Urban deciduous tree leaves as biomonitors of trace element (As, V and Cd) atmospheric pollution in Belgrade, Serbia

Leaves of common deciduous trees: horse chestnut (Aesculus hippocastanum) and linden (Tilia spp.) from three parks within the urban area of Belgrade were studied as biomonitors of trace element (As, V, and Cd) atmospheric pollution. The May–September trace element accumulation in the leaves, and their temporal trends, were assayed in a multi-year period (2002–2006). Significant accumulation in the leaves was evident for As and V, but not so regularly for Cd. Slightly decreasing temporal trends of V and As ac-cumulated in the leaf tissues were observed over the years. During the time span, the concentrations of Cd remained approximately on the same level, except in May 2002 and September 2005, when a rapid increase was observed. The May–September accumulations of As and V were higher in horse chestnut than in linden, although both may be used as biomonitors for these elements, and optionally for Cd in conditions of its high atmospheric loadings

A TPD-MS study of glassy carbon surfaces oxidized by CO2 and O-2

The temperature-programmed desorption (TPD) method combined with mass spectrometric (MS) analysis has been applied to investigate the surface properties of carbon materials. The apparatus consisting of a temperature-programmed furnace and a quadrupole Mass spectrometer was constructed in order to characterize the surface of differently treated glassy carbon samples. In this work, samples of glassy carbon exposed to air, CO2 and O-2 were examined. The desorption of H2O, CO and CO2, as major products, indicated the presence of different oxide groups. The amount of these groups for all samples was calculated. It is concluded that oxidation affects the nature and the amount of die surface oxide groups and contributes to their increased stability

Ionization energies of K2X (X=F, Cl, Br, I) clusters

The electronic structure and properties of dipotassiummonohalides are important for understanding the unique physical and chemical behavior of MnX systems. In the present study, K2X (here X=F, Cl, Br, I) clusters were generated in the vapor over salts of the corresponding potassium halide, using a magnetic sector thermal ionization mass spectrometer. The ionization energies obtained for K2F, K2Cl, K2Br, and K2I molecules were 3.82 +/- 0.1eV, 3.68 +/- 0.1eV, 3.95 +/- 0.1eV, and 3.92 +/- 0.1, respectively. These experimental values of ionization energies for K2X (X=F, Br, and I) are presented for the first time. The ionization energy of K2Cl determined by thermal ionization corresponds to previous results obtained by photoionization mass spectrometry, and it agrees with the theoretical ionization energy calculated by the ab initio method. The presently obtained results support previous theoretical predictions that the excess electron in dipotassiummonohalide clusters is delocalized over two potassium atoms, which is characteristic for F-center clusters. Copyright (C) 2011 John Wiley and Sons, Ltd

Analysis of selected elements in water in the drinking water preparation plants in Belgrade, Serbia

Belgrade's water supply relies mainly on the River Sava and groundwater supply wells, which are located in the vicinity of the river and Ada Ciganlija. In this paper, the content of aluminum, boron, chromium, manganese, cobalt, nickel, copper, zinc, arsenic, cadmium, barium and lead was analyzed in raw water as well as drinking water distributed by the Water Supply and Sewage of Belgrade. A total of 14 samples were examined from all water treatment plants that are part of the distribution system. The measurements were conducted using the inductively coupled plasma-mass spectrometry (ICP-MS) technique. The aim of this research was to examine the effectiveness of drinking water preparation process in the plants belonging to the Water Supply and Sewage of Belgrade. The content of certain elements varies considerably in raw water (river and groundwater): the concentration of boron in river water is two to three times lower than the concentration in groundwater; the concentration of arsenic in river water is ten to twenty five times lower than the concentration in groundwater; the concentration of aluminum in all groundwater samples was below the detection limit of the instrument (0.50 μg/dm3), whilst in the river water the content of aluminum was about 50 μg/dm3 and the concentration of manganese in the river water was up to 10 times lower than the concentrations in groundwater. In all drinking water samples the concentration of the elements were bellow the maximum allowed levels according to the Serbian regulations. Correlation coefficients determined for boron, manganese, cobalt, nickel, copper, zinc, arsenic, barium and lead, which were analyzed in raw waters, show that four groups of elements can be distinguished. Boron, manganese, arsenic and barium are related to each other and probably have a common natural origin; copper and lead probably have a common anthropogenic origin; correlation of nickel and cobalt was observed, while zinc was not in correlation with any other element

Production and ionization energies of KnF (n=2-6) clusters by thermal ionization mass spectrometry

RATIONALE The very small clusters of the type KnF are of particular importance since their first ionization energies (IEs) are lower than those of the alkali metal atoms. Theoretical calculation has demonstrated that this kind of cluster represents a potential building block for cluster-assembly materials with unique structural, electronic, optical, magnetic, and thermodynamic properties. To date, however, there have been no experimental results on the IEs of KnF (n GT 2) clusters. METHOD KnF (n?=?26) clusters were produced by the evaporation of a solid potassium fluoride salt using a modified thermal ionization source of modified design, and mass selected by a magnetic sector mass spectrometer where their IEs were determined. RESULTS Clusters KnF (n?=?36) were detected for the first time. The order of the ion intensities was K2F+ GT ? GT ?K4F+ GT ? GT ?K3F+K6F+? GT ?K5F+. The determined IEs were 3.99 +/- 0.20?eV for K2F, 4.16 +/- 0.20?eV for K3F, 4.27 +/- 0.20?eV for K4F, 4.22 +/- 0.20?eV for K5F, and 4.31 +/- 0.20?eV for K6F. The IEs of KnF increase slightly with the increase in potassium atom number from 2 to 6. We also observed that the presence of a fluorine atom leads to increasing ionization energy of bare metal potassium clusters. CONCLUSIONS The modified thermal ionization source provides an efficient way of obtaining the fluorine-doped potassium clusters. These results also present experimental proof that KnF (n?=?26) clusters belong to the group of superalkali species. Copyright (C)2012 John Wiley and Sons, Ltd

Surface characterization of silver and palladium modified glassy carbon

In this work, the influence of silver and palladium on the surface of undoped, boron doped and phosphorus doped glassy carbon has been studied. The silver and palladium concentrations in solution, after metal deposition, were measured by atomic absorption spectrophotometer. The morphology of metal coatings was characterized by scanning electron microscopy. In order to investigate the nature and thermal stability of surface oxygen groups, temperature-programmed desorption method combined with mass spectrometric analyses, was performed. The results obtained have shown that silver and palladium spontaneously deposit from their salt solutions at the surface of glassy carbon samples. Silver deposits have dendrite structure, whilst palladium forms separate clusters. The highest amount of both silver and palladium deposits at the surface of sample containing the highest quantity of surface oxide complexes. It has been concluded that carboxyl groups and structure defects are responsible for metal reduction. Calculated desorption energies have shown that the surface modification by metal deposition leads to the formation of more stable surface of undoped and doped glassy carbon samples

Study of factors affecting Ni2+ immobilization efficiency by temperature activated red mud

The waste red mud, remaining in remarkable quantities after the digestion of bauxite ores following the Bayer process, contains number of voluble minerals with excellent sorption properties towards aqueous heavy metals. Heating at 600 degrees C was found to be a favorable treatment for revalorization of rinsed red mud into an efficient Ni2+ sorbent (RBRM600). As potential practical application of RBRM600 for Ni2+ accumulation greatly depends on the solution composition and pH, the influence of these vital process variables was considered in this study. The initial pH rise from 2 to 3.5 caused the most evident increase in the amounts of Ni2+ removed: furthermore, the effect was more obvious for lower initial sorbate concentrations. Conversely, changes of the solution pH between 3.5 and 8 did not have a significant influence on the sorption. The increase of initial cation concentration caused the increase of the sorbed amount. following Langmuir isotherm model. The calculated maximum sorption capacity of 27.54 mg/g demonstrated capacity increase of approximately 20% in respect to inactivated rinsed red mud. Coexisting cations inhibited Ni2+ removal in the following order: Cu2+ GT Pb2+ GT = Zn2+ GT Cd2+ GT GT Ca2+, whereas the presence of Na+ and K+ did not affect the process. The investigated anions caused decrease of Ni2+ removal efficiency in the order: EDTA GT chromate GT acetate GT sulphate, however, fluoride slightly improved sorption. Low desorption of Ni2+ in various media showed that the heavy metal cations are tightly bound to RBRM600 surface, thus disposal or reuse of spent sorbent should be considered. (C) 2011 Elsevier B.V. All rights reserved

Zn2+/Poly(2-Hydroxyethyl Acrylate/Itaconic Acid) Hydrogels as Potential Antibacterial Wound Dressings

Antibacterial hydrogels, as an advanced approach, can create optimal conditions for wound healing, even in the fight against stubborn and difficult-to-treat wound infections. Interestingly, pH is an often neglected clinical parameter, although it has a significant impact on the wound healing process. At different stages of wound healing, the pH in the wound bed changes from slightly alkaline to neutral to acidic. To develop novel pH-sensitive antibacterial hydrogel dressings, Zn2+-loaded poly(2-hydroxyethyl acrylate/itaconic acid) hydrogels were synthesized. The hydrogels exhibit pH-sensitive swelling in the physiologically relevant pH range, with a pronounced swelling ability at neutral pH. The controlled release of Zn2+ occurs in a buffer of pH 7.40 at 37°C. The liquid transport mechanism and release kinetics are evaluated using the specific kinetic models of Ritger-Peppas and Peppas-Sahlin. The effect of Zn2+ on structural, thermal, swelling, cytocompatibility, and antibacterial properties is evaluated by Fourier transform infrared spectroscopy, differential scanning calorimetry, swelling studies, MTT, and antibacterial tests. The hydrogels show excellent antibacterial activity against Escherichia coli. The research opens new perspectives for efficient wound healing management, and the extension of the study will be orchestrated by optimising the hydrogel composition to achieve improved performance. This article is protected by copyright. All rights reserve

TIMS and MALDI TOF of endohedral Li-n"C-70 (n=1-3) metallofullerenes

Using the ion implantation technique (introducing negatively charged fullerene into a low temperature lithium plasma column by a strong axial magnetic field) endohedral fullerenes Li"C-70, Li-2"C-70 and Li-3"C-70 were produced. Mass spectral studies (both TIMS-thermal ionization mass spectrometry and MALDI TOF MS - matrix assisted laser desorption ionization time-of-flight mass spectrometry) of these endohedral fullerenes provided detailed structural and reactivity information about these unusual species. The fragmentation of the obtained ions is shown to be by a multiple C-2 loss (shrink-wrap mechanism). According to the fact that more atoms in the fullerene make the produced endohedral less stable, Li-3"C-70 shows a big degree of instability. The presence of Li-3"C-70 was observed on MALDI TOF MS

Effect of the pH of artificial saliva on ion release from commercially pure titanium

Due to their excellent characteristics, such as chemical inertness, mechanical resistance, low Young’s modulus, high corrosion resistance, and outstanding biocompatibility, titanium and its alloys are the most used metallic materials for biomedical applications. In dental practice, these materials have demonstrated success as biomedical devices which are used for repairing and replacing failed hard tissue. However, the oral cavity is constantly subjected to the changes in the pH value changes and such an environment is strongly corrosive for titanium dental implants. The objective of this study was to examine ion release from commercially pure titanium (cpTi) in artificial saliva with different pH values (4.0, 5.5 and 7.5). The concentrations of released titanium ions were determined after 1, 3 and 6 weeks using Inductively Coupled Plasma - Mass Spectrometry. The results indicate that the ion release from commercially pure titanium in the artificial saliva is dependent both on the pH of artificial saliva and duration of immersion. [Projekat Ministarstva nauke Republike Srbije, br. III46010 i br. ON 174004