Long-term trends of black carbon and particle number concentration in the lower free troposphere in Central Europe

Abstract

Background The implementation of emission mitigation policies in Europe over the last two decades has generally improved the air quality, which resulted in lower aerosol particle mass, particle number, and black carbon mass concentration. However, little is known whether the decreasing particle concentrations at a lower-altitude level can be observed in the free troposphere (FT), an important layer of the atmosphere, where aerosol particles have a longer lifetime and may affect climate dynamics. In this study, we used data from two high-Alpine observatories, Zugspitze-Schneefernerhaus (ZSF) and Jungfraujoch (JFJ), to assess the long-term trends on size-resolved particle number concentrations (PNCs) and equivalent black carbon (eBC) mass concentration separated for undisturbed lower FT conditions and under the influence of air from the planetary boundary layer (PBL) from 2009 to 2018. Results The FT and PBL-influenced conditions were segregated for both sites. We found that the FT conditions in cold months were more prevalent than in warm months, while the measured aerosol parameters showed different seasonal patterns for the FT and PBL-influenced conditions. The pollutants in the PBL-influenced condition have a higher chance to be transported to high-altitudes due to the mountainous topography, leading to a higher concentration and more distinct seasonal variation, and vice versa. The long-term trends of the measured aerosol parameters were evaluated and the decreased aerosol concentrations were observed for both FT and PBL-influenced conditions. The observed decreasing trends in eBC concentration in the PBL-influenced condition are well consistent with the reported trends in total BC emission in Germany and Switzerland. The decreased concentrations in the FT condition suggest that the background aerosol concentration in the lower FT over Central Europe has correspondingly decreased. The change of back trajectories in the FT condition at ZSF and JFJ was further evaluated to investigate the other possible drivers for the decreasing trends. Conclusions The background aerosol concentration in the lower FT over Central Europe has significantly decreased during 2009–2018. The implementation of emission mitigation policies is the most decisive factor and the decrease of the regional airmass occurrence over Central Europe also has contributed to the decreasing trends.

Assessment of Impact of Meteorology and Precursor in Long-term Trends of PM and Ozone in a Tropical City

“…Stagnant wind conditions should have concentrated and subsequently enhanced the PM mass. On the other hand, the prevailing wind direction, similar to previous studies (Sun et al, 2020(Sun et al, , 2021, may have contributed to the enhanced mass during the 2 nd half of the year. The Philippines experiences the southwest monsoon between June and November, which transports biomass burning pollutants from equatorial South East Asian countries during this period (Matsumoto et al, 2020;Yin, 2020).…”

Particles' phase state variability in the North Atlantic free troposphere during summertime determined by different atmospheric transport patterns and sources

“…The total particle concentration was around 300 cm -3 , and, in general, a higher concentration of particles (>400 particles cm-3) was observed during high CO concentration periods derived from the FLEXPART simulation. The size range and particle concentration were within this range for FT particles reported in the literature (Igel et al, 2017;Rose et al, 2017;Schmeissner et al, 2011;Sun et al, 2021).…”

Long-Term eBC Measurements with the Use of MAAP in the Polluted Urban Atmosphere (Poland)

“…Some, however, focus on the analysis of eBC concentrations during periods of increased pollutant concentration called episodes [50]. Long-term measurements were carried out, especially at sites located far from emission sources, and were focused primarily on the assessment of pollution of clean areas and the role of eBC in climate change [51,52]. Therefore, in our opinion, the research we conduct is very important in the context of the exposure of the population of urban areas to air pollution by soot and the assessment of the effectiveness of the preventive and control measures taken (see also Section 3.3).…”