Role of iodine oxoacids in atmospheric aerosol nucleation.

Iodic acid (HIO3) is known to form aerosol particles in coastal marine regions, but predicted nucleation and growth rates are lacking. Using the CERN CLOUD (Cosmics Leaving Outdoor Droplets) chamber, we find that the nucleation rates of HIO3 particles are rapid, even exceeding sulfuric acid-ammonia rates under similar conditions. We also find that ion-induced nucleation involves IO3 - and the sequential addition of HIO3 and that it proceeds at the kinetic limit below +10°C. In contrast, neutral nucleation involves the repeated sequential addition of iodous acid (HIO2) followed by HIO3, showing that HIO2 plays a key stabilizing role. Freshly formed particles are composed almost entirely of HIO3, which drives rapid particle growth at the kinetic limit. Our measurements indicate that iodine oxoacid particle formation can compete with sulfuric acid in pristine regions of the atmosphere.

Liquid chromatography-dopant-assisted atmospheric pressure photoionization-mass spectrometry: Application to the analysis of aldehydes in atmospheric aerosol particles.

A complete methodology based on LC-anisole-toluene dopant-assisted atmospheric pressure photoionization-IT-MS was developed for the determination of aldehydes in atmospheric aerosol particles. For the derivatization, ultrasound was used to accelerate the reaction between the target analytes and 2,4-dinitrophenylhydrazine. The developed methodology was validated for three different samples, gas phase, ultrafine (Dp = 30 ± 4 nm; where Dp stands for particle diameter) and all-sized particles, collected on Teflon filters. The method quantitation limits ranged from 5 to 227 pg. The accuracy and the potential matrix effects were evaluated using standard addition methodology. Recoveries ranged between 91.7 and 109.9%, and the repeatability and the reproducibility of the method developed between 0.5 and 8.0% and between 2.9 and 11.1%, respectively. The results obtained by the developed methodology compared to those provided by the previously validated method revealed no statistical differences. The method developed was applied to the determination of aldehydes in 16 atmospheric aerosol samples (30 nm and all-sized samples) collected at the Station for Measuring Forest Ecosystem-Atmosphere Relations II during spring 2011. The mean concentrations of aldehydes, and oxidation products of terpenes were between 0.05 and 82.70 ng/m(3).

Aliphatic and aromatic amines in atmospheric aerosol particles: comparison of three ionization techniques in liquid chromatography-mass spectrometry and method development.

A complete methodology was developed for the determination of ten aliphatic and nine aromatic amines in atmospheric aerosol particles. Before the liquid chromatography - tandem mass spectrometric separation and determination, the derivatization reaction of the analytes using dansyl chloride was accelerated by ultrasounds. From three different ionization techniques studied electrospray ionization was superior in terms of sensitivity, linearity, repeatability and reproducibility over atmospheric pressure chemical ionization and photoionization for the target analytes. The method developed was validated for the gas phase, 30 nm and total suspended atmospheric aerosol particles. The method quantification limits ranged between 1.8 and 71.7 pg. The accuracy and the potential matrix effects were evaluated using a standard addition methodology. Recoveries from 92.1% to 109.1%, the repeatability from 0.6% to 8.4% and the reproducibility from 2.3% to 9.8% were obtained. The reliability of the methodology was proved by the statistical evaluation. Finally, the developed methodology was applied to the determination of the target analytes in eight size separated ultrafine particulate (Dp=30±4 nm) samples and in eight total suspended particulate samples collected at the SMEAR II station. The mean concentrations for aliphatic amines were between 0.01 and 42.67 ng m(-3) and for aromatic amines between 0.02 and 1.70 ng m(-3). Thirteen amines were quantified for the first time in 30 nm aerosol particles.

Comprehensive two-dimensional gas chromatography, a valuable technique for screening and semiquantitation of different chemical compounds in ultrafine 30 nm and 50 nm aerosol particles.

Comprehensive two dimensional gas chromatography-time-of-flight mass spectrometry (GC×GC-TOF-MS) was used for screening and semiquantitation of semivolatile organic compounds in aerosol particles. As the volatility was a prerequisite parameter for the analysis, some compounds were transformed via derivatization such as silylation into more volatile ones. The identification of the analytes was made by comparing the GC retention indices and the TOF mass spectra with the NIST and the Golm metabolome database reference libraries. The data treatment was simplified by exploiting an additional classification of the identified compounds, namely the main functional group or specific element present in the molecule leading to different groups of compounds. This methodology was applied to identify compounds in 30 ± 4 nm, 50 ± 5 nm and total suspended particles (TSP) collected during spring and autumn of 2009 and summer of 2010 at the Station for Measuring Forest Ecosystem Atmosphere Relations (SMEAR II) at Hyytiälä (Finland). The number of identified compounds was higher than 400, which were the most relevant compounds present in the samples, in terms of concentrations. The analysis of aerosol particles of different sizes, collected simultaneously, revealed that the number of compounds increased with the particle size whereas the normalized response factor decreased in most of the cases, aldehydes being an exception. This decrease could be associated with the formation or aggregation of new compounds onto the particles when they grow in the atmosphere.

Determination of organic compounds from wood combustion aerosol nanoparticles by different gas chromatographic systems and by aerosol mass spectrometry.

Organic compounds in atmospheric nanoparticles have an effect on human health and the climate. The determination of these particles is challenged by the difficulty of sampling, the complexity of sample composition, and the trace-level concentrations of the compounds. Meeting the challenge requires the development of sophisticated sampling systems for size-resolved particles and the optimization of sensitive, accurate and simple analytical techniques and methods. A new sampling system is proposed where particles are charged with a bipolar charger and size-segregated with a differential mobility analyzer. This system was successfully used to sample particles from wood pyrolysis with particle sizes 30-100nm. Particles were analyzed by four techniques: comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry, gas chromatography-time-of-flight mass spectrometry, gas chromatography-quadrupole mass spectrometry, and aerosol mass spectrometry (aerosol MS). In the chromatographic techniques, particles were collected on a filter and analyzed off-line after sample preparation, whereas in the aerosol MS, particle analysis was performed directly from the particle source. Target compounds of the samples were polyaromatic hydrocarbons and n-alkanes. The analytical techniques were compared and their advantages and disadvantages were evaluated. The sampling system operated well and target compounds were identified in low concentrations.