and models for establishing evaluation index system and exploring the evaluation method of heavy mental pollution in groundwater.     

Bioaccumulation of heavy metals in oyster (Crassostrea virginica) tissue and shell

Oysters and sediment have been collected from most major US Gulf of Mexico bays and estuaries each year since 1986. Selected samples of oyster soft tissue, shell and sediments were analyzed for Cd, Cr, Cu, Fe, Mn, Pb, and Zn for this study. Concentrations varied considerably from place to place but ratios of metals remained relatively constant. Cu and Zn are greatly enriched in oyster tissues, which is related to their physiological function. Cd is enriched in oyster shell because of the easy substitution between Cd and Ca. The concentrations of Pb and Cr in oysters are significantly lower than that in sediment, suggesting a good discrimination against these metals by oysters. Metal variations are a result of both nature and human activity. Received: 13 September 1999 · Accepted: 8 December 1999     

Competitive adsorption,release and speciation of heavy metals in the Yellow River sediments,China

The competitive adsorption and the release of selected heavy metals and their speciation distribution before and after adsorption in the Yellow River sediments are discussed. The adsorption of metals onto sediments increases with increasing pH value and decreases with increasing ionic strength. The competitive coefficient K _c and the distribution coefficient K _d are obtained to analyze the competitive abilities of selected heavy metals, which are ranked as Pb > Cu >> Zn > Cd. The competition among selected heavy metals becomes more impetuous with increasing ion concentration in water. Speciation analysis was done by an improved analytical procedure involving five steps of sequential extraction. Cu, Pb and Zn were mainly transformed into the carbonate-bound form (50.8–87.7%) in adsorption. Most of (60.7–77.3%) Cd was transformed into the exchangeable form, and the percentage of carbonate-bound Cd was 19.7–30.4%. The release reaction was so quick that the release capacity of selected heavy metals from sediments to aqueous solution reached half of the maximum value only in 30 s. As opposed to adsorption, the release capacities of selected heavy metals were ranked as Cd > Zn >> Cu > Pb. In this study, Cd produces the most severe environmental hazards, because its concentration in the release solution is 85.8 times more than the human health criteria of US EPA.     

Adsorption Behavior and Mechanism of Environmental Pollutants on Graphene Oxide

Graphene oxide, as an emerging material for contaminants removal,possesses relatively large specific surface area, and it shows good dispersion in water phase due to the hydrophilicessence resulted from abundant oxygen-containing functional groups on the edge, thus leading to a potential excellent adsorbent. Current studies revealthat, because graphene oxide is negatively-charged in a wide range of pHs, the removal efficiency of heavy metals and cationic dyes by graphene oxide is significantly higher than by traditional adsorbents, like activated carbon. However, its applications are still limited due to its structural defects. For example, its π domain is destructed during fabrication process. Therefore, certain structural modifications need to be conducted on the purpose of improving its performance, achieving a better result in water purification. This paper presented the preparation and structure of graphene oxide, and reviewed the adsorption behaviors, adsorption mechanisms, adsorption models and influence factors of heavy metals and organic pollutants on graphene oxide and its composites, respectively. In view of unresolved issues, further research should focus on comprehensive adsorption mechanisms, more facile and effectivemethods for structural modifications and the treatment of graphene oxide after adsorption process.     

Supergene processes on ore deposits—a source of heavy metals

The study of supergene processes (i.e., secondary processes running in ore deposits and driven by thermodynamic nonequilibrium between ore-and rock-forming minerals and natural waters, gasses, etc.) is important in order to understand the migration of heavy metals from ore into their adjacent surroundings. The contamination of the local environment can be characterized by the composition of pore waters. The Pb-Zn-Cu ore deposits of Zlaté Hory (Czech Republic) have been chosen for a detailed study of pore solutions. A simple model has been created to describe the evolution of supergene processes in the ore deposits. This model is based on the determination of chemical composition of pore solutions. The dilution of pore solutions of such mineral deposits results in acid mine drainage. Pore solutions can have, during specific stages of their evolution, relatively high concentrations of Cu (0.09 mol/kg), Zn (0.1 mol/kg), SO₄ (0.8 mol/kg) and an extremely low pH (1.38). The supergene alteration of pyrite is the most important process determining the character of pore water. This reaction causes significant acidification and is a leading source of acid mine drainage. The leached zone originates from the interaction of pyrite and limonite. Increased concentrations of heavy metals and sulfates occur in pore waters. The dynamic composition of pore waters within ore deposits undergoing the supergene process can be used to distinguish: (1) three main zoneslimonite, transition, and primary zone and (2) two areas—an area with the highest intensity of weathering processes and an area of weathering initiation. In these areas the rate of sulfide oxidation is higher as a result of low pH. From the study of these zones and areas we can further our knowledge of ore body, pore solution, acid mine drainage, and contamination of the local environment.     

土壤中重金属形态分析方法研究

介绍了一种重金属形态分析连续多级提取新方法,用国家一级标样进行试验研究,并用国际标样做对比研究,表明该方法具有分组合理、更接近自然状态、操作简便易行、数据稳定可靠的特点,可为土壤环境中的重金属形态的研究及其环境危险评价提供更精确的元素信息。     

土壤中重金属有效态分析方法研究

土壤中重金属的不同形态决定了对于生物的有效性。自然界的重金属元素参与生态迁移能够被生物吸收利用的部分为生物有效态。土壤重金属可交换态的研究可以为其生物有效态研究提供参考。本文对于土壤中砷、汞、铬、镉、铅和铊的酸溶态、络合态和盐溶态这几种单一提取方式的可交换态的分析方法进行了研究比较,以其提取效率高的为有效态的表现方式,以p H值7.5为土壤酸碱度的界限,建立了土壤中的砷、汞、铬、镉、铅和铊在不同酸碱度下的分析方法。本方法的Cr的方法检出限为4.65ng/g;Cd的方法检出限为0.49ng/g;Pb的方法检出限为9.73ng/g;As的方法检出限为21.89ng/g;Hg的方法检出限为0.30ng/g;Tl的方法检出限为0.54ng/g。采用GBW7412,GBW7413,GBW7416这三个国家一级标准物质样品测得的方法精密度范围6.01%~19.3%。本方法适用于土地质量评估的要求。     

Spatial variations in heavy metals on tidal flats in the Yangtze Estuary,China

Surface samples are used to determine onshore-offshore variations in heavy metal concentrations on tidal flats on Chongming and Hengsha Islands in the Yangtze Estuary, China. The Mann-Whitney U-Test suggests that proximity to the estuarine turbidity maximum does not result in significantly higher metal concentrations on tidal flats. Principal Components Analysis shows that grain-size is the primary control on metal concentrations, reflecting the occurrence of salt marsh and mud and sand flats. Sediment quality is comparable to that of pristine estuaries because of dilution by high river sediment loads.     

Historical changes in heavy metals in the Yangtze Estuary, China

A 6-m-long core was used to examine historical changes in heavy metals on tidal flats in the Yangtze Estuary, China. Over the last 100 years, human impact was minimal. However, over the last few decades, vertical metal concentrations have been affected by human activities such as local industrialization, urbanization and construction of major sewage outlets. Copper, lead and arsenic were identified as contaminants in the Yangtze Estuary on the basis of national pollution standards and a comparison of metals in the upper core with those in the lower core.     

Regional distribution pattern of groundwater heavy metals resulting from agricultural activities

Contaminations of groundwater by heavy metals due to agricultural activities are growing recently. The objective of this study was to evaluate and map regional patterns of heavy metals (Cd, Zn and Cu) in groundwater on a plain with high agricultural activities. The study was conducted to investigate the concentration of heavy metals and distribution in groundwater in regions of Shush Danial and Andimeshk aquifers in the southern part of Iran. Presently, groundwater is the only appropriate and widely used source of drinking water for rural and urban communities in this region. The region covers an area of 1,100 km² between the Dez and Karkhe rivers, which lead to the Persian Gulf. For this study, the region was divided into four sub-regions A, B, C and D. Additionally, 168 groundwater samples were collected from 42 water wells during the earlier months of 2004. The flame atomic absorption spectrometry (AAS-Flame) was used to measure the concentration of heavy metals in water samples and the Surfer software was used for determination of the contour map of metal distribution. The results demonstrated that in all of the samples, Cd and Zn concentrations were below the EPA MCLG and EPA secondary standard, respectively. However, the Cu contents of 4.8 % of all samples were higher than EPA MCL. It is also indicated that the concentrations of metals were more pronounced at the southern part of the studied region than at the others. The analysis of fertilizers applied for agricultural activities at this region also indicated that a great majority of the above-mentioned heavy metals were discharged into the environment. Absence of confining layers, proximity to land surface, excess agricultural activities in the southern part and groundwater flow direction that is generally from the north to the southern parts in this area make the southern region of the Shush plain especially vulnerable to pollution by heavy metals than by other contaminants.     

利用黏土矿物计算背景值评估沉积物重金属污染

综合考虑样品性质及粒度的影响,提出利用黏土矿物计算背景值的方法。实例研究表明,研究区沉积剖面不同深度样品的背景值存在一定的差异。将实测值与背景值之比视为富集因子,发现As、Cr、Cu在剖面的中下部弱富集;Pb在剖面中部弱富集;Zn与Cd在剖面的不同位置的富集程度变化较大,在中部显著富集,表层及底部中度富集。与传统方法相比,该方法综合考虑了粒度和样品性质的影响,并且可以计算出不同位置样品的背景值,使得评估结果更加准确。