Originalarbeiten: Neuartiger Ionisationsdetektor zum gaschromatographischen Nachweis von Schadstoffen in Luft

Zur kontinuierlichen Überwachung der Luft auf Schadstoffe werden Analysatoren eingesetzt, die auf dem Prinzip der Aerosolionisationsgasanalyse beruhen. Der nachzuweisende Schadstoff wird in ein Aerosol übergeführt und in einer speziellen Ionisationskammer mit eingebauter Strahlungsquelle detektiert.

Derartige Analysatoren sind nur für den Nachweis eines Schadstoffes geeignet, wobei es schwierig ist. Querempfindlichkeiten zu beseitigen. Der selektive, gleichzeitige Nachweis einer groβen Zahl von Schadstoffen in Luft ist möglich, wenn der Aerosolionisationsgasanalysator so modifiziert wird, daβ er als Detektor für die Gaschromatographie geeignet ist. Diese Anforderung erfüllt ein von den Autoren zum Patent angemeldeter Aerosolionisationsdetektor. Der Aufbau, die Wirkungsweise und erste Ergebnisse mit Halogenkohlenwasserstoffen werden beschrieben.     

Absorption spectra and aqueous photochemistry of β-hydroxyalkyl nitrates of atmospheric interest

Molar absorption coefficients were measured for select alkyl nitrates and β-hydroxyalkyl nitrates in methanol. The presence of the β-hydroxyl group has a relatively minor effect on the absorption spectrum in the vicinity of the weak n → π* transition, which is responsible for photolysis of organic nitrates in the atmosphere. For both alkyl nitrates and β-hydroxyalkyl nitrates, there is an enhancement in the absorption coefficients in solution compared to the gas-phase values. The effect of the β-hydroxyl group on the spectra was modelled with molecular dynamics simulations using an OM2/GUGA-CI Hamiltonian for ethyl nitrate and β-hydroxyethyl nitrate. The simulation provided a qualitatively correct shape of the low energy tail of the absorption spectrum, which is important for atmospheric photochemistry. The role of direct aqueous photolysis in removal of β-hydroxyalkyl nitrates in cloud and fog water was modelled using a relative rate approach, and shown to be insignificant relative to gas-phase photochemical processes and aqueous OH oxidation under typical atmospheric conditions.     

Lunar eclipse theory revisited: Scattered sunlight in both the quiescent and the volcanically perturbed atmosphere

The residual brightness of the shadowed Moon during a lunar eclipse is attributed to unscattered sunlight rays refracted in the Earth's atmosphere. The classical theory of lunar eclipses is built on the premise that the sunlight scattered by the gases and particles in the atmosphere contributes negligibly to the brightness of the eclipsed Moon. The current work revisits the lunar eclipse theory, extending it to accommodate spectrally resolved observations and addressing the role of scattered sunlight. Predictions of both direct and diffuse sunlight are produced by integrating the radiative transfer equations over the Earth's disk. The investigation contemplates scenarios of normal aerosol loading as well as conditions representative of the months and years following a major volcanic eruption. It is shown that omitting scattered sunlight is an acceptable approximation for low and moderate aerosol loadings at visible and longer wavelengths. However, towards the ultraviolet, or at times when the atmosphere contains elevated aerosol amounts, the relative significance of direct and diffuse sunlight may reverse. Spectra of the sunlight that reaches the shadowed Moon during the eclipse are presented to illustrate the distinct contributions from both components. It is also shown that lunar eclipse spectra obtained up to 4-5 years after a major volcanic eruption, such as Mt. Pinatubo's in 1991, will reveal that the stratosphere remains perturbed above background aerosol levels.     

Measuring the thermal conducitivity of uranin

A convenient experimental method for measuring the thermal conductivity of uranin (fluorecein sodium, C₂₀H₁₀O₅Na₂) is described. Two similar blocks of uranin, produced from a strong uranin/water solution, were exposed to one-dimensional steady-state conduction. It was found that, for a mean bulk temperature ranging from ambient up to 55°C, the uranin has a constant thermal conductivity of 0.43 W/mK. Above these temperatures, the material begins to soften and the thermal conductivity is seen to decrease     

Analysis of α‐acyloxyhydroperoxy aldehydes with electrospray ionization–tandem mass spectrometry (ESI‐MSn)

A series of α‐acyloxyhydroperoxy aldehydes was analyzed with direct infusion electrospray ionization tandem mass spectrometry (ESI/MSⁿ) as well as liquid chromatography coupled with the mass spectrometry (LC/MS). Standards of α‐acyloxyhydroperoxy aldehydes were prepared by liquid‐phase ozonolysis of cyclohexene in the presence of carboxylic acids. Stabilized Criegee intermediate (SCI), a by‐product of the ozone attack on the cyclohexene double bond, reacted with the selected carboxylic acids (SCI scavengers) leading to the formation of α‐acyloxyhydroperoxy aldehydes. Ionization conditions were optimized. [M + H]⁺ ions were not formed in ESI; consequently, α‐acyloxyhydroperoxy aldehydes were identified as their ammonia adducts for the first time. On the other hand, atmospheric‐pressure chemical ionization has led to decomposition of the compounds of interest. Analysis of the mass spectra (MS² and MS³) of the [M + NH₄]⁺ ions allowed recognizing the fragmentation pathways, common for all of the compounds under study. In order to get detailed insights into the fragmentation mechanism, a number of isotopically labeled analogs were also studied. To confirm that the fragmentation mechanism allows predicting the mass spectrum of different α‐acyloxyhydroperoxy aldehydes, ozonolysis of α‐pinene, a very important secondary organic aerosol precursor, was carried out. Spectra of the two ammonium cationized α‐acyloxyhydroperoxy aldehydes prepared with α‐pinene, cis‐pinonic acid as well as pinic acid were predicted very accurately. Possible applications of the method developed for the analysis of α‐acyloxyhydroperoxy aldehydes in SOA samples, as well as other compounds containing hydroperoxide moiety are discussed. Copyright © 2013 John Wiley & Sons, Ltd.     

Laboratory millimeter wave measurements of atmospheric aerosols

Measurements made in an untuned resonator by Fourier Transform Spectroscopy of atmospheric aerosols are explained by a pumped phonon model due to Fröhlich.     

Statistical models for spatial patterns of heavy particles in turbulence

The dynamics of heavy particles suspended in turbulent flows is of fundamental importance for a wide range of questions in astrophysics, atmospheric physics, oceanography, and technology. Laboratory experiments and numerical simulations have demonstrated that heavy particles respond in intricate ways to turbulent fluctuations of the carrying fluid: non-interacting particles may cluster together and form spatial patterns even though the fluid is incompressible, and the relative speeds of nearby particles can fluctuate strongly. Both phenomena depend sensitively on the parameters of the system. This parameter dependence is difficult to model from first principles since turbulence plays an essential role. Laboratory experiments are also very difficult, precisely since they must refer to a turbulent environment. But in recent years it has become clear that important aspects of the dynamics of heavy particles in turbulence can be understood in terms of statistical models where the turbulent fluctuations are approximated by Gaussian random functions with appropriate correlation functions. In this review, we summarise how such statistical-model calculations have led to a detailed understanding of the factors that determine heavy-particle dynamics in turbulence. We concentrate on spatial clustering of heavy particles in turbulence. This is an important question because spatial clustering affects the collision rate between the particles and thus the long-term fate of the system.     

Liquid chromatography with tandem mass spectrometry method for the determination of nicotine and minor tobacco alkaloids in electronic cigarette refill liquids and second‐hand generated aerosol

A liquid chromatography with tandem mass spectrometry method for the simultaneous quantification of nicotine and seven minor tobacco alkaloids in both refill liquids for electronic cigarettes and their generated aerosol was developed and validated. The limit of detection and limit of quantification values were 0.3–20.0 and 1.0–31.8 ng/mL, respectively. Within‐laboratory reproducibility was 8.2–14.2% at limit of quantification values and 4.8–12.7% at other concentration levels. Interday recovery was 75.8–116.4%. The method was applied to evaluate the compliance of commercial liquids (n = 95) with their labels and to assess levels of minor alkaloids. Levels of nicotine and its corresponding compounds were also evaluated in generated aerosol. About 47% of samples showed differences above ±10 % of the stated nicotine concentration. About 78% of the “zero nicotine” liquids showed traces in the range of 1.3 ± 0.1–254.0 ± 14.6 μg/mL. Nicotine‐N ′‐oxides, myosmine, and anatabine were the most common minor alkaloids in liquids containing nicotine. Nicotine and N ′‐oxides were detected in all air samples when aerosol was generated from liquids containing nicotine. Nicotine average emissions from electronic cigarette (2.7 ± 0.9 μg/m³) were significantly lower (p < 0.01, t‐test) with respect to conventional cigarette (30.2 ± 1.5 μg/m³).     

Spatial Separation of Individual Substances in Effloresced Crystals of Ternary Ammonium Sulphate/Dicarboxylic Acid/Water Aerosols

This work examines the crystals resulting from the efflorescence of internally mixed aqueous aerosols comprising ammonium sulphate and different dicarboxylic acids. Most studies on the deliquescence of aerosols use previously effloresced aerosols in their experiments. However, during efflorescence a highly supersaturated solution crystallises in a kinetically controlled way unlike the case of thermodynamically controlled crystallisation. Herein the distribution of individual substances within the effloresced crystals is investigated using Raman scanning experiments. The data presented show an intriguingly complex behaviour of these ternary and quarternary aerosols. A spatial separation of substances in the crystals resulting from the efflorescence of previously internally mixed ternary salt/dicarboxylic acid/water aerosol droplets is demonstrated and mechanistic aspects are discussed.