Moss and Lichen as Biomonitors for Heavy Metals

Abstract

Concentrations of Zn, Pb and Cd in the mosses Hypnum cupressiforme and Hylocomium splendens were compared with the measurements of these elements in lichen-samples of Hypogymnia physodes at five sampling sites with different pollution situation in Switzerland. From measurements of several sites we found that the ratio of lichen to moss concentrations is a function of the the pollution situation determined in moss concentrations. This finding was controlled by further measurements of mosses and lichen samples from the Simmental region. These results fit well in this functional dependency, this is especially true for zinc and cadmium concentrations.     

Remediation of lead by pretreated red algae: adsorption isotherm,kinetic, column modeling and simulation studies

Batch and column biosorption experiments were carried on for lead uptake using ecofriendly biosorbents (raw and calcium chloride [CaCl₂] or formaldehyde pretreated form of red marine algae Jania ruben [Linnaeus]). The best-fit (linear and nonlinear) isotherms, kinetics, and column adsorption models were identified using statistical analysis. Freundlich, Langmuir, Temkin, Redlich–Peterson, and Elovich adsorption isotherm models were tested. Highest adsorption capacity (774 mg/g) has been observed with Jania algae pretreated with formaldehyde. Pseudo-first- and second-order adsorption kinetics were applicable. The column capacity for lead removal with Jania pretreated with CaCl₂ was found to be 1089.6 (mg/g) from the breakthrough curve area method. Thomas, Yoon-Nelson, Yan, and Clark column models were tested with regression analysis. Thomas model is the best column model with capacity q_Th = 1092.4 mg/g. Overall, 98.5% regeneration of column was achieved, indicating the suitability of using algae materials in multioperational cycles. Adsorbed lead present in algae material was confirmed by thermal analysis.     

晶体光输出非均匀性的测量和研究

利用²²Na放射源和符合测量方法实现了对钨酸铅晶体的光输出纵向非均匀性的精细测量.研究了改变晶体表面粗糙度对光输出非均匀性的影响.     

Investigation of the local structure of Cu2+ ions doped in alkali lead tetraborate glasses by their electron paramagnetic resonance and optical spectra

The local structure of the Cu²⁺ centers in alkali lead tetraborate glasses was theoretically studied based on the optical spectra data and high-order perturbation formulas of the spin Hamiltonian parameters (electron paramagnetic resonance g factors g_∥, g_⊥ and hyperfine structure constants A_∥, A_⊥) for a 3d⁹ ion in a tetragonally elongated octahedron. In these formulas, the relative axial elongation of the ligand O^2? octahedron around the Cu²⁺ due to the Jahn–Teller effect is taken into account by considering the contributions to the g factors from the tetragonal distortion which is characterized by the tetragonal crystal-field parameters Ds and Dt. From the calculations, the ligand O^2? octahedral around Cu²⁺ is determined to suffer about 19.2% relative elongation along the C₄ axis of the alkali lead tetraborate glass system, and a negative sign for A_∥ and a positive sign for A_⊥ for these Cu²⁺ centers are suggested in the discussion.     

强电场作用下反铁电锆钛酸铅的介电行为研究

采用电滞回线方法和偏置直流电场中叠加小交变电场方法研究了锆钛酸铅反铁电陶瓷材料在强电场作用下的介电行为.测量结果显示，锆钛酸铅反铁电材料的介电常数随外加电场强度呈非线性变化，在反铁电 铁电转变的电场区间形成介电峰.表征极化强度随电场强度变化率的微分介电常数εd峰值出现在反铁电 铁电转换电场强度处，最高达到41000.随着偏置电场增加反铁电向铁电体转变过程中，小信号介电常数εc减小；在电场降低铁电回复成反铁电过程中，小信号介电常数εc增大，小信号介电常数εc峰先于微分介电常数εd峰出现.根据电场作用下反铁电 关键词： 锆钛酸铅反铁电陶瓷 介电行为 强电场条件     

Energy levels of perturbed 6p<Emphasis Type="Italic">n</Emphasis>d <Emphasis Type="Italic">J</Emphasis>=2 Rydberg states of Pb I by multichannel quantum defect theory

Energy levels of the odd-parity 6pnd J=2 Rydberg states of atomic lead are analyzed by the multichannel quantum defect theory (MQDT) with previous experimental energy levels. The obtained. Using these parameters, admixture coefficients for each level are calculated to designate the level denotations. The results show that strong channel mixings exist for the levels near the 6pnd (3/2)[5/2]₂ ⁰ and 6p6d (3/2)[3/2]₂ ⁰ pertubers. The five-channel model different from that in literature is used to predict 21 energy positions of 6pnd (1/2)[3/2]₂ ⁰ levels and to determine the denotations of all the 6pnd J=2 Rydberg states under 59788 cm⁻¹ for Pb I.     

Transport properties of lead phosphate glass doped by cobalt,vanadium and chromium oxides

The electrical transport properties were investigated of a glass system of basic composition 50?mol. % Pb₃O₄–50?mol. % P₂O₅ containing CoO, Cr₂O₃ or V₂O₅ dopanys. The ac conductivity and the thermoelectric power were measured as a function of temperature. Properties such as dielectric constant, loss factor tangent and electrical conductivity are reported in the frequency range 200?Hz–100?kHz and temperature range 300–450?K. The variation in electrical conductivity with temperature was found to depend on the types of transition metal ions involved. The temperature dependence of the frequency exponent, s, was analyzed using different theoretical models. The variation of the thermoelectric power with temperature indicated the presence of more than one conduction mechanism for the investigated samples. This result was confirmed with the results of the dielectric properties at different frequencies. The introduction of cobalt ions in glass formers improves the electrical properties of non-crystalline ionic conductors.     

Spectroscopic analysis and laser modeling of neodymium-doped potassium lead chloride

We present a discussion of the low-phonon energy host material potassium lead chloride, KPb₂Cl₅, doped with neodymium. Crystal growth, spectroscopic measurements, and an analysis of the magnetic and electric dipole transitions based on the Judd-Ofelt model are presented. Concentration quenching of the fluorescence is also examined. Based on the spectroscopic data and the known resonances in energy spacing of the first three excited states in neodymium, we suggest the possibility of a 3-for-1 cross-relaxation process. This process may efficiently populate the first excited state, ⁴I_11/2, which we show to be metastable with lifetime on the order of a few milliseconds. Population inversion of this level should be possible enabling a laser based on the 5.5-μm, ⁴I_11/2 to ⁴I_9/2 transition.     

Phase transitions in Pb8O5(XO4)2 (X = As and V) compounds

Raman spectroscopy, polarized microscopy and thermal measurements were used to investigate the sequence of phase transition in the lead oxide salts Pb₈O₅(XO₄)₂ (where X = As and V). For Pb₈O₅(AsO₄)₂, a second‐order phase transition is observed at 500 K. For Pb₈O₅(VO₄)₂, a second‐order and a first‐order structural phase transitions are observed at 425 and 525 K, respectively. The ferroelastic character of Pb₈O₅(VO₄)₂ is also discussed. Copyright © 2011 John Wiley & Sons, Ltd.