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At least 379 records · Page 21Linked to original sources

PubMed2006

An effective means of biofiltration of heavy metal contaminated water bodies using aquatic weed Eichhornia crassipes.

Various aquatic plant species are known to accumulate heavy metals through the process of bioaccumulation. World's most troublesome aquatic weed water hyacinth (Eichhornia crassipes) has been studied for its tendency to bio-accumulate and bio-magnify the heavy metal contaminants present in water bodies. The chemical investigation of plant parts has shown that it accumulates heavy metals like lead (Pb), chromium (Cr), zinc (Zn), manganese (Mn) and copper (Cu) to a large extent. Of all the heavy metals studied Pb, Zn and Mn tend to show greater affinity towards bioaccumulation. The higher concentration of metal in the aquatic weed signifies the biomagnification that lead to filtration of metallic ions from polluted water. The concept that E. crassipes can be used as a natural aquatic treatment system in the uptake of heavy metals is explored.

Eichhornia↗

PubMed2004

Heavy metal removal from motorway stormwater using zeolites.

The possibility of using zeolites to reduce the levels of heavy metals present in motorway stormwater has been investigated. Currently, the primary pollutant removal mechanism used in treating stormwater is retaining the large volume of stormwater in detention ponds to allow time for the contaminants (mainly those associated with particulate matter) to separate out. There is also a need to reduce the levels of heavy metals in the dissolved phase, possibly by introducing some kind of ion exchange material into the treatment facility. Batch experiments have been conducted on two zeolites (synthetic MAP and natural mordenite) to test their ability to remove dissolved heavy metals from simulated and spiked motorway stormwater. Synthetic zeolite MAP showed almost complete removal (>91%) of the studied heavy metals (Zn, Cu, Pb, Cd) from both solutions. However, the use of such synthetic zeolites could have serious environmental implications as it was found to increase sodium levels to 295 mg/l, remove calcium and increase the pH of the spiked motorway stormwater to 8.5. Mordenite was less effective at reducing the levels of heavy metals (42-89% in synthetic solution, 6-44% in motorway stormwater) and exhibited a preference for Pb>Cu>Zn approximately Cd. It is proposed that the uptake of heavy metals is partially inhibited by the other dissolved contaminants present in motorway stormwater.

Journal Article↗

PubMed1991

The behaviour of heavy metals in sewage sludge-amended soils.

Soils amended with sewage sludges generally contain elevated concentrations of a wide range of heavy metals and are therefore of interest with regard to their potential impact on human health. This review considers the concentrations of heavy metals in sewage sludges and in the soils amended with them. The effects of sludge amendments on soil properties, the speciation of heavy metals and their bioavailability are reviewed. Variations in heavy metal accumulation between crop species are considered, together with the effects of sludge-borne heavy metals on soil microorganism activity. Perhaps the most important questions to be addressed are the changes in the bioavailability of the heavy metals and their distribution in the soil profile during the residual period. The consequences of the application of sewage sludges to agricultural soils, with regard to the long-term bioavailability and movement of metals in soil profiles, are incompletely understood.

Animals↗

PubMedDate not supplied

[Heavy metals in the environment and their impact on the organism].

Heavy metals are chief contaminants of the environment, having an adverse effect on the population, especially on children. Results of hygienic and clinical observations suggest to us that compounds of heavy metals might cause changes in functions of metabolism and structure of some organs and systems raising the level of morbidity. It is necessary that a common system be set up of investigations, based on achievements of hygienic science both in this country and abroad; comprehensive investigations designed to study effects of heavy metals on human health be conducted; methodological approaches to the assessment of complex studies be worked out.

Animals↗

PubMed2000

Incineration of doped sludges in fluidized bed. Fate and partitioning of six targeted heavy metals. I. Pilot plant used and results.

Incineration of sewage sludge doped with several heavy metals was studied at small pilot plant scale in a bubbling fluidized bed of 15cm i.d. and 5.2m height. Some ceramic and metallic filters were tested at a relatively high temperature (600-700 degrees C) to check their usefulness for partitioning of heavy metals in the flue gas. The work was focused on the fate of six selected heavy metals (Cr, Cd, Ni, Zn, Cu, Pb). In this process, there were four exit flows or discharges for these metals: bottom ash, coarse fly ash, cake filter or fine fly ash and flue exit gas. The distribution or partitioning of each heavy metal (HM) among these four exit flows was studied. Only cadmium and sometimes lead showed any difference between the different HMs considered. All other HMs seems to have the same fate, distribution or partitioning. Such distribution is governed or ruled by the fluid dynamics in the incinerator, cyclone and ceramic filter. Most of the HMs do not have enough residence time in this incinerator type to diffuse out of the ash particle and so remain in the particle. The amount of each HM in each exit flow in this process is governed by fluid dynamics and kinetics and not at all by thermodynamics.

Environmental Pollution↗

PubMedDate not supplied

Aquifer vulnerability assessment to heavy metals using ordinal logistic regression.

A methodology using ordinal logistic regression is proposed to predict the probability of occurrence of heavy metals in ground water. The predicted probabilities are defined with reference to the background concentration and the maximum contaminant level. The model is able to predict the occurrence due to different influencing variables such as the land use, soil hydrologic group (SHG), and surface elevation. The methodology was applied to the Sumas-Blaine Aquifer located in Washington State to predict the occurrence of five heavy metals. The influencing variables considered were (1) SHG; (2) land use; (3) elevation; (4) clay content; (5) hydraulic conductivity; and (6) well depth. The predicted probabilities were in agreement with the observed probabilities under existing conditions. The results showed that aquifer vulnerability to each heavy metal was related to different sets of influencing variables. However, all heavy metals had a strong influence from land use and SHG. The model results also provided good insight into the influence of various hydrogeochemical factors and land uses on the presence of each heavy metal. A simple economic analysis was proposed and demonstrated to evaluate the cost effects of changing the land use on heavy metal occurrence.

Forecasting↗

PubMed2004

Heavy metals monitoring using bivalves from Mediterranean Sea and Red Sea.

The concentrations of heavy metals (Cd, Co, Cu, Fe, Mn, Ni, Pd and Zn) were measured in the Bivalves (Modiolus auriculatus and Donax trunculus) collected from the Egyptian coasts of Mediterranean Sea and Brachiodonates sp. from the Egyptian coasts of Red Sea. The average concentrations of the heavy metals analyzed exhibited the following decreasing order: Fe > Zn > Cu > Mn > Ni > Co > Pb > Cd for both Mediterranean Sea and Red Sea. The analyses of Cd, Co, Ni, Pb, and Zn showed higher average concentrations for samples collected from Red Sea than that collected from Mediterranean Sea, while Fe, Cu and Mn showed the reverse results. Fe was used as a normalizing agent for all studied metals and exhibited presence of two locations from each of Mediterranean Sea and Red Sea have anthropogenic inputs of heavy metals. These results suggest that the coastal area in both Mediterranean Sea and Red Sea of Egypt might be considered relatively unpolluted with heavy metal.

Animals↗

PubMedDate not supplied

[Effect of heavy metals on wheat seedlings; activation of antioxidant enzymes].

Accumulation of heavy metals in wheat grain exposed to multicomponent pollutants (industrial waste-water) was studied. The absolute content of metals (Zn, Cd, Cu, Cr, Ni, Pb, and Mn) was found to be determined by the extent of purification of wastewater. An increase in the degree of grain contamination with heavy metals was accompanied by activation of antioxidant enzymes (superoxide dismutase, EC 1.15.1; catalase, EC 1.11.1.6; and peroxidase, EC 1.11.1.7) in leaves and activation of superoxide dismutase and peroxidase in roots. The ratio of activity of membrane enzymes to activity of cytosol enzymes was demonstrated to be high. It was concluded that the membrane-tropic effect of multicomponent contaminants was due to accumulation of heavy metals capable of inducing the antioxidant protection in the next generation of wheat seedlings.

Catalase↗

PubMed2003

The effects of soil amendments on heavy metal bioavailability in two contaminated Mediterranean soils.

Two heavy metal contaminated calcareous soils from the Mediterranean region of Spain were studied. One soil, from the province of Murcia, was characterised by very high total levels of Pb (1572 mg kg(-1)) and Zn (2602 mg kg(-1)), whilst the second, from Valencia, had elevated concentrations of Cu (72 mg kg(-1)) and Pb (190 mg kg(-1)). The effects of two contrasting organic amendments (fresh manure and mature compost) and the chelate ethylenediaminetetraacetic acid (EDTA) on soil fractionation of Cu, Fe, Mn, Pb and Zn, their uptake by plants and plant growth were determined. For Murcia soil, Brassica juncea (L.) Czern. was grown first, followed by radish (Raphanus sativus L.). For Valencia soil, Beta maritima L. was followed by radish. Bioavailability of metals was expressed in terms of concentrations extractable with 0.1 M CaCl2 or diethylenetriaminepentaacetic acid (DTPA). In the Murcia soil, heavy metal bioavailability was decreased more greatly by manure than by the highly-humified compost. EDTA (2 mmol kg(-1) soil) had only a limited effect on metal uptake by plants. The metal-solubilising effect of EDTA was shorter-lived in the less contaminated, more highly calcareous Valencia soil. When correlation coefficients were calculated for plant tissue and bioavailable metals, the clearest relationships were for Beta maritima and radish.

Animals↗

PubMed2001

Accumulation of heavy metals in epidermal glands of the waterlily (Nymphaeaceae).

This study investigates the anatomical aspects of heavy-metal accumulation in the waterlily (Nymphaea 'Aurora', Nymphaeaceae). Epidermal glands were identified by light microscopy on the abaxial side of the leaf laminae and on the epidermis of the rhizome; glandular trichomes were observed in the petiole epidermis. Glands were not observed in the roots. Accumulation of heavy metals in these glands was monitored using a scanning electron microscope equipped for energy-dispersive spectroscopy. Further experiments showed maximal cadmium and calcium accumulation in the mature leaf lamina in daylight, and this accumulation was inhibited by the herbicide 3-(3',4'-dichlorophenyl)-1,1-dimethylurea. These results suggest that, in Nymphaea, heavy metals are accumulated primarily in association with glands found in plant organs that have direct contact with water or mud. Deposition and storage of heavy metals by these glands may represent a stage in the sequestration and detoxification of the metals. Our results raise the possibility of utilizing waterlilies for the removal of heavy metals from polluted environments.

Cadmium↗

PubMed2003

Occurrence and fate of heavy metals in the wastewater treatment process.

The occurrence and the fate of heavy metals (Cd, Pb, Mn, Cu, Zn, Fe and Ni) during the wastewater treatment process were investigated in the wastewater treatment plant (WTP) of the city of Thessaloniki, northern Greece, operating in the activated sludge mode. For this purpose, wastewater and sludge samples were collected from six different points of the plant, namely, the influent (raw wastewater, RW), the effluent of the primary sedimentation tank (primary sedimentation effluent, PSE), the effluent of the secondary sedimentation tank (secondary sedimentation effluent, SSE), sludge from the primary sedimentation tank (primary sludge, PS), activated sludge from the recirculation stream (activated sludge, AS), and the digested/dewatered sludge (final sludge, FS).The distribution of metals between the aqueous and the solid phase of wastewater was investigated. Good exponential correlation was found between the metal partition coefficient, logK(p), and the suspended solids concentration. The mass balance of heavy metals in the primary, secondary and the whole treatment process showed good closures for all metal species. The relative distribution of individual heavy metals in the treated effluent and the sludge streams indicated that Mn and Cu are primarily (>70%) accumulated in the sludge, while 47-63% of Cd, Cr, Pb, Fe, Ni and Zn remain in the treated effluent.

Greece↗

PubMed2006

Application of the self-organizing map (SOM) to assess the heavy metal removal performance in experimental constructed wetlands.

The self-organizing map (SOM) model was applied to elucidate heavy metal removal mechanisms and to predict heavy metal concentrations in experimental constructed wetlands treating urban runoff. A newly developed SOM map showed that nickel in constructed wetland filters is likely to leach under high conductivity in combination with low pH in winter. In contrast, influent pH and conductivity were not shown to have clear relationships with copper (Cu) concentrations in the effluent, suggesting that the mobility of Cu was not considerably affected by salt increase during winter. The accuracy of prediction with SOM was highly satisfactory, suggesting heavy metals can be efficiently estimated by applying the SOM model with input variables such as conductivity, pH, temperature and redox potential, which can be monitored in real time. Moreover, domain understanding was not required to implement the SOM model for prediction of heavy metal removal efficiencies.

Electric Conductivity↗

PubMed2001

Heavy metal removal from wastewater and leachate co-treatment sludge by sulfur oxidizing bacteria.

Heavy metal concentration in sludge is one of the major obstacles for the application of sludge on land. There are various methods for the removal of heavy metals in sludge. Using sulfur oxidizing bacteria for microbiological removal of heavy metals from sludges is an outstanding option because of high metal solubilization rates and the low cost. In this study, bioleaching by indigenous sulfur oxidizing bacteria was applied to sludges generated from the co-treatment of municipal wastewater and leachate for the removal of selected heavy metals. Sulfur oxidizing bacteria were acclimated to activated sludge. The effect of the high organic content of leachate on the bioleaching process was investigated in four sets of sludges having different concentrations of leachate. Sludges in Sets A, B, C and D were obtained from co-treatment of wastewater and 3%, 5%, 7% and 10% (v/v) leachate respectively. The highest Cr, Ni and Fe solubilization was obtained from Set A. Sulfur oxidizing bacteria were totally inhibited in Set D that received the highest volume of leachate.

Bioreactors↗

PubMed2003

Reaction of detoxification mechanisms in suspension cultured spruce cells (Picea abies L. Karst.) to heavy metals in pure mixture and in soil eluates.

UNLABELLED: INTENTION, GOAL, BACKGROUND: The widespread and unconcerned use of chemicals in the past has led to an accumulation of pollutants in our environment. Numerous sites are polluted with a mixture of organic chemicals and heavy metals. The future use of these sites and the safe consumption of groundwater from these areas depends on our ability to assess risk by determining the bioavailability of trace levels of pollutants in the respective soil solutions. Soil eluates containing heavy metals in mixture as well as pure heavy metals in aqueous solution were added to a spruce cell culture to set up such a test system. OBJECTIVE: The present study aims at evaluating the response of cultured spruce cells to heavy metals in aqueous solution, and at characterizing these basic cellular responses as potential biomarkers. METHODS: In order to characterize cell reactions toward heavy metals, spruce cell cultures were incubated with CdSO4 (50 to 500 microM), Na2HAsO4 (1.5 to 80 microM) or PbCl2 (10 to 150 microM). Alternatively, the cells were incubated with a standard heavy metal mixture containing 80 microM Na2HAsO4, 150 microM CdSO4 and 150 microM PbCl2 in medium and with aqueous original soil eluates. Measurement of oxidative stress, antioxidants and basic detoxification enzymes involved in plant defence reactions were performed with the treated cells. RESULTS AND DISCUSSION: After 5 hrs of incubation, the onset of a strong oxidative burst was observed. H2O2 concentrations exceeded 40 microM in the culture media after 20 hrs. Concomitantly, glutathione levels showed drastic changes indicating the influence of the metals and/or the H2O2 on antioxidative systems. Following cadmium treatment, GSH and GSSG were elevated by 50 and 200% above controls. Whereas arsenic doubled GSSG levels, treatment with lead did not cause significant changes. However, a mixture of the metals decreased both metabolites by 50%. The effect of the metals was concentration-dependent and disappeared at high concentrations. Furthermore, strong induction of glutathione S-transferase (GST) subunits was observed and, although no novel subunit was expressed, the rise of a new GST isoform occurred. The most potent inducer of plant defence reactions is cadmium, followed by arsenate and lead in descending order of effectiveness. Counter ions seem to play an important role, e.g. lead chloride influenced the investigated parameters much more than lead acetate. CONCLUSIONS: The investigated metals activate gene expression through signal transduction pathways previously not associated with these metals, which points to new end points for resistance and toxicity testing. Especially a monitoring of GST subunit behaviour together with quantifying the oxidative burst seem to be promising for a biomonitoring concept. The close regulation of plant answers observed may facilitate the setup of an integrated biotest for heavy metal pollution that could be based on enzymological as well as proteome data. RECOMMENDATIONS AND OUTLOOK: Heavy metals cause stress to plant cells and elicit a whole range of answers, although specific for individual metal species. The differences observed in plant answers are suitable to distinguish between metals bioavailable in soil eluates and water samples, however only at concentrations in the microM range. It will be necessary to evaluate the effects on the RNA and transcript level. We recommend that similar plant metabolic end points and enzyme reactions be screened for their suitability as biotest systems.

Biomarkers↗

PubMed2001

Heavy metal solubility in podzolic soils exposed to the alkalizing effect of air pollutants.

The heavy metal content of pine forest soil was studied near the boundary between Russia and Estonia, an area characterized by large amounts of acidic and basic air pollutants, mainly sulfur dioxide and calcium. Alkalization dominates the processes in soil, since sulfur is adsorbed only in small quantities, and calcium is much better adsorbed. In addition to Ca, great amounts of Al, Fe, K, and Mg are accumulated in the humus layer due to air pollution. The heavy metal content has increased. The exchangeable content of heavy metals was in many cases much higher in polluted alkaline soils than in non-polluted acidic soils, even the ratio of exchangeable to total metal content being higher in alkaline plots. To avoid a dangerous increase in soluble heavy metal content, it is important to decrease not only the large sulfur emissions of local pollutant sources, but also the alkaline pollutants. A similar concern must be taken into account when liming of acidic forest soils is planned.

Air Pollutants↗

PubMed1977

Sulfide silver architectonics of rat, cat, and guinea pig spinal cord. A light microscopic study with Timm's method for demonstration of heavy metals.

The distribution of heavy metals in the spinal cord of the cat, rat, and guinea pig has been studied histochemically with Timm's sulfide silver method. There was considerable variation in the degree of staining of the neuropil. The dorsal horn showed a laminar staining pattern corresponding to the cytoarchitectonic lamination. Lamina I in the cat and guinea pig was light. Lamina II in all three species was heavily stained. In the rat and guinea pig it could be subdivided in a ventral and a dorsal layer, and moreover in the rat a darkly staining borderzone abutting on lamina III was present. Lamina III, characterized by heterogeneous staining, also appeared dark, although less obvious in the guinea pig. In the ventral horn the coarser stained particles in lamina IX contrasted with the surrounding lamina. Cell staining varied between different cell groups, and within single cell populations. In the cat thoracic cord the cells in nucleus intermedio-lateralis (IL) and nucleus intercalatus (IC) stained very weakly. In Clarke's column and in the motoneuron area cells, uniform in Nissl preparations, could be seen different after Timm staining. The results are discussed in relation to other histochemical patterns, cytoarchitectonics, and terminal fields of afferents. Considerable correlation of the Timm pattern to these data was found.

Animals↗

PubMed1980

Lipids in the liver and kidney of rats, fed various heavy metals.

Interference of few heavy metals, i.e. mercury, lead, molybdenum, copper, cadmium and zinc with the hepatic and renal lipids has been estimated employing histochemical and biochemical parameters. The results show that mercury and molybdenum stimulate the accumulation of lipids whereas cadmium and zinc inhibit their restoration both in the liver and kidney. Lead and copper only raised the lipid contents of the kidney. It has been suggested that mercury and molybdenum increase the input of free fatty acid causing triblyceride formation and inhibit mitochondrial phosphorylation. Partial loss of lipids after cadmium and zinc treatment has been explained by a reverse hypothesis. Inhibition of esterases has also been proposed as the reason for increased phospholipid accumulatin. However, differential effects of lead and copper on the liver and kidney suggested that a given mechanism may vary from one physiological state and pathological condition to the other.

Animals↗

PubMed1986

Microbes and heavy metals: an ecological overview.

Heavy metals are ubiquitous in nature in a wide range of concentrations. They have the potential to influence the ecology of microorganisms in many different ways; as trace elements some are essential for many natural processes but, as pollutants, most can severely disrupt ecosystem functioning.

Ecology↗