Heavy metal sorption and desorption capacity of soils containing endogenous contaminants

Soils on serpentinites in some regions of northwestern Spain have been the subject of agricultural management practices involving the use of fertilizers and various types of organic waste containing heavy metals. Although such practices have facilitated crop growth, they have also raised the natural contents in heavy metals of the soils. In this work, three ferralic Cambisols and another three mollic Leptosols with high Cr and Ni contents were used to study competitive sorption and desorption of six heavy metals via K(d100), which was employed as a measure of the ability of the soils to adsorb and retain each metal. Lead was found to be the metal sorbed and retained to the greatest extent, and Cd, Ni and Zn those sorbed and retained in the smallest amounts. Although the ferralic Cambisols were found to contain greater amounts of natural heavy metals, they exhibited an increased ability to adsorb and retain the body of metals relative to the mollic Leptosols by effect of their increased contents in clay and Fe, Mn and Al oxides, in addition to their higher ion-exchange capacity. Based on the results, Pb and Cu are strongly bound, and Zn, Cd and Ni weakly bound, to the soils. The ferralic Cambisols exhibited an increased capacity to adsorb and retain Cd, Ni, Zn and--especially--Cr than the mollic Leptosols; the latter, however, proved more effective in adsorbing and retaining Cu and Pb by virtue of their increased organic matter contents. Copper sorption and retention, and Pb retention, were found to be correlated with the content in organic matter and that in vermiculite--which was only present in the mollic Leptosols--in the clay fraction.     

Heavy metal accumulation from coal fly ash by cyanobacterial biofertilizers

Bioleaching of heavy metals (Cu, Zn, Cr and Pb) from coal fly ash by cyanobacterial strains (Nostoc muscorum, Anabaena variabilis, Tolypothrix tenuis and Aulosira fertilissimia), that are commonly used as biofertilizers in rice cultivation was studied to assess utilization of fly ash while mitigating its environmental metal toxicity. Cyanobacteria were grown at different concentration of fly ash at 0, 5, 10, and 20% was treated with different blue green algal strains (Nostoc muscorum, Anabaena variabilis, Tolypothrix tenuis, and Aulosira fertilissimia) in suitable growth medium (BG-11) and distilled water to observe their growth and metal accumulation. Nostoc muscorum (ARM 442?mg?g^?1) showed maximum uptake of Cr (3.65?mg?g^?1), Pb (2.12?mg?g^?1) at BG 11(-N) medium amended with 10% fly ash, respectively. Anabaena variabilis (ARM 441) showed maximum uptake of Cu (0.313?mg?g^?1) and Pb (2.01?mg?g^?1) in BG 11 (–N) medium amended with 5% fly ash whereas Cr uptake (1.21?mg?g^?1) at 10% fly ash and Zn uptake (0.697?mg?g^?1) at 20% fly ash grown in BG 11(-N) medium. Increased accumulation of metals in blue green algae biomass grown in BG 11(-N) medium amended fly ash confirms that metal concentration was balanced between the algal strains.     

Heavy metal contamination in soils and vegetables near an e-waste processing site, South China

Environmental pollution due to uncontrolled e-waste recycling activities has been reported in a number of locations of China. In the present study, metal pollution to the surrounding environment from a primitive e-waste processing facility was investigated. Soils at sites where e-waste is burned in the open air, those of surrounding paddy fields and vegetable gardens, as well as common vegetable samples were collected and analyzed for heavy metals. The results showed that the soils of former incineration sites had the highest concentrations of Cd, Cu, Pb, and Zn with mean values of 17.1, 11,140, 4500, and 3690 mg kg(-1), respectively. The soils of nearby paddy fields and vegetable gardens also had relatively high concentrations of Cd and Cu. In the edible tissues of vegetables, the concentrations of Cd and Pb in most samples exceeded the maximum level permitted for food in China. Sequential leaching tests revealed that the Cu, Pb, and Zn were predominantly associated with the residual fraction, followed by the carbonate/specifically adsorbed phases with the exception of Cd, which was mainly in the extractable form in paddy fields and vegetable soils. The data showed that uncontrolled e-waste processing operations caused serious pollution to local soils and vegetables. The cleaning up of former incineration sites should be a priority in any future remediation program.     

Distribution of naturally occurring radionuclides in soils of the southern districts of Bangladesh

The activity concentrations of naturally occurring radioactive materials in soil samples of an elevated radiation background area of nine southern districts of Bangladesh were determined using gamma-ray spectrometry with an aim of evaluating the environmental radioactivity. The outdoor and indoor external effective dose rates and the radiation hazard indices from the soil activity were evaluated with an aim of minimising the harmful effects of ionising radiation to the population of the area concerned. The activity of (137)Cs was measured and observed in some of the locations.     

Heavy metal fixing and heat resistance abilities of coal fly ash-waste glass based geopolymers by hydrothermal hot pressing

Hydrothermal hot pressing (HHP) was used to prepare high compressive strength fly ash-wasted glasses based geopolymers, which was subject to thermal analysis and the test of heat resistance as well as heavy metal solidification. Results showed that the geopolymers had good efficiency of encapsulating and fixing heavy metals. As for heavy metal element like Cu, Zn, Cd and Pb, the fixed efficiency reach at least 95%. Heat resistance test showed that the most mass-loss ratio of geopolymers was below 11.04% and the compressive strength was more than 55.27?MPa when it was calcined at 200–1000?°C for 2?h. During the calcining, geopolymers had gone through several main processes, including the evaporation of the free water, the bound water and constitutional water, the decomposition of carbonate, combustion of carbon, and crystallization reaction. XRD and FT-IR analysis showed that when calcined at 1000?°C, there produced several new crystallization phases with good heat resistance, including nepheline, kyanite, sillimanite. The improvement of this work does not only reflect that the hydrothermal hot pressing is featured by simple procedures, easy automation, timesaving and low cost, and also provide a long-term goal project, which could meet both demands: utilizing solid waste, saving resources and protecting the environment.     

Characterization of metal pollution in soils under two landuse patterns in the Angouran region, NW Iran; a study based on multivariate data analysis

The study presents the application of selected multivariate statistical methods (multivariate analysis of variance, discriminant analysis, principal component analysis) and geostatistical techniques to evaluate soil pollution status in arable lands of the Angouran region, NW Iran. Two representative landuse patterns, cropland and grassland, were selected for the purpose of this study. Seventy soil samples (35 topsoils and 35 subsoils) were collected from the two landuse types and 21 soil parameters including total element content and physicochemical properties were also determined. Results from application of the multivariate analysis of variance showed that the two landuse patterns were not statistically differentiated by subsoil variables, whereas significant differences existed between the two landuse patterns with respect to topsoil variables. Discriminant analysis rendered seven variables (Cu, As, Cd, OM, P, K and total N) as indicator parameters responsible for the discrimination between the two landuse types. Using the principal component analysis (PCA), two main components (PCs) explaining 71.71% of total variance were extracted. PC1, with a high contribution of Ni, Cr, Fe, Mn and clay content was hypothesized as lithogenic component and PC2, with high loadings for the seven discerning variables (Cu, As, Cd, OM, P, K and total N), was considered as an agrogenic component. Geostatistical analyses, including the calculation of semivariogram parameters and model fitting, further supported the PCA results. PC1 was generally characterized by moderate spatial dependence and long-range spatial variation (8000 m) influenced by soil parent martial composition, while PC2 was modelled by pure nugget effect probably reflecting the influences of agrogenic activities. The findings of this study could not only expand our knowledge regarding the soil pollution status in the study area, but would also provide decision makers with the information to manage the agrochemical application in the arable lands to improve the sustainability and safety of intensive-farming activities in the study area.     

Assessment of the occupational exposure at a fertiliser industry in the northern part of Greece

In the northern part of Greece, close to the city of Kavala, a phosphoric acid production industry has operated since 1965. The raw material used is the phosphate rock imported from the foreign countries. During industrial processes, naturally occurring radioactive materials (NORM) deposits exist in many facilities in the industry, causing increased levels of radiation exposure. Additionally, increased levels of NORM concentrations are also detected in the waste material of the production process, the phosphogypsum. According to the Greek Regulations for Radiation Protection (no. 216B, 5/3/2001), which is in accordance with the 96/29/EURATOM 31/5/1996, the action levels concerning the effective dose to workers at workplaces due to natural radiation sources are 1 mSv y(-1). Work activities where the corresponding doses exceed 6 mSv y(-1) are under the control of the Greek Atomic Energy Commission (GAEC). The mean yearly radon concentration action level at workplaces is 400 Bq m(-3), while the corresponding concentration limit is 3000 Bq m(-3), respectively. GAEC, according to its constitutional law, is the responsible organisation to enforce and to implement the law by means of in situ surveys and laboratory measurements. The first inspection of the area was performed in 2002 and the first measures were proposed. Periodic inspections were performed every 2 y in order to extend the operation licensing of the industry. In this work a dose assessment of the workers based on in situ and laboratory measurements is presented. In order to assess the doses to the workers the external and the internal doses are estimated.     

Study of natural radionuclide concentrations in an area of elevated radiation background in the northern districts of Bangladesh

The activity concentrations of naturally occurring radioactive materials in soil samples from an elevated radiation background area of three northern districts of Bangladesh were determined using gamma ray spectrometry. The outdoor and indoor external effective dose rates and the radiation hazard indices from these soil activities were evaluated. The dose rates were found to be about four times higher than the reported world average value. The concentration of natural radionuclides, derived radium equivalent activities and the representative level indices were also found to be higher. Recommendations on radiological and dosimetric measures have been suggested with an aim of minimising the harmful effects of ionising radiation to the population of the area concerned.     

Prediction of the PCB pollution in the soils of Bursa, an industrial city in Turkey

The purpose of this study was to predict the equilibrium soil concentrations and distributions of Sigma(41)Polychlorinated Biphenyl (PCB) congeners from the air data measured at 4 sites (urban, suburban, residential, and industrial) in Bursa between 2004 and 2005. The soil-air partition coefficient (K(SA)) was used for the predictions. Predicted soil concentrations ranged from 25 pg/g to 690 pg/g, while the atmospheric concentrations fluctuated between 35 pg/m(3) and 1112 pg/m(3). The soil concentrations were found to be in agreement with the lower range of European and global values, and below the regulatory limits. The urban and residential sites yielded higher PCB concentrations and a higher degree of heavier congeners than the sites characterized as suburban. The urban and residential sites were dominated by hexa-chlorinated biphenyls (CBs), followed by tri-CBs, while the industrial site was dominated by tri-CBs, followed by tetra-CBs. PCB congeners of 153, 180, 138, 118, and 101 were higher in all locations. The effect of the temperature changes on the concentrations was found to be insignificant, as the correlations ranged between 0.0009 and 0.22 for all sites. The K(SA) approach yielded reasonable results, and it is recommended to use this approach when there is limited data about the pollution levels of a certain media such as soil by using the measured levels of the other media such as air.     

Heavy metal stabilization in municipal solid waste incineration flyash using heavy metal chelating agents

Heavy metal chemical stabilization with synthesized heavy metal chelating agent was assessed for flyash from municipal solid waste incinerator. Flyash can contain heavy metals (e.g. Pb, Cd) which can leach. A new kind of heavy metal chelating agent showed more attractive competition than inorganic chemicals in stabilizing flyash. The synthesizing method of this kind of heavy metal chelating agent was explained in this paper, and the technology process and treatment efficiency of the chelating agent in treating flyash were experimentally studied, which was compared with the results of inorganic chemical agents such as sodium sulfide and lime. The heavy metals in flyash were stabilized more effectively by using heavy metal chelating agents than by using sodium sulfide and lime, furthermore, the stabilized products using the chelating agents can meet the landfill disposal controlling standards for heavy metal waste. pH-dependent leaching experiment showed the stabilized flyash by treatment with heavy metal chelating agent could keep long-term stabilization within a broad range of pH value. Thus, the risk of secondary pollution for the stabilized products was reduced dramatically when the environment condition changes during its disposal period.     

Heavy metal contamination in highway soils. Comparison of Corpus Christi,Texas and Cincinnati,Ohio shows organic matter is key to mobility

Heavy metal content of roadside soil samples from along the interstate highway systems in Corpus Christi, Texas and Cincinnati, Ohio was measured to assess the degree of contamination such soils contain and the likelihood that this contamination can be remobilized. High values of Ba, Cu, Pb, and Zn can be attributed to anthropogenic effects related to motor vehicles, whereas Cr and Ni variations are best ascribed to natural processes. The anthropogenic substances are strongly correlated to the amount of organic matter in the soil. Sequential extraction experiments, however, show that this organic matter is not extractable by agents that normally solubilize soil organic matter, so these metals are bound to an insoluble form of organic matter that is itself probably anthropogenic. The insolubility of the heavy metals and Ba indicates that these constituents are not likely to move in solution to water supplies, but they would still be subject to physical remobilization by roadway maintenance or even by grass mowing. Inhalation of small dust particles poses a potential health hazard to highway maintenance workers that needs to be assessed. Electronic Publication     

Phytochelatin synthase activity as a marker of metal pollution

The synthesis of phytochelatins is catalyzed by γ-Glu-Cys dipeptidyl transpeptidase called phytochelatin synthase (PCS). Aim of this study was to suggest a new tool for determination of phytochelatin synthase activity in the tobacco BY-2 cells treated with different concentrations of the Cd(II). After the optimization steps, an experiment on BY-2 cells exposed to different concentrations of Cd(NO₃)₂ for 3 days was performed. At the end of the experiment, cells were harvested and homogenized. Reduced glutathione and cadmium (II) ions were added to the cell suspension supernatant. These mixtures were incubated at 35 °C for 30 min and analysed using high performance liquid chromatography coupled with electrochemical detector (HPLC-ED). The results revealed that PCS activity rises markedly with increasing concentration of cadmium (II) ions. The lowest concentration of the toxic metal ions caused almost three fold increase in PCS activity as compared to control samples. The activity of PCS (270 fkat) in treated cells was more than seven times higher in comparison to control ones. K_m for PCS was estimated as 2.3 mM.     

Pattern, sources and toxic potential of PAHs in the agricultural soils of Delhi, India

Surface soil (0-5 cm) from various agricultural sites in Delhi was analyzed to discern the contents of 16 priority polycyclic aromatic hydrocarbons (PAHs). Reference and deuterated standards were used for identification and quantification of PAHs by high performance liquid chromatography (HPLC) with UV detection. summation operator(16)PAHs ranged from 830 to 3880 microg kg(-1) (dry wt.) with an arithmetic mean of 1910+/-1020 microg kg(-1) summation operator(16)PAHs values at the urban sites were 2-5 times higher as compared to the rural sites. In general, low molecular weight PAHs were predominant. Total organic carbon (TOC) was found to be significantly correlated with summation operator(16)PAHs. Isomer pair ratios and Principal component analysis (PCA) suggested biomass and fossil fuel combustion as the main sources of PAHs. The toxic equivalency factors (TEFs) were used to estimate benzo[a]pyrene-equivalent concentration (B[a]P(eq)). Therewith, PAH content of urban agricultural soil was found to have more carcinogenic potential.     

仁怀高粱中重金属元素含量的测定及评价

用原子吸收分光光度法对仁怀市五个乡镇种植的高梁进行了Cu、Zn、Pb、Cd元素含量的测定,采用单项污染指数和综合污染指数法对高粱进行重金属污染评价。结论:该方法灵敏度、准确度高,检出限低,相对标准偏差在0.48-2.88%之间,符合质量控制要求。所检样品中铜、锌含量低于国家食品卫生标准中允许的最低标准要求,高粱中铅、镉含量低于检出限未检出。仁怀市五个乡镇种植的高粱中单项污染指数均很低,其综合污染指数为0.51,因此,所检仁怀市乡镇高粱未受重金属元素污染。     

Enrichment of marsh soils with heavy metals by effect of anthropic pollution

The impact of waste disposal on marsh soils was assessed in topsoil samples collected at eight randomly selected points in the salt marsh in Ramallosa (Pontevedra, Spain) at 4-month intervals for 2 years. Polluted soil samples were characterized in physico-chemical terms and their heavy metal contents determined by comparison with control, unpolluted samples. The results revealed a marked effect of waste discharges on the soils in the area, which have low contents in heavy metals under normal environmental conditions. In fact, the studied soils were found to contain substantial amounts of total and DTPA-extractable Cd, Cu, Pb and Zn. Based on the relationship of the redox potential with the DTPA-extractable Cd, Cu, Pb, and Zn contents of the soils, strongly reductive conditions raised the total contents in these elements by effect of their remaining in the soils as precipitated sulphides. Such contents, however, decreased as oxidative conditions gradually prevailed. The contents in DTPA-extractable metals increased with increasing Eh through the release of the metals in ionic form to the soil solution under oxidative conditions. The contents in heavy metals concentrating in the polluted soils were several times higher than those in the control soils (viz. 2 vs. 6 for Cd, 4 vs. 6 for Cu, 4 vs. 20 for Pb, and 2 vs. 15 for Zn, all in mg kg⁻¹). This can be expected to influence the amounts of available heavy metals present in the soils, and hence the environmental quality of the area, in the near future. Based on its geoaccumulation index (Class ≥3 for Cd and Cu, and 1–4 for Pb and Zn), the Ramallosa marsh is highly polluted with Cd and moderately to highly polluted with Cu, Pb and Zn. The enrichment factors obtained confirm that the salt marsh is highly polluted (especially with Cd) as the primary result of anthropic activity.     

Assessing soil heavy metal pollution in the water-level-fluctuation zone of the Three Gorges Reservoir, China

The water-level-fluctuation zone (WLFZ) between the elevations of 145-175 m in China's Three Gorges Reservoir has experienced a novel hydrological regime with half a year (May-September) exposed in summer and another half (October-April) submerged in winter. In September 2008 (before submergence) and June 2009 (after submergence), soil samples were collected in 12 sites in the WLFZ and heavy metals (Hg, As, Cr, Cd, Pb, Cu, Zn, Fe, and Mn) were determined. Enrichment factor (EF), factor analysis (FA), and factor analysis-multiple linear regression (FA-MLR) were employed for heavy metal pollution assessment, source identification, and source apportionment, respectively. Results demonstrate spatial variability in heavy metals before and after submergence and elements of As, Cd, Pb, Cu, and Zn are higher in the upper and low reaches. FA and FA-MLR reveal that As and Cd are the primary pollutants before submergence, and over 45% of As originates from domestic sewage and 59% of Cd from industrial wastes. After submergence, the major contaminants are Hg, Cd, and Pb, and traffic exhaust contributes approximately 81% to Hg and industrial effluent accounts about 36% and 73% for Cd and Pb, respectively. Our results suggest that increased shipping and industrial wastes have deposited large amounts of heavy metals which have been accumulated in the WLFZ during submergence period.     

涂料中重金属元素的危害及检测方法的概述

本文结合国家相关强制性标准规定,对涂料中重金属的来源、及其对人体的危害和目前对各种重金属的检测方法进行概述。     

Reduction of metal leaching in brown coal fly ash using geopolymers

Current regulations classify fly ash as a prescribed waste and prohibit its disposal in regular landfill. Treatment of the fly ash can reduce the leach rate of metals, and allow it to be disposed in less prescribed landfill. A geopolymer matrix was investigated as a potential stabilisation method for brown coal fly ash. Precipitator fly ash was obtained from electrostatic precipitators and leached fly ash was collected from ash disposal ponds, and leaching tests were conducted on both types of geopolymer stabilised fly ashes. The ratio of fly ash to geopolymer was varied to determine the effects of different compositions on leaching rates. Fourteen metals and heavy metals were targeted during the leaching tests and the results indicate that a geopolymer is effective at reducing the leach rates of many metals from the fly ash, such as calcium, arsenic, selenium, strontium and barium. The major element leachate concentrations obtained from leached fly ash were in general lower than that of precipitator fly ash. Conversely, heavy metal leachate concentrations were lower in precipitator fly ash than leached pond fly ash. The maximum addition of fly ash to this geopolymer was found to be 60wt% for fly ash obtained from the electrostatic precipitators and 70wt% for fly ash obtained from ash disposal ponds. The formation of geopolymer in the presence of fly ash was studied using 29Si MAS-NMR and showed that a geopolymer matrix was formed. X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) imaging showed the interaction of the fly ash with the geopolymer, which was related to the leachate data and also the maximum percentage fly ash addition.     

微波消解-AAS测定垃圾焚烧飞灰中重金属

采用微波消解法对城市生活垃圾焚烧飞灰样品进行预处理,在此基础上优化了城市生活垃圾焚烧飞灰的微波消解酸体系及消解程序.优化后的微波消解酸体系及用量比例为HNO3:HF:HClO4=3:4:1;消解程序的四个工步分别为:3min(5×101 kPa),3min(10×101 kPa),4min(15×101 kPa),6min(20×101 kPa).该方法的相对标准偏差为1.2%～4.5%,加标回收率为95.9%～103.7%,应用于实际的城市生活垃圾焚烧飞灰样品取得了良好的效果.