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Chemical characterization of PM2.5 and source apportionment of organic aerosol in New Delhi, India
Urs Baltensperger, Griša Močnik, Surender Singh, Suresh Tiwari, Deewan Bisht, Atul Srivastava, Suneeti Mishra, Navaneeth Thamban, Ashutosh Shukla, Vipul Lalchandani, Francesco Canonaco, Deepika Bhattu, Anna Tobler, Sachchida Tripathi, J. G. Slowik, André S. H. Prévôt, 2020, original scientific article

Abstract: Delhi is one of the most polluted cities worldwide and a comprehensive understanding and deeper insight into the air pollution and its sources is of high importance. We report 5 months of highly time-resolved measurements of non-refractory PM2.5 and black carbon (BC). Additionally, source apportionment based on positive matrix factorization (PMF) of the organic aerosol (OA) fraction is presented. The highest pollution levels are observed during winter in December/January. During that time, also uniquely high chloride concentrations are measured, which are sometimes even the most dominant NR-species in the morning hours. With increasing temperature, the total PM2.5 concentration decreases steadily, whereas the chloride concentrations decrease sharply. The concentrations measured in May are roughly 6 times lower than in December/January. PMF analysis resolves two primary factors, namely hydrocarbon-like (traffic-related) OA (HOA) and solid fuel combustion OA (SFC-OA), and one or two secondary factors depending on the season. The uncertainties of the PMF analysis are assessed by combining the random a-value approach and the bootstrap resampling technique of the PMF input. The uncertainties for the resolved factors range from ±18% to ±19% for HOA, ±7% to ±19% for SFC-OA and ±6 % to ±11% for the OOAs. The average correlation of HOA with eBCtr is R2 = 0.40, while SFC-OA has a correlation of R2 = 0.78 with eBCsf. Anthracene (m/z 178) and pyrene (m/z 202) (PAHs) are mostly explained by SFC-OA and follow its diurnal trend (R2 = 0.98 and R2 = 0.97). The secondary oxygenated aerosols are dominant during daytime. The average contribution during the afternoon hours (1 pm–5 pm) is 59% to the total OA mass, with contributions up to 96% in May. In contrast, the primary sources are more important during nighttime: the mean nightly contribution (22 pm–3 am) to the total OA mass is 48%, with contributions up to 88% during some episodes in April.
Found in: osebi
Keywords: New Delhi, PM2.5, Source apportionment, PMF
Published: 20.07.2020; Views: 1446; Downloads: 0
.pdf Fulltext (4,71 MB)

Elucidating local pollution and site representativeness at the Jungfraujoch, Switzerland through parallel aerosol measurements at an adjacent mountain ridge
Martin Gysel, Maxime Hervo, Urs Baltensperger, Markus Christian Leuenberger, Martine Collaud Coen, Stéphane Affolter, Günther Wehrle, Griša Močnik, Benjamin Brem, Nicolas Bukowiecki, 2021, original scientific article

Abstract: Many long-term air pollution and climate monitoring stations face the issue of increasing anthropogenic activities in their vicinity. Furthermore, the spatial representativeness of the sites is often not entirely understood especially in mountainous terrain with complex topographic features. This study presents a 5-year comparison of parallel aerosol measurements (total particle number concentration and equivalent black carbon mass concentration) at the Jungfraujoch in the Swiss Alps (JFJ, 3580 m a.s.l.), and an adjacent mountain ridge, the Jungfrau East Ridge (JER, 3705 m a.s.l.), in 1000 m air-line distance to the main site. The parallel aerosol measurements reveal characteristic differences in the diurnal variations between the two sites under certain specific meteorological conditions. Our analysis estimates that on 20-40% of the days local activities at the Jungfraujoch have a clear influence on the measured time series of the total aerosol number concentration and the equivalent black carbon mass concentration. This influence is mainly seen in form of strong isolated spikes rather than by an increase in the on-site background concentration. They can thus be flagged during the data quality assurance process and filtered from those measurement parameters available at high time resolution. Removing the spikes from the original time series results in daily mean values for the total aerosol number concentration and equivalent black carbon mass concentration that are 5-10 % lower compared to the original signals. During nighttime with hardly any local pollution sources that cause spikes this percentage decreases towards 0%. The signal baselines at the Jungfraujoch and Jungfrau East Ridge correlate well during more than 50% of the days.
Found in: osebi
Keywords: aerosol long-term monitoring, equivalent black carbon, aerosol number concentration, spatial variation
Published: 15.03.2021; Views: 962; Downloads: 42
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Equal abundance of summertime natural and wintertime anthropogenic Arctic organic aerosols
Olga Popovicheva, Tuuka Petäjä, Andreas Massling, Jakob K. Nøjgaard, Jean-Luc Jaffrezo, Lin Huang, Heidi Hellén, Hannele Hakola, Wendy Zhang, Mika Vestenius, Henrik Skov, Sangeeta Sharma, Mirko Severi, Jürgen Schnelle-Kreis, Claire E. Moffett, Konstantinos Eleftheriadis, Giulia Calzolai, Silvia Becagli, Wenche Aas, Pragati Rai, Francesco Canonaco, Kaspar R. Daellenbach, Houssni Lamkaddam, Roberto Casotto, Deepika Bhattu, Katja Dzepina, Vaios Moschos, Rebecca J. Sheesley, Rita Traversi, Karl Espen Yttri, Julia Schmale, André S. H. Prévôt, Urs Baltensperger, Imad El Haddad, 2022, original scientific article

Abstract: Aerosols play an important yet uncertain role in modulating the radiation balance of the sensitive Arctic atmosphere. Organic aerosol is one of the most abundant, yet least understood, fractions of the Arctic aerosol mass. Here we use data from eight observatories that represent the entire Arctic to reveal the annual cycles in anthropogenic and biogenic sources of organic aerosol. We show that during winter, the organic aerosol in the Arctic is dominated by anthropogenic emissions, mainly from Eurasia, which consist of both direct combustion emissions and long-range transported, aged pollution. In summer, the decreasing anthropogenic pollution is replaced by natural emissions. These include marine secondary, biogenic secondary and primary biological emissions, which have the potential to be important to Arctic climate by modifying the cloud condensation nuclei properties and acting as ice-nucleating particles. Their source strength or atmospheric processing is sensitive to nutrient availability, solar radiation, temperature and snow cover. Our results provide a comprehensive understanding of the current pan-Arctic organic aerosol, which can be used to support modelling efforts that aim to quantify the climate impacts of emissions in this sensitive region.
Found in: osebi
Keywords: Arctic, Organic aerosols, Emission sources, Climate change
Published: 01.03.2022; Views: 412; Downloads: 0
.pdf Fulltext (1,89 MB)

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