2020, Laj, Paolo, Bigi, Alessandro, Rose, Clémence, Andrews, Elisabeth, Lund Myhre, Cathrine, Collaud Coen, Martine, Lin, Yong, Wiedensohler, Alfred, Schulz, Michael, Ogren, John A., Fiebig, Markus, Prenni, Anthony, Reisen, Fabienne, Romano, Salvatore, Sellegri, Karine, Sharma, Sangeeta, Schauer, Gerhard, Sheridan, Patrick, Sherman, James Patrick, Schütze, Maik, Schwerin, Andreas, Tuch, Thomas, Sohmer, Ralf, Sorribas, Mar, Steinbacher, Martin, Sun, Junying, Titos, Gloria, Toczko, Barbara, Tulet, Pierre, Tunved, Peter, Vakkari, Ville, Velarde, Fernando, Velasquez, Patricio, Villani, Paolo, Vratolis, Sterios, Wang, Sheng-Hsiang, Weinhold, Kay, Gliß, Jonas, Weller, Rolf, Yela, Margarita, Yus-Diez, Jesus, Zdimal, Vladimir, Zieger, Paul, Zikova, Nadezda, Mortier, Augustin, Pandolfi, Marco, Petäja, Tuukka, Kim, Sang-Woo, Aas, Wenche, Putaud, Jean-Philippe, Mayol-Bracero, Olga, Keywood, Melita, Labrador, Lorenzo, Aalto, Pasi, Ahlberg, Erik, Alados Arboledas, Lucas, Alastuey, Andrés, Andrade, Marcos, Artíñano, Begoña, Ausmeel, Stina, Arsov, Todor, Asmi, Eija, Backman, John, Baltensperger, Urs, Bastian, Susanne, Bath, Olaf, Beukes, Johan Paul, Brem, Benjamin T., Bukowiecki, Nicolas, Conil, Sébastien, Couret, Cedric, Day, Derek, Dayantolis, Wan, Degorska, Anna, Eleftheriadis, Konstantinos, Fetfatzis, Prodromos, Favez, Olivier, Flentje, Harald, Gini, Maria I., Gregorič, Asta, Gysel-Beer, Martin, Hallar, A. Gannet, Hand, Jenny, Hoffer, Andras, Hueglin, Christoph, Hooda, Rakesh K., Hyvärinen, Antti, Kalapov, Ivo, Kalivitis, Nikos, Kasper-Giebl, Anne, Kim, Jeong Eun, Kouvarakis, Giorgos, Kranjc, Irena, Krejci, Radovan, Kulmala, Markku, Labuschagne, Casper, Lee, Hae-Jung, Lihavainen, Heikki, Lin, Neng-Huei, Löschau, Gunter, Luoma, Krista, Marinoni, Angela, Martins Dos Santos, Sebastiao, Meinhardt, Frank, Merkel, Maik, Metzger, Jean-Marc, Mihalopoulos, Nikolaos, Nguyen, Nhat Anh, Ondracek, Jakub, Pérez, Noemi, Perrone, Maria Rita, Petit, Jean-Eudes, Picard, David, Pichon, Jean-Marc, Pont, Veronique, Prats, Natalia

Aerosol particles are essential constituents of the Earth's atmosphere, impacting the earth radiation balance directly by scattering and absorbing solar radiation, and indirectly by acting as cloud condensation nuclei. In contrast to most greenhouse gases, aerosol particles have short atmospheric residence times, resulting in a highly heterogeneous distribution in space and time. There is a clear need to document this variability at regional scale through observations involving, in particular, the in situ near-surface segment of the atmospheric observation system. This paper will provide the widest effort so far to document variability of climate-relevant in situ aerosol properties (namely wavelength dependent particle light scattering and absorption coefficients, particle number concentration and particle number size distribution) from all sites connected to the Global Atmosphere Watch network. High-quality data from almost 90 stations worldwide have been collected and controlled for quality and are reported for a reference year in 2017, providing a very extended and robust view of the variability of these variables worldwide. The range of variability observed worldwide for light scattering and absorption coefficients, single-scattering albedo, and particle number concentration are presented together with preliminary information on their long-term trends and comparison with model simulation for the different stations. The scope of the present paper is also to provide the necessary suite of information, including data provision procedures, quality control and analysis, data policy, and usage of the ground-based aerosol measurement network. It delivers to users of the World Data Centre on Aerosol, the required confidence in data products in the form of a fully characterized value chain, including uncertainty estimation and requirements for contributing to the global climate monitoring system.

2020, Madueño, Leizel, Kecorius, Simonas, Andrade, Marcos, Wiedensohler, Alfred

The 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.

2019, Chauvigné, Aurélien, Aliaga, Diego, Sellegri, Karine, Montoux, Nadège, Krejci, Radovan, Močnik, Griša, Moreno, Isabel, Müller, Thomas, Pandolfi, Marco, Velarde, Fernando, Weinhold, Kay, Ginot, Patrick, Wiedensohler, Alfred, Andrade, Marcos, Laj, Paolo

This study documents and analyses a 4-year continuous record of aerosol optical properties measured at the Global Atmosphere Watch (GAW) station of Chacaltaya (CHC; 5240a.s.l.), in Bolivia. Records of particle light scattering and particle light absorption coefficients are used to investigate how the high Andean Cordillera is affected by both long-range transport and by the fast-growing agglomeration of La Paz-El Alto, located approximately 20km away and 1.5km below the sampling site. The extended multi-year record allows us to study the properties of aerosol particles for different air mass types, during wet and dry seasons, also covering periods when the site was affected by biomass burning in the Bolivian lowlands and the Amazon Basin. The absorption, scattering, and extinction coefficients (median annual values of 0.74, 12.14, and 12.96Mm-1 respectively) show a clear seasonal variation with low values during the wet season (0.57, 7.94, and 8.68Mm-1 respectively) and higher values during the dry season (0.80, 11.23, and 14.51Mm-1 respectively). The record is driven by variability at both seasonal and diurnal scales. At a diurnal scale, all records of intensive and extensive aerosol properties show a pronounced variation (daytime maximum, night-time minimum), as a result of the dynamic and convective effects. The particle light absorption, scattering, and extinction coefficients are on average 1.94, 1.49, and 1.55 times higher respectively in the turbulent thermally driven conditions than the more stable conditions, due to more efficient transport from the boundary layer. Retrieved intensive optical properties are significantly different from one season to the other, reflecting the changing aerosol emission sources of aerosol at a larger scale. Using the wavelength dependence of aerosol particle optical properties, we discriminated between contributions from natural (mainly mineral dust) and anthropogenic (mainly biomass burning and urban transport or industries) emissions according to seasons and local circulation. The main sources influencing measurements at CHC are from the urban area of La Paz-El Alto in the Altiplano and from regional biomass burning in the Amazon Basin. Results show a 28% to 80% increase in the extinction coefficients during the biomass burning season with respect to the dry season, which is observed in both tropospheric dynamic conditions. From this analysis, long-term observations at CHC provide the first direct evidence of the impact of biomass burning emissions of the Amazon Basin and urban emissions from the La Paz area on atmospheric optical properties at a remote site all the way to the free troposphere. © Author(s) 2019.