Redistribution Of Lead Research Articles

Lead redistribution in a mine soil treated with three manures and incubated at two different temperatures

ABSTRACTThe study of heavy metals’ redistribution between different fractions allows to know their bioavailability and mobility in soils. Soil samples were collected from a lead mine in Hamadan provinces, NW Iran. In a factorial experiment soil was treated with cow, sheep and poultry manures (20 g kg−1 soil) separately and incubated near field capacity at 10°C and 37°C. An untreated soil (as control) was also incubated at the same temperatures. After 0 and 120 days, a sequential extraction scheme was used to fractionate Pb of incubated samples into soluble-exchangeable (Sol-Exch), organic matter associated (AOM), carbonates associated (ACar), and residual (Res) forms. Soil Pb in Sol-Exch and AOM fractions were increased by manure application significantly. The AOM and ACar forms of Pb were higher in soils treated with the manures and incubated in lower temperature. In contrast, the Sol-Exch and Res chemical forms of Pb were higher in the soils incubated at 37°C. These results may be related to the higher calcium carbonate dissolution and organic matter decomposition because of better biological activity in the soils incubated in higher temperature. The increase of the Res fraction (stable form) in this condition may resulted in lower toxicity and mobility in soil environment.

Lead anthropogenic transfer and transformation in China

Information on lead redistribution and speciation changes in anthrosphere can help to analyze the whole lead cycle on the earth. Lead life cycle was traced based on the concepts of anthropogenic transfer and transformation. Lead transfer and the distribution of chemical species throughout the anthropogenic flow were identified in 2010 in China. The results show that 1.85 Mt lead ore was consumed (besides 1.287 Mt imported concentrated ore and 1.39 Mt lead scraps. After undergoing transformations, 3.53 Mt lead entered end services in chemical species of Pb, PbO2 and PbSO4, altogether accounting for over 80% of the total lead products. Finally, 2.10 Mt ore was emitted into the environment in such species as PbSO4 (26%), PbO (19%) and Pb (15%). Lead transfer begins in primary raw material sectors, and then transfers to manufacturing sectors. Lead provides services mainly in such industrial sectors as transportation, electrical power and buildings or construction.

Effects of time, soil organic matter, and iron oxides on the relative retention and redistribution of lead, cadmium, and copper on soils.

In order to predict the bioavailability of toxic metals in soils undergoing degradation of organic matter (OM) and iron oxides (IOs), it is vital to understand the roles of these soil components in relation to metal retention and redistribution with time. In this present work, batch competitive sorptions of Pb(II), Cu(II), and Cd(II) were investigated between 1 and 90 days. Results showed that competition affected Cd(II) sorption more than Cu(II) and Pb(II). The sorption followed the trend Pb(II) > > Cu(II) > Cd(II), irrespective of aging, and this high preference for Pb(II) ions in soils reduced with time. Removal of OM led to reduction in distribution coefficient (K d) values of ≈33% for all cations within the first day. However, K d increased nearly 100% after 7 days and over 1000% after 90-day period. The enhanced K d values indicated that sorptions occurred on the long run on surfaces which were masked by OM. Removal of IO caused selective increases in the K d values, but this was dependent on the dominant soil constituent(s) in the absence of IO. The K d values of the IO-degraded samples nearly remained constant irrespective of aging indicating that sorptions on soil components other than the IO are nearly instantaneous while iron oxides played greater role than other constituents with time. Hence, in the soils studied, organic matter content determines the immediate relative metal retention while iron oxides determine the redistribution of metals with time.

Effect of Wetting-Drying Cycles on Redistribution of Lead in Some Semi-Arid Zone Soils Spiked with a Lead Salt

Mobility and bioavailability of lead (Pb) could be affected considerably by soil physicochemical properties; however, less is known about the effect of Pb levels and aging time. This study was conducted to evaluate the effects of Pb levels and wetting-drying (WD) cycles on distribution and bioavailability of Pb in three semi-arid zone soils treated with different levels of Pb(NO3)2. Wetting-drying cycles simulated the actual field irrigation in the semi-arid soils. A soil with a long history of Pb contamination was also taken as a reference soil. The soils were spiked with various levels of Pb and incubated under WD cycles for 160 d. Sequential extractions and batch sorption experiments were performed to assess the fractionation of Pb in the spiked soils. Redistribution index (Uts) and reduced partitioning parameter (IR) were applied to semi-quantify the distribution of Pb in the spiked soils. A small amount of Pb sorbed was desorbed by the soils, indicating a strong and irreversible binding of Pb in the studied soils. Contribution of carbonate-bound (Car) and residual (Res) Pb fractions to the total Pb of the soils was more than 97%. The Car, soluble plus exchangeable (SE), and organic matter-bound (OMB) fractions of Pb were transferred to the Res fraction under the WD cycles. The IR and Uts values were influenced by Pb loading levels and WD; therefore, the Pb lability and/or redistribution pattern could semi-quantitatively be assessed via these parameters. At the end of the experiment, the Ir and Uts values for the Pb salt-spiked soils did not show the quasi-equilibrium state. The lability of Pb in the soils decreased with increasing incubation time and showed a strong dependence on Pb levels and soil chemical composition. WD cycles significantly affected the overall lability of Pb in soils through influencing the redistribution of Pb among solid-phase components.

Effect of annealing atmosphere on domain structures and electromechanical properties of Pb(Zn1/3Nb2/3)O3-based ceramics

Annealing atmosphere effects on domain structures and electrical properties of Pb[(Zn1/3Nb2/3)0.5(Zr0.47Ti0.53)0.5]O3 (PZN–PZT) ferroelectric materials were investigated. The PZN–PZT specimens were annealed in argon, air, oxygen, and PbZrO3 atmospheres after being sintered at 1100 °C in air. The as-sintered specimens were composed of large plate-like domains. When the specimen was annealed in flowing oxygen atmosphere for 8 h at 960 °C, the domains were refined into fine twin-like domains; whereas when the specimen was annealed in argon atmosphere, the domains were modified into needle-like structures. These modifications to the domain structures have a strong effect on the electromechanical properties of this material. The formation and redistribution of lead and oxygen vacancies during thermal annealing were responsible for those variations in domain structures and electrical properties.

Radiochemical assessment of the readsorption and redistribution of lead in the SM&T sequential extraction procedure

The objective of this study was to employ radiochemical methods to assess the importance and extent of the readsorption and redistribution of lead in the standards, measurement and testing programme’s (SM&T) sequential extraction procedure. Step-wise tests indicated that 60% to over 90% of the lead extracted from the exchangeable fraction was readsorbed. Approximately 35% to over 85% of the lead extracted from the reducible fraction was readsorbed, while negligible readsorption was detected for the oxidisable fraction. Statistically significant correlations were observed between readsorption from the first two fractions and both the total iron content and the organic carbon matter even at low organic contents (i.e. less than 6 wt.%). By following the radiotracer activity through the first two steps of the method, the reducible fraction was shown to play an important role in scavenging lead released from the exchangeable soil fraction. The radiotracer partitioning results were employed to “correct” for the redistribution effects yielding the “true” fractionation of the Pb in the samples.

Structure and properties of aluminum bronze-lead composite material

The effect of sintering regime on the structure and properties of aluminum bronze-lead composite material is studied by experiment. It is established that in order to prepare material with a uniform lead distribution and high mechanical properties the sintering duration should not exceed 5 min. More prolonged heat treatment leads to redistribution of lead with formation of a coarse-grained structure and and a drop in the material mechanical properties.

The effects of variable oxygen partial pressures during Bi-2223 tape processing

The effect of changes in the oxygen partial pressure during the heat treatment of Bi-2223 tapes has been investigated. Distinct differences were observed in the phase assemblages, compositions, and critical current densities. Of particular importance in the correlation of transport properties and microstructure was the redistribution of lead in both the secondary phases and the Bi-2223 matrix. The highest Jc values were associated with tapes that contained Ca2PbO4 as part of the phase assemblage coupled with lower concentrations of lead in the superconducting phase. The high Jc of 30.4 kA/cm2 was obtained in tapes processed at 820 °C where the oxygen partial pressure was increased from 10% O2/Ar to 20% O2/Ar after 25 h of each 50-h sinter cycle. Samples processed only in 10% O2/Ar at 820 °C did not contain Ca2PbO4, had slightly higher concentrations of lead in the superconducting phase, and had significantly lower Jc values.

Metal excretion and magnesium retention in patients with intermittent claudication treated with intravenous disodium EDTA

Sixty patients with intermittent claudication participated in a double-blind placebo-controlled trial of 20 courses of intravenous chelation therapy with 3 g of disodium EDTA vs placebo during 5-9 weeks. After the first infusion, the 24-h urinary excretion of lead and zinc was approximately 25-fold higher in the EDTA-treated group; relative differences for copper and calcium were smaller. Urinary magnesium excretion in the EDTA-treated group was one-third less than in the control group. After the treatment period, the blood lead concentration had decreased by approximately 73% and the serum zinc concentration by approximately 34%; other changes in blood concentrations were negligible. The loss of essential minerals and the possible redistribution of lead in the body may constitute a disadvantage that should be taken into account in repeated intravenous EDTA treatment.

Heavy metal contamination in some soils of the McMurdo Sound region, Antarctica

Soil samples from eight sites at Marble Point and Pram Point, McMurdo Sound region, contaminated by human activities were examined for heavy metal content, using sequential extraction methods. The redistribution of lead, zinc and copper arising from point sources of these metals was demonstrated. The levels found are not considered to represent serious pollution but do indicate that human activities can change the chemistry of the Antarctic environment in localized areas.

Stable isotopic tracers of lead mobilized by DMSA chelation in low lead-exposed rats

The ability of DMSA to mobilize skeletal lead or effect a redistribution of endogenous lead to other target organs in low lead-exposed organisms is unclear. Discrepant results of past studies of DMSA and other lead chelators (e.g., CaNa 2EDTA) may be due, in part, to experimental differences and difficulties in distinguishing mobilized skeletal lead from other endogenous or exogenous lead sources. Therefore, the influence of DMSA on the mobilization and redistribution of lead in skeletal and soft tissue compartments of low lead-exposed female Wistar (115–125 g) rats was investigated using ultraclean stable lead isotope tracer techniques. Rats that had been reared on a low lead-level diet (lead intake ≈80 ng Pb/g body/day) were fed 206Pb-enriched drinking water (210 ng Pb/ml) for 1.5 days and then were chelated with a single ip injection of a 0.11 mmol/kg dose of DMSA. Blood, kidney, brain, tibia, urine and feces were collected 24 hr after chelation and analyzed for lead concentrations by graphite furnace atomic absorption spectrometry and for lead isotopic compositions by thermal ionization mass spectrometry. These analyses demonstrated that DMSA chelation significantly increased (15-fold) the diuresis of labile soft tissue lead, but not skeletal lead. DMSA also appeared to effect a redistribution and input of a comparable amount of lead to the skeleton and smaller relative amounts of lead to the soft tissues (blood, kidney) of the chelated animals. The clinical significance of these latter observations beyond the context of this preliminary study is not clear.

Glasshouse experiments on the uptake of foliar applied lead

The radioactive tracer 210Pb has been used to examine the foliar uptake and redistribution of lead in three plant species grown under glasshouse conditions for periods of 8–12 weeks. In radish a small amount (0.05–0.28%) of the lead applied to the leaf surfaces was transported to the swollen storage organ. This movement occured through intact and damaged cuticles, with an indication of an enhanced effect for damaged cuticles. Carrot plants absorbed and transported a fraction (0·43%) of the applied activity. By the end of the experiment this had reached the lower portion of the leaf petiole. Transport of lead to the tap root was <0·01% of that applied. In the case of dwarf French beans no movement of lead into pod or seed tissue was detected. It is estimated for radish that foliar absorption of lead and transport to the root could account for about 35% of the internal lead burden of root storage tissues. For carrot this pathway contributes about 3%.

Mechanical damping in leaded and in lead-free alpha brass

Using the piezoelectric composite oscillator at 40kHz and strain amplitude of 2.7 × 10 −7−5.5 × 10 −6 we have measured the mechanical damping of leaded and lead free alpha brass at 25–400°C. We observed in the leaded brass on heating a decrease in mechanical damping starting at 319°C followed by a sharp peak at 327°C and on cooling an increase in damping starting at 305°C and reaching the original damping values for heating at 280°C. We attribute these effects to the melting and redistribution of lead since no such effects were observed in the lead-free brass.

Distribution of lead in blood as affected by edathamil calcium-disodium.

The effectiveness of edathamil calciumdisodium (calcium disodium ethylenediamine tetraacetate [Ca EDTA] ) in stimulating the excretion of lead * suggests that it must exert a profound influence upon the binding of lead to tissue sites. The experiments to be reported were designed to determine whether a redistribution of lead from cells to extracellular fluid does occur during the therapy of lead poisoning. EXPERIMENTAL DATA Patients with history, physical examination, and bone x-ray changes suggestive of lead poisoning were treated with edathamil calcium-disodium subcutaneously, a single 1 gm. dose as a 1% solution in saline. Blood specimens were drawn and heparinized at intervals up to eight hours and separated into plasma and cells. Lead was determined on aliquots of blood and urine by a semimicro modification of the colorimetric diphenylthiocarbazone (Dithizone) method developed in this laboratory. 9 Five patients were studied, including three children and two adults. Data on the entire course of