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PubMed2004

Assessment of arsenic and heavy metal concentrations in water and sediments of the Rio Grande at El Paso-Juarez metroplex region.

The Rio Grande located along the US-Mexico border is affected by anthropogenic activities along its geographical course. Runoff and wind deposition of smelting residues may contribute to the pollution of the Rio Grande in the El Paso-Ciudad Juarez area. Few studies have addressed the presence or impacts of heavy metals or arsenic in this ecosystem. This study reports a survey of heavy metals (Cr, Cu, Cd, Ni, Pb, and Zn) and arsenic (As) in water and sediments of the Rio Grande collected from seven sites in the El Paso-Juarez region. Since water quality influences metal content in water, physical (temperature, flow and conductivity), and chemical (pH, dissolved oxygen, nitrates, alkalinity, and water hardness) parameters were measured at each site. Arsenic and heavy metal levels were determined using Inductively Couple Plasma (ICP) emission spectroscopy following EPA procedures. Zinc and lead were found as both total and dissolved metals in most of the samples, with concentrations of total recoverable metals reaching up to 105 and 70 microg/l, respectively. Most metals were found in sediment samples collected from four of seven sites. The highest Cu concentration (35 mg/l) was found at the American Dam site. Concentrations of metals found through this survey will be used as a reference for future studies in monitoring arsenic, heavy metals, and their impacts in the Rio Grande.

Arsenic↗
PubMed2003

The molecular recognition of tetra(p-t-butyl)tetrathiocalix[4]arene and its derivatives to heavy metal ions.

The molecular recognition of tetra(p-t-butyl)tetrathiocalix[4]arene (I)and its three derivatives to heavy metal ions has been investigated by UV spectroscopy and solvent extraction. These derivatives include 5,11,17,23,-tetra-t-butyl-25,26,27,28-tetrakis(acetylmethoxy)tetrathiocalix[4]arene (II), 5,11,17,23-tetra-t-butyl-25,26,27,28-tetrakis(2'-hydroxypropyloxy) tetrathiocalix[4]arene (III), 5,11,17,23,-tetra-t-butyl-25,27-bis(3'-hydroxy propyloxy)tetrathiocalix[4]arene (IV). The UV spectra and solvent extraction of I show that it has an effective molecular recognition to heavy metal ions, especially to Cd(2+), while IV has a special molecular recognition to Ag(+) ion. These results confirmed the feasibilities for I to be applied in separation for toxic heavy metal ions Pb(2+), Cd(2+) and IV to be used as the sensor compound of Ag(+) ion-selective electrode.

Calixarenes↗
PubMed1998

Characterization of a heavy metal ion transporter in the lysosomal membrane.

Lysosomes are thought to play a role in various aspects of heavy metal metabolism. In the present study we demonstrate for the first time the presence of a heavy metal ion transport protein in the lysosomal membrane. Uptake of radioactive silver both in highly purified lysosomal membrane vesicles and in purified intact lysosomes showed the typical kinetics of a carrier-mediated process. This transport was stimulated by ATP hydrolysis, and showed specificity for Ag+, Cu2+, and Cd2+. All biochemical properties of this lysosomal metal ion transporter could classify it as a heavy metal transporting P-type ATPase. Long Evans Cinnamon (LEC) rats, an animal model for the copper transport disorder Wilson disease, showed normal lysosomal silver transport.

Adenosine Triphosphatases↗
PubMed2006

Sorption kinetics and leachability of heavy metal from the contaminated soil amended with immobilizing agent (humus soil and hydroxyapatite).

Release of heavy metals onto the soil as a result of agricultural and industrial activities may pose a serious threat to the environment. This study investigated the kinetics of sorption of heavy metals on the non-humus soil amended with (1:3) humus soil and 1% hydroxyapatite used for in situ immobilization and leachability of heavy metals from these soils. For this, a batch equilibrium experiment was performed to evaluate metal sorption in the presence of 0.05 M KNO(3) background electrolyte solutions. The Langmuir isotherms applied for sorption studies showed that the amount of metal sorbed on the amended soil decreased in the order of Pb(2+)>Zn(2+)>Cd(2+). The data suggested the possibility of immobilization of Pb due to sorption process and immobilization of Zn and Cd by other processes like co-precipitation and ion exchange. The sorption kinetics data showed the pseudo-second-order reaction kinetics rather than pseudo-first-order kinetics. Leachability study was performed at various pHs (ranging from 3 to 10). Leachability rate was slowest for the Pb(2+) followed by Zn(2+) and Cd(2+). Out of the metal adsorbed on the soil only 6.1-21.6% of Pb, 7.3-39% of Zn and 9.3-44.3% of Cd leached out from the amended soil.

Acetic Acid↗
PubMed2006

Seasonal variability of heavy metals in surface sediment of Lake Sapanca, Turkey.

Lake Sapanca is exposed to heavy urbanization and industrialization because of its natural beauty and its proximity to the metropolitan Istanbul, Turkey. In this study, it was aimed to investigate seasonal changes of some heavy metals (Pb, Cr, Cu, Mn, Ni, Zn and Cd) concentration of surface sediment. Nine different stations were chosen as sampling points. Samples were taken every three months and the seasonal and annual average concentration of the elements were determined. Seasonal highest values of heavy metals were observed as follows; Cr, Cu, Mn, Ni and Zn in Summer, Cd in Autumn. There was no seasonal difference for Pb, Cr and Cd. It seems that Lake Sapanca has not been polluted yet. However, it was found that Cu and Ni concentrations in surface sediment exceed lowest effect level.

Geologic Sediments↗
PubMed2000

Characterization of large plasmids encoding resistance to toxic heavy metals in Salmonella abortus equi.

Salmonella abortus equi vaccine strains were found to be resistant to high levels of toxic heavy metals--arsenic, chromium, cadmium, and mercury. The two strains 157 and 158 were resistant to ampicillin also. Curing of these strains resulted in loss of one or more resistance marker indicating plasmid borne resistance. Plasmid profile of strain 157 showed presence of three plasmids of 85, 54, and 0.1 Kb, whereas 158 strain showed presence of 85 Kb and 2 Kb plasmids. Plasmids were isolated from strain 157 and introduced into E. coli DH5alpha with a transformation efficiency of 2 x 10(3) transformants/microg DNA. Interestingly the transformants were resistant to antibiotics, heavy metals (As, Cr, Cd, Hg) and was also able to utilize citrate, a trait specific to Salmonella species. We report and establish for the first time the transferable large plasmids encoding resistance to various heavy metals, antibiotics and biochemical nature of S. abortus equi.

Ampicillin Resistance↗
PubMed2005

Heavy-metal remediation by a fungus as a means of production of lead and cadmium carbonate crystals.

We show here that reaction of the fungus, Fusarium oxysporum, with the aqueous heavy-metal ions Pb2+ and Cd2+ results in the one-step formation of the corresponding metal carbonates. The metal carbonates are formed by reaction of the heavy-metal ions with CO2 produced by the fungus during metabolism and thus provide a completely biological method for production of crystals of metal carbonates. The PbCO3 and CdCO3 crystals thus produced have interesting morphologies that are shown to arise because of interaction of the growing crystals with specific proteins secreted by the fungus during reaction. An additional advantage of this approach is that the reaction leads to detoxification of the aqueous solution and could have immense potential for bioremediation of heavy metals. Under conditions of this study, the metal ions are not toxic to the fungus, which readily grows after exposure to the metal ions.

Biotechnology↗
PubMed2002

Effect of mixed cadmium, copper, nickel and zinc at different pHs upon alfalfa growth and heavy metal uptake.

Alfalfa plants were grown in soil-pots contaminated with a mixture of Cd(II), Cu(II), Ni(II), and Zn(II), (at 50 mg/kg each) at pHs of 4.5, 5.8, and 7.1. The plants were fertilized using a nutrient solution, which was adjusted appropriately to the same pH. Plants in the control treatment were grown in the absence of the heavy metals mixture. The growth of the control plants was the same at the three pHs studied and the heavy metal stressed plants also showed similar behavior at each pHs. There were statistically significant differences (P<0.05) between the shoot length of the control treatment plants and the length of plants grown in the presence of the heavy metal mixture. Under the effects of the heavy metal mixture, nickel was the most accumulated element in the shoot tissue, with 437, 333, and 308 ppm at pH 7.1, 5.8, and 4.5, respectively. Cadmium was found to be second in accumulated concentrations with 202 ppm, 124 ppm, and 132 ppm at pH 7.1, 5.8, and 4.5, respectively, while zinc was third, followed by copper. The maximum relative uptakes (element in plant/element in soil-water-solution) were found to be 26 times for nickel, 23 times for cadmium, 12 times for zinc. and 6 times for copper. We considered these relations as indicative of the ability of alfalfa plants to take up elements from a soil matrix contaminated with a mixture of cadmium, copper, nickel, and zinc.

Cadmium↗
PubMed2001

Biological leaching of heavy metals from anaerobically digested sewage sludge using indigenous sulfur-oxidizing bacteria and sulfur waste in a closed system.

The utilization of indigenous sulfur-oxidizing bacteria and sulfur waste was investigated in order to remove heavy metals from anaerobically digested sewage sludge economically. Indigenous sulfur-oxidizing bacteria existing in anaerobically digested sewage sludge were activated by adding elemental sulfur to the sludge and then the bacteria were isolated. It was found that indigenous sulfur-oxidizing bacteria could utilize sulfur waste generated by desulfurization of digestion gas as a substrate. Then, biological leaching of heavy metals from anaerobically digested sewage sludge was carried out using indigenous sulfur-oxidizing bacteria and sulfur waste. By adding sulfur waste to sewage sludge, sulfuric acid was produced by the bacteria and the sludge pH decreased. Heavy metals in sewage sludge were effectively removed owing to the decrease of pH. The optimum amount of sulfur waste added to decrease the pH sufficiently was 5g/L when the sludge concentration was 2%. It was presented that the biological leaching of heavy metals from sewage sludge can be carried out in a closed system, where all required materials are obtained in a sewage treatment plant.

Environmental Pollution↗
PubMed2000

Interference of heavy metal cations with fluorescent Ca2+ probes does not affect Ca2+ measurements in living cells.

In studies about the effects of heavy metals on intracellular Ca2+, the use of fluorescent probes is debated, as metal cations are known to affect the probe signal. In this study, spectrofluorimetric experiments in free solution, using Fluo-3 and Fura-2, showed that Zn2+ and Cd2+ enhanced the probe signal, Cu2+ quenched it, and Hg2+ had no effect. Addition of GSH prevented most of these effects, suggesting the occurrence of a similar protective role in living cells. Digital imaging of living mussel haemocytes loaded with Fura-2/AM or Fluo-3/AM showed that Hg2+, Cu2+ and Cd2+ induced a rise in probe fluorescence, whereas up to 200 microM Zn2+ had no effect. In particular, Cd2+ produced the strongest probe signal rise in free solution, but the lowest fluorescence increase in cells. Probe calibration yielded [Ca2+]i values characteristic of resting levels in control and Zn2+-exposed cells, and, as expected, indicated Ca2+ homeostasis impairment in cells exposed to Cd2+, Cu2+ and Hg2+. Our results show that Ca2+ probe responses to heavy metals in living cells are completely different from those obtained in free solution, indicating that fluorescent probes can be a suitable tool to record the effects of heavy metals on [Ca2+]i.

Aniline Compounds↗
PubMed2004

Coupled reduction of chlorinated hydrocarbons and heavy metals by zerovalent silicon.

The feasibility of using zerovalent silicon (Si0) as a novel reductant to remove chlorinated compounds and heavy metals in contaminated sites was investigated. The kinetics and degradation mechanism of carbon tetrachloride (CT) by Si0 were also examined. Results showed that zerovalent silicon could effectively dechlorinate the chlorinated compounds. A nearly complete dechlorination of CT by Si0 was obtained within 14 h. The produced concentrations of chloroform (CF) accounted for 71-88% loss of CT, showing that reductive dechlorination is the major degradation pathway for the degradation of chlorinated hydrocarbons by Si0. The degradation followed pseudo first-order kinetics and the normalized surface reaction rate constant (k(sa)) for CT dechlorination ranged between 0.0342 and 0.0454 L m(-2) h(-1) when CT concentrations were in the range of 3-20 microM. A linear relationship between the k(sa) and pH value was also established. In addition, zerovalent silicon has a high capability in the removal of heavy metals. 83% of Cr(VI) was removed by 0.5g Si0 within 5 h, which is higher than that by Fe0. The removal efficiency of divalent metal ions by Si0 followed the order of Cu(II) > Pb(II) > Ni(II). This indicates that zerovalent silicon is an alternative reductant and can undergo coupled reduction of heavy metals and chlorinated hydrocarbons in contaminated groundwater.

Carbon Tetrachloride↗
PubMed2006

Heavy metal accumulation in four species of sea turtles from the Baja California peninsula, Mexico.

Heavy metals were assessed in four species of sea turtles from the Baja California Peninsula, Mexico, representing the first report of heavy metal concentrations in tissues of post-yearling sea turtles from the Eastern Pacific. Concentrations of Cd measured in C. mydas kidney (653 microg/g dry wt) were the highest ever reported for any sea turtle species. Cd accumulated preferentially in kidney and the ratios of kidney to liver Cd in Baja California turtles were among the highest reported for sea turtles globally. Zn, Ni, and Mn concentrations were also significantly higher in kidney than other tissues, while Cu and Fe were greatest in liver, and all metals were lowest in muscle. With the exception of one value (69.9 microg/g in kidney of C. caretta), Pb was low in all tissues from Baja California. In comparisons across species, kidney of C. mydas had greater Zn and Ni concentrations as compared to other species, although there was no difference in liver metal levels among the species. Positive correlations were detected in the concentrations of Cd, Cu and Ni with the straight carapace length of C. caretta.

Animals↗
PubMed2006

Toxicity of heavy metals on embryogenesis and larvae of the marine sedentary polychaete Hydroides elegans.

The toxicity of heavy metals to marine invertebrates has been widely investigated; however, the effects on marine sedentary polychaetes have largely been ignored. The toxicity of copper, aluminium, lead, nickel, and zinc on fertilization, embryogenesis, and larvae of Hydroides elegans was examined in laboratory acute-toxicity tests. Exposure to metal during fertilization or early developmental stages leads to fertilization block and arrested development, which resulted in morphologic abnormalities in embryo and larvae. Fertilization rate showed a drastic decrease at the highest metal concentration tested. Embryos of H. elegans showed a differential response to metals, and the responses were stage-specific. The different morphologic effects of heavy metals reflect differentiation of the early embryonic cells. For individual metals, the toxicity ranking for 24-hour trochophore larvae was Cu > Al > Pb > Ni > Zn, with EC(50) values of 0.122, 0.210, 0.231, 0.316, and 0.391 mg l(-1), respectively. Rate of larval development and embryogenesis were the most sensitive end points, although the latter is more advisable for routine assessment of seawater quality because of its greater simplicity. In addition to bivalves and sea urchins, polychaete embryos can provide biologic criteria for seawater quality taking into account the sensitivity of a polychaete and contributing to the detection of harmful chemicals with no marked effect on the species currently in use in seawater quality bioassays.

Animals↗
PubMed2005

Comparative evaluation of short-term leach tests for heavy metal release from mineral processing waste.

Evaluation of metal leaching using a single leach test such as the Toxicity Characteristic Leaching Procedure (TCLP) is often questionable. The pH, redox potential (E(h)), particle size and contact time are critical variables in controlling metal stability, not accounted for in the TCLP. This paper compares the leaching behavior of metals in mineral processing waste via short-term extraction tests such as TCLP, Field Leach Test (FLT) used by USGS and deionized water extraction tests. Variation in the extracted amounts was attributed to the use of different particle sizes, extraction fluid and contact time. In the controlled pH experiments, maximum metal extraction was obtained at acidic pH for cationic heavy metals such as Cu, Pb and Zn, while desorption of Se from the waste resulted in high extract concentrations in the alkaline region. Precipitation of iron, caused by a pH increase, probably resulted in co-precipitation and immobilization of Cu, Pb and Zn in the alkaline pH region. A sequential extraction procedure was performed on the original waste and the solid residue from the E(h)-pH experiments to determine the chemical speciation and distribution of the heavy metals. In the as-received waste, Cu existed predominantly in water soluble or sulfidic phases, with no binding to carbonates or iron oxides. Similar characteristics were observed for Pb and Zn, while Se existed mostly associated with iron oxides or sulfides. Adsorption/co-precipitation of Cu, Se and Pb on precipitated iron hydroxides was observed in the experimental solid residues, resulting in metal immobilization above pH 7.

Hydrogen-Ion Concentration↗
PubMed1996

Differential regulation of cardiac heme oxygenase-1 and vascular endothelial growth factor mRNA expressions by hemin, heavy metals, heat shock and anoxia.

Increasing attention has been paid to the effects of hypoxia, heavy metals and heat shocks on gene expression and to the similarities in their actions. This paper compares mRNA levels of two putative hypoxia, heavy metal and heat shock sensitive genes: heme oxygenase-1 (HO-1) and vascular endothelial growth factor (VEGF) in myocyte-enriched cultures of neonatal rat heart cells. HO-1 mRNA expression is stimulated by hemin, Cd2+, Co2+ and heat shocks but not by Ni2+ or Mn2+. It is stimulated by long (13h) but not by short (4h) periods of anoxia. Conversely, VEGF mRNA expression is stimulated by short as well as long periods of anoxia, by Cd2+, Co2+, Ni2+ and Mn2+ but not by hemin or heat shocks. The results suggest that heavy metals, anoxia and heat shocks exert their effects on VEGF and HO-1 mRNA expression through separate though potentially overlapping mechanisms. Increased expressions of HO-1 and VEGF may be both cardioprotective under hypoxic/ischemic conditions.

Animals↗
PubMed2002

Effects of temperature on the sensitivity of sludge worm Tubifex tubifex Müller to selected heavy metals.

The present study evaluates the effect of temperature on the sensitivity of the freshwater tubificid sludge worm Tubifex tubifex Müller to 10 heavy metal ions. Metals used in this study were cadmium, chromium, cobalt, copper, iron, lead, manganese, mercury, nickel, and zinc. The acute toxicity of these heavy metals was studied at 15, 20, 25, and 30 degrees C. The percentage mortality, relative toxicity, and EC50 values and their 95% confidence limits from 24 to 96 h were determined at varying temperatures. The EC50 values (mg/liter) of metal ions at 15 degrees C were Hg2+, 0.034; Cu2+, 0.340; Cr6+, 1.846; Zn2+, 10.99; Ni2+, 25.10; Cd2+, 56; Fe3+, 86.09; Co2+, 239.39; Pb2+, 456.76; and Mn2+, 164.55. At 30 degrees C the values were Hg2+, 0.014; Cu2+, 0.031; Cr6+, 0.872; Zn2+, 3.37; Ni2+, 18; Cd2+, 28.55; Fe3+, 71.26; Co2+, 95.35; Pb2+, 165.22; and Mn2+, 239.39. The results indicate that the acute toxicity of cadmium, chromium, cobalt, copper, lead, mercury, nickel, and zinc increases with temperature increase. The toxicity of manganese was not influenced by temperature, and temperature had little effect on iron toxicity. The rank order of toxicity of metal ions at 15, 20, 25, and 30 degrees C is presented and discussed. It is concluded that temperature is an important factor in short-term acute toxicity tests. The study indicates that seasonal temperature changes are an important variable in determining the amount of heavy metals that may be safely released from metal industries and other similar sources into the aquatic environment. Influence of temperature on the short- and long-term toxicity of chemicals should be considered for establishing appropriate water-quality criteria and standards to protect aquatic flora and fauna and human health.

Adaptation, Physiological↗
PubMed2004

[The effect of occupational exposure to heavy metals and arsenic on serum concentrations of carotenoids in copper foundry workers].

BACKGROUND: The aim of the project was to analyze the effect of occupational exposure to heavy metals on the efficiency of antioxidative defensive mechanisms, represented by the concentration of carotenoids (KTND) in serum. MATERIALS AND METHODS: The study involved 96 workers exposed to heavy metals in a copper foundry. Two subgroups of workers--those exposed only to lead and those to the combination of lead and arsenic--were analyzed. The control group consisted of 81 subjects not exposed to heavy metals. We measured concentrations of lead and cadmium in whole blood, selenium, manganese, copper, zinc, calcium, magnesium and carotenoids in serum, arsenic in urine and free erythrocyte protoporphyrin (FEP). RESULTS: Serum carotenoids concentration was significantly lower in workers exposed to heavy metals than in the control group (48.76 +/- 15.32 vs. 68.36 +/- 21.46 microg/dl; p < 0.001). There were no significant differences between serum concentrations of carotenoids in the subgroup exposed only to lead and the subgroup exposed to both lead and arsenic ((48.62 +/- 16.64 vs. 48.86 +/- 14.41 microg/dl). We found significant positive correlation between blood cadmium levels and serum carotenoids in the control group (r = -0.3406, p < 0.05). In the multiple regression analysis (optimal model), there was significant negative influence of blood lead on serum KTND levels and positive influence of blood cadmium on serum KTND concentrations in the subgroup of workers exposed only to lead (R(2) A = 0.9102; p < 0.001). In smelters exposed to both lead and arsenic, we observed significant negative influence of FEP and positive influence of arsenic on KTND concentrations in serum in the optimal model of multiple regression (R(2) A = 0.9249; p < 0.001). CONCLUSIONS: Occupational exposure to lead and arsenic in moderate doses affects serum carotenoids concentration in exposed humans.

Adult↗