Pb Interactions Research Articles

(Anti-)deuteron production in pp collisions at sqrt{s}=13 text {TeV}

The study of (anti-)deuteron production in pp collisions has proven to be a powerful tool to investigate the formation mechanism of loosely bound states in high-energy hadronic collisions. In this paper the production of text {(anti-)deuterons} is studied as a function of the charged particle multiplicity in inelastic pp collisions at sqrt{s}=13 TeV using the ALICE experiment. Thanks to the large number of accumulated minimum bias events, it has been possible to measure (anti-)deuteron production in pp collisions up to the same charged particle multiplicity ({mathrm {d} N_{ch}/mathrm {d} eta } sim 26) as measured in p–Pb collisions at similar centre-of-mass energies. Within the uncertainties, the deuteron yield in pp collisions resembles the one in p–Pb interactions, suggesting a common formation mechanism behind the production of light nuclei in hadronic interactions. In this context the measurements are compared with the expectations of coalescence and statistical hadronisation models (SHM).

Clinical biochemical parameters associated with the exposure to multiple environmental metals in residents from Kabwe, Zambia

Lead (Pb) interferes with various bodily functions. Although high blood Pb (Pb–B) levels in residents from Kabwe, Zambia have been reported, the accumulation pattern of other metals remains unknown. The study was designed to determine the Pb–B, blood cadmium (Cd–B), and zinc (Zn–B) values of 504 representative samples from Kabwe, as well as the potential associated adverse health effects. The Pb–B level ranged from 0.79 to 154.75 μg/dL and generally increased in areas near the mine. A significant elevation of Cd–B was observed in two areas (0.37 ± 0.26 and 0.32 ± 0.30 μg/L) where the two highest mean Pb–B levels were recorded. By contrast, the Zn–B values did not differ greatly with respect to area. Some blood biochemical parameters relating to hepatic and renal functions were out of the normal range in approximately 20–50% of studied adult participants. The δ-aminolevulinic acid dehydratase (δ-ALAD) activity was significantly inhibited in the two areas contaminated by Pb and Cd. A significant negative relationship was observed between metal levels and clinical parameters, e.g., between Pb–B and δ-ALAD for all the age categories and between Cd–B and the estimated glomerular filtration rate for all the age categories except 0–4 years. The elevated Cd–B in areas near the mine relative to the other areas suggested the potential adverse health effects of Cd and/or the interaction of Pb and Cd. A significant association of metal levels with clinical parameters also indicated the effects of metal exposure on hematopoietic, hepatic, and renal systems.

Upgrade of the ALICE inner tracking system: Construction and commissioning

ALICE (A Large Ion Collider Experiment) is the CERN LHC experiment optimized for the study of the strongly interacting matter produced in heavy-ion collisions, in particular the characterization of the quark-gluon plasma. After the successful operation of the experiment during the first two runs of the LHC, the ALICE collaboration is currently working on a major upgrade of its detectors, to be installed during the 2019–2020 Long Shutdown (LS2). The main goal is to increase the readout capabilities and allow recording of Pb–Pb minimum bias events at rates in excess of 50 kHz, which is the expected Pb–Pb interaction rate at the LHC after LS2. One key part of the upgrade is the construction of a new Inner Tracking System (called ITS2) that will significantly improve the impact parameter resolution of the tracks, tracking efficiency, and readout capacity which enables precise measurements of low momentum charged particles. The ITS2 consists of seven approximately-cylindrical detector layers of CMOS Monolithic Active Pixel Sensors (MAPS) with the sensor matrix and readout integrated on a single chip, named ALPIDE (ALice PIxel DEtector), covering an area of 10 m2 and containing about 12.5 billion pixels. All layers are mounted on ultra-lightweight carbon support structures with an embedded cooling system. This allows a reduction of the material budgets down to about 0.3% X0 for the inner layers and 1% X0 for the outer layers, with respect to the previous ITS system. After a brief overview of the upgrade motivation, details of the overall layout will be given as well as the construction and commissioning status and plans.

ϒ production in p–Pb collisions at [formula omitted

ϒ production in p–Pb interactions is studied at the centre-of-mass energy per nucleon–nucleon collision sNN=8.16 TeV with the ALICE detector at the CERN LHC. The measurement is performed reconstructing bottomonium resonances via their dimuon decay channel, in the centre-of-mass rapidity intervals 2.03<ycms<3.53 and −4.46<ycms<−2.96, down to zero transverse momentum. In this work, results on the ϒ(1S) production cross section as a function of rapidity and transverse momentum are presented. The corresponding nuclear modification factor shows a suppression of the ϒ(1S) yields with respect to pp collisions, both at forward and backward rapidity. This suppression is stronger in the low transverse momentum region and shows no significant dependence on the centrality of the interactions. Furthermore, the ϒ(2S) nuclear modification factor is evaluated, suggesting a suppression similar to that of the ϒ(1S). A first measurement of the ϒ(3S) has also been performed. Finally, results are compared with previous ALICE measurements in p–Pb collisions at sNN=5.02 TeV and with theoretical calculations.

Interaction of lead and cadmium on growth and leaf morphophysiological characteristics of European hackberry (Celtis australis) seedlings

BackgroundIn the present study, different concentrations of lead (factor A; 0, 15, and 30 mg L −1) and cadmium (factor B; 0 and 5 mg L −1) were applied via irrigation water during 6 months to evaluate their effects on growth of European hackberry (Celtis australis L.) plants. The experiment was arranged in factorial with completely randomized design and four replications under greenhouse conditions.ResultsApplication of 5 mg L −1 Cd or the lead levels (15 and 30 mg L −1) significantly reduced new shoot growth, plant leaf area, SPAD value, leaf water conductance and leaf photosynthesis, whereas significant increase in number of chlorotic and necrotic leaves, leaf transpiration rate, leaf proline and soluble sugars was observed. Higher reduction in new shoot growth and leaf water conductance and higher increase in leaf soluble sugars and proline was observed over the interaction of 5 mg L −1 Cd and 30 mg L −1 Pb. The highest soluble sugars and proline were in Pb30Cd5 (a3b2) treatment. Leaf Pb or Cd concentration was increased following their treatment. Application of cadmium significantly reduced leaf Pb, and similarly leaf Cd was significantly reduced by application of lead at both levels compared to untreated plants.ConclusionThe results showed that the hackberry growth was influenced by positive and negative interactions of Pb and Cd applied in irrigation water. The extent of growth reduction indicates that hackberry represents a relatively tolerant ornamental tree to high Pb and Cd levels.

Altered clearance of beta-amyloid from the cerebrospinal fluid following subchronic lead exposure in rats: Roles of RAGE and LRP1 in the choroid plexus

Formation of amyloid plaques is the hallmark of Alzheimer’s disease. Our early studies show that lead (Pb) exposure in PDAPP transgenic mice increases β-amyloid (Aβ) levels in the cerebrospinal fluid (CSF) and hippocampus, leading to the formation of amyloid plaques in mouse brain. Aβ in the CSF is regulated by the blood-CSF barrier (BCB) in the choroid plexus. However, the questions as to whether and how Pb exposure affected the influx and efflux of Aβ in BCB remained unknown. This study was conducted to investigate whether Pb exposure altered the Aβ efflux in the choroid plexus from the CSF to blood, and how Pb may affect the expression and subcellular translocation of two major Aβ transporters, i.e., the receptor for advanced glycation end-products (RAGE) and the low density lipoprotein receptor protein-1 (LRP1) in the choroid plexus. Sprague-Dawley rats received daily oral gavage at doses of 0, 14 (low-dose), and 27 (high-dose) mg Pb/kg as Pb acetate, 5 d/wk, for 4 or 8 wks. At the end of Pb exposure, a solution containing Aβ40 (2.5 μg/mL) was infused to rat brain via a cannulated internal carotid artery. Subchronic Pb exposure at both dose levels significantly increased Aβ levels in the CSF and choroid plexus (p < 0.05) by ELISA. Confocal data showed that 4-wk Pb exposures prompted subcellular translocation of RAGE from the choroidal cytoplasm toward apical microvilli. Furthermore, it increased the RAGE expression in the choroid plexus by 34.1 % and 25.1 % over the controls (p < 0.05) in the low- and high- dose groups, respectfully. Subchronic Pb exposure did not significantly affect the expression of LRP1; yet the high-dose group showed LRP1 concentrated along the basal lamina. The data from the ventriculo-cisternal perfusion revealed a significantly decreased efflux of Aβ40 from the CSF to blood via the blood-CSF barrier. Incubation of freshly dissected plexus tissues with Pb in artificial CSF supported a Pb effect on increased RAGE expression. Taken together, these data suggest that Pb accumulation in the choroid plexus after subchronic exposure reduces the clearance of Aβ from the CSF to blood by the choroid plexus, which, in turn, leads to an increase of Aβ in the CSF. Interaction of Pb with RAGE and LRP1 in choroidal epithelial cells may contribute to the altered Aβ transport by the blood-CSF barrier in brain ventricles.

Interaction of Pb2+ ions in water with two-dimensional molybdenum disulfide

The removal of heavy metal contaminants from water is important for public health, and recently many two-dimensional (2D) materials with high specific surface areas are being studied as promising new active components in water purification. In particular, 2D MoS2 nanosheets have been used for the removal of various heavy metals, but usually in either in complex geometries and composites, or in the chemically exfoliated metallic 1T-MoS2 phase. However, the interaction of heavy metals dissolved in water with unmodified semiconducting 2H-MoS2 is not well studied. In this paper, we report a detailed fundamental investigation of how Pb2+ ions interact with 2H-MoS2. We observe small solid clusters that form on the MoS2 surfaces after exposing them to Pb(NO3)2 aqueous solutions as shown by atomic force microscopy and transmission electron microscopy, and for liquid phase exfoliated MoS2 we observe the nanosheets precipitating out of dispersion along with insoluble solid granules. We use a combination of x-ray photoelectron spectroscopy and x-ray diffraction to identify these solid clusters and granules as primarily PbSO4 with some PbMoO4. We put forth an interaction mechanism that involves MoS2 defects acting as initiation sites for the partial dissolution in aqueous oxygenated conditions which produces MoO42− and SO42− ions to form the solids with Pb2+. These results are an important contribution to our fundamental understanding of how MoS2 interacts with metal ions and will influence further efforts to exploit MoS2 for water remediation applications.

Integrating the (311) facet of MnO2 and the fuctional groups of poly(m-phenylenediamine) in core–shell MnO2@poly(m-phenylenediamine) adsorbent to remove Pb ions from water

Exposed active facets and functional groups are critical for adsorbents obtaining excellent adsorption properties. In the present study, MnO2@PmPD with exposed active facets was successfully prepared. MnO2,which came from KMnO4 by the sacrificial reductant of PmPD, deposited on the surface of PmPD. Meanwhile, we combined experimental study and theoretical calculations to elucidate the distinct adsorption nature of MnO2@PmPD towards Pb. The surface adsorption of MnO2@PmPD toward Pb was achieved by the interaction between Pb and O atoms on the surface of MnO2. The DFT calculations revealed the facet-dependent adsorption of MnO2 toward Pb. The adsorption affinity of facets toward Pb was in the order of (311) > (111) > (400) > (440), and (311) facet was predominantly adsorption site for Pb. The analysis of partial density of state revealed the strong hybridization between the Pb-p state and O-p states of MnO2. Additionally, the pores of MnO2 provide the interstitial channels for the transportation of Pb into PmPD. The Pb entered the internal of MnO2@PmPD was bonded by the amine and newly formed carboxy groups on PmPD. This study not only develops an efficient adsorbent for heavy metals removing, but also throws light on exemplifying the interaction of Pb with MnO2 based materials.

Seasonal drivers of chemical and hydrological patterns in roadside infiltration-based green infrastructure

Infiltration-based green infrastructure has become a popular means of reducing stormwater hazards in urban areas. However, the long-term effects of green infrastructure on the geochemistry of roadside environments are poorly defined, particularly given the considerable roadside legacy metal contamination from historic industrial activity and vehicle emissions (e.g., Pb). Most current research on green infrastructure geochemistry is restricted to time periods of less than a year or limited sets of chemical species. This further limits our understanding of systems that evolve over time and are subject to seasonal variability. Between 2016 and 2018, two infiltration trenches in Pittsburgh, PA, were monitored to determine infiltration rates and dissolved nutrient and metal content. The trench water was analyzed to characterize seasonal patterns in both trench function and chemistry. Shifting patterns in infiltration rate and geochemical activity show trends corresponding with seasonal changes. Trench function is dependent on the local water table, with the highest infiltration rates occurring when evapotranspiration is active and groundwater elevation is low. Two seasonal chemical patterns were identified. The first is driven by road salt application in the winter and interaction of the salt pulse increase Pb and Cu concentrations. The second is driven by the formation of summer reducing environments that increase dissolved Fe and Mn. These findings suggest that chemical and hydrological activity in infiltration-based green infrastructure varies seasonally and may remobilize legacy contamination.

Efficient graphene-coated iron oxide (GCIO) nanoadsorbent for removal of lead and arsenic ions

ABSTRACT The graphene-coated iron oxide (GCIO) was used for the removal of Pb2+ and As3+ ions from aqueous solution. For the characterization of GCIO, several techniques (FTIR, XRD, EDX, SEM, TEM, TGA, DSC and vibrating sample magnetometry) were used which indicated the interaction of Pb2+ and As3+ with adsorbent. In addition, the effects of adsorbate concentration, different composition of adsorbent, temperature, pH of the solution and contact time of adsorbate–adsorbent were studied. After analysis of these experiments, it was found that GCIO offered very fast removal of Pb2+ and As3+ with small amount of GCIO (0.09 g) in 100 mg/L adsorbate solution. The maximum removal of Pb2+ ions (up to 97.62%) was achieved when 100 mg/L standard solution of metal ion was treated with GCIO for 35 min at 45°C in weak acidic medium (5 pH). The adsorption of Pb2+ ions followed Freundlich model with high correlation coefficient 0.98 R 2. In case of As3+ ions, maximum removal of metal ion (up to 86.62%) was attained when 100 mg/L adsorbate solution is treated with GCIO for 25 min in slightly acidic medium (6 pH) at 25°C. The adsorption of As3+ ions followed D–R model with 0.98 R 2 value. The adsorption of both metal ions (Pb2+ and As3+) follows second-order kinetic model. The high percentage removal of metal ions with little quantity of GCIO confirmed that GCIO is an excellent, effective and economic adsorbent.

Structure-activity of chelating collectors for flotation: A DFT study

Based on density functional theory calculations, the molecular frontier orbital of six types of chelating collector were studied, including S-S, S-N, N-N, S-O, N-O and O-O types, and mercaptobenzothiazole, ethyl xanthate, diethyldithiophosphate, and diethyldithiocarbamate, dithizone (keto form and enol form), dimethylglyoxime, thiocarboxylic acid, 8-hydroxyquinoline, salicylaldoxime, salicylhydroxamic acid, oleic acid, and cupferron were selected as representatives. The calculation results of the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO) and the orbital coefficients show that the chelating atoms of the collectors have great activity and large coefficient. For S-S type of collectors, the interactions of Cu, Fe Pb and Zn metal ions with double bond S, single-coordinated S and two-coordinated S are different. Moreover, mercaptobenzothiazole is more likely to chelate metal ions by means of S-N but not S-S. In S-N type, the interactions of Cu, Fe Pb and Zn metal ions with N atom are weaker than with S atom. For dimethylglyoxime (N-N type), the interactions of metal with the two N atom are nearly the same. For N-O type, the activity of N atom in a benzene ring is weaker than in a strain chain. The metal-O interactions are also different in S-O, N-O and O-O types of chelating collectors. Calculated results suggest that the electronic structure and spatial structure of an atom are very important to its interaction with metals and minerals.

Interactive effects of multiple heavy metal(loid)s on their bioavailability in cocontaminated paddy soils in a large region

Heavy metal(loid) pollution in large regions is often highly complex due to the coexistence and interactions of metal(loid)s and complex soil environments. However, the interaction effects of heavy metal(loid)s on their bioavailability in large regions remain obscure. Here, we identified the interaction effects of Pb, Cd and As on their bioavailability in cocontaminated paddy soils of Shaoguan City, China. The results showed that pH (12.40%) was the most important impact factor among the key soil properties of the pH, CEC, and SOM for the bioconcentration factor (BCF) of Cd. As the soil Pb content decreased and the soil Cd content increased, the interaction of soil Pb and Cd increased the BCF of Pb. As the soil Pb content increased and the soil Cd content decreased, the interaction of soil Pb and Cd increased the BCF of Cd. The synergistic interaction of Pb and Cd in soil promoted the accumulation of both Pb and Cd in rice under certain soil conditions. Specifically, when the average pH and CEC were below 6.19 ± 0.82 and above 7.23 ± 2.55 cmol (+)/kg, respectively, the average BCF of Cd varied from 0.70 ± 0.80 to 1.47 ± 0.62 due to the interactive effect of soil Cd and Pb on the BCF of Cd. When the average pH was above 6.19 ± 0.82 and the average SOM was below and above 27.12 ± 20.34 mg/kg, respectively, the corresponding average BCF of Cd varied from 0.70 ± 0.63 to 0.10 ± 0.26. As the average soil Cd and As contents increased, the interactive effect of soil As and Cd on the average BCF of As decreased. The negative interaction of As and Cd in soil mitigated As accumulation in rice at certain soil Cd and As contents. Our results suggest that to achieve the large-scale control of heavy metal(loid) pollution, the interactions among multiple metal(loid)s and soil properties should be considered.

Color-Tuning and Near-Sunlight White Emission in Highly Stable Rod-Spacer MOFs with Defective Dicubane Based Lead(II)-Carboxyl Chains.

The active lone pair electron effect and highly flexible coordination geometry of Pb2+ prevented the rational construction of metal-organic frameworks (MOFs) but promoted excellent fluorescence tuning. The regulation on organic and alkali templates facilitated the assemblies of three new Pb-MOFs: [Pb2(pia)2(DMA)]·DMA (1), [Pb2(pia)2(DMF)]·1.5DMF (2), and [Pb2(pia)2(DMF)]·NEt3 (3). They were rigid rod-spacer and double-walls frameworks, which possess defective dicubane [Pb4O6] based metal-carboxyl chains constructed from both semidirected and holodirected Pb2+ ions. These MOFs exhibited thermal stability up to 370 °C and unprecedented chemical stability in H2O and acidic (pH 2) and alkaline (pH 12) aqueous solutions, found for the first time in Pb-MOFs. A single-phase and rare-earth-free white-emitting phosphor, 1, was screen out, which showed a near-sunlight and human-vision-friendly broadband spectrum covering the full visible region, possessing the close-to-pure-white chromaticity coordinates of (0.332, 0.347), a near-daylight color temperature of 5696 K, and a high color rendering index of 95. The replacement of DMF as apical ligand and guest in 2 resulted in an intrinsic single and narrow emission at 562 nm with yellow color. The convenient yellow-and-blue color-tuning until white for 2 was realized by either solution or solid blending with blue-emissive H2pia, benefited from their highly matched excitation spectra. Using large NEt3 as template guest induced great framework distortion for 3 and led to white emission with chromaticity coordinates of (0.302, 0.294), stemming from nonequivalent dual emission at 450 and 545 nm. In-depth structure analysis revealed intra-/interchain Pb···Pb interactions in the lead(II)-carboxyl chains greatly affected the photochemical output.

Co-exposure of cadmium and lead on bone health in a southwestern Chinese population aged 40-75years.

Both cadmium (Cd) and lead (Pb) are associated with bone health, but studies exploring the effects of Cd and Pb co-exposure on bone health are rare. This study aimed to assess the interactive effects of Cd and Pb co-exposure on bone health. In total, 799 participants, living in the targeted areas (located in southwestern China) for more than 15years, aged 40-75years, and subsisted on homegrown rice and vegetables were investigated. Cd and Pb levels in urine and blood samples, as well as bone mineral density, T- and Z-score were determined. After being adjusted for covariates, the T-score was negatively correlated with blood Pb in men (P<.05); for women and non-smoking women, the T-score was negatively correlated with urinary Pb (P<.05). Moreover, after being adjusted for covariates, the Z-score was negatively correlated with urinary Pb in non-smoking women (P<.05). No positive association of prevalence of osteoporosis with Cd and Pb exposure was found. However, at an additive scale, positive interactions of urinary Cd and Pb on the prevalence of osteoporosis for women and non-smoking women, and the same interactions to blood Cd and Pb for men were found. There was also a positive interaction of urinary Cd and Pb for women at a multiplicative scale. This study suggests Cd and Pb exposure could exert detrimental effects on bone health, with possible underlying interactions. Nevertheless, more studies are needed to explore the interactive effects of heavy metal co-exposure.

Experimental study on fluid migration mechanism related to Pb–Zn super-enrichment: Implications for mineralisation mechanisms of the Pb–Zn deposits in the Sichuan–Yunnan–Guizhou, SW China

This study focuses on the problem of Pb–Zn super-enrichment, and is based on a new conceptualisation of fluid–rock interactions → change in fluid properties → Pb–Zn hydrolysis → complex instability. Non-magmatic, epigenetic, hydrothermal Pb–Zn deposits in carbonates were used to perform Pb–Zn hydrolysis experiments under normal pressure. Lead–zinc fluid and carbonate interaction experiments, as well as Pb–Zn hydrolysis kinetics experiments during fluid–rock interaction, were performed analyse the roles of pH and fluid–rock interactions in Pb–Zn transport and precipitation, and to investigate the main reasons for the grade disparity between Mississippi Valley-type (MVT) deposits and Pb–Zn deposits found in the Sichuan–Yunnan–Guizhou region of China. Our results show that a pH = 4 is the threshold value for the large-scale hydrolysis of Pb and Zn. When reactions between acidic solutions containing Pb and Zn (pH = 1.0–6.0) and carbonate rocks (i.e., the surrounding rock) reach equilibrium, the final pH of the solution stabilises at 5.2–6.2, which is not associated with the lithology of the surrounding carbonate rocks (dolomite or limestone), crystallite size or the initial pH of the solution, and is negatively correlated with rock particle size. Fluid–rock interactions cause pH to increase, Pb and Zn to partially hydrolysis, and minerals to precipitate, with the maximum precipitation rate reaching ~20%. When hydroxide precipitates are mixed with fluids containing reduced S, the precipitates are converted into sulphides. Thus, mineralisation fluid pH, the driving force of fluid migration, Pb–Zn hydrolysis, and fluid–rock interactions combine to restrict the formation of Pb–Zn deposits in carbonates. Among these factors, differences in Pb–Zn hydrolysis are the main causes of disparities among deposit grades. This study not only provides an in-depth consideration of the geochemical behaviour of Pb and Zn in a carbonate-hosted hydrothermal system, but also serves to clarify the mineralisation mechanisms of Pb–Zn deposits in the Sichuan–Yunnan–Guizhou region.

Colorimetric and paper-based detection of lead using PVA capped silver nanoparticles: Experimental and theoretical approach

We report a plasmonic colorimetric sensing strategy using polyvinyl alcohol (PVA) modified silver nanoparticles (AgNPs) and paper-based analytical devices (PADs) for selective detection of lead (Pb). Method is based on the measurement of red shift of localized surface plasmon resonance (LSPR) absorption band of AgNPs/PVA in visible region after the addition of Pb(II) using UV–Vis spectrophotometry and color intensity of PADs was recorded with Smartphone followed by the processing in ImageJ software. The mechanism of color change and red shift (∆λ) of LSPR band from 410 nm to 550 nm is due to the interaction of Pb(II) ions towards the PVA through strong ion-dipole interaction perturbing the stability AgNPs which further directed the aggregation of particles. The density functional theory (DFT) using Gaussian (C.01) program assisted by experimental data was used to elucidate the plausible mechanism for selective detection of analyte. The calibration curve gave a good linearity in the range of 20–1000 μgL−1 with limit of detection (LOD) of 8 μgL−1 by colorimetry and 50–1000 μgL−1 with LOD value of 20 μgL−1 using PADs. In addition, the results obtained with UV–Vis and PADs were compared with ICP-AES for quantitative determination of Pb(II) in different water samples. The advantages of using AgNPs/PVA as plasmonic colorimetric probe and PADs found to be simple, low cost and selective for determination of lead from surface water and industrial waste water samples.

Structural and X-ray spectroscopy studies of Pb1-xBax(NO3)2 solid solutions

Pb0.75(3)Ba0.25(3)(NO3)2, Pb0.68(3)Ba0.32(3)(NO3)2, Ba0.58(3)Pb0.42(3)(NO3)2, Ba0.81(3)Pb0.19(3)(NO3)2 crystals were grown for the first time when studying the Pb(NO3)2–Ba(NO3)2–H2O system. The crystals were grown in water solution with different relation of Pb(NO3)2 and Ba(NO3)2. It was found that series of solid solutions were formed by interaction of simple Pb(NO3)2 and Ba(NO3)2 compounds with a slow increase of volume and cell parameters from pure lead nitrate to pure barium nitrate. The crystal structure of all obtained Pb1-xBax(NO3)2 crystals belong to a cubic space group Pa-3. In these structures, Pb and Ba cations have the same coordination number 12, but different ionic radii (1.49 and 1.61 Å, respectively), anionic group is an equilateral triangle with O–O–O angle of 60° and O–O bond lengths ranging from 2.1305(8) to 2.2585(7) Å. The Pb2+ ion has a lone pair of electrons that are likely to be stereochemically active in these solid solutions leading to a significant amount of local disorder which explains the spread in the lattice parameters. The Pb1-xBax(NO3)2 solid solutions were characterized by X-ray photoelectron spectroscopy (XPS) by measuring the binding energies of the core-levels of constituting atoms and the shapes of the valence band. The XPS measurements indicate that the substitution of Pb for Ba does not cause changes in the charge states of the atoms constituting the Pb1-xBax(NO3)2 crystals. Matching the XPS valence-band spectra and the X-ray emission O Kα bands on a common energy scale indicates that the principal contributions of O 2p states occur at the top of the valence band of the crystals under study with also their substantial input in the upper and central portions of the band.

Active and passive biosorption of Pb(II)using live and dead biomass of marine bacterium Bacillus xiamenensis PbRPSD202: Kinetics and isotherm studies

A highly lead(II) resistant (up to 2200 mg/l) bacterium PbRPSD202 was selected among 210 lead resistant bacteria isolated from marine environment of Paradeep Port, Odisha for possible biosoption of toxic Pb (II) ions from metals polluted environments. The bacterium was identified as Bacillus xiamenensis following the phenotypic as well as 16S rRNA gene sequence analysis. In addition to Pb(II), it also showed resistance towards other heavy metals like Cd(II), Cr(VI), As(III), Cu(II), Ni(II) and Zn(II). Batch biosorption of Pb(II) using both live and dead biomass of this strain was investigated under different operational parametric conditions such as pH, temperature, NaCl concentration, shaking speed, treatment time, biomass concentration and initial Pb(II) concentration. The maximum Pb(II) uptake of 216.75 and 207.4 mg/g biomass was obtained with live and dead biomass, respectively, at the optimum condition (4% w/v NaCl, pH 6.0, 35 °C, 140 rpm and 1 g/l biosorbent dose). Both active as well as passive Pb(II) bio-sorption process showed best fit with the pseudo-second-order kinetic model. The sorption mechanism was favoured with Langmuir isotherm model indicating monolayer type adsorption. FTIR and FESEM-EDX analysis further ensured the possible interactions of Pb(II) with bacterial cell surface ligands like hydroxyl, carbonyl, carboxyl and amine groups during surface adsorption. TEM analysis revealed the intracellular accumulation of lead ions. This investigation highlights the potential application of this bacterium for bioremediation of lead(II) from the multiple metals contaminated saline environment through biosorption.

Oxidative stress links response to lead and Acyrthosiphon pisum in Pisum sativum L.

This study demonstrates the impact of lead at hormetic (0.075 mM Pb(NO3)2) and sublethal (0.5 mM Pb(NO3)2) doses on the intensity of oxidative stress in pea seedlings (Pisum sativum L. cv. ‘Cysterski’). Our first objective was to determine how exposure of pea seedlings to Pb alters the plant defence responses to pea aphid (Acyrthosiphon pisum Harris), and whether these responses could indirectly affect A. pisum. The second objective was to investigate the effects of various Pb concentrations in the medium on demographic parameters of pea aphid population and the process of its feeding on edible pea. We found that the dose of Pb sublethal for pea seedlings strongly reduced net reproductive rate and limited the number of A. pisum individuals reaching the phloem. An important defence line of pea seedlings growing on Pb-supplemented medium and next during combinatory effect of the two stressors Pb and A. pisum was a high generation of superoxide anion (O2−). This was accompanied by a considerable reduction in superoxide dismutase (SOD) activity, and a decrease in the level of Mn2+ ions. A the same time, weak activity of Mn-SOD was detected in the roots of the seedlings exposed to the sublethal dose of Pb and during Pb and aphid interaction. Apart from the marked increase in O2−, an increase in semiquinone radicals occurred, especially in the roots of the seedlings treated with the sublethal dose of Pb and both infested and non-infested with aphids. Also, hydrogen peroxide (H2O2) generation markedly intensified in aphid-infested leaves. It reached the highest level 24 h post infestation (hpi), mainly in the cell wall of leaf epidermis. This may be related to the function of H2O2 as a signalling molecule that triggers defence mechanisms. The activity of peroxidase (POX), an important enzyme involved in scavenging H2O2, was also high at 24 hpi and at subsequent time points. Moreover, the contents of thiobarbituric acid reactive substances (TBARS), products of lipid peroxidation, rose but to a small degree thanks to an efficient antioxidant system. Total antioxidant capacity (TAC) dependent on the pool of fast antioxidants, both in infested and non-infested and leaves was higher than in the control. In conclusion, the reaction of pea seedlings to low and sublethal doses of Pb and then A. pisum infestation differed substantially and depended on a direct contact of the stress factor with the organ (Pb with roots and A. pisum with leaves). The probing behavior of A. pisum also depended on Pb concentration in the plant tissues.

Interaction of epitaxial graphene with heavy metals: towards novel sensing platform

Development of next-generation sensors based on graphene materials, especially epitaxial graphene (EG) as the most promising representative, with desirable cross-reactivity to heavy metals (HMs) is of great technological significance in the virtue of enormous impact on environmental sensorics. Nevertheless, the mechanisms by which EG responds to toxic HMs exposure and then produces the output signal are still obscure. In the present study, the nature of interaction of toxic HMs, e.g. Cd, Hg and Pb in neutral charge state and EG on Si-face SiC in the absence and in the presence of pure water solution has been investigated using density functional theory with the inclusion of dispersion correction and cluster model of EG. The gas-phase calculations showed that adsorbed electron-donating Cd and Hg adatoms on EG are most stable when bonded to hollow sites, while Pb species prefer to sit above bridge sites. By using non-covalent interaction analysis, charge decomposition analysis, overlap population density of states analysis and topological analysis, it was found that the interaction between Cd or Hg and EG is non-bonding in nature and is mainly governed by van der Waals forces, while Pb adsorption is followed by the formation of anti-bonding orbitals in vacuum conditions and bonding orbitals in water. The role of solvent in the adsorption behavior of HMs is studied and discussed. The present theoretical analysis is in good agreement with recent experimental results towards discriminative electrochemical analysis of the toxic HMs in aqueous solutions at critically low concentrations.