Inorganic Pb Research Articles

Evaluation of the Nutrient Status of Some Hydrophytes in the Water Courses of Nile Delta, Egypt

The nutritive values of three dominant hydrophytes along the water courses in Nile Delta, Egypt (Echinochloa stagnina, Eichhornia crassipes, and Ceratophyllum demersum) were evaluated in terms of estimating their phytomass, organic, and inorganic chemical compositions. Shoots were collected seasonally from 25 permanent stands representing the distribution of the three species along 15 canals and 10 drains distributed in 5 localities within the Nile Delta. Living and dead parts and total phytomass were estimated. Their inorganic (Na, K, Ca, Mg, P, Cu, Mn, and Pb) and organic (carbohydrates, total nitrogen, total protein, ether extract, digestible nutrient, digestible energy, metabolized energy, and net energy) contents were estimated. The vegetative phase of E. stagnina extended during winter, spring, and summer, while it is flowering and fruiting during autumn. On the other hand, E. crassipes and C. demersum attained their maximum flowering during spring and maximum fruiting during summer, while maximum vegetative phase during autumn and winter. E. stagnina had the highest mean annual phytomass, while C. demersum had the lowest. The living parts of C. demersum had the highest concentrations of Na, Ca, and Mg, while the living parts of E. crassipes had the highest of K and N. C. demersum had the ability to accumulate more concentrations of heavy metals than the other studied species. E. crassipes had the highest values of total carbohydrate and total proteins, while E. stagnina had the highest of crude fibers, and C. demersum had the highest of ether extract and ash contents. The living parts of E. crassipes and C. demersum were considered as excellent forages, while the dead parts of all species and the living parts of E. stagnina were evaluated as poor forage.

Synthesis and characterization of a new organic–inorganic Pb 2+ selective composite cation exchanger acrylonitrile stannic(IV) tungstate and its analytical applications

A new polymeric–inorganic cation exchanger acrylonitrile stannic(IV) tungstate composite was synthesized by sol–gel technique by incorporating stannic(IV) tungstate precipitate with acrylonitrile. Composite materials formed by the combination of inorganic ion exchangers of multivalent metal acid salts and organic polymers (acrylonitrile, cellulose acetate, polyaniline, polypyrrole, polythiophene, etc.), providing a new class of ‘organic–inorganic’ composite exchangers with better mechanical and granulometric properties, good ion exchange capacity, higher stability, reproducibility and selectivity for heavy metals. The physico-chemical characterization was carried out by elemental analysis, TGA, SEM, XRD, FTIR and TEM studies. Ion exchange capacity, pH titrations, elution and distribution behavior were also carried out to understand the ion exchange behavior of the material. The adsorption behavior of heavy metal ions has been reported in nitric acid and two surfactants media by batch processes. The analytical applications of the material have been explored by achieving some analytically important binary separations from aqueous solution on its columns. The practical applicability of acrylonitrile stannic(IV) tungstate was demonstrated in the quantitative separation of Fe 3+and Zn 2+ contents of a commercially available pharmaceutical sample namely Fefol-Z.

Alternative Thermodiffusion Interface for Simultaneous Speciation of Organic and Inorganic Lead and Mercury Species by Capillary GC-ICPMS Using Tri-n-propyl-lead Chloride as an Internal Standard

An alternative thermodiffusion interface (TDI) was designed and constructed for the effective online coupling of capillary gas chromatography (cGC) and inductively coupled plasma mass spectrometry (ICPMS). Pb(2+), (CH3)3Pb(+), (C2H5)3Pb(+), Hg(2+), CH3Hg(+) and C2H5Hg(+) were derived as Pb(C4H9)4, (CH3)3PbC4H9, (C2H5)3PbC4H9, (C4H9)2Hg, CH3HgC4H9, and C2H5HgC4H9 when butyl magnesium bromide was employed as a derivatization reagent for a proof-of-concept study, avoiding the loss of their species specific information. All these derivatives together with the neutral fully saturated (CH3)4Pb and (C2H5)4Pb could be quantitatively separated within 7 min using a 15 m long capillary column, allowing the determination and speciation of organic and inorganic Pb and Hg species in a single run. The method detection limits (3sigma) for Me4Pb, Et4Pb, Me3Pb(3+), Pb(2+), MeHg(+), EtHg(+), and Hg(2+) are 0.07, 0.06, 0.04, 7.0, 0.09, 0.1, and 0.2 pg g(-1), respectively. Moreover, tri-n-propyl-lead chloride was synthesized and used as an alternative internal standard for the accurate and simultaneous speciation analysis of Pb and Hg in complicated environmental and biological samples for the first time. This cGC-TDI-ICPMS method was validated by analyzing Pb and Hg species in certified reference materials and then was applied to simultaneous speciation analysis of Pb and Hg in real-life samples. It is expected that these approaches can be extended to the speciation of other organometallic compounds after suitable modifications and so will aid in monitoring the occurrence, pathways, toxicity, and/or biological effects of these compounds in the environment and in organisms.

Quantification of the release of inorganic elements from biofuels

The release of inorganic elements, mainly K, Na, Zn, Pb, S, and Cl, from a number of well-characterized biofuels (wood chips, bark, waste wood, and straw) was quantified as a function of temperature in a lab-scale fixed-bed reactor, and as a function of residence time in a lab-scale entrained flow reactor. The fuels were characterized by use of wet chemical analysis, and also by advanced techniques: chemical fractionation analysis (of the raw fuels) and simultaneous thermal analysis (of ash samples derived from the fuels at 550 °C). In parallel to the experimental release investigation and fuel characterization, global equilibrium analysis, simulating the experimental combustion conditions, was performed.The objective of this work was to compare the lab-scale release data with the results from the fuel characterization techniques and from the equilibrium calculations. Furthermore, the results from the lab-scale fixed-bed release tests were compared to pilot-scale mass balance tests.While large differences were seen between the lab-scale release data and the release information obtained by the fuel characterization techniques, a good correlation was found between the lab-scale and pilot-scale fixed-bed release data.In conclusion, it is recommended to perform the described lab-scale tests in order to obtain reliable quantitative data on the release of inorganic elements under grate-firing or suspension-firing conditions. Advanced fuel characterization by use of chemical fractionation and simultaneous thermal analysis, and global equilibrium analysis of thermal fuel conversion systems, provide valuable information on the association of inorganic elements in the fuel, the transformations and release of inorganic species upon heating, and the possible forms in which the inorganic elements are thermodynamically stable as a function of temperature. This information is needed for the interpretation of the lab-scale release data. Thus, for the purpose of modeling ash or aerosol formation, fuel characterization methods should be combined with lab-scale release measurements. Pilot-scale mass balance test runs provide useful information on the distribution of the inorganic elements among the different ash fractions during grate-firing, from which the release of inorganic elements can be calculated.This paper provides an outline of each of the experimental and analytical methods applied, a comparison of the release data obtained, as well as a discussion of the limitations and the assumptions made.

The value of metals bioavailability and speciation information for ecological risk assessment in arid soils

When evaluating the risk chemicals may pose to mammals and birds in ecological risk assessments (ERAs), it is common practice to conservatively assume that all (100%) of a chemical in an environmental medium is bioavailable to receptors. This assumption often leads to overestimating ecological risk and may ultimately result in costly and unnecessary risk management actions. While effects of bioavailability and speciation of metals such as arsenic (As) and lead (Pb) have been considered in human health risk assessment, these effects are rarely taken into consideration when assessing risks to mammals and birds. An ERA was conducted at the former Col-Tex refinery site in Colorado City, Texas, USA, to characterize risks to select wildlife species from exposure to chromium (Cr) and Pb found in soils. The focus on these metals was based on results of a screening-level ERA that found that Cr and Pb were posing ecological risks at the site. Soils were analyzed for total Cr and Pb, trivalent Cr (CrIII), hexavalent Cr (CrVI), organic Pb, and the bioavailability and speciation of Pb. Results for Pb and Cr indicated that >94% of the Cr was present as the less toxic and immobile Cr(III) and that >99% of the Pb in soils was present as inorganic Pb. Lead bioaccessibility measured by in vitro testing ranged from 8% to 77.8%, depending on location of individual soil samples. Results demonstrated that Pb and Cr bioavailability and speciation information can raise soil cleanup concentrations while being protective of ecological receptors. The costs of performing the ERA were de minimus compared to the reduction in remediation costs at the site. The refined hazard estimates allowed informed decision making in the management and segregation of soils, allowing for effective risk management at the site.

Syntheses and characterization of new polydentate amide ligands with inorganic tin (II) and lead (II) ions

Complexes of inorganic Sn(II) and Pb(II) with new ligands N′,N″-bis(3-carboxy-1-oxopropanyl) 2-amino-N-arylbenzamidine (C21H21N3O6) and N′,N″-bis(3-carboxy-1-oxophenelenyl) 2-amino-N-arylbenzamidine (C29H21N3O6) have been synthesized and characterized by elemental analyses, vibrational spectra, electronic spectra, 1H NMR spectra, TOF-mass spectra, thermal studies and X-ray powder diffraction studies. The infrared and 1H NMR spectral data are in agreement with coordination of amide and carboxylate oxygen of the ligands giving a MO4 tetrahedral chromophore. The elemental analyses and mass spectral data are consistent with the formation of ML complexes. Kinetic and thermodynamic parameters were computed from the thermal data using Coats and Redfern method, which confirm first order kinetics. X-ray powder diffraction determines the cell parameters of the complexes. Molecular structures of the complexes have been optimized by MM2 calculations and suggest a tetrahedral geometry around metal (II) ions.

Pb2+ reduces PKCs and NF-κB in vitro

The mechanism of lead (Pb(2+))-induced neurotoxicity has not yet been fully elucidated. The purpose of this study was to examine the effects of Pb(2+) on several protein kinase C (PKC) isoforms and the nuclear factor-kappaB (NF-kappaB)-I-kappaB kinase-alpha (IKK-alpha) axis in cultured neuronal cells. Neurons were isolated from rat fetal brain at the 18th day of gestation of pregnant Sprague Dawley rats and cultured for 10 days before use. Neurons were exposed to Pb(2+) at concentrations of 10(-10), 10(-9), 10(-8), and 10(-7) mol/L for 14 h and antigens of typical PKC-alpha,beta,gamma; novel PKC (epsilon, delta), atypical PKC (lambda), NF-kappaB (p50), and IKK-alpha were enriched by immunoprecipitation and determined by western blotting. Total, calcium-dependent and independent PKC activities were also determined by counting the transferred gamma-(32) P in the substrate-histone. The results indicated that inorganic Pb(2+) significantly reduced all PKC isoforms (alpha,beta,gamma, epsilon, lambda) except delta, inhibiting the total, calcium-dependent and calcium-independent PKC activities in a dose-dependent manner. Additionally, Pb(2+) gradually reduced NF-kappaB (p50) and IKK-alpha protein levels. This suggests that Pb(2+) exhibits varying preference for individual PKC isoforms but reduces the NF-kappaB-IKK-alpha axis to a similar extent.

A comparative in vitro study of the toxic potency of five inorganic lead compounds on a rat liver epithelial cell line (REL)

Relative insolubility of inorganic Pb compounds is one of the major problems in the evaluation of the toxicological profile of this metal. Different characteristics of Pb-containing solutions may, in fact, alter the biological properties of Pb compounds and influence their toxic potency. To investigate these aspects, we used selected experimental conditions to evaluate and compare the specific biological effects of five inorganic Pb compounds (soluble salts and oxide) on the viability and proliferation rate of a rat liver-derived cell line (REL cells). The study was performed according to classical toxicological criteria (dose– and time–response, reversibility/transience of the effect). Each Pb compound was accurately solubilised and the quantification of the real concentration of Pb(II) ions was performed either on the culture media used for each treatment, or on the extracts of exposed cells. Our study shows that four, out of the five Pb compounds we tested, induce the same dose- and time-related anti-proliferative effects on REL cells, being these effects also reversible, transient and directly related to the intracellular content of the metal. Since the intracellular concentration of the metal and, consequently, its biological effects on REL cells, directly depends on the bioavailability of the Pb(II) cation present in the treatment solutions, our results indicate that, in the experimental procedures aimed to assess the toxic potency of this metal, the solubility of each Pb compound should be carefully evaluated and taken into account.

Chemical speciation of dissolved copper, lead and zinc in a ria coastal system: the role of resuspended sediments

The chemical speciation of dissolved Cu, Pb and Zn was studied in a ria coastal system applying differential pulse anodic stripping voltammetry using a hanging mercury dropping electrode. Cu and Pb were found to be strongly complexed with organic ligands in solution: inorganic Pb was not detected in the samples, whereas inorganic Cu only accounted for <3% of total dissolved metal. Organic complexation of Zn was weaker, ranging from 48 to 72% of total dissolved metal. Sediment resuspension experiments were carried out in order to study the desorption of organic ligands to the water column. Results from the sediment resuspension study showed a desorption of organic ligands (together with metals) presenting similar complexing abilities of those found in the water column. This has important implications from an ecotoxicological point of view, since the potential danger to the aquatic biota from significant concentrations of desorbed metals – which is critical when contaminated sediments are considered – is in part buffered by the in situ desorption of organic ligands.

Decline in the quality of suspended fine particulate matter as a food resource for chironomids downstream of an urban area

Summary1. Urbanization and its associated contamination could degrade the quality of suspended fine particulate organic matter (SFPM) (20 μm to 1 mm) as a food resource for aquatic insects. SFPM was collected at four sites along the main stem of the Chattahoochee River, which drains metropolitan Atlanta at base and high flow during four seasons.2. Composition of SFPM was estimated using measures conventionally associated with food quality: bacteria, N/C ratio, caloric content, % inorganic, and % lipids, and metal (Cd, Cu, Pb, and Zn) concentration. In SFPM collected during base flow, % inorganic matter, calories, Cu, Pb, and Zn concentrations increased with cumulative permitted wastewater treatment discharge (an indicator of extent of urbanization upstream). In SFPM samples collected during high flow, % diatoms, Cu, Pb and Zn concentrations increased with urbanization.3. A growth assay was used as an integrated and direct measure of SFPM quality as a food resource. The instantaneous growth rate (IGR) of chironomids fed SFPM collected during base flow declined downstream of the city. IGRs of chironomids fed SFPM collected at all sites during high flow were as low as the lowest IGR measured during base flow.4. Insects fed SFPM collected from the Chattahoochee River had IGRs only 20% of those of chironomids fed SFPM collected from the Little Tennessee River, a relatively undisturbed river in North Carolina. The mortality rate of chironomids fed SFPM was not different among sites or rivers. While the decline in SFPM quality in the Chattahoochee River is probably attributable to some aspect of urbanization, the decline was not related to conventional measures of food quality or metal contamination.

Crystal engineering of a versatile building block toward the design of novel inorganic-organic coordination architectures.

Six novel inorganic-organic coordination supramolecular networks based on a versatile linking unit 4-pyridylthioacetate (pyta) and inorganic Co(II), Cu(II), Ag(I), Zn(II), Mn(II) and Pb(II) salts have been prepared in water medium and structurally characterized by single-crystal X-ray diffraction analysis. Reaction of CoCl(2).6H(2)O with Hpyta afforded a neutral mononuclear complex [Co(pyta)(2)(H(2)O)(4)](1), which exhibits a two-dimensional (2-D) layered architecture through intermolecular O-HO interactions. Reaction of CuCl(2.2H(2)O with Hpyta yielded a neutral one-dimensional (1-D) coordination polymer [[Cu(pyta)(2)(H(2)O].0.5H(2)O](n)(2) consisting of rectangle molecular square units, which show a three-dimensional (3-D) supramolecular network through S...S and O-H...O weak interactions. However, when AgNO(3), Zn(OAc)(2).2H(2)O or MnCl(2).4H(2)O salts were used in the above self-assembled processes, the neutral 2-D coordination polymers [Ag(pyta)](n)(3), [[Zn(pyta)(2)].4H(2)O](n)(4) or [[Mn(pyta)(2)(H(2)O)]](n)(5) with different topologies were obtained, respectively. While substituting the transition metal ions used in 1-5 with Pb(OAc)(2).3H(2)O, a one-dimensional coordination polymer [Pb(pyta)(2)](n)(6), which shows a novel 2-fold interpenetrating 2-D supramolecular architecture through weak SS interactions, was isolated. It is interesting to note that the building block pyta anion exhibits different configurations and coordination modes in the solid structures of complexes 1-6. These results indicate that the versatile nature of this flexible ligand, together with the coordination preferences of the metal centers, play a critical role in construction of these novel coordination polymers or supramolecules. The spectral and thermal properties of these new materials have also been investigated.

Greenhouse studies on the phyto-extraction capacity of Cynodon nlemfuensis for lead and cadmium under irrigation with treated wastewater

For over 30 years, discharge of sewage effluent and sludge on pasturelands has been used in Zimbabwe as a cheap method for secondary treatment of wastewater without any monitoring of accumulation of heavy metals in soils and grasses, let alone in animals grazing on the pastures. Cynodon nlemfuensis (star grass) has been the main grass planted on the wastewater irrigated pasturelands. This study was conducted to assess the capacity of star grass to accumulate lead (Pb) and cadmium (Cd) and develop models incorporating grass yield, metal uptake and soil bio-available (EDTA extractable) metal content, that could be used to determine critical grass and soil concentrations at which grass productivity declines. Star grass was planted in 30 fertilized pots containing sandy soil within a greenhouse. The pots consisted of nine treatments of varying levels of added inorganic Pb and Cd subjected to treated wastewater application and one control that had no added metals and received water application only. The elements were applied to the soils once just after planting the grass. Chemical analyses showed that star grass had a relatively high phyto-extraction capacity of Pb and Cd, comparable to that of hyper-accumulating grasses such as Lolium perenne (rye grass). It accumulated Pb and Cd to levels far beyond the recommended maximum limits for pasture grass. Analysis of variance on log-normal transformed data showed that bio-available soil metal concentrations correlated strongly with grass metal content and grass metal content correlated strongly with the yield. There was however a weak correlation between the yield and bio-available soil levels. The yield versus grass metal content models that were developed for the first crop and re-growth predicted similar critical metal concentrations and yields. Using the critical grass metal concentrations in the soil bio-available metal concentration versus grass metal concentration models allowed for the prediction of the corresponding critical soil concentrations.

Recent history of sediment deposition in marl- and sand-based marshes of Belize, Central America

There are two contrasting types of wetlands in Belize: marl- and sand-based marshes. We measured accumulation rates of sediment in six cores from marl- and sand-based marshes of northern Belize and compared biogeochemical characteristics to assess recent wetland history (∼1850 to present). Sediment depth increments were analysed for bulk density, LOI, nutrients (C, N, P, S, Ca, Mg, K and Na) and snail shell density and species diversity. Cores were dated using 210Pb and a constant rate of supply model. Unsupported 210Pb inventories of the cores ranged from 6.16 to 8.92 pCi cm −2. Marl-based marshes showed the maximum peak of 210Pb activity from 4 to 10 cm below the sediment surface. 210Pb peaks corresponded with the bottom of a marl layer containing chlorophyll a and we suggest that this relationship reflects the high growth and decomposition rates of cyanobacterial mat. Inorganic carbon, Ca, Mg, K, Na, S and Pb contents and accumulation rates were much greater in the marl-based marshes than in the sand-based marshes. Average dry mass accumulation rates in the six marshes ranged from 113 to 572 g m −2 year −1 over the past 100 years. Average linear sedimentation rates during the last 100 years in the two types were not significantly different (0.93 and 1.08 mm year −1, respectively). Increased sediment accumulation by human activities such as soil washout from adjacent roads was recorded in a sand-based marsh near roads. Sediment cores in the marl-based marshes display changes of marsh vegetation, apparently caused by water level changes. The vegetation change occurred at the end of the 1800s and the beginning of 1900s and is represented by a band of dark peat in otherwise marl-dominated sediments. Overall, the sediment cores show that conditions were relatively undisturbed by human activities in the recent past.

Self-Assembly and X-ray Structure Determination of the Novel 2-D Layered Organic–Inorganic Hybrid Pb–X Compound: [PbX2(4,4′-bipy)]n (X = I, Br)

Abstract Two novel organic–inorganic hybrid compounds, [PbI2(4,4′-bipy)]n (1) and [PbBr2(4,4′-bipy)]n (2), are synthesized by self-assembly. X-ray crystallography analysis shows that the [PbI2]n chains in 1 are linked by 4,4′-bipyridine to form a layer, via Pb–N bonding along the direction of the ‘b’ axis.

Seasonal variation in phytomass and nutrient status of Phragmites australis along the water courses in the middle Nile Delta, Egypt.

The present study provides an evaluation of the nutrient status of Phragmites australis, which is one of the most important weeds along the water courses in the middle Nile Delta Egypt. Shoots were collected seasonally from twenty-five permanent stands. Living and dead parts and total phytomass were estimated. The inorganic (Na, K, Ca, Fe, Mg, P, Cu, Mn, Zn, Pb and Co) and organic (carbohydrates, total nitrogen, total protein, ether extract, crude fiber and ash) contents were estimated. Some digestible and energy parameters (digestible protein, total digestible nutrient, digestible energy, metaboilse energy, and net energy) were calculated. Based on the nutrient analysis, the present study evaluated the nutritive value of plant as a poor forage.

Determination of the speciation of organolead compounds in airborne particulate matter by gas chromatography–inductively coupled plasma mass spectrometry

The speciation of organolead compounds in airborne particulate matter was determined by gas chromatography–inductively coupled plasma mass spectrometry. The analytes were extracted from the sample using 0.5 M acetic acid in methanol. The ionic organolead compounds were extracted into hexane using diethydithiocarbamate at pH 9 in the presence of EDTA to complex inorganic Pb. Derivatisation of the organolead species was performed with butylmagnesium chloride. Separation and detection of the butylated trimethyllead (TML), dimethyllead (DML), triethyllead (TEL) and diethyllead (DEL) was achieved. Detection limits, as Pb, were 3.2 fg for TML, 2.4 fg for DML, 1.8 fg for TEL and 9 fg for DEL for a 1 μl sample injection. Typical precision of repetitive injections was 1.5–4% using tetraethyllead (TrEL) as internal standard. The method proposed was validated by the determination of TML in the reference material CRM 605 and was applied to the analysis of airborne particulate matter in the atmosphere of the city of Oviedo. DML, DEL and methylethyllead (MEL) were detected at pg m −3 levels.

Treatment of inorganic contaminants using permeable reactive barriers

Permeable reactive barriers are an emerging alternative to traditional pump and treat systems for groundwater remediation. This technique has progressed rapidly over the past decade from laboratory bench-scale studies to full-scale implementation. Laboratory studies indicate the potential for treatment of a large number of inorganic contaminants, including As, Cd, Cr, Cu, Hg, Fe, Mn, Mo, Ni, Pb, Se, Tc, U, V, NO 3, PO 4 and SO 4. Small-scale field studies have demonstrated treatment of Cd, Cr, Cu, Fe, Ni, Pb, NO 3, PO 4 and SO 4. Permeable reactive barriers composed of zero-valent iron have been used in full-scale installations for the treatment of Cr, U, and Tc. Solid-phase organic carbon in the form of municipal compost has been used to remove dissolved constituents associated with acid-mine drainage, including SO 4, Fe, Ni, Co and Zn. Dissolved nutrients, including NO 3 and PO 4, have been removed from domestic septic-system effluent and agricultural drainage.

Biochemical removal of HAP precursors from coal — INEEL slurry column testing

A combined physical/biochemical process for the precombustion removal of 13 inorganic hazardous air pollutant (HAP) precursors, i.e., Sb, As, Be, Cd, Cr, Cl, Co, F, Pb, Hg, Mn, Ni and Se, from coal was tested. Biochemical processes for removal of HAP precursors from coal potentially offer advantages of deeper cleaning, more specificity and less coal loss. The slurry column is a second-generation process for the beneficiation of fine (60-mesh × 10µm) coal by a combination of physical separation of mineral matter and biooxidation of pyrite. Sixty-seven percent removal of pyrite from a 60-mesh Pittsburgh #8 coal was achieved at a 35% (w/w) slurry concentration and a five-day reactor residence time. Ninety percent of the heating value of the feed coal was recovered. Among the HAP precursors of most concern, over half of the Se, As and Hg were removed from the feed coal. From 40% to 70% of most HAP precursors were removed from the feed coal. Hg in the feed coal was reduced from 0.12 to 0.054 µg/g in the product coal, while waste coal contained 0.24 µ/g.

Effects of lubricating-oil additives on the friction and wear properties of polymers and their composites sliding against steel under oil-lubricated conditions

The effects of lubricating-oil additive zinc dialkyldithiophosphate (ZDDP) on the friction and wear properties of polymers and their composites sliding against GCr15 bearing steel were studied by using an MHK-500 ring-on-block wear tester (Timken wear tester). Then the frictional surfaces of the friction pairs were examined by using electron probe microanalysis (EPMA). Experimental results show that the ZDDP contained in liquid paraffin has little effect on the friction coefficients of the polyimide (PI) or polyamide 66 (PA66) against GCr15 bearing steel friction pairs compared with that under the lubrication of liquid paraffin, but it slightly reduces the friction coefficients of polytetrafluoroethylene (PTFE) or its composites against GCr15 bearing steel friction pairs. Under lubrication of liquid paraffin containing 2 wt % ZDDP, the ZDDP film absorbed on the frictional surfaces of the PTFE composites–GCr15 bearing steel friction pairs exhibits obvious antiwear properties; it greatly reduces the wear of pure PTFE and the PTFE composites filled with Pb, PbO, and MoS2; and the wear of the PTFE composites can be reduced by one order of magnitude compared with that under lubrication of pure liquid paraffin. Meanwhile, the inorganic fillers Pb, PbO, and MoS2 contained in PTFE have little effect on the absorption of ZDDP to the frictional surfaces, so they have little effect on the friction coefficients of the PTFE composites–GCr15 bearing steel friction pairs under the lubrication of liquid paraffin containing 2 wt % ZDDP. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1240–1247, 2000

Effects of four inorganic lead compounds on the proliferation and junctional coupling of cultured REL liver cells.

Chronic, low-level exposure to inorganic lead (Pb) has been involved in a number of human diseases, including tumors. In this study, the effect of four different inorganic Pb compounds (acetate, chloride, monoxide, and sulfate) was evaluated, in vitro, on liver-derived REL cells, known to be very sensitive to tumor promoters. Cytotoxicity and effects on intercellular communication (GJIC) were evaluated, respectively, by cell- density/proliferation and dye-transfer assays. Pb concentration in the media solutions used for each treatment was quantified by atomic absorption spectroscopy-electrothermal atomization. Each of the Pb compounds we tested showed a typical dose- and time-related effect on REL cell proliferation, this effect not being related to the free metal concentration. Contrary to classical tumor promoters, none of the compounds significantly affected REL GJIC (1-hour treatment). Our results are indicative of specificity in the effects of the different Pb compounds. The mechanism(s) of their action need further investigations.