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PubMed2002

Phytochelatins and metallothioneins: roles in heavy metal detoxification and homeostasis.

Among the heavy metal-binding ligands in plant cells the phytochelatins (PCs) and metallothioneins (MTs) are the best characterized. PCs and MTs are different classes of cysteine-rich, heavy metal-binding protein molecules. PCs are enzymatically synthesized peptides, whereas MTs are gene-encoded polypeptides. Recently, genes encoding the enzyme PC synthase have been identified in plants and other species while the completion of the Arabidopsis genome sequence has allowed the identification of the entire suite of MT genes in a higher plant. Recent advances in understanding the regulation of PC biosynthesis and MT gene expression and the possible roles of PCs and MTs in heavy metal detoxification and homeostasis are reviewed.

Amino Acid Sequence↗

PubMed2004

Effects of heavy metal pollution on red wood ant (Formica s. str.) populations.

We studied the species composition, mound population densities, relative abundance and colony sizes of red wood ants along a well known air pollution gradient of a copper smelter in Southwest Finland. The dominant species, Formica aquilonia, was further studied for heavy metal (Al, Cu, Cd, Ni, Zn, As, Pb, Hg) levels and morphological characters (body mass, head width, labial gland disease) of workers. We found five species belonging to Formica s. str., and two of them showed changes in their relative abundance, which could not be explained by natural habitat differences. Nest mound volumes were 34% smaller in the polluted area, suggesting that smaller colonies can be maintained there. The heavy metal levels in F. aquilonia workers were higher in the polluted area for all metals, except Hg. The largest relative differences between the study areas (polluted/unpolluted) were found for As (4.1), Ni (2.4), Cu (2.1) and Pb (1.8). Morphological characters of workers were not related to the heavy metal levels. Our data showed that red wood ants can tolerate relatively high amounts of heavy metals and maintain reproducing colonies even in a heavily polluted area, but on the basis of smaller colony sizes, pollution stress may also cause trade-offs in reproduction.

Air Pollutants↗

PubMed2001

Distribution behavior of heavy metals investigated in a laboratory-scale incinerator.

The distribution behavior of Pb, Cd, Fe, Cu, Mo and Zn was determined in a laboratory-scale incinerator. Points of interest were the influence of the temperature and combustion atmosphere on the emission rates of those metals, orientating at frequent combustion conditions of accidental fires. The experiments were carried out at 600 degrees C and 800 degrees C in N2, air, N2 + HCl and air + HCl atmospheres. Furthermore, the influence of the matrix (quartz, polyethylene and cellulose powder) on the distribution behavior of the heavy metals was investigated as well. It was determined whether the distribution behavior of Cu, Pb and Cd were affected by the other heavy metals. In conclusion, it was found that in air and N2 atmosphere a temperature increase from 600 degrees C to 800 degrees C and the addition of the matrix had no effect on the evaporation rates of the heavy metals, except for Cd. Addition of gaseous HCl led to increased evaporation of the heavy metals. The increase of the evaporation rates during the experiments with matrix was higher for Fe, remained the same for Pb, Cd, Zn, and lower for Mo and Cu compared to the experiments without matrix.

Air Pollutants↗

PubMed2001

Heavy metal accumulation in the gastropod, Cerithium scabridum L., from the Kuwait Coast.

An in-depth study on various locations along the Kuwait Coast differentiated by the nature of coastal topography, human habitation and industrialization was made during the year 1995-1997 in relation to the gills of the gastropod, Cerithium scabridum, a bio-indicator of heavy metal pollution. The maximum concentration of heavy metals in the gills of C. scabridum, seawater and particulate matter was observed in Stations III when compared to the metal concentrations in the other seven stations. Co-efficient Variance (CV) revealed an increase in the accumulation of Cu and Pb in gills, seawater and particulate matter in winter than in summer. However, the CV was noted to be lower in winter than in summer in the case of Cr and V, in gills of C. scabridum and Ni in the case of seawater samples. Further, by ANOVA, except V, significant relationships were noted between the heavy metals (Cu, Cr, Pb and Ni) and various locations in the gills of C. scabridum.

Animals↗

PubMed1998

Genotoxic effects of heavy metals: comparative investigation with plant bioassays.

The potential use of micronucleus assays in plants for the detection of genotoxic effects of heavy-metal ions was investigated. Three different plant systems were comparatively investigated in micronucleus tests with Tradescantia pollen mother cells (Trad MCN) and micronucleus tests with meristematic root tip cells of Allium cepa and Vicia faba (Allium/ Vicia MCN). As3+, Pb2+, Cd2+, Zn2+ caused a dose-dependent increase of MCN frequencies in all three test systems. Cu2+ gave consistently negative responses in all three tests; Zn2+ caused only a moderate, statistically not significant increase of MCN frequencies in Vicia. The ranking of genotoxic potencies in all three tests was in the descending order: As3+ > Pb2+ > Cd2+ > Zn2+ Cu2+. In experiments with Tradescantia, induction of MCN was observed in a concentration range between 1 and 10 mM, whereas in tests with root tip cells, higher concentrations (10-1,000 mM) were required to show significant effects. Further increase of the exposure levels caused toxic effects (reduction of root growth), cell division delays, and a decrease of MCN frequencies. Comparisons by linear regression analyses indicated that the sensitivity of the three bioassays for heavy metals decreases in the order: Trad MCN > Vicia root MCN > Allium root MCN. In further experimental series, a soil sample which contained high concentrations of the five metals and a control soil were investigated. Aqueous soil extracts induced only weak effects in Trad MCN tests and no effects in the root tip assays, whereas cultivation of the plants in the soils resulted in a pronounced induction of MCN in the Tradescantia system and moderate effects in Vicia and Allium. In conclusion, the results of the study indicate that the Trad MCN assay detects the genotoxic effects of heavy metals and can be used for biomonitoring metal-contaminated soils.

Biological Assay↗

PubMed1991

Availability of heavy metals from sewage sludge and its possible impact on regulatory activity in Italy.

This paper reports the preliminary results obtained by a sequential extraction method based on Rudd's procedure that can be used to determine various chemical forms of heavy metals present in sludge. The impact of heavy metals present in sewage sludge for agricultural use is determined by their mobility and bioavailability. These parameters heavily depend on the chemical forms of the metals present. This study proposes a procedure that may be adopted in further studies for a more appropriate normative than the present European Economic Community Directive no. 278/86. By providing data on both metal mobility and total heavy metal concentration, the researcher may draw adequate guidelines that reflect the true environmental risk involved in the use of sludge for agriculture.

Agriculture↗

PubMed1981

Lemna (duckweed) as an indicator of water pollution. I. The sensitivity of Lemna paucicostata to heavy metals.

The environmental conditions affecting the growth and multiplication of Lemna paucicostata in the presence of heavy metals were examined to establish a phytometer method for water pollution using the duckweed, Lemna. The pH of the medium, concentration, and composition of the nutrient in the medium, and the temperature at which cultures were maintained, were found to affect the sensitivity of Lemna to heavy metals. Therefore, if the growth and multiplication of Lemna is maintained by a Bonner-Devirian's medium (pH 6.1, 7.1) above 25 degrees C, heavy metals can be detected in water.

Metals↗

PubMed2006

Heavy metal adsorption by modified oak sawdust: thermodynamics and kinetics.

This paper describes the adsorption of heavy metal ions from aqueous solutions by oak (Quercus coccifera) sawdust modified by means of HCl treatment. Our study tested the removal of three heavy metals: Cu, Ni, and Cr. The optimum shaking speed, adsorbent mass, contact time, and pH were determined, and adsorption isotherms were obtained using concentrations of the metal ions ranging from 0.1 to 100mgL(-1). The adsorption process follows pseudo-second-order reaction kinetics, as well as Langmuir and D-R adsorption isotherms. The paper discusses the thermodynamic parameters of the adsorption (the Gibbs free energy, entropy, and enthalpy). Our results demonstrate that the adsorption process was spontaneous and endothermic under natural conditions. The maximum removal efficiencies were 93% for Cu(II) at pH 4, 82% for Ni(II) at pH 8, and 84% for Cr(VI) at pH 3.

Adsorption↗

PubMed2006

Heavy metal profile in five fish species included in human diet, domiciled in the end flow of river Neretva (Croatia).

Concentration of three heavy metals (mercury (Hg), lead, (Pb), and cadmium, (Cd)) and one metalloid (arsenic [As]), were determined by atomic absorption spectrophotometry in five tissues (muscles, liver, kidneys, gills, and gonads) of five fish species (carp-Cyprinus carpio, tench-Tinca tinca, sval-Leuciscus svallizi, gray mullet-Mugil cephalus, and eel-Anguilla anguilla) taken out from the end fIow (last 20 km) of the river Neretva, south Croatia, in the wider region of town Metković, during the summer of the year 2003. Only Cd concentration in all fish types was higher than the maximal allowed concentration (MAC) in Croatia, but its concentration in muscles reaches this value only in four samples. However, in carp, tench, and mullet, Cd concentrations higher than MAC in some other countries were found. Hg concentration is much lower than MAC in the most countries. Pb is found in higher quantities only in carp, some values reaching MAC in Germany, and many values being higher than MAC in Denmark (with exception of gonads). As concentrations are much lower than MAC in all countries, but it seems that mullet tends to accumulate this metalloid, especially in the muscles. Therefore, in several samples, muscle As concentration in mullet reached half of the MAC value in the most countries. Of the analyzed fish types, eel, containing the smallest quantities of heavy metals, is recommended for human diet, while carp, consumed most frequently by local inhabitants and numerous tourists, shares with mullet the last place on the recommendation list. Also, it is suggested that meals prepared with analyzed fish sorts should not contain some inner organs (kidneys and liver), as well as gills (alternatively, the whole head). Our final conclusion is that fish types eating predominantly meat contain less heavy metal in their tissues, and therefore are more suitable for human diet.

Animals↗

PubMed2003

Evaluation of estrogenicity of major heavy metals.

We have employed an estrogen receptor dependent transcriptional expression assay and E-Screen assay systems to evaluate the estrogenicity of various heavy metals and their species. Using the former, the following estrogenicity ranking was measured: bis(tri-n-butyltin)>cadmium chloride>antimony chloride>barium chloride=chromium chloride>lithium hydroxide>sodium selenate=lead acetate>stannous chloride. Using the latter, the following estrogenicity ranking was measured: bis(tri-n-butyltin)>cadmium chloride>antimony chloride>lithium hydroxide>barium chloride>sodium selenate>chromium chloride. Especially, bis(tri-n-butyltin), cadmium chloride, antimony chloride, lithium hydroxide, barium chloride, and chromium chloride showed estrogenicity in both assay systems. Recent studies suggesting that bis(tri-n-butyltin), cadmium chloride, and lithium hydroxide have estrogenicities are compatible with the present findings. Furthermore, our studies are the first to suggest that antimony, barium, chromium may be estrogenic. A range of estrogenicity was observed for different species of the same heavy metal. The results demonstrate that an estrogen receptor dependent transcriptional expression assay and the E-Screen assay systems could serve as a useful method to assess the estrogenicity of heavy metals.

Biological Assay↗

PubMed2004

Speciation of heavy metals in landfill leachate: a review.

The literature was reviewed with respect to metal speciation methods in aquatic samples specifically emphasizing speciation of heavy metals in landfill leachate. Speciation here refers to physical fractionation (particulate, colloidal, dissolved), chemical fractionation (organic complexes, inorganic complexes, free metal ions), as well as computer-based thermodynamic models. Relatively few landfill leachate samples have been speciated in detail (less than 30) representing only a few landfills (less than 15). This suggests that our knowledge about metal species in landfill leachate still is indicative. In spite of the limited database and the different definitions of the dissolved fraction (< 0.45 microm or < 0.001 microm) the studies consistently show that colloids as well as organic and inorganic complexes are important for all heavy metals in landfill leachate. The free metal ion constitutes less than 30%, typically less than 10%, of the total metal concentration. This has significant implications for sampling, since no standardized procedures exist, and for assessing the content of metals in leachate in the context of its treatment, toxicity and migration in aquifers.

Databases, Factual↗

PubMed2005

Investigation and risk assessment modeling of As and other heavy metals contamination around five abandoned metal mines in Korea.

Tailings, agricultural soils, vegetables and groundwater samples were collected from abandoned metal mines (Duckum, Dongil, Dongjung, Myoungbong and Songchun mines) in Korea. Total concentrations of arsenic (As) and heavy metals (Cd, Cu, Pb and Zn) were analyzed to investigate the contamination level. Several digestion methods (Toxicity characteristics leaching procedure (TCLP), synthetic precipitation leaching procedure (SPLP), 0.1 N/1 N HCl) and sequential extraction analysis for mine tailings were conducted to examine the potential leachability of As and heavy metals from the tailings. The order of urgent remediation for the studied mines based on the risk assessment and remedial goals was suggested. The Songchun mine tailings were most severely contaminated by As and heavy metals. Total concentrations of As and Pb in the tailings were 38,600-58,700 mg/kg (av. 47,400 mg/kg) and 11,800-16,800 mg/kg (av. 14,600 mg/kg), respectively. Agricultural soils having high As concentrations were found at the all mines. Average concentrations of Cd in the vegetables exceeded the normal value at all mines areas, while As only at the Dongjung, Myoungbong, and Songchun mine area. One groundwater sample each from the Dongil and Myoungbong mines, and 4 groundwater samples from the Songchun mine had values above 10 mug/L of As concentration. The TCLP method revealed that only Pb in the Songchun tailings, 6.49 mg/L, exceeded the regulatory level (5 mg/L). Employing the 1-N HCl digestion method, the concentration of As in the Songchun mine tailings, 4,250 mg/kg, was up to 3,000 times higher than its Korean countermeasure standard. Results from the sequential extraction of As in the tailings showed that the easily releasable fraction in the Myoungbong and Songchun mine tailings was more than 30% and the residual fraction was less than 40%. Based on results showing the exposure health risk employing the hazard quotient and cancer risk of As, Cd and Zn, the Dongil mine needs the most urgent remedial action. The concentration reduction factor (CRF) of As in both soil and groundwater follows the order: Songchun>Dongjung>Dongil>Myoungbong>Duckum mine.

Agriculture↗

PubMed2005

Speciation of heavy metals during co-composting of sewage sludge with lime.

During composting the humification of organic matter will have a significant effect on the physicochemical form of existence of heavy metals. Therefore the present study was conducted to investigate the effect of co-composting sewage sludge with lime on heavy metal speciation and the changes in DTPA extractable metals. Metal speciation was conducted to evaluate the redistribution of Cu, Mn, Ni, Pb and Zn in sewage sludge composted with lime. Sewage sludge was mixed with sawdust in 2:1 (w/w fresh weight) and then composted with lime at 0%, 0.63%, 1% or 1.63% (dry weight) for 100 days. The lime addition did not cause any changes in the different forms of Cu and Mn, but the composting process caused transformations of residual form of Cu and Mn into oxidizable and reducible form, respectively. For Ni, the reducible form was mainly transformed into residual form and lime addition decreased this transformation. Major transformation of different forms of Pb was not found, however the residual form of Pb increased with lime addition. The predominant residual form of Zn was mainly transformed into oxidizable form and the lime addition reduced this transformation. Addition of lime to sewage sludge during composting resulted in lower DTPA extractable metal contents. Therefore, lime is a suitable material to co-compost with sewage sludge to reduce the availability of heavy metals.

Calcium Compounds↗

PubMed2001

Decomposition of coniferous forest litter along a heavy metal pollution gradient, south-west Finland.

The decomposition of Scots pine (Pinus sylvestris) fine root and needle litter was examined along a heavy metal pollution gradient in the vicinity of Harjavalta Metals Smelter complex at Harjavalta, south-west Finland. The study area was found to exhibit a defined gradient of copper and nickel soil contamination along a 8 km long transect starting at 0.5 km from the point emission source with the highest levels found at this site. The background site is located 200 km from the point source. The majority of the heavy metals are confined to the soil organic layer. Litter decomposition and litter quality were compared between litter types after 12, 18, and 30 months incubation at each of four sites. The analyses clearly showed differences in accumulated mass loss, C:N ratio, and nutrient composition that were related to the site of incubation. Needle and fine root litter that was incubated at 0.5 km had a lower accumulated mass loss, 28.1 and 40.9%, respectively, over time when compared to litter incubated at the background site (37.9 and 50.9%, respectively). Concentrations of exchangeable cations in the litter incubated at 0.5 km were considerably less. The heavy metal contamination may provide an explanation for the amount of mass lost and the litter quality through impacts on the soil microbiota.

Air Pollutants↗

PubMed2004

Mobilisation of heavy metals by deicing salts in a roadside environment.

The seasonal variations of some selected heavy metals (Cd, Cu, Pb and Zn) and principal anions in soil solutions were monitored as a function of distance from the road at two field sites in Sweden. During the winter, the conductivity, concentrations of dissolved sodium and chloride increased dramatically due to the application of deicing agents (i.e. NaCl). Due to ion exchange, the pH decreased one unit in the soil solutions, whereas the concentrations of total organic carbon decreased due to coagulation and/or sorption to stationary solids. The heavy metal concentrations increased during the winter, but through different mechanisms. Cadmium concentrations in the aqueous phase increased as a response to ion exchange, possibly also enhanced by the formation of chloride complexes. Similarly, the concentrations of zinc increased, due to ion exchange, with calcium and protons. The mechanisms of mobilisation for copper and lead were not that clear probably due to association with coagulated or sorbed organic matter in combination with colloid dispersion.

Colloids↗

PubMed2003

Heavy metal toxicity on dehydrogenase activity on rhizospheric soil of ectomycorrhizal pine seedlings in field condition.

The present investigation was carried out to study the toxicity of heavy metals (Zn, Cd, Cu, Ni, Pb and Al) on the dehydrogenase activity of ectomycorrhizal (Suillus leutus, Scleroderma aurantium, Cenococcum graniforme and Boletus spp.) and non-mycorrhizal rhizospheric soil of pine seedlings. The treatment of heavy metals adversely affected the dehydrogenase activity. Inoculation of mixed ectomycorrhizal fungi harbored increased activity of dehydrogenase. It was observed that in absence of ectomycorrhizae, heavy metals drastically reduced the enzyme activity at higher concentration of metals.

Analysis of Variance↗

PubMed2005

Soil characteristics, heavy metal availability and vegetation recovery at a former metallurgical landfill: Implications in risk assessment and site restoration.

Pedological and botanical characteristics of a former metallurgical landfill were examined to assess the risks of heavy metals mobility and to evaluate remediation feasibility. In addition to very high heavy metals levels (Cu, Cr, Mn, Ni, Pb, Zn), the soil was characterized by a lack of clear horizonation, a relatively high pH, a high mineral and organic carbon contents, a low nitrogen level and a high C/N ratio. A two step sequential extraction showed that heavy metals were poorly labile (i.e. not soluble in diluted CaCl2), indicating that their leaching under natural conditions was probably very low. However, extraction with DTPA generated significant amounts of metals (mainly Pb and Cu), suggesting they were potentially mobilizable. A botanical survey of the area showed a biodiverse plant community (28 species and 11 families), with no obvious toxicity symptoms. Measurements of metal contents in dominant species confirmed that they were closely similar to those reported for species growing in unpolluted environments. Consequently, for an effective site restoration, indigenous species could be well suited to cope with local conditions in a phytostabilization strategy.

Biological Availability↗

PubMed2001

Speciation of heavy metals in environmental water by ion chromatography coupled to ICP-MS.

Biogenic (e.g. phytochelatins, porphyrins, DOM) as well as anthropogenic (e.g. NTA, EDTA, phosphonates) chelators affect the mobility and cycling of heavy metals in environmental waters. Since such chelators can form strongly bound anionic heavy metal complexes that are stable and highly mobile, anion-exchange chromatography coupled to ICP-MS was investigated. A narrow bore HPLC system was connected to a micro concentric nebuliser for in-line sample introduction. A new chromatographic procedure based on a synthetic hydrophilic quaternary ammonium anion exchanger in combination with nitrate as a strong eluent anion, and gradient elution, provided high separation selectivity and a large analytical window. Low detection limits (nmol L(-1)) were achieved by on-column matrix removal and sample preconcentration. This allowed the method to be successfully applied to different environmental research areas. In ecotoxicological studies of heavy metal effects on algae low concentrations of metal EDTA complexes were determined in nutrient solutions without interference from high (buffer) salt concentrations. In groundwater, infiltrated by a polluted river, mobile metal EDTA species were observed. In river water of different pollution levels beside CuEDTA other anionic Cu-complexes were found in nmol L(-1) concentrations.

Animals↗