1. Development and evaluation of an improved offline aerosol mass spectrometry techniqueChristina Vasilakopoulou, Kalliopi Florou, Christos Kaltsonoudis, Iasonas Stavroulas, Nikolaos Mihalopoulos, Spyros N. Pandis, 2023, original scientific article Abstract: Abstract. The offline aerosol mass spectrometry technique is
a useful tool for the source apportionment of organic aerosol (OA) in areas
and periods during which an aerosol mass spectrometer (AMS) is not available. However, the technique is
based on the extraction of aerosol samples in water, while several
atmospheric OA components are partially or fully insoluble in water. In this work an improved offline technique was developed and evaluated in an effort to capture most of the partially soluble and insoluble organic aerosol material, reducing significantly the uncertainty of the corresponding source
apportionment. A major advantage of the proposed approach is that no
corrections are needed for the offline analysis to account for the limited
water solubility of some OA components. The improved offline AMS analysis
was tested in three campaigns: two during winter and one during summer.
Collocated online AMS measurements were performed for the evaluation of the offline method. Source apportionment analysis was performed separately for the online and the offline measurements using positive matrix
factorization (PMF). The PMF results showed that the fractional contribution of each factor to the total OA differed between the online and the offline PMF results by less than 15 %. The differences in the AMS spectra of the
factors of the two approaches could be significant, suggesting that the use
of factor profiles from the literature in the offline analysis may lead to
complications. Part of the good agreement between the online and the
offline PMF results is due to the ability of the improved offline AMS
technique to capture a bigger part of the OA, including insoluble organic
material. This was evident by the significant fraction of submicrometer
suspended insoluble particles present in the water extract and by the
reduced insoluble material on the filters after the extraction process. More than half of the elemental carbon (EC) was on average missing from the
filters after the water extraction. Significant EC concentrations were
measured in the produced aerosol that was used as input to the AMS during
the offline analysis.
Keywords: organic aerosol, receptor modeling, offline PMF, Greece
Published in RUNG: 10.05.2024; Views: 129; Downloads: 2
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2. The effect of the averaging period for PMF analysis of aerosol mass spectrometer measurements during offline applicationsChristina Vasilakopoulou, Iasonas Stavroulas, Nikolaos Mihalopoulos, Spyros N. Pandis, 2022, original scientific article Abstract: Offline aerosol mass spectrometer (AMS) measurements can
provide valuable information about ambient organic aerosols in areas and
periods in which online AMS measurements are not available. However, these
offline measurements have a low temporal resolution, as they are based on
filter samples usually collected over 24 h. In this study, we examine
whether and how this low time resolution affects source apportionment
results. We used a five-month period (November 2016–March 2017) of online
measurements in Athens, Greece, and performed positive matrix factorization (PMF)
analysis to both the original dataset, which consists of 30 min
measurements, and to time averages from 1 up to 24 h. The 30 min results
indicated that five factors were able to represent the ambient organic
aerosol (OA): a biomass burning organic aerosol factor (BBOA), which contributed
16 % of the total OA; hydrocarbon-like OA (HOA) (29 %); cooking OA (COA) (20 %); more-oxygenated OA (MO-OOA) (18 %); and less-oxygenated OA (LO-OOA) (17 %). Use of the daily averages resulted in estimated average contributions that were within 8 % of the total OA compared with the high-resolution analysis for the five-month period. The most important difference was for the BBOA contribution, which was overestimated (25 % for low resolution versus 17 % for high resolution) when daily averages were used. The estimated secondary OA varied from 35 % to 28 % when the averaging
interval varied between 30 min and 24 h. The high-resolution results are
expected to be more accurate, both because they are based on much larger
datasets and because they are based on additional information about the
temporal source variability. The error for the low-resolution analysis was
much higher for individual days, and its results for high-concentration days in particular are quite uncertain. The low-resolution analysis
introduces errors in the determined AMS profiles for the BBOA and LO-OOA
factors but determines the rest relatively accurately (theta angle around
10∘ or less).
Keywords: AMS, offline PMF, ACSM, organic aerosols
Published in RUNG: 10.05.2024; Views: 134; Downloads: 3
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3. Capturing and Storing Exhaled Breath for Offline AnalysisIain R. White, Stephen J. Fowler, 2019, independent scientific component part or a chapter in a monograph Abstract: In this chapter we will summarize and discuss methods for the capture and storage of exhaled breath, prior to offline (and indirect online) analysis. We will detail and compare methods currently in use, including their applications, key strengths, and limitations. In synthesizing the best features of each technique, we will propose an ideal standardized breath sampling solution, and give a personal vision on the next steps to be taken in this exciting area of breath research.
Keywords: Breath analysis, Breath sampling, Offline analysis, Thermal desorption, Gas chromatography-mass spectrometry
Published in RUNG: 22.07.2019; Views: 3443; Downloads: 0
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4. AugerPrime implementation in the Offline simulation and reconstruction frameworkDavid Schmidt, Andrej Filipčič, Gašper Kukec Mezek, Ahmed Saleh, Samo Stanič, Marta Trini, Darko Veberič, Serguei Vorobiov, Lili Yang, Danilo Zavrtanik, Marko Zavrtanik, 2017, published scientific conference contribution Keywords: AugerPrime, Offline simulation and reconstruction, Pierre Auger Observatory
Published in RUNG: 19.02.2018; Views: 3492; Downloads: 152
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