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- ItemExposure and Respiratory Tract Deposition Dose of Equivalent Black Carbon in High Altitudes(Basel, Switzerland : MDPI AG, 2020) Madueño, Leizel; Kecorius, Simonas; Andrade, Marcos; Wiedensohler, AlfredThe traffic microenvironment accounts for a significant fraction of the total daily dose of inhaled air pollutants. The adverse effects of air pollution may be intensified in high altitudes (HA) due to increased minute ventilation (MV), which may result in higher deposition doses compared to that at sea level. Despite this, air quality studies in regions with combined high pollution levels and enhanced inhalation are limited. The main goals of this study are to investigate how the choice of travel mode (walking, microbus, and cable car ride) determines (i) the personal exposure to equivalent black carbon (eBC) and (ii) the corresponding potential respiratory deposited dose (RDD) in HA. For this investigation, we chose La Paz and El Alto in Bolivia as HA representative cities. The highest eBC exposure occurred in microbus commutes (13 μg m-3), while the highest RDD per trip was recorded while walking (6.3 μg) due to increased MV. On the other hand, the lowest eBC exposure and RDD were observed in cable car commute. Compared with similar studies done at sea level, our results revealed that a HA city should reduce exposure by 1.4 to 1.8-fold to achieve similar RDD at sea level, implying that HA cities require doubly aggressive and stringent road emission policies compared to those at sea level. © 2020 by the authors.
- ItempH- and Temperature-Dependent Kinetics of the Oxidation Reactions of OH with Succinic and Pimelic Acid in Aqueous Solution(Basel, Switzerland : MDPI AG, 2020) Schaefer, Thomas; Wen, Liang; Estelmann, Arne; Maak, Joely; Herrmann, HartmutRate constants for the aqueous-phase reactions of the hydroxyl radical with the dicarboxylic acids, succinic acid and pimelic acid were determined using the relative rate technique over the temperature range 287 K ≤ T ≤ 318 K and at pH = 2.0, 4.6 or 4.9 and 8.0. OH radicals were generated by H2O2 laser flash photolysis while thiocyanate was used as a competitor. The pH values were adjusted to obtain the different speciation of the dicarboxylic acids. The following Arrhenius expressions were determined (in units of L mol-1 s-1): succinic acid, k(T, AH2) (2.1 x 0.1) ± 1010 exp[(-1530 x 250 K)/T], k(T, AH-) (1.8 x 0.1) ± 1010 exp[(-1070 x 370 K)/T], k(T, A2-) (2.9 x 0.2) ± 1011 exp[(-1830 x 350 K)/T] and pimelic acid, k(T, AH2) (7.3 x 0.2) ± 1010 exp[(-1040 x 140 K)/T], k(T, AH-) (1.8 x 0.1) ± 1011 exp[(-1200 x 240 K)/T], k(T, A2-) (1.4 x 0.1) ± 1012 exp[(-1830 x 110 K)/T]. A general OH radical reactivity trend for dicarboxylic acids was found as k(AH2) < k(AH-) < k(A2-). By using the pH and temperature dependent rate constants, source and sinking processes in the tropospheric aqueous phase can be described precisely. © 2020 by the authors.
- ItemDifferences and Similarities of Central Asian, African, and Arctic Dust Composition from a Single Particle Perspective(Basel, Switzerland : MDPI AG, 2020) Kandler, Konrad; Schneiders, Kilian; Heuser, Johannes; Waza, Andebo; Aryasree, Sudharaj; Althausen, Dietrich; Hofer, Julian; Abdullaev, Sabur F.; Makhmudov, Abduvosit N.Mineral dust composition affects a multitude of processes in the atmosphere and adjacent compartments. Dust dry deposition was collected near source in northwest Africa, in Central Asia, and on Svalbard and at three locations of the African outflow regime. Samples were subjected to automated scanning electron microscopy with energy-dispersive X-ray analysis to obtain size and composition of 216,000 individual particles. Results show low temporal variation in estimated optical properties for each location, but considerable differences between the African, Central Asian, and Arctic regimes. No significant difference was found between the K-feldspar relative abundances, indicating comparable related ice-nucleation abilities. The mixing state between calcium and iron compounds was different for near source and transport regimes, potentially in part due to size sorting effects. As a result, in certain situations (high acid availability, limited time) atmospheric processing of the dust is expected to lead to less increased iron solubility for near-source dusts (in particular for Central Asian ones) than for transported ones (in particular of Sahelian origin). © 2020 by the authors. Licensee MDPI, Basel, Switzerland.
- ItemUnmanned Aerial Systems for Investigating the Polar Atmospheric Boundary Layer—Technical Challenges and Examples of Applications(Basel, Switzerland : MDPI AG, 2020) Lampert, Astrid; Altstädter, Barbara; Bärfuss, Konrad; Bretschneider, Lutz; Sandgaard, Jesper; Michaelis, Janosch; Lobitz, Lennart; Asmussen, Magnus; Damm, Ellen; Käthner, Ralf; Krüger, Thomas; Lüpkes, Christof; Nowak, Stefan; Peuker, Alexander; Rausch, Thomas; Reiser, Fabian; Scholtz, Andreas; Zakharov, Denis Sotomayor; Gaus, Dominik; Bansmer, Stephan; Wehner, Birgit; Pätzold, FalkUnmanned aerial systems (UAS) fill a gap in high-resolution observations of meteorological parameters on small scales in the atmospheric boundary layer (ABL). Especially in the remote polar areas, there is a strong need for such detailed observations with different research foci. In this study, three systems are presented which have been adapted to the particular needs for operating in harsh polar environments: The fixed-wing aircraft M2AV with a mass of 6 kg, the quadrocopter ALICE with a mass of 19 kg, and the fixed-wing aircraft ALADINA with a mass of almost 25 kg. For all three systems, their particular modifications for polar operations are documented, in particular the insulation and heating requirements for low temperatures. Each system has completed meteorological observations under challenging conditions, including take-offand landing on the ice surface, low temperatures (down to-28 °C), icing, and, for the quadrocopter, under the impact of the rotor downwash. The influence on the measured parameters is addressed here in the form of numerical simulations and spectral data analysis. Furthermore, results from several case studies are discussed: With the M2AV, low-level flights above leads in Antarctic sea ice were performed to study the impact of areas of open water within ice surfaces on the ABL, and a comparison with simulations was performed. ALICE was used to study the small-scale structure and short-term variability of the ABL during a cruise of RV Polarstern to the 79° N glacier in Greenland. With ALADINA, aerosol measurements of different size classes were performed in Ny-Alesund, Svalbard, in highly complex terrain. In particular, very small, freshly formed particles are difficult to monitor and require the active control of temperature inside the instruments. The main aim of the article is to demonstrate the potential of UAS for ABL studies in polar environments, and to provide practical advice for future research activities with similar systems. © 2020 by the authors.