Transformation of heavy metal speciation during sludge drying: mechanistic insights

Speciation can fundamentally affect on the stability and toxicity of heavy metals in sludge from wastewater treatment plants. This research investigated the speciation of heavy metals in sludge from both municipal and industrial sources, and metal speciation change as a result of drying process to reduce sludge volume. The changes in sludge properties including sludge moisture content, temperature, density, and electrical conductivity were also monitored to provide insights into the mechanisms causing the change in heavy metal speciation. The results show that the drying process generally stabilized Cr, Cu, Cd, and Pb in sludge by transforming acid-soluble, reducible, and oxidizable species into structurally stable forms. Such transformation and stabilization occurred regardless of the sludge source and type, and were primarily caused by the changes in sludge properties associated with decomposition of organic matter and sulfide. The results enhanced our understanding of the geochemical behavior of heavy metals in municipal sludge, and are useful for designing a treatment system for environment-friendly disposal of sludge.

Bioleaching of metals from printed circuit boards supported with surfactant-producing bacteria

This study has evaluated the possibility of bioleaching zinc, copper, lead, nickel, cadmium and chromium from printed circuit boards by applying a culture of sulphur-oxidising bacteria and a mixed culture of biosurfactant-producing bacteria and sulphur-oxidising bacteria. It was revealed that zinc was removed effectively both in a traditional solution acidified by a way of microbial oxidation of sulphur and when using a microbial culture containing sulphur-oxidising and biosurfactant-producing bacteria. The average process efficiency was 48% for Zn dissolution. Cadmium removal was similar in both media, with a highest metal release of 93%. For nickel and copper, a better effect was obtained in the acidic medium, with a process effectiveness of 48.5% and 53%, respectively. Chromium was the only metal that was removed more effectively in the bioleaching medium containing both sulphur-oxidising and biosurfactant-producing bacteria. Lead was removed from the printed circuit boards with very low effectiveness (below 0.5%). Aerating the culture medium with compressed air increased the release of all metals in the medium with sulphur and biosurfactant, and of Ni, Cu, Zn and Cr in the acidic medium. Increasing the temperature of the medium (to 37°C) had a more significant impact in the acidic environment than in the neutral environment.

Toxicity assessment of size-fractionated urban road dust using ostracod Heterocypris incongruens direct contact test

Urban road dusts (URDs, n=10) were collected from arterial, residential, parking area in highway and highway roads in and around Tokyo, Japan, to characterize toxicity of size-fractions by the ostracod Heterocypris incongruens direct contact test. The URDs were collected with vacuum cleaner and highway sweeping vehicles, dried and size-fractionated before conducting toxicity test. The LC20 and LC50 of URDs varied (v/v) from 1.6 to 49%, and 3.8 to 67% respectively. Cluster analysis of URDs based on the concentration of heavy metal and PAHs standardized with the organic matter content was able to differentiate URDs into two groups, one group of higher toxicity and the other group of medium and lower toxicity. Mortality of ostracod decreased for some of the URDs when holding time of URD-water mixture was changed from 1h to 24h prior to the toxicity test. Fraction of fine particles was not always more toxic than the other fractions of coarse and medium particles. Site specific differences in toxicity of size-fractionated URDs indicated the complexity in defining URD toxicity as there could be co-existence of various non-targeted toxicants.

Copper, aluminum, iron and calcium inhibit human acetylcholinesterase in vitro

Acetylcholinesterase (AChE) is an important part of cholinergic nerves where it participates in termination of neurotransmission. AChE can be inhibited by e.g. some Alzheimer disease drugs, nerve agents, and secondary metabolites. In this work, metal salts aluminum chloride, calcium chloride, cupric chloride, ferric chloride, potassium chloride, magnesium chloride and sodium chloride were tested for their ability to inhibit AChE. Standard Ellman assay based on human recombinant AChE was done and inhibition was measured using Dixon plot. No inhibition was proved for sodium, potassium and magnesium ions. However, aluminum, cupric, ferric and calcium ions were able to inhibit AChE via noncompetitive mechanism of inhibition. Though the inhibition is much weaker when compared to e.g. drugs with noncompetitive mechanism of action, biological relevance of the findings can be anticipated.

Survey of mercury, cadmium and lead content of household batteries

The objective of this work was to provide updated information on the development of the potential impact of heavy metal containing batteries on municipal waste and battery recycling processes following transposition of the new EU Batteries Directive 2006/66/EC. A representative sample of 146 different types of commercially available dry and button cells as well as lithium-ion accumulators for mobile phones were analysed for their mercury (Hg)-, cadmium (Cd)- and lead (Pb)-contents. The methods used for preparing the cells and analysing the heavy metals Hg, Cd, and Pb were either developed during a former study or newly developed. Several batteries contained higher mass fractions of mercury or cadmium than the EU limits. Only half of the batteries with mercury and/or lead fractions above the marking thresholds were labelled. Alkaline-manganese mono-cells and Li-ion accumulators, on average, contained the lowest heavy metal concentrations, while zinc-carbon batteries, on average, contained the highest levels.

Biochar-supported zerovalent iron for removal of various contaminants from aqueous solutions

This work describes the synthesis and testing of a novel environmental sorbent that combines the advantages of biochar, chitosan, and zerovalent iron (ZVI). Chitosan was used as a dispersing and soldering reagent to attach fine ZVI particles onto bamboo biochar surfaces. Characterization of the resulted ZVI-biochar composites (BBCF) indicated that chitosan effectively soldered the iron particles onto carbonaceous surfaces within the biochar pore networks. The BBCF showed enhanced ability to sorb heavy metals (Pb(II), Cr(VI), and As(V)), phosphate (P), and methylene blue (MB) from aqueous solutions. The removal of Pb(II), Cr(VI), and MB by the biochar-supported ZVI was mainly controlled by both the reduction and surface adsorption mechanisms. Removal of anionic contaminants (As(V) and P) was likely controlled by electrostatic attraction with the iron particles on the BBCF surfaces. An additional benefit is that the contaminant-laden BBCF could be removed from aqueous solution easily by magnetic attraction.

The protective effect of clay minerals against damage to adsorbed DNA induced by cadmium and mercury

The adsorption of Salmon Sperm DNA on three kinds of raw clay (rectorite, montmorillonite and sericite) was investigated as a function of pH, ionic strength and the concentrations of DNA and phosphate ions in solution. The DNA adsorption was reduced in the following order: rectorite>montmorillonite>sericite. Based on these findings, there is a strong evidence that the mechanisms for DNA adsorption on clay involve electrostatic forces, cation bridging and ligand exchange. Cyclic voltammetry (CV) and UV-vis absorption and fluorescence spectroscopy were used to compare the properties of unbound DNA and the absorbed DNA on rectorite, both in the absence and presence of Cd(2+) and Hg(2+) inaqueous solutions. The interaction of heavy metals with the unbound DNA was evidenced by the disappearance of reduction peaks in CV, a small bathochromic shift in UV-vis spectroscopy and an incomplete quenching in the emission spectra. Such changes were not observed in the DNA-rectorite hybrids, which is evidence that adsorption on the clay can reduce the extent of the DNA damage caused by heavy metals. Therefore, in these experience the rectorite played an important role in protecting DNA against Cd(2+) and Hg(2+) induced damage.

Polyamidoamine dendrimers as sweeping agent and stationary phase for rapid and sensitive open-tubular capillary electrophoretic determination of heavy metal ions

Polyamidoamine (PAMAM) dendrimer generation 2.5 was synthesized and evaluated as sweeping agent for in-column enrichment and as stationary phase for capillary electrochromatographic separation of heavy metal ions, viz., Pb(II), Cu(II), Hg(II), Zn(II) and Co(II), in a running buffer containing 4-(2-pyridylazo)resorcinol (PAR) as a chromogenic reagent. During experiment, a plug of aqueous PAMAM generation 2.5 solution was first introduced to the capillary, followed by electrokinetic injection of the heavy metal ions under a positive voltage. In this step, PAMAM acted as a sweeping agent, stacking the metal ions on the analyte/PAMAM boundary by forming metal ion-PAMAM complexes. The second preconcentration process occurred when PAR, a stronger ligand, moving toward the injection end under the electric field, reached and re-swept the metal ion-PAMAM zone, forming metal ion-PAR complexes. During separation, the neutral PAMAM moved toward the detector with the electroosmotic flow, dynamically coating the capillary wall, forming stationary phases that affected the separation of the metal ions. Due to the function of PAMAM, the detection sensitivity and resolution of the heavy metal ions improved significantly. Under the optimum conditions, the detection limits were 0.299, 0.184, 0.774, 0.182 and 0.047 μg/L for Pb(II), Cu(II), Hg(II), Zn(II) and Co(II), respectively. The method was successfully applied to the determination of heavy metals in snow, tap and rain water samples.

Presence of Fe3+ and Zn2+ promoted biotransformation of Cd-citrate complex and removal of metals from solutions

The promotion to Cd-citrate complex biotransformation via addition of Fe(3+) and Zn(2+) was investigated. Single Fe(III)- or Zn-citrate complex was completely degraded by Pseudomonas sp. MBR, Cd-citrate complex was not. In the Cd-citrate media with molar ratio of 1:2 and 1:3, pH increase obtained from the metabolism of excess citrate slightly promoted the biotransformation of Cd-citrate complex, Cd remained in solutions. The presence of Fe(3+) and Zn(2+) resulted in complete biotransformation of Cd-citrate complex in the 1:1:2 Fe:Cd:citrate and Zn:Cd:citrate and 1:1:1:3 Fe:Zn:Cd:citrate media. Alkaline pH obtained from biotransformation of metal-citrate complexes caused almost complete removal of metals (>98%) through precipitation and co-precipitation. Pseudomonas sp. MBR potentially could be used to treat wastewater containing mixed citrate complexes of Fe(III), Zn and Cd.

Integrated study of metal behavior in Mediterranean stream ecosystems: a case-study

The objective of the present work was to assess the ecosystem status of Francolí river (Catalonia, Spain), a Mediterranean stream basin with contrasting human influences. An integrated approach was designed by combining physicochemical, biological and ecotoxicological analyses. The content of metals (As, Cd, Cr, Co, Cu, Hg, Ni, Pb, and Zn) was analyzed in samples of water, benthic sediments and aquatic macroinvertebrates. In addition, the potentially bioavailable fraction of metals in water and sediments was determined by using diffusive gradient in thin-films (DGTs) and sequential extraction of sediments (BCR), respectively. The biological quality was evaluated through aquatic macroinvertebrate communities, while the ecotoxicological status was assessed by Microtox(®) with Vibrio fischeri. Finally, an analysis of acid-volatile sulfide (AVS) and simultaneously extracted metals (SEM) was performed to evaluate the sediment toxicity associated to metal content. According to the results, DGTs and BCR are suitable methodologies to predict the potential bioavailable fraction of metals in freshwater systems. Moreover, ecotoxicity evaluation by means of V. fischeri, in combination with the chemical characterization and the biological quality assessment, should be complementarily used to get a better diagnose of freshwater systems.

Combination of two-dimensional correlation spectroscopy and parallel factor analysis to characterize the binding of heavy metals with DOM in lake sediments

Enhanced knowledge on the binding of heavy metal (HM) with dissolved organic matter (DOM) is essential for understanding the toxicity and migration of HMs. In this study, two-dimensional correlation spectroscopy (2D-COS) and parallel factor (PARAFAC) analysis were combined to characterize the metal binding properties of DOMs, which were respectively extracted from macrophyte- and algal-dominant sediments (named MDOM and ADOM) in a eutrophic shallow lake. 2D absorption COS revealed that MDOM exhibited more HM binding sites (193, 195, 196, 199, 201, 203, 205, 207, 208, 212, 217 nm) than ADOM (201, 205 nm). PARAFAC analysis identified one protein- and two humic-like components from all titrated samples, with each component exhibiting different binding behaviors. The modified Stern-Volmer model showed that PARAFAC-derived components in MDOM had higher conditional stability constants (logKM) than in ADOM, suggesting that macrophyte-dominant sediments might play a more important role in the detoxification of HMs. Meanwhile, low binding abilities of Zn(II)-DOM complexes indicated that the toxicity of zinc in eutrophic lakes should not be overlooked. More aromatic functional groups and binding sites were suggested to be responsible for the high binding ability. 2D-COS was a better approach than PARAFAC analysis for exploring HM-DOM interaction.

Managing heavy metal toxicity stress in plants: biological and biotechnological tools

The maintenance of ion homeostasis in plant cells is a fundamental physiological requirement for sustainable plant growth, development and production. Plants exposed to high concentrations of heavy metals must respond in order to avoid the deleterious effects of heavy metal toxicity at the structural, physiological and molecular levels. Plant strategies for coping with heavy metal toxicity are genotype-specific and, at least to some extent, modulated by environmental conditions. There is considerable interest in the mechanisms underpinning plant metal tolerance, a complex process that enables plants to survive metal ion stress and adapt to maintain growth and development without exhibiting symptoms of toxicity. This review briefly summarizes some recent cell biological, molecular and proteomic findings concerning the responses of plant roots to heavy metal ions in the rhizosphere, metal ion-induced reactions at the cell wall-plasma membrane interface, and various aspects of heavy metal ion uptake and transport in plants via membrane transporters. The molecular and genetic approaches that are discussed are analyzed in the context of their potential practical applications in biotechnological approaches for engineering increased heavy metal tolerance in crops and other useful plants.

Cadmium triggers kidney cell apoptosis of purse red common carp (Cyprinus carpio) without caspase-8 activation

Caspase-8, the essential initiator caspase, is believed to play a pivotal role in death receptor-mediated apoptotic pathway. It also participates in mitochondria-mediated apoptosis via cleavage of proapoptotic Bid in mammals. However, its role in fish remains elusive in Cadmium-induced apoptotic pathway. In this study, we isolated the caspase-8 gene from common carp, one of the most important industrial aquatic animals in China using rapid amplification of cDNA ends (RACE). The deduced amino acid sequence of caspase-8 comprised 475 amino acids, which showed approximately 64.1% identity and 79.8% similarity to zebrafish (Danio rerio) caspase-8, possessed two conserved death effector domains, a large subunit and a small subunit. Phylogenetic analysis demonstrated that caspase-8 formed a clade with zebrafish caspase-8. In kidney, cadmium (Cd) exposure triggered apoptosis and increased caspase-3 and -9 activities, whereas it did not affect caspase-8 activity. Real-time quantitative PCR analysis revealed that caspase-8 transcriptional level was not significantly increased in kidney after exposure to Cd. Using Western blot analysis, no caspase-8 cleaved fragment was detected and no significant alteration of procaspase-8 level was found with the same Cd-treated condition. Moreover, the immunopositive staining was predominantly limited to the cytoplasm of renal tubular epithelial cells and no remarkable changes of immunoreactivities were observed using immunohistochemical detection after Cd treatment. The results reveal that Cd can trigger apoptosis, while it cannot activate caspase-8 in purse red common carp.

HISN3 mediates adaptive response of Chlamydomonas reinhardtii to excess nickel

Investigation of genes for heavy metal [e.g. nickel (Ni) and zinc (Zn)] absorption and detoxification in green algae is of great importance because some of the metals have become one of the major contaminants in the aquatic ecosystem. In plants, overload of heavy metals modifies many aspects of biological processes. However, the mechanisms by which heavy metals exert detrimental effects are not fully understood. The present study identified a biological role for HISN3 (the gene coding for phosphoribosylformimino-5-aminoimidazole carboxamide ribonucleotide isomerase) in regulating the response of Chlamydomonas reinhardtii, a unicellular green alga, to Ni toxicity. In higher plants, HISN3 encodes an enzyme catalyzing the fourth step in the histidine biosynthesis pathway, but its functional importance is yet to be identified. Transgenic algae overexpressing HISN3 in C. reinhardtii showed high tolerance to excess Ni, with a 48.3-57.4% increase in cell population and moderate histidine accumulation compared with the wild type. HISN3 overexpression improved accumulation of Chl and photosynthesis efficiency, but suppressed Ni-induced generation of reactive oxygen species and lipid peroxides. Interestingly, more Ni and other metals [Zn, iron (Fe), copper (Cu), manganese (Mn) and magnesium (Mg)] were accumulated in HISN3-overexpressing cells than in the wild type. In contrast, RNA interference of HISN3 depressed Ni accumulation but caused cellular sensitivity to Ni. The elevated metal absorption in the HISN3-overexpressing algae implies that the metals can be removed from water media. Thus, our work presents an example for algae genetically designed to improve tolerance to metal toxicity and environmental restoration of metal-contaminated aquatic ecosystems.

Study on bioadsorption and biodegradation of petroleum hydrocarbons by a microbial consortium

A microbial consortium isolated from Shengli oilfield polluted sludge was capable of degrading naphthalene (NAP), phenanthrene (PHE), pyrene (PYR) and crude oil. It performed high biodegradation activity and emulsifiability for petroleum hydrocarbons, and was tolerant to 6.2mM Cu(2+), 2.7 mM Zn(2+) and 9.5mM Pb(2+). Biodegradation rates of NAP, PHE, PYR and crude oil were 53%, 21%, 32% and 44% in the presence of heavy metal (Cu(2+), 1.7 mM and Zn(2+), 2mM), respectively. Exploration on the adsorption and uptake of petroleum hydrocarbons by microbe suggested the stability of surface adsorption and cell uptake by live microbial consortium followed a decreasing order of NAP > PHE ≈ PYR > crude oil. The adsorption by heat-killed microbial consortium was constant for PAHs, while decreased for crude oil. Experiments on enzymatic degradation indicated that the metabolic efficiency of periplasmic, cytoplasmic and extracellular enzymes secreted by the microbial consortium for diverse substrates was different.

Heavy metal risk management: case analysis

To prepare measures for practical policy utilization and the control of heavy metals, hazard control related institutions by country, present states of control by country, and present states of control by heavy metals were examined. Hazard control cases by heavy metals in various countries were compared and analyzed. In certain countries (e.g., the U.S., the U.K., and Japan), hazardous substances found in foods (e.g., arsenic, lead, cadmium, and mercury) are controlled. In addition, the Joint FAO/WHO Expert Committee on Food Additives (JECFA) recommends calculating the provisional tolerable weekly intake (PTWI) of individual heavy metals instead of the acceptable daily intake (ADI) to compare their pollution levels considering their toxicity accumulated in the human body. In Korea, exposure assessments have been conducted, and in other countries, hazardous substances are controlled by various governing bodies. As such, in Korea and other countries, diverse food heavy metal monitoring and human body exposure assessments are conducted, and reducing measures are prepared accordingly. To reduce the danger of hazardous substances, many countries provide leaflets and guidelines, develop hazardous heavy metal intake recommendations, and take necessary actions. Hazard control case analyses can assist in securing consumer safety by establishing systematic and reliable hazard control methods.

A study on characteristics of atmospheric heavy metals in subway station

In this study, we investigated the atmospheric heavy metal concentrations in the particulate matter inside the subway stations of Seoul. In particular, we examined the correlation between the heavy metals and studied the effect of the heavy metals on cell proliferation. In six selected subway stations in Seoul, particulate matter was captured at the platforms and 11 types of heavy metals were analyzed. The results showed that the mean concentration of iron was the highest out of the heavy metals in particulate matter, followed by copper, potassium, calcium, zinc, nickel, sodium, manganese, magnesium, chromium and cadmium in that order. The correlation analysis showed that the correlations between the heavy metals was highest in the following order: (Cu vs Zn) , (Ca vs Na) , (Ca vs Mn) , (Ni vs Cr) , (Na vs Mn) , (Cr vs Cd) , (Zn vs Cd) , (Cu vs Cd) , (Ni vs Cd) , (Cu vs Ni) , (K vs Zn) , (Cu vs K) , (Cu vs Cr) , (K vs Cd) , (Zn vs Cr) , (K vs Ni) , (Zn vs Ni) , (K vs Cr) , and (Fe vs Cu) . The correlation coefficient between zinc and copper was 0.937, indicating the highest correlation. Copper, zinc, nickel, chromium and cadmium, which are generated from artificial sources in general, showed correlations with many of the other metals and the correlation coefficients were also relatively high. The effect of the heavy metals on cell proliferation was also investigated in this study. Cultured cell was exposed to 10 mg/l or 100 mg/l of iron, copper, calcium, zinc, nickel, manganese, magnesium, chromium and cadmium for 24 hours. The cell proliferation in all the heavy metal-treated groups was not inhibited at 10 mg/l of the heavy metal concentration. The only exception to this was with the cadmium-treated group which showed a strong cell proliferation inhibition. This study provides the fundamental data for the understanding of simultaneous heavy metal exposure tendency at the time of particulate matter exposure in subway stations and the identification of heavy metal sources. Moreover, this study can be used as the fundamental data for the cell toxicity study of the subway-oriented heavy metal-containing particulate matter.

The association of heavy metal of blood and serum in the Alzheimer's diseases

This study has attempted to establish an analysis method through validation against heavy metals in the body (Pb, Cd and Hg) using ICP-MS and Gold amalgamation and find out the relevance between heavy metal and Alzheimer’s disease after analyzing the distribution of heavy metal concentration (Pb, Cd and Hg) and correlations between a control group and Alzheimer’s disease group. In this study, Pb and Cd levels in the blood and serum were validation using ICP-MS. For analysis of Hg levels in the blood and serum, the gold amalgamation-based ‘Direct Mercury Analyzer’ has been used. According to an analysis on the heavy metal concentration (Pb, Cd and Hg concentration) in the blood, Cd concentration was high in the Alzheimer’s disease group. In the serum, on the contrary, Pb and Hg were high in the Alzheimer’s disease group. For analysis of correlations between heavy metal levels in the blood and serum and Alzheimer’s disease, t-test has been performed. Even though correlations were observed between the blood lead levels and Alzheimer’s disease, they were statistically insignificant because the concentration was higher in a control group. No significance was found in Cd and Hg. In the serum, on the other hand, no statistical significance was found between the heavy metal (Pb, Cd and Hg) and Alzheimer’s disease. In this study, no statistical significance was observed between heavy metal and decrease in cognitive intelligence. However, it appears that a further study needs to be performed because the results of the conventional studies were inconsistent.

Bioaccumulation and histopathological alteration of total lead in selected fishes from Manila Bay, Philippines

This study aims to assess the bioaccumulation of total lead and the effect of heavy metal on the muscles of fish obtained in the coastal lagoon of the Manila Bay. Fish species muscles were assessed for lead concentrations and were examined for histological alterations. Results showed that lead bioaccumulation in the muscles, and a degree of disintegration in the muscle fibers of all the fish examined were found.

Acid-volatile sulfide and simultaneously extracted metals in surface sediments of the southwestern coastal Laizhou Bay, Bohai Sea: concentrations, spatial distributions and the indication of heavy metal pollution status

Surface sediments were collected from the coastal waters of southwestern Laizhou Bay and the rivers it connects with during summer and autumn 2012. The acid-volatile sulfide (AVS) and simultaneously extracted metals (SEM) were measured to assess the sediment quality. The results showed that not all sediments with [SEM]-[AVS]>0 were capable of causing toxicity because the organic carbon is also an important metal-binding phase in sediments. Suppose the sediments had not been disturbed and the criteria of US Environmental Protection Agency had been followed, heavy metals in this area had no adverse biological effects in both seasons except for few riverine samples. The major ingredient of SEM was Zn, whereas the contribution of Cd - the most toxic metal studied - to SEM was <1%. The distributions of AVS and SEM in riverine sediments were more easily affected by anthropogenic activity compared with those in marine sediments.

Bioremediation of copper-containing wastewater by sulfate reducing bacteria coupled with iron

In order to treat copper-containing wastewater effectively using sulfate reducing bacteria (SRB), iron (Fe(0)) was added to enhance the activity of SRB. The SRB system and the SRB + Fe(0) system were operated under continuous operation. The sulfate reduction efficiency of the SRB + Fe(0) system was twice as much as that of the SRB system with the sulfate loading rate at 125  mg L(-1) h(-1). The effect of COD/SO4(2-) on sulfate reduction indicates an enhanced activity of SRB by adding Fe(0). 99% of total sulfate was deducted in both systems at pH 4.0-7.0, and temperature slightly influenced the removal of sulfate in the SRB + Fe(0) system. In the copper-containing wastewater treatment, the SRB + Fe(0) system shows a better performance since sulfate removal in this system was higher than the SRB system, and the removal ratio of Cu(2+) was held above 95% in SRB + Fe(0) system at all influent Cu(2+) concentrations.

Thermal and hydrometallurgical recovery methods of heavy metals from municipal solid waste fly ash

Heavy metals in fly ash from municipal solid waste incinerators are present in high concentrations. Therefore fly ash must be treated as a hazardous material. On the other hand, it may be a potential source of heavy metals. Zinc, lead, cadmium, and copper can be relatively easily removed during the thermal treatment of fly ash, e.g. in the form of chlorides. In return, wet extraction methods could provide promising results for these elements including chromium and nickel. The aim of this study was to investigate and compare thermal and hydrometallurgical treatment of municipal solid waste fly ash. Thermal treatment of fly ash was performed in a rotary reactor at temperatures between 950 and 1050°C and in a muffle oven at temperatures from 500 to 1200°C. The removal more than 90% was reached by easy volatile heavy metals such as cadmium and lead and also by copper, however at higher temperature in the muffle oven. The alkaline (sodium hydroxide) and acid (sulphuric acid) leaching of the fly ash was carried out while the influence of temperature, time, concentration, and liquid/solid ratio were investigated. The combination of alkaline-acidic leaching enhanced the removal of, namely, zinc, chromium and nickel.

Heavy metal pollution status in surface sediments of Swan Lake lagoon and Rongcheng Bay in the northern Yellow Sea

The national 'Shandong Peninsula Blue Economic Zone Development Plan' compels the further understanding of the distribution and potential risk of metals pollution in the east coast of China, where the rapid economic and urban development have been taken off and metal pollution has become a noticeable problem. Surface sediments collected from the largest swan habitat in Asia, the Swan Lake lagoon and the surrounding coastal area in Rongcheng Bay in northern Yellow Sea, were analyzed for the total metal concentrations and chemical phase partitioning of five heavy metals (Cu, Zn, Pb, Cd, and Cr). Metal contents in the studied region have increased significantly in the past decade. The speciation analyzed by the sequential extraction showed that Zn and Cr were present dominantly in the residual fraction and thus of low bioavailability, while Cd, Pb and Cu were found mostly in the non-residual fraction thus of high potential availability, indicating significant anthropogenic sources. Among the five metals, Cd is the most outstanding pollutant and presents high risk, and half of the surface sediments in the studied region had a 21% probability of toxicity based on the mean Effect Range-Median Quotient. At some stations with comparable total metal contents, remarkably different non-residual fraction portions were determined, pointing out that site-specific risk assessment integrating speciation is crucial for better management practices of coastal sediments.

Diet composition as a cause of different contaminant exposure in two sympatric passerines in the Middle Urals, Russia

Contaminant exposure can vary between species but primary causes of it are often unclear. In order to estimate heavy metal intake of two sympatric passerines - Ficedula hypoleuca Pall. and Parus ater L. - we studied nestling diet and metal concentrations in prey invertebrates, near the Middle Ural copper smelter and in an unpolluted area. Diet of P. ater contained more Cu, Cd and Zn compared to F. hypoleuca and the same amount of Pb. Contribution of different prey taxa to bird metal intake was not equal to their dietary proportion. Proportion of Cu, Zn, Pb and Cd provided to birds by spiders and molluscs, as well as Cd and Pb provided by ants and imagoes Diptera, exceeded their dietary fraction by several times. In contrast, the contribution of Lepidoptera and sawfly larvae to bird metal intake was less than their dietary proportion. Pollution-related changes in the diet modified bird contaminant exposure along with pollutant concentrations in preys.

Flow analysis of heavy metals in a pilot-scale incinerator for residues from waste electrical and electronic equipment dismantling

The large amount of residues generated from dismantling waste electrical and electronic equipment (WEEE) results in a considerable environmental burden. We used material flow analysis to investigate heavy metal behavior in an incineration plant in China used exclusively to incinerate residues from WEEE dismantling. The heavy metals tested were enriched in the bottom and fly ashes after incineration. However, the contents of heavy metals in the bottom ash, fly ash and exhaust gas do not have a significant correlation with that of the input waste. The evaporation and recondensation behavior of heavy metals caused their contents to differ with air pollution control equipment because of the temperature difference during gas venting. Among the heavy metals tested, Cd had the strongest tendency to transfer during incineration (TCd=69.5%) because it had the lowest melting point, followed by Cu, Ni, Pb and Zn. The exchangeable and residual fractions of heavy metals increased substantially in the incineration products compared with that of the input residues. Although the mass of residues from WEEE dismantling can be reduced by 70% by incineration, the safe disposal of the metal-enriched bottom and fly ashes is still required.

Molecular cloning, immunohistochemical localization, characterization and expression analysis of caspase-9 from the purse red common carp (Cyprinus carpio) exposed to cadmium

Caspase-9, the essential initiator caspase is believed to play a central role in mitochondria-mediated apoptosis signaling. In this study, we isolated the caspase-9 gene from common carp, one of the most important industrial aquatic animals in China using rapid amplification of cDNA ends (RACE). The deduced amino acid sequence of caspase-9, composed of 436 amino acids, showed approximately 47.6% identity and 64.7% similarity to human caspase-9. It also possessed a conserved caspase-associated recruitment domain (CARD), a large subunit and a small subunit. Phylogenetic analysis clearly demonstrated that caspase-9 formed a clade with cyprinid fish caspase-9. Real-time quantitative PCR analysis revealed that caspase-9 transcripts were not significantly increased in kidney after exposure to cadmium (Cd). Whereas caspase-9 cleaved fragments were detected using Western blot analysis with the same Cd treatment condition. Furthermore, the result of immunohistochemical detection showed immunoreactivities were predominantly limited to the cytoplasm of renal tubular epithelial cells and no remarkable changes of immunopositive staining were observed after Cd treatment. Accordingly, the results signify that caspase-9 may play an essential role in Cd induced apoptosis.

A glutathione S-transferase from Proteus mirabilis involved in heavy metal resistance and its potential application in removal of Hg²⁺

Glutathione S-transferases (GSTs) are a family of multifunctional proteins playing important roles in detoxification of harmful physiological and xenobiotic compounds in organisms. In our study, a gene encoding a GST from Proteus mirabilis strain V7, gstPm-4, was cloned and conditionally expressed in Escherichia coli strain BL21(DE3). The purified GstPm-4 protein, with an estimated molecular mass of approximately 23kDa, was able to conjugate 1-chloro-2,4-dinitrobenzene and bind to the GSH-affinity matrix. Real-time reverse transcriptase PCR suggested that mRNA level of gstPm-4 was increased in the presence of CdCl2, CuCl2, HgCl2 and PbCl2, respectively. Correspondingly, overexpression of gstPm-4 in the genetically engineered bacterium Top10/pLacpGst exhibited higher heavy metal resistance compared to the control Top10/pLacP3. Another genetically engineered bacterium Top10/pBATGst, in which the DNA encoding GstPm-4 protein was fused with the DNA encoding Pfa1-based auto surface display system, was built. Top10/pBATGst could constitutively express the chimeric GstPm-4 and anchor it onto the cell surface subsequently. Almost 100% of the Hg(2+) within the range of 0.1-100 nM was adsorbed by Top10/pBATGst, and 80% of the bounded Hg(2+) could be desorbed from bacterial cells when pH was adjusted to 6.0. Thus, Top10/pBATGst can be potentially used for efficient treatment of Hg(2+)-contaminated aquatic environment.

Chronic exposure of Rutilus rutilus caspicus fingerlings to ambient copper: Effects on food intake, growth performance, biochemistry and stress resistance

An 8-week trial was conducted to investigate the effect of ambient copper (Cu) on growth performance, physiological characteristics and stress resistance of Caspian roach, Rutilus rutilus caspicus. Fish were exposed to 0 (control), 0.02, 0.04 and 0.06 ppm Cu, and their food intake and growth performance were fortnightly recorded. Also, serum cortisol, glucose, alanine aminotransferase (ALT) and sodium (Na) levels were determined after 2 and 8 weeks exposure to ambient Cu. At the end of trial, serum total protein, albumin, globulin and albumin-globulin ratio (A:G) levels, whole body proximate composition and stress tolerance of the fish were measured. Results showed that Cu exposure resulted in a significant suppression in food intake after 2 weeks, which was eliminated after 4 weeks in 0.02 ppm groups and after 6 weeks in 0.04 and 0.06 ppm groups. Cu exposure brought about an inferior growth that recovered in line with the experiment progression, following a dose-dependent manner. Cu-exposed fish showed a dose-dependent increase in serum cortisol, glucose and ALT as well as decrease in serum Na, after 2 weeks. These parameters showed a full recovery in 0.02 ppm group and a partial recovery in 0.04 and 0.06 ppm groups, at the 8th week. Significant suppression in serum total protein, albumin, globulin and A:G levels and whole body dry matter, lipid and protein levels as well as stress resistance was observed in 0.04 and 0.06 ppm groups. It is concluded that Cu exposure could adversely affect growth performance, physiological characteristics and stress resistance of Caspian roach, which might affect its ecological features.

Bioleaching of heavy metal from woody biochar using Acidithiobacillus ferrooxidans and activation for adsorption

A woody biochar which was the byproduct of gasification of sawdust was treated with bioleaching by Acidithiobacillus ferrooxidans. After bioleaching, most heavy metal was removed from biochar. Leaching efficiency of heavy metal was efficient in a wide pulp density range from 1% to 10% (w/v) and decreased only a little with the increase in pulp density. It made application of biochar free of heavy metal risk. Benefitting from the improvement in functional group composition and pore structure after bioleaching, adsorption capacity of biochar to methylene blue and heavy metal was enhanced greatly. Adsorption of methylene blue could be described by pseudo-second-order model and Langmuir equation and the enhancement was mainly caused by the modification of physical character of biochar. Adsorption of heavy metal could be described by Freundlich equation and was mainly determined by chemical character of biochar.

Concentrations and health risks of lead, cadmium, arsenic, and mercury in rice and edible mushrooms in China

In this study, four common heavy metals, lead (Pb), cadmium (Cd), arsenic (As) and mercury (Hg) in rice and edible mushrooms of China were studied to evaluate contamination level and edible safety. Ninety two (92) rice samples were collected from the main rice growing regions in China, and 38 fresh and 21 dry edible mushroom samples were collected from typical markets in Nanjing City. The analyzed metal concentrations were significantly different between rice and edible mushroom samples (p<0.05). The results showed that Pb, Cd and As contents in 4.3%, 3.3% and 2.2% rice samples respectively, were above maximum allowable concentration (MAC). In fresh edible mushroom, Pb and Hg contents in 2.6% samples were above MAC, respectively. However, only Hg content in 4.8% dry edible mushroom samples was above its MAC. Therefore, more than 95% rice and edible mushroom samples in our test had high edible safety.

Enhancement stabilization of heavy metals (Zn, Pb, Cr and Cu) during vermifiltration of liquid-state sludge

This paper illustrated the potential effect of earthworms on heavy metal stabilization after vermifiltration of liquid-state sludge. Significant enhancement of organics degradation in sludge caused an increase of heavy metal concentrations in VF effluent sludge. However, the analysis of heavy metal chemical speciation indicated earthworms made unstable fractions of heavy metals transformed into stable fractions. Further investigation using principal component analysis revealed that transformations of heavy metal fractions were mainly due to the changes in sludge physico-chemical properties of pH, soluble chemical oxygen demand and available phosphorus. The bioassay of earthworms indicated that only zinc was accumulated by earthworms because the unstable fraction was its main chemical speciation. Furthermore, risk analysis demonstrated that earthworm activities weakened heavy metal risk due to the formation of stable fractions although their total concentrations increased. These results indicated that earthworms in vermifilter had a positive role in stabilizing heavy metals in sewage sludge.

Identification of toxicity variations in a stream affected by industrial effluents using Daphnia magna and Ulva pertusa

A comprehensive toxicity monitoring study from August to October 2011 using Daphnia magna and Ulva pertusa was conducted to identify the cause of toxicity in a stream receiving industrial effluents (IEs) from a textile and leather products manufacturing complex. Acute toxicity toward both species was observed consistently in IE, which influenced toxicity of downstream (DS) water. A toxicity identification evaluation (TIE) confirmed that both Cu and Zn were key toxicants in the IE, and that the calculated toxicity based on Cu and Zn concentrations well simulated the variation in the observed toxicity (r(2)=0.9216 and 0.7256 for D. magna and U. pertusa, respectively). In particular, U. pertusa was sensitive enough to detect acute toxicity in DS and was useful to identify Zn as a key toxicant. Activities of catalase, superoxide dismutase, glutathione peroxidase, glutathione S-transferase, and malondialdehyde were induced significantly in D. magna, although acute toxicity was not observed. In addition, higher levels of antioxidant enzymes were expressed in DS than upstream waters, likely due to the Cu and Zn from IE. Overall, TIE procedures with a battery of bioassays were effective for identifying the cause of lethal and sub-lethal toxicity in effluent and stream water.

Effects of chloride, sulfate and natural organic matter (NOM) on the accumulation and release of trace-level inorganic contaminants from corroding iron

This study examined effects of varying levels of anions (chloride and sulfate) and natural organic matter (NOM) on iron release from and accumulation of inorganic contaminants in corrosion scales formed on iron coupons exposed to drinking water. Changes of concentrations of sulfate and chloride were observed to affect iron release and, in lesser extent, the retention of representative inorganic contaminants (vanadium, chromium, nickel, copper, zinc, arsenic, cadmium, lead and uranium); but, effects of NOM were more pronounced. DOC concentration of 1 mg/L caused iron release to increase, with average soluble and total iron concentrations being four and two times, respectively, higher than those in the absence of NOM. In the presence of NOM, the retention of inorganic contaminants by corrosion scales was reduced. This was especially prominent for lead, vanadium, chromium and copper whose retention by the scales decreased from >80% in the absence of NOM to <30% in its presence. Some of the contaminants, notably copper, chromium, zinc and nickel retained on the surface of iron coupons in the presence of DOC largely retained their mobility and were released readily when ambient water chemistry changed. Vanadium, arsenic, cadmium, lead and uranium retained by the scales were largely unsusceptible to changes of NOM and chloride levels. Modeling indicated that the observed effects were associated with the formation of metal-NOM complexes and effects of NOM on the sorption of the inorganic contaminants on solid phases that are typical for iron corrosion in drinking water.

Heavy metal pollution and assessment in the tidal flat sediments of Haizhou Bay, China

The heavy metal inventory and the ecological risk of the tidal flat sediments in Haizhou Bay were investigated. Results show that the average concentrations of heavy metals in the surface sediments exceeded the environment background values of Jiangsu Province coastal soil, suggesting that the surface sediments were mainly polluted by heavy metals (Cd, Cr, Cu, Mn, Pb and Zn). In addition, the profiles of heavy metals fluxes can reflect the socio-economic development of Lianyungang City, and heavy metals inputs were attributed to anthropogenic activities. Cr, Cu, Pb and Zn were mainly present in the non-bioavailable residual form in surface sediments, whereas Cd and Mn were predominantly in the highly mobile acid soluble and reducible fractions. The ecological risk of the polluted sediments stemmed mainly from Cd and Pb. According to the Sediment quality guidelines (SQGs), however, the adverse biological effects caused by the heavy metals occasionally occurred in tidal flat.

Biomass assisted synthesis of alumina by Gardenia Jasminoides Ellis and their application for removal of Ni(II) from aqueous solution

A simple and novel process has been proposed to synthesize alumina using gardenia extract and aluminum salts in an aqueous solution. The alumina sample notated as "bio-Al₂O₃" was characterized by X-ray diffraction (XRD) and nitrogen adsorption-desorption experiment. The results indicated that the existence of the gardenia biomass enlarged the surface area of alumina and reached 256 m(2)/g. The thermo gravimetric (TG), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) results showed that gardenia biomass bound to the surface of the alumina has substantially improved the adsorption capacity of Ni(II) and the adsorption behavior of nickel ion was related to the biomass functional groups. The results of three adsorption-desorption cycles showed that the bio-Al₂O₃ using as the adsorbent for Ni(II) was relatively stable. The kinetic of the Ni(II) adsorption by the bio-Al₂O₃ followed pseudo-second-order equation. Langmuir and Freundlich isotherm models were applied to analyze the experimental data and the result demonstrated that the adsorption isotherms followed Langmuir isotherm model.

Interactive effect of oxytetracycline and lead on soil enzymatic activity and microbial biomass

Interactive effect of oxytetracyline (OTC) and lead on soil enzymatic activity and population of microbes was studied in the paper. The results showed effect of pollutants on bacteria, actinomycetes and enzymatic activity increased in the order: (OTC+Pb)>Pb>OTC, (OTC+Pb)>Pb>OTC and (OTC+Pb)>OTC>Pb, respectively. However, impact of pollutants on fungi decreased in the order: (OTC+Pb)<Pb<OTC. The analysis of X-ray photoelectron spectroscopy (XPS) showed that binding energy and atomic percentage of Al, Fe, C, O, N, Si, Mg and Ca altered after the amended with OTC or Pb. The decrease of oxygen atom density and increase of binding energy can be associated to the charge transfer, resulting from oxygen and carbon atoms coordinated with metal ions, other chemicals or partial decomposition. Thus, the findings of this study can provide a better insight into the interaction of both pollutants and their impacts on soil quality.

Mobility, bioavailability and pH-dependent leaching of cadmium, zinc and lead in a contaminated soil amended with biochar

The effect of biochar application on the fate of Cd, Zn and Pb was investigated in a contaminated soil amended with three different rates of biochar (1%, 5% and 10%; w/w). In an incubation experiment, the 0.01M CaCl2-extractability of metals after 1h of incubation significantly decreased with increasing rate of biochar application. This effect was mostly attributed to the raise in soil pH. In the presence of 5% and 10% of biochar, the metal extractability continued to decrease over the next 56days, likely due to aging reactions. In a pot experiment, the metal concentration in shoots of ryegrass (Lolium multiflorum Lam.) harvested at 28 and 56days after sowing decreased with increasing rate of biochar application. Using a pH-dependent leaching test, we found that the metal release at a defined pH was not affected by the presence of biochar. However, because the acid neutralizing capacity (ANC) increased with increasing rate of biochar application, the time required to reach a hazardous pH can be predicted to be longer after biochar application. It is concluded that the application of biochar for in situ metal immobilization can be feasible provided soil pH is monitored over time.

Expression of HvHMA2 in tobacco modifies Zn-Fe-Cd homeostasis

HvHMA2 is a plasma membrane P1B-ATPase from barley that functions in Zn/Cd root-to-shoot transport. To assess the usefulness of HvHMA2 for modifying the metal content in aerial plant parts, it was expressed in tobacco under the CaMV35S promoter. Transformation with HvHMA2 did not produce one unique pattern of Zn and Cd accumulation; instead it depended on external metal supply. Thus Zn and Cd root-to-shoot translocation was facilitated, but not at all applied Zn/Cd concentrations. Metal uptake was restricted in HvHMA2-transformed plants and the level in the shoot was not enhanced. It was shown that HvHMA2 localizes to the plasma membrane of tobacco cells, and overloads the apoplast with Zn, which could explain the overall decrease in metal uptake observed. Despite the lower levels in the shoot, HvHMA2 transformants showed increased Zn sensitivity. Moreover, introduction of HvHMA2 into tobacco interfered with Fe metabolism and Fe accumulation was modified in HvHMA2-transformants in a Zn- and Cd-concentration dependent manner. The results indicate that ectopic expression of the export protein HvHMA2 in tobacco interferes with tobacco metal Zn-Cd-Fe cross-homeostasis, inducing internal mechanisms regulating metal uptake and tolerance.

Characterization and environmental risk assessment of heavy metals found in fly ashes from waste filter bags obtained from a Chinese steel plant

The environmental risk of exposure to six heavy metals (Cu, Pb, Zn, Cr, Ni, and Cd) found in fly ashes from waste filter bags obtained from a steel plant was estimated based on the mineralogical compositions, total concentrations and speciation of the metals in the fly ashes. The results indicated that the fly ashes mainly consisted of hematite, magnetite, cyanite, spinel, coesite and amorphous materials. The concentrations of Zn and Pb were much higher than that of other materials. After Zn and Pb, Ni was present in the highest concentration, followed by Cu, Cr and Cd. Each heavy metal was distributed differently in fly ashes. The levels of Zn, Cd and Pb in the active fraction were very high, and ranged from 64.83 to 81.96%, 34.48 to 82.4% and 6.92 to 79.65% respectively, while Cu, Cr and Ni were mainly present in the residual fraction. The risk assessment code (RAC) values of fly ashes showed that the Zn and Cd present in the H3 sample presented a very high risk, with RAC values greater than 50%. The Cu present in the H3 sample, Cd in the H2 sample and Zn in the H4 and H5 samples presented a high risk. The Pb present in the H2 sample, Cd in the H4 sample, Ni in the H1 and H5 samples, and Zn in the H1 sample presented a medium risk. A low risk was presented by the Cu present in the H1, H2, H4 and H5 samples, the Pb in the H1, H3 and H5 samples, the Cd in the H1 and H5 samples, and the Ni in the H2 sample. No risk was presented by Cr in any sample.

Investigation of heavy metal pollutants at various depths in the Gulf of Izmit

In this study, we report results concerning the accumulation of heavy metals in seawater from Izmit Bay. The bay was divided into the three parts: the eastern, the central and the western basins. The goal of this study was to determine levels of heavy metals at various depths in the bay between April 2008 and May 2010. Liquid-liquid extractions were performed on seawater samples. An atomic absorption spectrophotometer was used to measure levels of six metals: lead, cadmium, chromium, iron, manganese and zinc. We applied our results to evaluate the status of pollution in the Gulf of Izmit. Significant seasonal differences in metal concentrations and higher concentrations of many metals in water near the shore are evidence for uncontrolled release of pollutants in the water.

The link between selenium binding protein from Sinonovacula constricta and environmental pollutions exposure

Selenium binding proteins (SeBPs) play a crucial role in controlling the oxidation/reduction in many physiological processes. Here we reported the isolation and characterization of a cDNA of SeBP gene from Sinonovacula constricta (denoted as ScSeBP). The full-length cDNA of ScSeBP was of 2345 bp, consisting of a 5'UTR of 246 bp, a 3' UTR of 626 bp, and a complete ORF of 1473 bp encoding a polypeptide with 491 amino acid residues. The predicted molecular mass of deduced amino acid of ScSeBP was 54.85 kDa and the theoretical pI was 6.44. Tissue distribution analysis of the ScSeBP revealed that the mRNA transcripts of ScSeBP were constitutively expressed in all examined tissues with the higher expressions in gill, gonad and the haemocytes. The temporal expression of ScSeBP in gill and haemocytes after B[α]P and heavy metals exposure were recorded by qPCR. B[α]P exposure at 0.5 and 5 mg L(-1) caused significant increase in mRNA expression of ScSeBP in haemocytes, but down-regulated ScSeBP mRNA expression in gill. Concerning heavy metals stresses, the suppressed expression patterns were detected in gill and haemocyte except lower concentration of PbCl2 exposure in haemocytes at 12 h. All our results indicated that ScSeBP was one of key effectors in mediating B[α]P and heavy metals exposure.

Removal of Cu, Pb and Zn by foam fractionation and a soil washing process from contaminated industrial soils using soapberry-derived saponin: a comparative effectiveness assessment

The feasibility of using the eco-friendly biodegradable surfactant saponin (a plant-based surfactant) from soapberry and surfactin from Bacillus subtilis (BBK006) for the removal of heavy metals from contaminated industrial soil (6511mgkg(-1) copper, 4955mgkg(-1) lead, and 15090mgkg(-1) zinc) by foam fractionation and a soil flushing process was evaluated under variation of fundamental factors (surfactant concentration, pH, temperature and time). The results of latter process showed that 1-2% Pb, 16-17% Cu and 21-24% Zn was removed by surfactin after 48h, whereas the removal of Pb, Cu and Zn was increased from 40% to 47%, 30% to 36% and 16% to 18% in presence of saponin with an increase from 24 to 72h at room temperature by the soil washing process at pH 4. In the foam fractionation process, the metal removal efficiencies were increased with increases in the saponin concentration (0.075-0.15gL(-1)) and time (24-72h), whereas the efficiency was decreased with increasing pH (4-10) and temperature (>40°C). The removal efficiencies of Pb, Cu and Zn were increased significantly from 57% to 98%, 85% to 95% and 55% to 56% with an increase in the flow rate from 0.2 to 1.0Lmin(-1) at 0.15gL(-1) saponin (pH 4 and 30°C). The present investigation indicated that the foam fractionation process is more efficient for the removal of heavy metal from contaminated industrial soil in comparison to the soil washing process. The plant-based eco-friendly biodegradable biosurfactant saponin can be used for environmental cleanup and pollution management.

Effects of heavy metal wastewater on the anoxic/aerobic-membrane bioreactor bioprocess and membrane fouling

Heavy metals have significant negative effects on anoxic/aerobic-membrane bioreactors (A/O-MBR). The changes in the performance of A/O-MBR fed with municipal wastewater containing 0.25-2.56 mg/L (low concentrations) and 3.7-32.3mg/L (high concentrations) of zinc, copper, lead, and cadmium were studied in this paper. The nitrification rate decreased to 27% and 46%, whereas the denitrification rate decreased to 20% and 34% under treatment with low/high concentrations of heavy metals, which indicate that heavy metals more significantly affect nitrification than denitrification. Heavy metals also resulted in the increase of carbohydrate of extracellular polymer substances and a smaller particle size distribution. Scanning electron microscope images, energy-dispersive X-ray spectroscopy and atomic absorption spectrometry analysis of fouled membranes showed solid inorganic scale deposits on the membrane. All these results suggest that heavy metals affect membrane fouling in two ways: (a) modification of sludge characteristics; and (b) contribution to inorganic fouling.

Novel magnetic beads based on sodium alginate gel crosslinked by zirconium(IV) and their effective removal for Pb²⁺ in aqueous solutions by using a batch and continuous systems

Novel magnetic sodium alginate gel beads (Fe3O4@SA-Zr) were successfully prepared by using zirconium(IV) as crosslinking ions, and used as adsorbent for removal of Pb(2+) ions from aqueous solutions in batch and fixed-bed column systems. Fe3O4@SA-Zr was characterized by SEM, FT-IR, XRD and VSM. Fe3O4@SA-Zr had the macroporous structure, exhibited greater stability and possessed a sensitive magnetic response. More importantly, Fe3O4@SA-Zr exhibited high adsorption capacity, fast kinetics and high selectivity towards Pb(2+) ions. Experimental data was well described by Langmuir isotherm with a maximum adsorption capacity of 333.33 mg/g. FTIR and XPS indicated that the carboxyl and hydroxyl groups of SA and hydroxyl groups binding to Fe and Zr species were involved in Pb(2+) adsorption. Fixed-bed column packed with Fe3O4@SA-Zr exhibited higher removal efficiency for Pb(2+)ions. Consequently, Fe3O4@SA-Zr with excellent absorbability, stability and reusability could be used as a promising adsorbent for Pb(2+) removal in wastewaters.

Methylmercury exposure increases lipocalin related (lpr) and decreases activated in blocked unfolded protein response (abu) genes and specific miRNAs in Caenorhabditis elegans

Methylmercury (MeHg) is a persistent environmental and dietary contaminant that causes serious adverse developmental and physiologic effects at multiple cellular levels. In order to understand more fully the consequences of MeHg exposure at the molecular level, we profiled gene and miRNA transcripts from the model organism Caenorhabditis elegans. Animals were exposed to MeHg (10 μM) from embryo to larval 4 (L4) stage and RNAs were isolated. RNA-seq analysis on the Illumina platform revealed 541 genes up- and 261 genes down-regulated at a cutoff of 2-fold change and false discovery rate-corrected significance q < 0.05. Among the up-regulated genes were those previously shown to increase under oxidative stress conditions including hsp-16.11 (2.5-fold), gst-35 (10.1-fold), and fmo-2 (58.5-fold). In addition, we observed up-regulation of 6 out of 7 lipocalin related (lpr) family genes and down regulation of 7 out of 15 activated in blocked unfolded protein response (abu) genes. Gene Ontology enrichment analysis highlighted the effect of genes related to development and organism growth. miRNA-seq analysis revealed 6-8 fold down regulation of mir-37-3p, mir-41-5p, mir-70-3p, and mir-75-3p. Our results demonstrate the effects of MeHg on specific transcripts encoding proteins in oxidative stress responses and in ER stress pathways. Pending confirmation of these transcript changes at protein levels, their association and dissociation characteristics with interaction partners, and integration of these signals, these findings indicate broad and dynamic mechanisms by which MeHg exerts its harmful effects.

On the simultaneous adsorption of a reactive dye and hexavalent chromium from aqueous solutions onto grafted chitosan

In the present work, the simultaneous adsorption of Remazol Red 3BS (reactive dye) and Cr(VI) onto chitosan powder grafted with poly(ethylene imine) and cross-linked with epichlorohydrin is experimentally studied. Such a combination of a dye molecule and a heavy metal can be found in real/practical conditions of environmental pollutants' removal, so their mutual interaction on the adsorption efficiencies is very important. The experimental data revealed a competitive type of interaction between the dye molecule and heavy metal ion. An attempt is made to quantitatively describe the data through appropriate isotherms and kinetic equations. The data demonstrated that the common thermodynamic equilibrium is not obtained for the present problem and the final composition of the adsorbed phase depends also on the kinetics. A new scenario of irreversible kinetic-based equilibrium was introduced and examined in detail. None of the scenarios considered here is fully able to cover the whole data, so semi-empirical equations are introduced for their description. It is shown that further development of phenomenological models requires more complicated experimental protocols than simple simultaneous adsorption of the species.

Influence of exogenous application of glutathione on rubisco and rubisco activase in heavy metal-stressed tobacco plant grown in vitro

The effect of glutathione on the influences of heavy metals affecting rubisco and rubisco activase was studied in tobacco plants grown in vitro where the shoot explants of the tobacco plant cultured on MS medium under aseptic conditions and two explants were placed in the control, 0.1 mM GSH, 1 mM GSH, 0.2 mM Cd, 0.2 mM Cu, 0.2 mM Zn, and a mixture of Cd and GSH, Cu and GSH, Zn and GSH, respectively. The effect of GSH on the growth of the tobacco plant was minimal, but the heavy metals clearly retarded its growth. GSH recovered the growth retarded by heavy metals, and the concentration of GSH required to recover the growth differed depending on the heavy metals. The content of chlorophyll in the plant increased through GSH and Zn, and decreased through Cd and Cu. The chlorophyll content which decreased due to Cd and Cu was recovered by GSH, and the content which increased due to Zn was decreased by 1 mM GSH. The content of rubisco decreased due to GSH and heavy metals, and the content which decreased due to heavy metals was recovered by GSH, and when GSH was treated with Zn, the increased rate was maximum compared to other heavy metals. The activity of rubisco was increased due to GSH and heavy metals, and the activity increased by Cd and Zn decreased through GSH. In the case of Cu, the activity of GSH increased even more. There was no effect of GSH on the influences of heavy metals on the content and activity of rubisco activase. The activity of rubisco decreased by thiourea among six denaturing agents, and increased by l-cysteine, and in most cases the activity level was recorded as high. The activity of rubisco activase all decreased as a result of six denaturing agents, and the effect caused by EDTA and guanidine-HCl was the greatest, while the effect caused by l-cysteine and urea was minimal.

Biosorption of heavy metals by lactic acid bacteria and identification of mercury binding protein

Heavy metals cause various health hazards. Using lactic acid bacteria (LAB), we tested the biosorption of heavy metals e.g. cadmium (Cd) (II), lead (Pb) (II), arsenic (As) (III), and mercury (Hg) (II). Cd (II) sorption was tested in 103 strains using atomic absorption spectrophotometery (AAS). Weissella viridescens MYU 205 (1 × 10(8) cells/ml) decreased Cd (II) levels in citrate buffer (pH 6.0) from one ppm to 0.459 ± 0.016 ppm, corresponding to 10.46 μg of Cd (II). After screening, 11 LAB strains were tested using various pH (pH 4.0, 5.0, 6.0, 7.0) showing the sorption was acid sensitive; and was cell concentration dependent, where the Cd (II) concentration decreased from one ppm to 0.042 (max)/0.255 (min) ppm at 1 × 10(10) cells/ml. Additionally, the biosorption of Pb (II), As (III), and Hg (II) were tested using an inductively coupled plasma mass spectrometer (ICP-MS). The Hg (II) concentration was reduced the most followed by Pb (II) and As (III). Many of the bacterial cell surface proteins of W. viridescens MYU 205 showed binding to Hg (II) using the Hg (II) column assay. Having a CXXC motif, a ∼14 kDa protein may be one of the Hg (II) binding proteins. LAB biosorption may aid the detoxification of people exposed to heavy metals.

Toxicogenomic approaches for understanding molecular mechanisms of heavy metal mutagenicity and carcinogenicity

Heavy metals that are harmful to humans include arsenic, cadmium, chromium, lead, mercury, and nickel. Some metals or their related compounds may even cause cancer. However, the mechanism underlying heavy metal-induced cancer remains unclear. Increasing data show a link between heavy metal exposure and aberrant changes in both genetic and epigenetic factors via non-targeted multiple toxicogenomic technologies of the transcriptome, proteome, metabolome, and epigenome. These modifications due to heavy metal exposure might provide a better understanding of environmental disorders. Such informative changes following heavy metal exposure might also be useful for screening of biomarker-monitored exposure to environmental pollutants and/or predicting the risk of disease. We summarize advances in high-throughput toxicogenomic-based technologies and studies related to exposure to individual heavy metal and/or mixtures and propose the underlying mechanism of action and toxicant signatures. Integrative multi-level expression analysis of the toxicity of heavy metals via system toxicology-based methodologies combined with statistical and computational tools might clarify the biological pathways involved in carcinogenic processes. Although standard in vitro and in vivo endpoint testing of mutagenicity and carcinogenicity are considered a complementary approach linked to disease, we also suggest that further evaluation of prominent biomarkers reflecting effects, responses, and disease susceptibility might be diagnostic. Furthermore, we discuss challenges in toxicogenomic applications for toxicological studies of metal mixtures and epidemiological research. Taken together, this review presents toxicogenomic data that will be useful for improvement of the knowledge of carcinogenesis and the development of better strategies for health risk assessment.

Biodegradation of petroleum hydrocarbons in the presence of nickel and cobalt

Bioremediation of environments co-contaminated with hydrocarbons and heavy metals often pose a challenge as heavy metals exert toxicity to existing communities of hydrocarbon degraders. Multi-resistant bacterial strains were studied for ability to degrade hydrocarbons in chemically defined media amended with 5.0 mM Ni(2+), and Co(2+). The bacteria, Pseudomonas aeruginosa CA207Ni, Burkholderia cepacia AL96Co, and Corynebacterium kutscheri FL108Hg, utilized crude oil and anthracene without lag phase at specific growth rate spanning 0.3848-0.8259 per day. The bacterial populations grew in hydrocarbon media amended with nickel (Ni) and cobalt (Co) at 0.8393-1.801 days generation time (period of exponential growth, t = 15 days). The bacteria degraded 96.24-98.97, and 92.94-96.24% of crude oil, and anthracene, respectively, within 30 days without any impedance due to metal toxicity (at 5.0 mM). Rather, there was reduction of Ni and Co concentrations in the axenic culture 30 days post-inoculation to 0.08-0.12 and 0.11-0.15 mM, respectively. The metabolic functions of the bacteria are active in the presence of toxic metals (Ni and Co) while utilizing petroleum hydrocarbons for increase in biomass. These findings are useful to other baseline studies on decommissioning of sites co-contaminated with hydrocarbons and toxic metals.