CARBONIZED FIBROUS RESIN AS A NEW SORBENT FOR SAMPLING POLYCYCLIC AROMATIC HYDROCARBONS (PAHS) IN AMBIENT AIR

1. INTRODUCTION When investigating contaminated sites it is often essential to determine specific pollutants in a large number of ambient air samples. Amongst these sites, polycylic aromatic hydrocarbons (PAHs) are a major class of compounds that hav…     

阴离子嵌段共聚的交联聚苯乙烯的网络链长多分散性与网络结构非均一性

用链长分布不同的活性聚苯乙烯子聚物与二乙烯基苯进行阴离子嵌段共聚,合成了一系列两相模型交联网络。以作者等提出的方法测定了所合成网络的结构非均一因子Z。实验测定的网络结构非均一因子Z与交联前聚苯乙烯活性链的分子量分布宽度指数d之间有平行的相应变化规律,表明所给予的非均一因子Z的物理意义是合理的。同时说明,子聚物链长分布较宽时,在网络的高交联区中除了二乙烯基苯外,还有一些对溶胀无贡献的子聚物以悬挂链的形式存在。     

Small angle X-ray scattering investigations of thermodynamic properties of fluid mixtures

Absolute small angle X-ray studies of concentration fluctuations were performed in order to determine thermodynamic properties of a model blend, consisting ofn-hexane and perfluoro-n-hexane. The quantities which we determined were the second derivate of the Gibbs free energy of mixing with respect to the concentration of the components, the location of the spinodal, interaction and solubility parameters, the energy gradient density coefficient as well as the correlation length of the fluctuations at various compositions and temperatures, particularly in the neighbourhood of the spinodal and the critical point. The data obtained were compared with those obtainable from the well known location of the binodal, to test the reliability of the scattering method.     

Theoretical mechanistic studies on oxidation reactions of some saturated and unsaturated organic molecules

This account describes the results collected by our group during the last years on some themes of environmental/mechanistic interest. Theoretical quantum-mechanical investigations have been carried out to help clarifying the mechanism of some oxidation reactions, which involve mainly unsaturated but also saturated organics as substrates, and, as reactive oxidants, triplet or singlet dioxygen, hydroxyl, ozone, and nitrogen oxides. Depending on the problem, the calculations are either multi-configurational (as CAS-MCSCF, CAS-PT2, MC-QDPT2), or based on the Density Functional Theory for the heavier systems. Research work has thus been developed along the following lines: hydrocarbon oxidations under atmospheric or combustion conditions; definition of a model for soot particles and their interaction with species as HO, O₂, O₃, NO, NO₂, NO₃, etc.; investigation on the reaction mechanism of ¹Δ_g dioxygen with organic unsaturated systems (cycloaddition and ene reactions).     

Determination of trace elements in ambient aerosol samples

A microwave-assisted digestion procedure using HNO₃, HF, and H₂O₂ has been developed for analysis of elements in ambient particulate matter (PM). The samples are collected on cellulose filters and analyzed by inductively coupled plasma mass spectrometry (ICP-MS). The ICP-MS is calibrated with external standards, and recovery of analytes is tested with NIST SRM 1648 Urban Dust. This method has been used to quantify the airborne concentrations of a large number of elements, including Ag, As, Ba, Be, Ca, Cd, Ce, Co, Cr, Cs, Cu, Fe, Ga, K, Li, Mg, Mn, Mo, Ni, Pb, Rb, Se, Sb, Sr, Ti, Tl, V, and Zn. For the majority of these elements, recovery of the NIST SRM is within 15% of the certified values.     

RELATIONSHIPS BETWEEN X—H STRETCHING OVERTONE FREQUENCIES AND BOND LENGTHS/BOND ANGLES

A relationship between the X-H (X = N, O, C, and so on) equilibrium bond length in a Morse oscillator and the X-H stretching overtone frequency shifts is obtained theoretically. We use the equation to discuss the empirical linear relationships that have been proposed for heterocyclics, alkanes and fluorinated benzenes. On the other hand, a unified relationship between the X-H bond angles and the experimental quantities (ω(?) and the coupling strength λ) is also presented for XH2, XH, and XH4 molecules or molecular fragments. Calculations of X-H bond angles for a number of molecules show that the results from our equations are in excellent agreement with the experimental values. Also we can extract the information of relative magnitude of bond coupling force field.     

Melt‐state polymer chain dimensions as a function of temperature

The unperturbed chain dimensions (〈R²〉_o/M) of cis/trans‐1,4‐polyisoprene, a near‐atactic poly(methyl methacrylate), and atactic polyolefins were measured as a function of temperature in the melt state via small‐angle neutron scattering (SANS). The polyolefinic materials were derived from polydienes or polystyrene via hydrogenation or deuteration and represent structures not encountered commercially. The parent polymers were prepared via lithium‐based anionic polymerizations in cyclohexane with, in some cases, a polymer microstructure modifier present. The polyolefins retained the near‐monodisperse molecular weight distributions exhibited by the precursor materials. The melt SANS‐based chain dimension data allowed the evaluation of the temperature coefficients [dln 〈R²〉_o/dT(κ)] for these polymers. The evaluated polymers obeyed the packing length (p)‐based expressions of the plateau modulus, G = kT/np³ (MPa), and the entanglement molecular weight, M_e = ρN_anp³ (g mol^?1), where n_t denotes the number (～21) of entanglement strands in a cube with the dimensions of the reptation tube diameter (d_t) and ρ is the chain density. The product np³ is the displaced volume (V_e) of an entanglement that is also expressible as pd or kT/G. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1768–1776, 2002     

Material transport between the atmosphere and sediment of the Lake Balaton

A monitoring system was developed to gain information on the present level of pollutants in the Lake Balaton, Hungary. Determination of 13 polycyclic aromatic hydrocarbons (PAHs) and inorganic pollutants (mostly toxic metals) in aerosol, precipitation and sediment samples was carried out. The aim of collecting aerosol and precipitate samples in the same site at the same period was to determine the distribution of elements in two depositions. For the fractionation by particle size, aerosols were sampled by a cascade impactor. A simple three-stage sequential leaching procedure was applied to establish the distribution of metals among environmentally mobile, bound to carbonates and oxides, and environmentally immobile, (bound to silicates) fractions in aerosols. Sediment samples were collected from 17 different sites inside of the lake and 10 sites at harbors at 30–70 cm in depth. Core samples were cut to 10-cm pieces, dried at room temperature, and finally passed through a 63-μm sieve. Total concentrations of elements were determined by atomic absorption spectrometry (AAS) after an acidic digestion. The concentrations of PAHs were determined by HPLC method with fluorescence detection.In aerosol samples collected from September 6, 2002 to January 26, 2003, concentration of Cd was <0.1 μg/m³, and the majority of Cd has been found in the mobile fraction. Cadmium was associated to particles between 0.25 and 2 μm indicating the anthropogenic origin. Similar distribution of Pb was obtained in all seasons, and the highest concentration of Pb was found as 8.6 ng/m³ in particle size of 0.7 and 1.4 μm. Results of total concentration of elements of bottom sediments of the Lake Balaton and harbors were compared to Interim Sediment Quality Guideline (ISQG) values and the Probable Effect Level (PEL) values. Data showed that the average concentrations of elements were usually less than those of ISQGs and other background data for soils and geochemical values. The sediment is not polluted and its disposal is feasible. There is no direct correlation between the concentration of elements deposited onto the surface of the lake from dry and wet deposition and the upper part of the sediment. So, from the budget of the deposition, the concentration of elements in the upper layer of the sediment cannot be predicted.Seasonal changes of the concentration of PAHs in aerosol was observed, samples collected at winter contained the highest values. In December–January 2002/2003, the wet deposition was found as 64 μg/m² period. Among the individual compounds, the wet deposition rate of phenantrane, fluoranthene and pyrene was dominant, while for dry deposition, these compounds were fluoranthene and pyrene. The concentrations of ∑PAHs found for all sites and depth of sediment samples ranged from 11 to 1734 μg/kg dry weight with an average of 132 μg/kg. These values represent a quite low pollution level compared to other sediment with anthropogenic influence. Based on the results, it can be definitely confirmed that the chemical quality of the water and sediment of the Lake Balaton is satisfactory.     

Simultaneous Determination of Triptolide and Tripdiolide in Extract of Tripterygium wilfordii Hook. f. by LC–APCI-MS

A novel method using liquid chromatography coupled with atmospheric pressure chemical ionization mass spectrometry in the negative selected ion monitoring mode has been developed and validated for rapid simultaneous determination of triptolide and tripdiolide in the extract of Tripterygium wilfordii Hook. f. The molecular ions m/z [M–H]⁻ 359 and 375 were selected for the quantification in selected ion monitoring mode for triptolide and tripdiolide. Standard calibration curve was linear over the concentration range of 0.12–24 and 0.15–30 μg mL⁻¹ for triptolide and tripdiolide. The relative standard deviations of intra- and inter-day were in the range of 4.7–9.9 and 8.9–12.6%. The average recoveries were between 96.4 and 104.6%. The limits of quantitation were 2.0 × 10⁻³ and 2.5 × 10⁻³ μg mL⁻¹ for triptolide and tripdiolide.     

Correlation analysis of quantum chemical data and the polarizability effect in H-complexes

The study is concerned with analysis of the energies of formation (E), frequency shifts (Δν) in IR spectra, ionization potentials (IP) of H-complexes, hydrogen bond lengths (r), and spin densities (sd) in H-complexes involving radical cations, obtained from quantum chemical calculations for 20 series of H-complexes. It was for the first time established that the E, IP, r, and sd values and the changes in enthalpy (δH) depend not only on the inductive and resonance effects but also on the polarizability effect of the substituents bound to the donor and acceptor centers in the H-complexes. Interrelations between the polarizability effect and the molecular structure of H-complexes are considered. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 602–608, April, 2006.