Long range transport of biomass aerosol to Greenland: Multi-spectroscopic investigation of particles deposited in the snow

Summary Results are given from the NIST component of a pilot (“winter-over”) study of seasonal patterns of natural and anthropogenic species in air and snow transported to Summit, Greenland. Central to this research is the quantitative apportionment of fossil and biomass particulate carbon, based on advanced (micromolar) ¹⁴C accelerator mass spectrometry (AMS) applied to remote snow samples containing as little as 9 µg C/kg. The measurements were made practicable through stringent attention to the nature and sources of the isotopic-chemical blank, resulting in a blank reduction from »5 µg C to <0.5 µg C. An important result of this work is the first evidence of a seasonal pattern in biomass-C particles in Greenland snow. Although ¹⁴C AMS data serve to resolve fossil and biomass carbon quantitatively, a deeper understanding of the aerosol sources and character demands a multidisciplinary approach. This is illustrated with “multi-spectrometric” macro- and micro-analytical data for two cases involving substantial incursions of biomass aerosol to the Summit, Greenland snow.     

Iron-modified mesoporous SBA-15 silica: Preparation and characterization studies

Fe-SBA-15 materials with different Si/Fe ratios (Si/Fe = 100, 60, 15) have been synthesized by hydrothermal method and characterized by several spectroscopic techniques. Electron spin resonance and Mössbauer spectroscopy, along with electron microscopy and X-ray diffraction, allowed differentiation of several iron species. These species correspond to hematite particles, very small “isolated” or oligomeric Fe^III species possibly incorporated in the mesoporous silica wall, and Fe^III oxide clusters either isolated or agglomerated, forming “rafts” at the surface of the silica and exhibiting ferromagnetic ordering. Because of their agglomeration, these clusters appear with a two-peak size distribution, with one peak corresponding to the isolated clusters formed in the mesopores and still embedded in them and the other corresponding to the agglomerates spread on the surface of the mesoporous silica particles.     

“In situ” ESR and UV-visible spectroscopic studies of iron phthalocyanine films deposited on gold electrodes

The electrochemical behaviour of iron phthalocyanine (Fe^IIPc) films, supported on gold substrates, was studied in 3.5 M NaOH solution, using cyclic voltammetry and coupled “in situ” ESR and UV-visible spectroscopic techniques. Two types of electron transfer were observed in the potential range from −0.45 to −1.0 V vs. Hg/HgO. According to the “in situ” spectroscopy investigations, these two processes were assigned respectively to electron transfers involving first the ligand ring, and then the centre iron ion.     

Investigation of a cylindrical chemosorptive denuder for sampling and phase separation of toluene diisocyanate aerosols

A cylindrical chemosorptive denuder in series with a glass fibre filter has been evaluated for sampling toluene diisocyanate (TDI) aerosols. The sampler is designed for measuring personal exposure to diisocyanates. Several denuder coatings and derivatising reagents were investigated. Dimethylpolysiloxane (SE-30) and 5% phenyl dimethylpolysiloxane (SE-54) with either dibutylamine (DBA) or dipentylamine (DPeA) as derivatising reagents yielded the lowest vapour breakthrough (the amount (%) of the vapour that passes through the denuder), close to values predicted by theory. Immobilisation of the SE-30 denuder coating by in-situ cross-linking yielded comparable results. With an SE-30/DBA-coated denuder operating within an airflow range of 100–500 mL min^–1, the phase separation was shown to be consistent with theoretical predictions derived by use of the Gormley–Kennedy equation. This provides a means of calculating the vapour breakthrough and correcting experimentally obtained values with regard to vapour–particulate phase distribution, suggesting that the denuder can provide accurate phase-distribution measurements. The SE-30/DBA denuder can be used over a concentration range spanning nearly six orders of magnitude. Its capacity is sufficient to perform 15-min exposure measurements of a TDI aerosol with air concentrations as high as 1,700 g m^–3, 40 times higher than the Swedish occupational exposure limit (OEL). At the other end of the range, the estimated limit of detection (LOD) was less than 2 ng m^–3 for both the vapour and the aerosol phases when LC–ESI–MS–MS was used for chemical analysis.Electronic Supplementary Material Supplementary material for this article is available at     

Bridging the gaps in analytical atomic absorption spectrometry

The techniques of analytical, valence electron, atomic spectrometry (absorption, fluorescence and emission), by themselves, are mainly for the determination of the amount of an element in a sample which has been prepared as a . For a large fraction of trace element analysis such an approach is satisfactory. However, there are some other very important requirements in trace element analysis not now adequately being addressed by analytical atomic spectrometry. A selection of these, familiar to the present writer, will be covered in this presentation. Some interesting initiatives to “bridge the gaps” are now being made. The topics to be discussed are; elemental speciation, direct analysis of solids, elemental and natural isotope analysis using plasma sources, micro analysis by laser probe and vapour generation approaches to improved detection limits. This is not intended to be an exhaustive review of these subject areas but will present material of interest together with recently published key papers. Greatest emphasis is given to the very important topic of speciation.     

Conventional and unconventional infrared spectrometry and their quantitative interpretation

In condensed matter, optical properties can be described by a dielectric function (DF), and the structures observed in spectra are then related to the poles and zeros of the DF. As an example, model functions are calculated by a fit to measured spectroscopic data for polystyrene and silica. The first material shows weak, narrow bands and the latter strong, broad bands and a negative real part of the DF.Based on these model DFs, spectra are simulated which are expected to be obtained by “conventional” methods such as transmittance or reflectance measurements, or by “unconventional” methods such as reflectance at oblique incidence, diffuse reflectance, photoacoustic spectroscopy and attenuated total reflectance. A variety of simulated, typical spectra are plotted as a small “atlas”. Conditions are discussed that allow a straightforward procedure for interpreting the spectra quantitatively, i.e., the evaluation of the resonance frequency and the concentration of the oscillators under consideration.It is shown that for systems characterized by weak, narrow oscillator lines, mostly an intuitive interpretation is possible, looking only at the position and strength of “lines” in the spectra. Materials showing strong polar vibrations, however, require more sophisticated procedures for interpreting the spectra.     

Theoretical treatment of multiple site reactivity in large molecules

The method of electrostatic potentials is generalized via a double perturbation theory to describe the simultaneous attack of a large molecule by two or more charged species. The interaction term is found to reproduce accurately the full “super-molecule” calculation. The scheme is illustrated by treating the diprotonation of adenine and N7-methyladenine. For adenine, the most stable diprotonated species is found to be the N1, N7 combination, while the N3, N9 couple is predicted for the N7 substituted derivative if N3 is the first protonation site.     

Synthesis and properties of novel thermotropic liquid crystalline copoly(ester-imide)s

Four novel copoly(ester-imide)s based on 3,3',4,4'-biphenyltetracarboxylic dianhydride,bis(trimellitic acid anhydride) phenyl ester and di-p-aminophenyl ester of dicarboxylic acids were synthesized via two-step method in order to investigate whether two imide mesogenic units with different conformation and polarity could control the formation of LC-phase.Polarizes light microscopy(PLM) and differential scanning calorimetry(DSC) have shown that three polymers formed the nematic phase with thread schlieren...     

Characteristics of Size-Fractionated Urban Aerosols and Trace Gases in Budapest

An air pollution study was conducted at two urban residential sites in Budapest from 9 April to 17 May 1996. Size-fractionated aerosol samples were simultaneously collected on a daily basis, and meteorological conditions were recorded at both sampling sites. Stacked filter units (SFUs) with an upper size inlet cutoff were used as sampling devices separating the urban aerosol into coarse [about 2- to 10-μm equivalent aerodynamic diameter (EAD)] and fine (<2 μm EAD) size fractions. In addition, atmospheric concentrations of some criteria pollutants, i.e., NO, NO₂, SO₂, CO, and total mass of the suspended particulate matter (TSP) were measured every half-hour at one of the sampling sites with commercial equipment. The SFU filters were weighed and analyzed by a light reflectance technique, particle-induced X-ray emission analysis, and instrumental neutron activation analysis. Atmospheric concentrations for 31 aerosol species have been obtained so far. The analytical results were used to characterize the levels and the multielemental composition of the urban aerosol at both sampling sites and for both size fractions, to investigate the atmospheric concentrations and diurnal variation of the criteria pollutants, and to compare the time trends of aerosols and trace gases. The present paper reports on the status of the air pollution study and gives a discussion of the results.     

Versuche mit einem tiefgekühlten Zwillingsholkathoden-Interferometer—Spektrometer—II. Das optische System

The optical arrangement consists of a double beam imaging system an interferometer spectrometer attached to it. The two cathode spots are projected by the imaging system to the flip-flop mirror in the optical axis of the interferometer. One of the two cathode spots can be projected either to the slit of a spectroscope or to that of a spectrograph, respectively, for preliminary observation. For measuring the intensity ratios, neutral wedges are built into the imaging system. The principal component of the system is a piezo-electrically controlled Fabry—Perot interferometer spectrometer. The deparallelisation of the Fabry—Perot mirrors during the scanning, caused by the “fatigue” of the piezo-electrical system, was eliminated using suitable circuits. The good performance of the interferometer was checked by measuring of the finesse and resolution of selected spectral lines of different spectral lamps and the resonance radiation of a He---Ne gas laser. The optical set-up is suitable for general spectroscopic and spectrographic observations, for measuring radial intensity distributions, for obtaining high resolution spectra and for the determination of intensity ratios in the radiation of the twin hollow cathode source in the visible spectral range.     

Effect of spatial inhomogeneities on the rate of homogeneous nucleation in systems with aerosol particles

The presence of growing particles in a system leads to spatial inhomogencities in the vapor concentration. The effect of these spatial variations on the rate of formation of new particles by homogeneous nucleation is examined theoretically using a cell model. Results indicate that the presence of these inhomogeneities in systems both with and without initial aerosol has generally little effect on the final number concentration of particles following a nucleation “event.”     

Determination of fatty acids in atmospheric samples via GC/MS

Summary Atmospheric precipitation and aerosol samples are characterized by a complex mixture of several organic compounds. A simple method for the simultaneous determination of the main compound classes by GC/MS is presented. In detail, seasonal variations of C₈–C₃₂ fatty acids in precipitation in a semirural area have been studied. Total fatty acids concentrations of 7–53 g/l were detected. Summer rain is characterized by high amounts of fatty acids >C₂₀ and lower amounts of C₁₁–C₂₀ species. Two effects may be responsible: larger emission rates of fatty acids during vegetation periods and an increased influence of vapour phase due to higher temperatures during summer. CPI values showed no general trend; lower CPI values for winter rain could not be observed. This would be expected if anthropogenic sources play an important role. Monounsaturated fatty acids (C_16:1, C_18:1) were more abundant during winter than in summer. High concentrations of polyunsaturated fatty acids (C_18:x) could be detected during summer. High relative concentrations of the potential oxidation products of the unsaturated species, nonanedioic acid and w-oxononanoic acid, are associated with relatively low concentrations of their precursors.     

沉积有机质的加氢热解及其地球化学信息研究

用加氢热解(hydropyrolysis)释放高演化源岩干酪根和沥青分子网络中共价键结合的生物标志物,在恢复原始有机地球化学信息方面具有重要的意义,可应用于源岩有机质生源确定、成熟度确定、古沉积环境判识以及油/源对比等.实验表明,样品沥青“A“与加氢热解产物中生物标志物的组成存在一定的差异,加氢热解产物中含有丰富的地球化学信息.加氢热解具有产物收率高、结构重排少、生物特征保持完整等特点,能够合理地释放出沉积有机质分子骨架中具有原生性的组分,保持完整的原始生物标志物结构和立体化学特征.加氢热解技术为油气地球化学研究开辟了新途径.     

Neue C-spektroskopische untersuchungen zur struktur von allylmetall-verbindungen

High-resolution ¹³C NMR spectra of terminally monodeuterated allyl(earth)-alkalimetal compounds confirm earlier structure assignments: allylmagnesium bromide exists in a σ-covalent structure, which rapidly and reversibly goes over into its “metallomeric” mirror-image; allyllithium forms a distorted π-complex; allylpotassium and allylcaesium have the shape of perfectly symmetrical or slightly asymmetrical π-complexes. No NMR spectroscopic evidence is found in tetrahydrofuran solution for the presence of aggregates and mixed aggregates resulting from dimerization or oligomerization of monomeric allylmetal species.     

An infrared spectroscopic study of hydrogen bonding in ethyl phenol: A model system for polymer phenolics

A detailed analysis of the bands appearing in the OH stretching region of the infrared spectrum of ethyl phenol solutions is presented. In cyclohexane solutions, the band due to “free” (non-hydrogen-bonded groups) contains overlapping contributions from both monomeric and end-group species. Other assignments are made on the basis of whether the proton and oxygen in a particular OH group are both involved in hydrogen bonds (as “donors” and “acceptors”, respectively), or if only the proton is acting as a donor. The strongest band in the spectra obtained at the highest concentration of ethyl phenol is due to OH groups present in linear chains of hydrogen-bonded OH groups (as recognized in numerous other studies), but a band due to cyclic trimers has also been identified. The assignment of other modes is more uncertain and various possibilities are discussed. In toluene solutions, assignments are more complicated, because bands due to OH–π hydrogen bonds are observed instead of free groups. Finally, the data from cyclohexane solutions was used to calculate equilibrium constants capable of describing the distribution of species present. A new methodology for determining the equilibrium constant describing association in the form of dimers is described.     

Recent developments and applications of NSE in soft matter

Neutron Spin Echo is probably the youngest spectroscopic method in neutron scattering. After a brief introduction I will try to give a short account of recent progress on the instrumentation. Through some recent examples I will illustrate that NSE is a powerful tool in colloid science applied to both “old” and recent problems. With new instrumentation we will be able to tackle new problems and one of those areas in which there has been recently exciting progress is the field of surface science.     

Controlling Two‐Step Multimode Switching of Dihydroazulene Photoswitches

We present the synthesis and switching studies of systems with two photochromic dihydroazulene (DHA) units connected by a phenylene bridge at either para or meta positions, which correspond to a linear or cross‐conjugated pathway between the photochromes. According to UV/Vis absorption and NMR spectroscopic measurements, the meta‐phenylene‐bridged DHA–DHA exhibited sequential light‐induced ring openings of the two DHA units to their corresponding vinylheptafulvenes (VHFs). Initially, the VHF–DHA species was generated, and, ultimately, after continued irradiation, the VHF–VHF species. Studies in different solvents and quantum chemical calculations indicate that the excitation of DHA–VHF is no longer a local DHA excitation but a charge‐transfer transition that involves the neighboring VHF unit. For the linearly conjugated para‐phenylene‐bridged dimer, electronic communication between the two units is so efficient that the photoactivity is reduced for both the DHA–DHA and DHA–VHF species, and DHA–DHA, DHA–VHF, and VHF–VHF were all present during irradiation. In all, by changing the bridging unit, we can control the degree of stepwise photoswitching.     

Distribution of Co(II) between immiscible phases formed in water + 1-butanol system

Heterogeneous equilibria for the distribution of Co²⁺ between the two layers formed in water + 1-butanol (1-BuOH) system have been investigated at ambient conditions. The study (confined to only 28 °C) reveals an interesting feature of the distribution equilibrium for the system whereby Co²⁺ has been found to exist in both the phases as the same species namely its aqua-complex thus directly demonstrating strong selective solvation of Co²⁺ by the water molecules. Almost constant values of refractive indices and densities were exhibited by the two layers regardless in which ratio the component liquids were mixed together. However, relative volumes of the layers varied smoothly on gradually changing the ratio of the two liquids in the overall “solvent system”. Also the Co²⁺ distribution coefficient (K_D) changed appreciably on going to alcohol-richer “solvent systems” but K_D remained fairly constant on adding different amounts of cobalt dichloride to any given “solvent system”.