Showing papers by "Pauli Paasonen published in 2022"

The missing base molecules in atmospheric acid–base nucleation

Abstract: Abstract Transformation of low-volatility gaseous precursors to new particles affects aerosol number concentration, cloud formation and hence the climate. The clustering of acid and base molecules is a major mechanism driving fast nucleation and initial growth of new particles in the atmosphere. However, the acid–base cluster composition, measured using state-of-the-art mass spectrometers, cannot explain the measured high formation rate of new particles. Here we present strong evidence for the existence of base molecules such as amines in the smallest atmospheric sulfuric acid clusters prior to their detection by mass spectrometers. We demonstrate that forming (H2SO4)1(amine)1 is the rate-limiting step in atmospheric H2SO4-amine nucleation and the uptake of (H2SO4)1(amine)1 is a major pathway for the initial growth of H2SO4 clusters. The proposed mechanism is very consistent with measured new particle formation in urban Beijing, in which dimethylamine is the key base for H2SO4 nucleation while other bases such as ammonia may contribute to the growth of larger clusters. Our findings further underline the fact that strong amines, even at low concentrations and when undetected in the smallest clusters, can be crucial to particle formation in the planetary boundary layer.

Supplementary material to "The effect of COVID-19 restrictions on atmospheric new particle formation in Beijing"

Abstract: Abstract. During the COVID-19 lockdown, the dramatic reduction of anthropogenic emissions provided a unique opportunity to investigate the effects of reduced anthropogenic activity and primary emissions on atmospheric chemical processes and the consequent formation of secondary pollutants. Here, we utilize comprehensive observations to examine the response of atmospheric new particle formation (NPF) to the changes in the atmospheric chemical cocktail. We find that the main clustering process was unaffected by the drastically reduced traffic emissions, and the formation rate of 1.5 nm particles remained unaltered. However, particle survival probability was enhanced due to an increased particle growth rate (GR) during the lockdown period, explaining the enhanced NPF activity in earlier studies. For GR at 1.5–3 nm, sulfuric acid (SA) was the main contributor at high temperatures, whilst there were unaccounted contributing vapors at low temperatures. For GR at 3–7 nm and 7–15 nm, oxygenated organic molecules (OOMs) played a major role. Surprisingly, OOM composition and volatility were insensitive to the large change of atmospheric NOx concentration; instead the associated high particle growth rates and high OOM concentration during the lockdown period were mostly caused by the enhanced atmospheric oxidative capacity. Overall, our findings suggest a limited role of traffic emissions in NPF.

The effect of COVID-19 restrictions on atmospheric new particle formation in Beijing

Abstract: Abstract. During the COVID-19 lockdown, the dramatic reduction of anthropogenic emissions provided a unique opportunity to investigate the effects of reduced anthropogenic activity and primary emissions on atmospheric chemical processes and the consequent formation of secondary pollutants. Here, we utilize comprehensive observations to examine the response of atmospheric new particle formation (NPF) to the changes in the atmospheric chemical cocktail. We find that the main clustering process was unaffected by the drastically reduced traffic emissions, and the formation rate of 1.5 nm particles remained unaltered. However, particle survival probability was enhanced due to an increased particle growth rate (GR) during the lockdown period, explaining the enhanced NPF activity in earlier studies. For GR at 1.5–3 nm, sulfuric acid (SA) was the main contributor at high temperatures, whilst there were unaccounted contributing vapors at low temperatures. For GR at 3–7 and 7–15 nm, oxygenated organic molecules (OOMs) played a major role. Surprisingly, OOM composition and volatility were insensitive to the large change of atmospheric NOx concentration; instead the associated high particle growth rates and high OOM concentration during the lockdown period were mostly caused by the enhanced atmospheric oxidative capacity. Overall, our findings suggest a limited role of traffic emissions in NPF.

Influence of Aerosol Chemical Composition on Condensation Sink Efficiency and New Particle Formation in Beijing

Abstract: Relatively high concentrations of preexisting particles, acting as a condensation sink (CS) of gaseous precursors, have been thought to suppress the occurrence of new particle formation (NPF) in urban environments, yet NPF still occurs frequently. Here, we aim to understand the factors promoting and inhibiting NPF events in urban Beijing by combining one-year-long measurements of particle number size distributions and PM2.5 chemical composition. Our results show that indeed the CS is an important factor controlling the occurrence of NPF events, with its chemical composition affecting the efficiency of the background particles in removing gaseous H2SO4 (effectiveness of the CS) driving NPF. During our observation period, the CS was found to be more effective for ammonium nitrate-rich (NH4NO3-rich) fine particles. On non-NPF event days, particles acting as CS contained a larger fraction of NH4NO3 compared to NPF event days under comparable CS levels. In particular, in the CS range from 0.02 to 0.03 s–1, the nitrate fraction was 17% on NPF event days and 26% on non-NPF event days. Overall, our results highlight the importance of considering the chemical composition of preexisting particles when estimating the CS and their role in inhibiting NPF events, especially in urban environments.

Observed coupling between air mass history, secondary growth of nucleation mode particles and aerosol pollution levels in Beijing

Abstract: Atmospheric aerosols have significant effects on the climate and on human health. New particle formation (NPF) is globally an important source of aerosols but its relevance especially towards aerosol mass loadings in highly polluted regions is still controversial. In addition, uncertainties remain regarding the processes leading to severe pollution episodes, concerning e.g. the role of atmospheric transport. In this study, we utilize air mass history analysis in combination with different fields related to the intensity of anthropogenic emissions in order to calculate air mass exposure to anthropogenic emissions (AME) prior to their arrival at Beijing, China. The AME is used as a semi-quantitative metric for describing the effect of air mass history on the potential for aerosol formation. We show that NPF events occur in clean air masses, described by low AME. However, increasing AME seems to be required for substantial growth of nucleation mode (diameter < 30 nm) particles, originating either from NPF or direct emissions, into larger mass-relevant sizes. This finding assists in establishing and understanding the connection between small nucleation mode particles, secondary aerosol formation and the development of pollution episodes. We further use the AME, in combination with basic meteorological variables, for developing a simple and easy-to-apply regression model to predict aerosol volume and mass concentrations. Since the model directly only accounts for changes in meteorological conditions, it can also be used to estimate the influence of emission changes on pollution levels. We apply the developed model to briefly investigate the effects of the COVID-19 lockdown on PM2.5 concentrations in Beijing. While no clear influence directly attributable to the lockdown measures is found, the results are in line with other studies utilizing more widely applied approaches.

Measurement report: A multi-year study on the impacts of Chinese New Year celebrations on air quality in Beijing, China

Abstract: Abstract. This study investigates the influence of the Chinese New Year (CNY) celebrations on local air quality in Beijing from 2013 through 2019. CNY celebrations include burning of fireworks and firecrackers, which consequently has a significant short-term impact on local air quality. In this study, we bring together comprehensive observations at the newly constructed Aerosol and Haze Laboratory at Beijing University of Chemical Technology – West Campus (BUCT-AHL) and hourly measurements from 12 Chinese government air quality measurement stations throughout the Beijing metropolitan area. These datasets are used together to provide a detailed analysis of air quality during the CNY over multiple years, during which the city of Beijing prohibited the use of fireworks and firecrackers in an effort to reduce air pollution before CNY 2018. Datasets used in this study include particulate matter mass concentrations (PM2.5 and PM10), trace gases (NOx, SO2, O3, and CO), and meteorological variables for 2013–2019; aerosol particle size distributions; and concentrations of sulfuric acid and black carbon for 2018 and 2019. Studying the CNY over several years, which has rarely been done in previous studies, can show trends and effects of societal and policy changes over time, and the results can be applied to study problems and potential solutions of air pollution resulting from holiday celebrations. Our results show that during the 2018 CNY, air pollutant concentrations peaked during the CNY night (for example, PM2.5 reached a peak around midnight of over 250 µg cm−3, compared to values of less than 50 µg cm−3 earlier in the day). The pollutants with the most notable spikes were sulfur dioxide, particulate matter, and black carbon, which are emitted in burning of fireworks and firecrackers. Sulfuric acid concentration followed the sulfur dioxide concentration and showed elevated overnight concentration. Analysis of aerosol particle number size distribution showed direct emissions of particles with diameters around 100 nm in relation to firework burning. During the 2019 CNY, the pollution levels were somewhat lower (PM2.5 peaking at around 150 µg cm−3 on CNY compared to values around 100 µg cm−3 earlier in the day), and only minor peaks related to firework burning were observed. During both CNYs 2018 and 2019 secondary aerosol formation in terms of particle growth was observed. Meteorological conditions were comparable between these 2 years, suggesting that CNY-related emissions were less in 2019 compared to 2018. During the 7-year study period, it appears that there has been a general decrease in CNY-related emissions since 2016. For example, the peak in PM2.5 in 2016 was over 600 µg cm−3, and in the years following, the peak was less each year, with a peak around 150 µg cm−3 in 2019. This is indicative of the restrictions and public awareness of the air quality issues having a positive effect on improving air quality during the CNY. Going into the future, long-term observations will offer confirmation for these trends.

The effect of COVID-19 restrictions on atmospheric new particle formation in Beijing

Abstract: Abstract. During the COVID-19 lockdown, the dramatic reduction of anthropogenic emissions provided a unique opportunity to investigate the effects of reduced anthropogenic activity and primary emissions on atmospheric chemical processes and the consequent formation of secondary pollutants. Here, we utilize comprehensive observations to examine the response of atmospheric new particle formation (NPF) to the changes in the atmospheric chemical cocktail. We find that the main clustering process was unaffected by the drastically reduced traffic emissions, and the formation rate of 1.5 nm particles remained unaltered. However, particle survival probability was enhanced due to an increased particle growth rate (GR) during the lockdown period, explaining the enhanced NPF activity in earlier studies. For GR at 1.5–3 nm, sulfuric acid (SA) was the main contributor at high temperatures, whilst there were unaccounted contributing vapors at low temperatures. For GR at 3–7 nm and 7–15 nm, oxygenated organic molecules (OOMs) played a major role. Surprisingly, OOM composition and volatility were insensitive to the large change of atmospheric NOx concentration; instead the associated high particle growth rates and high OOM concentration during the lockdown period were mostly caused by the enhanced atmospheric oxidative capacity. Overall, our findings suggest a limited role of traffic emissions in NPF.

The effect of COVID-19 restrictions on atmospheric new particle formation 1 in Beijing

Abstract: The effect of COVID-19 restrictions on atmospheric new particle formation 1 in Beijing 2 3 Chao Yan1,2,#, Yicheng Shen3,#, Dominik Stolzenburg2, Lubna Dada2,4, Ximeng Qi5, Simo 4 Hakala2, Anu-Maija Sundström6, Yishuo Guo1, Antti Lipponen7, Tom V. Kokkonen5, Jenni 5 Kontkanen2, Runlong Cai2,3, Jing Cai1,2,Tommy Chan2, Liangduo Chen5, Biwu Chu2, Chenjuan 6 Deng3, Wei Du1,2, Xiaolong Fan1, Xu-Cheng He2 , Juha Kangasluoma1,2, Joni Kujansuu1,2, 7 Mona Kurppa2, Chang Li1, Yiran Li3, Zhuohui Lin1, Yiliang Liu8, Yuliang Liu5, Yiqun Lu8, 8 Wei Nie5, Jouni Pulliainen6, Xiaohui Qiao3, Yonghong Wang1,2, Yifan Wen3, Ye Wu3, Gan 9 Yang8, Lei Yao2, Rujing Yin3, Gen Zhang9, Shaojun Zhang3, Feixue Zheng1, Ying Zhou1, Antti 10 Arola7, Johanna Tamminen6, Pauli Paasonen2, Yele Sun10, Lin Wang8, Neil M. Donahue11, 11 Yongchun Liu1, Federico Bianchi2, Kaspar R. Daellenbach2,4, Douglas R. Worsnop2,12, Veli12 Matti Kerminen2, Tuukka Petäjä2,5, Aijun Ding5,*, Jingkun Jiang3,*, Markku Kulmala1,2,5* 13 14 Affiliations: 15 1 Aerosol and Haze Laboratory, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, 16 Beijing University of Chemical Technology, Beijing, China 17 2 Institute for Atmospheric and Earth System Research / Physics, Faculty of Science, University of Helsinki, 18 Finland 19 3 State Key Joint Laboratory of Environment Simulation and Pollution Control, State Environmental Protection 20 Key Laboratory of Sources and Control of Air Pollution Complex, School of Environment, Tsinghua University, 21 Beijing, China 22 4 Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland. 23 5 Joint International research Laboratory of Atmospheric and Earth System Research (JirLATEST), School of 24 Atmospheric Sciences, Nanjing University, Nanjing, China. 25 6 Finnish Meteorological Institute, 00560 Helsinki, Finland 26 7 Finnish Meteorological Institute, 70211 Kuopio, Finland 27 8 Department of Environmental Science & Engineering, Fudan University, Shanghai, China 28 9 State Key Laboratory of Severe Weather & Key Laboratory of Atmospheric Chemistry of China Meteorological 29 Administration (CMA), Chinese Academy of Meteorological Sciences, Beijing 100081, China 30 10 Institute of Atmospheric Physics, Chinese Academy of Science, Beijing, China 31 11 Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, PA, USA 32 12Aerodyne Research Inc., Billerica, Massachusetts 01821, USA 33 # these authors contributed equally to this work 34 * Correspondence to: 35 Markku Kulmala, markku.kulmala@helsinki.fi 36 Jingkun Jiang, jiangjk@tsinghua.edu.cn 37 Aijun Ding, dingaj@nju.edu.cn 38 39

Aerosol pollution in the Moscow megacity environment and its impact on radiative and meteorological properties of the atmosphere

Abstract: &lt;p&gt;Urban aerosol pollution has a significant effect on solar irradiance and meteorological characteristics. Using the two online integrated meteorology &amp;#8211; atmospheric composition modelling systems&amp;#160; -&amp;#160; COSMO-Ru2-ART (Consortium for Small-scale Modeling &amp;#8211; Aerosols and Reactive Trace gases) and Enviro-HIRLAM (Environment &amp;#8211; High Resolution Limited Area Model) ) taking into account urbanization effects, we studied the effects of aerosol pollution and its impact on radiative and meteorological characteristics of the atmosphere with focus on the Moscow megacity region (Russia). For the models&amp;#8217; runs, the initial and boundary conditions from the ICON-COSMO-Ru7 and ERA-5 &amp;#160;as well as the CAMS redistributed inventory emissions were utilized.&lt;/p&gt;&lt;p&gt;In order to account for the absorbing aerosol properties of the Moscow urban atmosphere black carbon (BC) emissions were applied according to the ECLIPSE emission inventory, which demonstrated a satisfactory agreement in BC/PM10 ratio with experimental data in Moscow.&amp;#160; A series of models&amp;#8217; simulations over an area of 300x300 km&amp;#160; was performed with a 2 km horizontal grid step with the effects of urban areas (building effects/ BEP, anthropogenic heat fluxes/ AHF in Enviro-HIRLAM and TERRA_URB scheme in COSMO-Ru2-ART), and without their consideration. The estimates of urban aerosol content were made for typical conditions in April-May 2019 and during spring of 2020, when lowered anthropogenic emissions were observed in the Moscow region due to strict lockdown conditions of COVID-19 pandemic.&lt;/p&gt;&lt;p&gt;In this study, we accounted for the changes in emissions for the lockdown situation according to the recommendations (Le Qu&amp;#233;r&amp;#233; et al., 2020), which were mainly in agreement with the official statements.&amp;#160; The estimates of aerosol urban properties were tested against the difference between the AERONET measurements obtained in the Moscow megacity and in a relatively clean region at Zvenigorod Scientific Station of the Institute of Atmospheric Physics, Russian Academy of Sciences.&amp;#160; The quality of surface aerosol estimation was verified using the MosEcoMonitoring Agency dataset. The variability of concentration of different aerosol species at ground level and changes in aerosol optical depth and its absorbing properties in the total atmospheric column are discussed.&amp;#160; The various aerosol radiative effects - direct, semidirect and indirect - and the influence of aerosol on selected meteorological characteristics (such as temperature, humidity, cloud cover, etc.) are analyzed. The features of spatio-temporal changes in urban aerosol fields and their effects on meteorology in conditions of elevated and lower emissions of pollutants in typical and lockdown conditions are investigated.&amp;#160;&lt;/p&gt;&lt;p&gt;This study is partially supported by the Ministry of Education and Science of the Russian Federation (grant number 075-15-2021-574) and the Finnish Flagship &amp;#8220;Atmosphere and Climate Competence Center&amp;#8221; (Academy of Finland grant 337549). &amp;#160;This research was performed according to the Development Programme of the Interdisciplinary Scientific and Educational School of MSU &amp;#8220;Future Planet and Global Environmental Change&amp;#8221;. The CSC - IT Center for Science Computing (Finland), is acknowledged for computational resources.&lt;/p&gt;&lt;p&gt;References:&lt;/p&gt;&lt;p&gt;Le Qu&amp;#233;r&amp;#233; C. et all (2020): Temporary reduction in daily global CO&lt;sub&gt;2&lt;/sub&gt; emissions during the COVID-19 forced confinement, Nat. Clim. Change, 10, 647&amp;#8211;653.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;