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PubMed2005

Heavy metal accumulation of urban domestic rubbish compost in turfgrass by EDTA chelating.

Seven kinds of heavy metal accumulation of rubbish compost in turfgrass by EDTA chelating were investigated. With EDTA application, heavy metal accumulation by two species of turfgrass was increased significantly. The enrichment coefficients of Lolium perenne L(L) and Festuca arundinacea L(F) to Cr reached 9.45 and 6.15 respectively. In the range of EDTA dosages given, heavy metal accumulation in turfgrass increased with increasing EDTA level. There were significant differences in remediation of different metals by applying EDTA. L had high ability to accumulate Cr, Cd, Ni and Zn, showing better remediation to heavy metals of rubbish compost. In contrast, F showed high ability to accumulate Cr, Ni, Cu and Zn. Low EDTA level increased aboveground net primary production (ANP) of turfgrass, but EDTA would considerably inhibit it when EDTA was higher than 20 mmol/kg. The results demonstrated that the optimum dosage of EDTA for remediating heavy metals in rubbish compost by turfgrass was between 10 mmol/kg and 20 mmol/kg.

Biodegradation, Environmental↗

PubMed2005

Transformation of heavy metal forms during sewage sludge bioleaching.

The transformation of heavy metal forms during sewage sludge bioleaching with elemental sulfur as substrate was investigated. The sequential selective extraction procedure was an effective way to reflect the variation in heavy metal forms. The exchangeable form of Cu, Pb and Zn after bioleaching accounted for 81.6, 40.2 and 75.8%, respectively. Cu at initial sludge mainly existed as sulfide precipitate form, most of which turned to exchangeable form during bioleaching, and was solubilized mostly by direct mechanism. The original forms of Pb and Zn were mainly carbonate precipitate and organically bound. Most of the carbonate precipitate Pb transformed into exchangeable form but a little of organically bound Pb. Pb was dissolved from the sludge due to transformation of carbonate precipitated and sulfide precipitated to exchangeable form by cooperation of both direct and indirect mechanisms. A majority of exchangeable Zn was transformed from organically bound and carbonate precipitated forms, and the bioleaching mechanism of Zn was mainly indirect. After bioleaching, the sewage sludge could be applied to land more safely because the heavy metals mainly existed in stable forms. The exchangeable Cu and Pb achieved an obvious increase at pH about 2, while exchangeable Zn showed higher percentage at pH about 3. The transformation of chemical forms for Cu had good relationship with ORP during bioleaching, but Zn was not influenced by ORP of sludge, which appeared to have high bioleaching efficiency at ORP less than 200 mV.

Hydrogen-Ion Concentration↗

PubMed2006

Heavy metal contents of the karasu creek sediments, Nigde, Turkey.

Heavy metal contamination in sediments of the Karasu spring was investigated in the presented study. In this respect, sediment samples were collected from contaminant sites along the spring starting from the spring water manifestation site, base of the Akkaya dam to the dam exit site. Heavy metal concentrations were determined by X-ray Fluorescence Spectrometer. Cobalt, copper, arsenic, tin, nickel, zinc, cadmium, lead, aluminum, iron, titan, chromium and manganese contents of the Karasu creek sediments are found as 18.30-69.00, 12.40-595.0 5.50-345.3, 5.80-15.1, 10.9-64.1, 28.90-103,300, 4.1-356.2, 7.70-37,840, 13,460-109,400, 11,740-62,900, 22.18-59.04, 41.70-369 and 12.09-3,480 mg/kg, respectively. Results indicate the presence of a contamination in the Karasu creek. All the metal concentrations were found to be exceeding their acceptable limit values. Eutrophication is developed in the Karasu creek and the Akkaya dam. It is thought that heavy metal accumulation in the creek is originated from discharge from mine quarries, industrial and domestic wastes. Protection zones should be defined and all necessary measures must be taken along the Karasu creek.

Geologic Sediments↗

PubMed2003

Heavy metal resistance of biofilm and planktonic Pseudomonas aeruginosa.

A study was undertaken to examine the effects of the heavy metals copper, lead, and zinc on biofilm and planktonic Pseudomonas aeruginosa. A rotating-disk biofilm reactor was used to generate biofilm and free-swimming cultures to test their relative levels of resistance to heavy metals. It was determined that biofilms were anywhere from 2 to 600 times more resistant to heavy metal stress than free-swimming cells. When planktonic cells at different stages of growth were examined, it was found that logarithmically growing cells were more resistant to copper and lead stress than stationary-phase cells. However, biofilms were observed to be more resistant to heavy metals than either stationary-phase or logarithmically growing planktonic cells. Microscopy was used to evaluate the effect of copper stress on a mature P. aeruginosa biofilm. The exterior of the biofilm was preferentially killed after exposure to elevated concentrations of copper, and the majority of living cells were near the substratum. A potential explanation for this is that the extracellular polymeric substances that encase a biofilm may be responsible for protecting cells from heavy metal stress by binding the heavy metals and retarding their diffusion within the biofilm.

Animals↗

PubMed2000

Spatial variation of heavy metals in surface sediments of Hong Kong mangrove swamps.

The degree of heavy metal contamination in the fine-grained (<63 microm) and sand-sized (2 mm-63 microm) fractions of surface sediments in 18 different mangrove swamps (144 random samples) in Hong Kong was examined. Higher concentrations of heavy metals were found in the fine-grained than the sand-sized fractions of the sediment; however, the differences between these two fractions became less significant when the swamp was more contaminated. The principal component analyses show that the 18 mangrove swamps, according to the median concentrations of total heavy metals, were clustered into four groups. The first group included three mangrove swamps in Deep Bay region which are seriously contaminated, with heavy metal concentrations in sediments around 80 microg g(-1) Cu, 240 microg g(-1) Zn, 40 microg g(-1) Cr, 30 microg g(-1) Ni, 3 microg g(-1) Cd and 80 microg g(-1) Pb. The second cluster, made up of another four swamps distributed in different geographical locations (two in Sai Kung district and two in Tolo region), also had elevated levels of Cu, Pb, Ni and Cr in the sediments. Field observation reveals that these seven stands received industrial, livestock and domestic sewage as well as pollution from mariculture activities, suggesting that anthropogenic input is the main source of heavy metal contamination in Hong Kong mangroves. The sediments from other mangrove swamps were relatively uncontaminated.

Journal Article↗

PubMedDate not supplied

[Toxicological assessment of exposure to heavy metals].

The present paper describes the most important pathways of human exposure to heavy metals (food, beverages, and drinking water; heavy metals in suspended matter, dust fall-out, soil and house dust; tobacco smoking; amalgam fillings). In recent years there has been a significant decrease of the concentrations of heavy metals in suspended matter and dust fall-out. The lead levels in food has also decreased. Human exposure to heavy metals can be assessed by means of biological monitoring on an individuals basis. Some principals concerning the toxicological evaluation of metal concentrations in human body fluids and tissues are discussed.

Body Burden↗

PubMed1987

Inhibition of rabbit reticulocyte lysate protein synthesis by heavy metal ions involves the phosphorylation of the alpha-subunit of the eukaryotic initiation factor 2.

The effect of heavy metal ions (in particular Cd2+, Hg2+, and Pb2+) on protein synthesis in hemin-supplemented reticulocyte lysates was investigated. Heavy metal ions were found to inhibit protein synthesis in hemin-supplemented lysates with biphasic kinetics. The shut off of protein synthesis occurred in conjunction with the phosphorylation of the alpha-subunit of the eukaryotic initiation factor (eIF) 2, the loss of reversing factor (RF) activity, and the disaggregation of polyribosomes. Addition of eIF-2 or RF to heavy metal ion-inhibited lysates restored protein synthesis to levels observed in hemin-supplemented controls. The stimulation of protein synthesis observed upon the addition of cAMP to heavy metal ion-inhibited lysates correlated with the inhibition of eIF-2 alpha phosphorylation and the restoration of RF activity. The partial restoration of protein synthesis observed upon the addition of MgGTP to heavy metal ion-inhibited lysates correlated with a partial inhibition of eIF-2 alpha phosphorylation. Addition of glucose 6-phosphate was found to have no effect on protein synthesis of eIF-2 alpha phosphorylation under these conditions. Antiserum raised to the reticulocyte heme-regulated eIF-2 alpha kinase inhibited the phosphorylation of eIF-2 alpha catalyzed by Hg2+-inhibited lysate. The inhibition of protein synthesis observed in the presence of heavy metal ions correlated with the relative biological toxicity of the ions. Highly toxic ions (AsO-2, Cd2+, Hg2+, Pb2+) inhibited protein synthesis by 50% at concentrations of 2.5-10 microM. Cu2+, Fe3+, and Zn2+, which are moderately to slightly toxic ions, inhibited protein synthesis by 50% at concentrations of 40, 250, and 300 microM, respectively. The data presented here indicate that heavy metal ions inhibit protein chain initiation in hemin-supplemented lysates by stimulating the phosphorylation of eIF-2 alpha apparently through the activation of the heme-regulated eIF-2 alpha kinase rather than through inhibition of the rate of eIF-2 alpha dephosphorylation.

Animals↗

PubMed1997

[Ecopathology of the kidneys and individual sensitivity to heavy metal salts].

Investigations performed in the region contaminated with heavy metal salts revealed high prevalence of renal diseases in children. The test for blood polymorphic proteins indicated signs of genetic predisposition to renal damage. Greater occurrence in the population with econephropathy of a rare allele of transferrin C3 may be the cause of enhanced oxidative-radical processes in renal cells. Individual sensitivity of children to heavy metal salts assessed by leukocytolysis and high incidence of somatic mutations to determine T-lymphocyte microclones deficient by HGPRT may help in specification of the affections detected in the regions contaminated with heavy metal salts.

Adolescent↗

PubMed2003

Heavy metals extraction by microemulsions.

The objective of this study is the heavy metal extraction by microemulsion, using regional vegetable oils as surfactants. Firstly, the main parameters, which have influence in the microemulsion region, such as: nature of cosurfactant, influence of cosurfactant (C)/surfactant (S) ratio and salinity were studied, with the objective of choosing the best extraction system. The extraction/reextraction process by microemulsion consists of two stages. In the first one, the heavy metal ion present in the aqueous phase is extracted by the microemulsion. In a second step, the reextraction process occurs: the microemulsion phase, rich in metal, is acidified and the metal is recovered in a new aqueous phase, with higher concentration. The used system had the following parameters: surfactant-saponified coconut oil; cosurfactant-n-butanol; oil phase-kerosene; C/S ratio=4; salinity-2% (NaCl); temperature of 27+/-1 degrees C; water phase-aqueous solution that varied according to the heavy metal in study (Cr, Cu, Fe, Mn, Ni and Pb). A methodology of experimental planning was used (Scheffé Net) to study the behavior of the extraction in a chosen domain. The extraction was accomplished in one step and yielded extraction percentage higher than 98% for all metals. In the reextraction HCl-8M was used as reextraction agent and the influence of the pH and time were verified. This work showed the great efficiency of the microemulsion, indicating that it is possible to extract selectively the heavy metals from the aqueous phase.

Emulsions↗

PubMed2003

The removal by crab shell of mixed heavy metal ions in aqueous solution.

In order to examine the inhibition effect of other heavy metal ions on the removal by crab shell of heavy metal ions in aqueous solutions, three ions (Pb(2+), Cd(2+), Cr(3+)) were used in single, binary and ternary systems. In single heavy metal ion systems, the removals of Cr(3+) and Pb(2+) were much higher than that of Cd(2+). In binary heavy metal ions systems, Cd(2+) did not affect Pb(2+) removal while Cr(3+) had a severe inhibition effect on the removal of Pb(2+). Cd(2+) removal was slightly affected by the presence of Pb(2+); however, it was severely affected by the presence of Cr(3+). The inhibitory effect of Cd(2+) on Cr(3+) was relatively lower than that of Pb(2+).

Animals↗

PubMedDate not supplied

Heavy metal interactions with phosphatic clay: sorption and desorption behavior.

Heavy metals produced and released during agricultural and industrial activities may pose a serious threat to the environment. This study investigated the effectiveness of phosphatic clay, a by-product of the phosphate mining industry, for immobilizing heavy metals (Pb(+2), Cd(+2), and Zn(+2)) from aqueous solutions. A batch equilibrium technique was adopted to evaluate metal sorption in the presence of 0.05 M KNO3 background electrolyte solution. The amounts of metals sorbed onto phosphatic clay decreased in the order Pb(+2) > Cd(+2) > Zn(+2). Desorption data suggest that a large fraction of metals sorbed onto phosphatic clay stayed intact under a wide variation in extracting solution pH (ranging from 3 to 10). Desorption rates were slowest for Pb followed by Cd and Zn. Only 8.1 to 23.1% of Pb, 8.4 to 45% of Cd, and 21.9 to 73.9% of Zn sorbed on phosphatic clay was mobilized by USEPA toxicity characteristic leaching procedure (TCLP) solutions at pH 2.93+/-0.05 and 4.93+/-0.05, respectively. Formation of fluoropyromorphite [Pb10(PO4)6(F2)], confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD), after reaction of aqueous Pb with phosphatic clay suggested that precipitation remained the dominant mechanism for Pb removal from aqueous solution. In the case of aqueous Cd and Zn interaction with phosphatic clay, we are not able to confirm the formation of a new amorphous and/or crystalline phase on the basis of available information. Other possible sorption mechanisms for Cd and Zn may include sorption and coprecipitation. Thus, phosphatic clay may be an effective amendment for in situ immobilization of heavy metals in contaminated soils and sediments.

Absorption↗

PubMed2006

[Thermal analysis and the distribution rule of heavy metals during electroplating sludge combustion].

A representative hazardous waste containing heavy metal is electroplating sludge, Thermal characteristic and the distribution of different heavy metal elements (Pb, Cd, Cu, Zn, Ni and Mn) was studied. The results of experiment show that from thermal analysis, in the process of experiment of thermal gravity there are some peaks of weight loss as 100 degrees C, 150 degrees C and 600 degrees C among these peaks, the peaks of 100 degrees C and 150 degrees C is caused by that the volatile separated out and organic matter combusted and pyrolysed at the same time, the peak of 600 degrees C is produced by the carbonate decomposed. From EDS analysis, electroplating sludge is composed by these main elements which are O, S, Al, Ca, Cr and Fe, and other secondary elements such as Mg, Cu, Zn, P, Cl and C. In the process of temperature promoted, the quantity of nonmetal such as C and Cl is decreased, and the quantity of Cr, Fe, and Mg is steady within 900 degrees C. From the experiment of distribution rule, the quantity of Mn, Pb, Ni and Cu decreased in the process of combustion while the furnace temperature raised,among these heavy metal the quantity of Ni decrease most obviously,and on the contrary the quantity of Cd enrich obviously in this process.

Electroplating↗

PubMed1999

Heavy metal pollution of soils affected by the Guadiamar toxic flood.

Total heavy metal concentrations were determined in soil samples of seven selected areas along the Guadiamar river valley affected by the toxic flood, after removal of the deposited sludge. Mean total concentrations of nine elements (As, Au, Bi, Cd, Cu, Pb, Sb, Tl and Zn) out of the 23 (As, Au, Ba, Be, Bi, Cd, Co, Cr, Cu, In, Mn, Mo, Ni, Pb, Sb, Sc, Sn, Th, Tl, U, V, Y and Zn) analysed were higher in sludge-covered soils than in unaffected soils. Mean values of total As, Au, Pb, Sb, Tl and Zn in sludge-affected soils were higher than the upper limits for normal soils world-wide. Mean concentrations of Bi, Cd and Cu were within these ranges, although some individual values exceeded the upper limits. In all sampling areas, severe heavy metal pollution was observed in the superficial layers (0-20 cm) of most of the affected soils, which decreased downward in the soil profile. Generally, in soils with more than 25% of clay, concentration of heavy metals below the 20-cm depth decreased to values close to those of the background level of the Guadiamar valley soils, while in coarser soils, heavy metal pollution penetrated below this depth, being noticeable down to a depth of at least 50-80 cm.

Accidents, Occupational↗

PubMed2000

Bacterial metal-resistance proteins and their use in biosensors for the detection of bioavailable heavy metals.

We have expressed and purified metal-resistance and metal regulatory proteins from the bacterial determinants of resistance to heavy metals and utilised these in the development of biosensors for heavy metals. Both the metallothionein from the cyanobacterium Synechococcus PCC 7942 and the MerR regulatory protein from transposon Tn501 allow the detection of non-specific metal binding down to 10(-15) M concentrations of Hg(II), Cu(II), Zn(II) and Cd(II) in pure solution. Differential effects of the metals can be detected at both low and high concentrations, and the shape of the capacitance curves may reflect biologically relevant responses of the proteins to metals. Further work is required to establish the relationship between the detected binding of metal and the biological response of the protein, or to provide biosensors of use in the natural environment.

Bacterial Proteins↗

PubMed2006

Effect of quaternary ammonium cation loading and pH on heavy metal sorption to Ca bentonite and two organobentonites.

Sorption of four heavy metals (Pb, Cd, Zn and Hg) to calcium bentonite (Ca bentonite), hexadecyltrimethylammonium bentonite (HDTMA bentonite) and benzyltriethylammonium bentonite (BTEA bentonite) was measured as a function of the quaternary ammonium cation (QAC) loading at 25, 50 and 100% of the clay's cation-exchange capacity (CEC). The effects of pH on the surface charge of the clays and heavy metal sorption were also measured. Sorption of Cd, Pb, and Zn was non-linear and sorption of all three metals by HDTMA and BTEA bentonites decreased as the QAC loading increased from 25 to 100%. In most cases, sorption of these metals to 25% BTEA and 25% HDTMA bentonite was similar to or greater than sorption to Ca bentonite. Hg sorption was linear for both HDTMA and BTEA bentonite. No significant effect on Hg sorption was observed with increasing QAC loading on BTEA bentonite. However, an increase of Hg sorption was detected with increasing QAC loading on HDTMA bentonite. This behavior suggests that a process different than cation exchange was the predominant Hg sorption mechanism. Cd, Pb, and Zn sorption decreased with pH. However, this effect was stronger for Cd and Pb than Zn. Hg sorption varied inversely with pH. QAC loading affected the surface charge of the clays. Twenty-five and 50% loading of BTEA cations increased the negative charge on the clay's surface relative to the untreated clay, without affecting the zero point of charge (ZPC) of the clay. Increased QAC loading on HDTMA bentonite causes the surface charge to become more positive and the ZPC increased. One hundred percent of HDTMA bentonite maintained a positive surface charge over the range of pH values tested. The organoclays studied have considerable capacity for heavy metal sorption. Given that prior studies have demonstrated the strong sorption capacity of organoclays for nonionic organic pollutants, it is likely that organoclays can be useful sorbents for the treatment of effluent streams containing both organic contaminants and heavy metals.

Adsorption↗

PubMed1996

Inhibitory effects of heavy metals on cytochrome P4501A induction in permanent fish hepatoma cells.

The interactions in vitro of heavy metals Cd(II), Co(II), Cu(II), Ni(II), Pb(II), and Zn(II) with cytochrome P4501A (CYP1A) induction response and enzyme activity were studied in fish hepatoma cells PLHC-1. Cells were simultaneously exposed to heavy metals and to 3-methylcholanthrene (3-MC), an inducer of CYP1A. Heavy metals were added to the cells in different concentrations. Cytotoxicity were measured in the neutral red (NR) assay, relative CYP1A protein contents in an enzyme-linked immunosorbent assay (ELISA), and CYP1A activities in the ethoxyresorufin-O-deethylase (EROD) assay. All metals had a more pronounced effect on EROD activity than on CYP1A protein content and cytotoxicity. For the most active metal Cd(II), a 50% inhibition of EROD activity was observed at significantly lower concentrations (2.2 x 10(-5) M) than a 50% reduction of CYP1A protein (5.3 x 10(-5) M), and a 50% cytotoxicity (1.4 x 10(-4) M). The inhibitory potency of the metals had the following order: Cd(II) > Ni(II) > Cu(II) > Co(II) = Zn(II) > Pb(II). In a second set of experiments, lysates of 3-MC-induced cells were exposed to heavy metals. Cd(II) and Cu(II) caused a 50% inhibition of EROD activity at significantly lower concentrations than in the experiments with living cells, at 8.2 x 10(-6) M and 1.3 x 10(-5) M, respectively, whereas the effect by Co(II) occurred at a significantly higher concentration (8.2 x 10(-4) M). The results indicate that Cd(II) and Cu(II) in particular may affect the CYP1A system of the liver of fish at low concentrations through direct inhibition of the CYP1A enzyme activity. CYP1A induction response in fish liver is increasingly being used in biomonitoring programs. In the environment, interactions of CYP1A-inducing and CYP1A-inhibiting components (such as heavy metals) can be expected and must be taken into consideration.

Animals↗

PubMed2005

Heavy metal precipitation by polycation-polyanion complex of PEI and its phosphonomethylated derivative.

The removal of various heavy metal ions such as Cu2+, Co2+, Zn2+, Ni2+ and Pb2+ from aqueous solutions by precipitation with polyelectrolyte complex of PPEI and PEI was conducted. Heavy metal binding with PPEI was initially allowed to occur and then upon equilibration, PEI was added to initiate precipitation of the polyelectrolyte complex together with the heavy metal ion. The PPEI-PEI system was found effective for heavy metal scavenging purposes even in the presence of high concentrations of non-transition metal ions like Na+. Heavy metal concentration may be reduced beyond emission standards for industrial wastewaters. The PPEI-PEI polyelectrolyte complex was found to be more effective than traditional precipitation methods for the treatment of a representative electroless Ni plating waste solution.

Chemical Precipitation↗

PubMed2001

A new pathway for heavy metal detoxification in animals. Phytochelatin synthase is required for cadmium tolerance in Caenorhabditis elegans.

Increasing emissions of heavy metals such as cadmium, mercury, and arsenic into the environment pose an acute problem for all organisms. Considerations of the biochemical basis of heavy metal detoxification in animals have focused exclusively on two classes of peptides, the thiol tripeptide, glutathione (GSH, gamma-Glu-Cys-Gly), and a diverse family of cysteine-rich low molecular weight proteins, the metallothioneins. Plants and some fungi, however, not only deploy GSH and metallothioneins for metal detoxification but also synthesize another class of heavy metal binding peptides termed phytochelatins (PCs) from GSH. Here we show that PC-mediated heavy metal detoxification is not restricted to plants and some fungi but extends to animals by demonstrating that the ce-pcs-1 gene of the nematode worm Caenorhabditis elegans encodes a functional PC synthase whose activity is critical for heavy metal tolerance in the intact organism.

Aminoacyltransferases↗