@article{
 title = {Look Up: Probing the Vertical Profile of New Particle Formation and Growth in the Planetary Boundary Layer with Models and Observations},
 type = {article},
 year = {2023},
 keywords = {NPF,SOA,mixed layer,new particle formation,nucleation,planetary boundary layer},
 pages = {e2022JD037525},
 volume = {n/a},
 websites = {https://doi.org/10.1029/2022JD037525},
 month = {1},
 publisher = {John Wiley & Sons, Ltd},
 day = {20},
 id = {e990969d-e2a4-382b-825f-9017c7e89fda},
 created = {2023-01-31T22:46:12.003Z},
 file_attached = {false},
 profile_id = {2e2b0bf1-6573-3fd8-8628-55d1dc39fe31},
 last_modified = {2023-01-31T22:46:12.003Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 source_type = {JOUR},
 notes = {https://doi.org/10.1029/2022JD037525},
 private_publication = {false},
 abstract = {Abstract The processes of new particle formation (NPF) and growth are important contributors to cloud condensation nuclei (CCN) concentrations, and CCN are important for climate from their impact on planetary radiative forcing. While the general ubiquity and importance of NPF is understood, the vertical extent and governing mechanisms of NPF and growth in the lower troposphere are uncertain. We present an analysis of four NPF events and two non-NPF events during the HI-SCALE field campaign at the Southern Great Plains observatory in Oklahoma, USA. Firstly, we analyzed airborne and ground-based observations of aerosol and gas-phase properties. Secondly, we used a column aerosol chemistry and microphysics model to probe factors that influence the vertical profile of NPF. During HI-SCALE, we found several instances of enhanced NPF occurring several hundred meters above the surface; however, the spatio-temporal characteristics of the observed NPF made comparisons between airborne- and ground-based observations difficult. The model represented the observed NPF (or lack of NPF) and particle growth at the surface to final diameters within 10 nm. The model predicted enhanced NPF rates in the upper mixed layer, and this enhancement is primarily due to the temperature dependence in the NPF schemes, but this was also dependent on the vertical profile of gas-phase precursors measured during HI-SCALE. We found vertical mixing in the model either enhanced or suppressed NPF rates, aerosol number concentrations, and particle growth rates at the surface. Finally, our analysis provides insights for future field campaigns and modeling efforts investigating the vertical profile of NPF.},
 bibtype = {article},
 author = {O’Donnell, Samuel E and Akherati, Ali and He, Yicong and Hodshire, Anna L and Shilling, John E and Kuang, Chongai and Fast, Jerome D and Mei, Fan and Schobesberger7, Siegfried and Thornton, Joel A and Smith, James N and Jathar, Shantanu H and Pierce, Jeffrey R},
 doi = {https://doi.org/10.1029/2022JD037525},
 journal = {Journal of Geophysical Research: Atmospheres},
 number = {n/a}
}

Abstract The processes of new particle formation (NPF) and growth are important contributors to cloud condensation nuclei (CCN) concentrations, and CCN are important for climate from their impact on planetary radiative forcing. While the general ubiquity and importance of NPF is understood, the vertical extent and governing mechanisms of NPF and growth in the lower troposphere are uncertain. We present an analysis of four NPF events and two non-NPF events during the HI-SCALE field campaign at the Southern Great Plains observatory in Oklahoma, USA. Firstly, we analyzed airborne and ground-based observations of aerosol and gas-phase properties. Secondly, we used a column aerosol chemistry and microphysics model to probe factors that influence the vertical profile of NPF. During HI-SCALE, we found several instances of enhanced NPF occurring several hundred meters above the surface; however, the spatio-temporal characteristics of the observed NPF made comparisons between airborne- and ground-based observations difficult. The model represented the observed NPF (or lack of NPF) and particle growth at the surface to final diameters within 10 nm. The model predicted enhanced NPF rates in the upper mixed layer, and this enhancement is primarily due to the temperature dependence in the NPF schemes, but this was also dependent on the vertical profile of gas-phase precursors measured during HI-SCALE. We found vertical mixing in the model either enhanced or suppressed NPF rates, aerosol number concentrations, and particle growth rates at the surface. Finally, our analysis provides insights for future field campaigns and modeling efforts investigating the vertical profile of NPF.

@article{
 title = {Observations of gas-phase products from the nitrate-radical-initiated oxidation of four monoterpenes},
 type = {article},
 year = {2022},
 pages = {9017-9031},
 volume = {22},
 websites = {https://acp.copernicus.org/preprints/acp-2021-1020/,https://acp.copernicus.org/preprints/acp-2021-1020/acp-2021-1020.pdf},
 month = {1},
 publisher = {Copernicus Publications},
 day = {10},
 id = {8b1c9f8a-184a-3e3d-898a-7f57f6363bf5},
 created = {2022-06-30T18:35:11.136Z},
 file_attached = {false},
 profile_id = {2e2b0bf1-6573-3fd8-8628-55d1dc39fe31},
 last_modified = {2023-01-31T22:46:18.421Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 source_type = {JOUR},
 private_publication = {false},
 abstract = {Chemical ionization mass spectrometry with the nitrate reagent ion (NO3- CIMS) was used to investigate the products of the nitrate radical (NO3) initiated oxidation of four monoterpenes in laboratory chamber experiments. α-Pinene, β-pinene, Δ-3-carene, and α-thujene were studied. The major gas-phase species produced in each system were distinctly different, showing the effect of monoterpene structure on the oxidation mechanism and further elucidating the contributions of these species to particle formation and growth. By comparing groupings of products based on the ratios of elements in the general formula CwHxNyOz, the relative importance of specific mechanistic pathways (fragmentation, termination, and radical rearrangement) can be assessed for each system. Additionally, the measured time series of the highly oxidized reaction products provide insights into the ratio of relative production and loss rates of the high-molecular-weight products of the Δ-3-carene system. The measured effective O:C ratios of reaction products were anticorrelated with new particle formation intensity and number concentration for each system; however, the monomer : dimer ratios of products had a small positive trend. Gas-phase yields of oxidation products measured by NO3- CIMS correlated with particle number concentrations for each monoterpene system, with the exception of α-thujene, which produced a considerable amount of low-volatility products but no particles. Species-resolved wall loss was measured with NO3- CIMS and found to be highly variable among oxidized reaction products in our stainless steel chamber.},
 bibtype = {article},
 author = {Dam, Michelia and Draper, Danielle C. and Marsavin, Andrey and Fry, Juliane L. and Smith, James N.},
 doi = {10.5194/acp-22-9017-2022},
 journal = {Atmospheric Chemistry and Physics},
 number = {13}
}

Chemical ionization mass spectrometry with the nitrate reagent ion (NO3- CIMS) was used to investigate the products of the nitrate radical (NO3) initiated oxidation of four monoterpenes in laboratory chamber experiments. α-Pinene, β-pinene, Δ-3-carene, and α-thujene were studied. The major gas-phase species produced in each system were distinctly different, showing the effect of monoterpene structure on the oxidation mechanism and further elucidating the contributions of these species to particle formation and growth. By comparing groupings of products based on the ratios of elements in the general formula CwHxNyOz, the relative importance of specific mechanistic pathways (fragmentation, termination, and radical rearrangement) can be assessed for each system. Additionally, the measured time series of the highly oxidized reaction products provide insights into the ratio of relative production and loss rates of the high-molecular-weight products of the Δ-3-carene system. The measured effective O:C ratios of reaction products were anticorrelated with new particle formation intensity and number concentration for each system; however, the monomer : dimer ratios of products had a small positive trend. Gas-phase yields of oxidation products measured by NO3- CIMS correlated with particle number concentrations for each monoterpene system, with the exception of α-thujene, which produced a considerable amount of low-volatility products but no particles. Species-resolved wall loss was measured with NO3- CIMS and found to be highly variable among oxidized reaction products in our stainless steel chamber.

@article{
 title = {Insufficient Condensable Organic Vapors Lead to Slow Growth of New Particles in an Urban Environment},
 type = {article},
 year = {2022},
 keywords = {high NOx,nanoparticle composition,new particle growth,oxygenated organic molecules,urban environments},
 pages = {9936-9946},
 volume = {56},
 id = {9e3d1694-d5b1-3111-8b4d-3a3b7763ab6f},
 created = {2023-01-11T22:48:15.124Z},
 file_attached = {false},
 profile_id = {2e2b0bf1-6573-3fd8-8628-55d1dc39fe31},
 last_modified = {2023-01-31T22:46:17.611Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 source_type = {JOUR},
 private_publication = {false},
 abstract = {Atmospheric new particle formation significantly affects global climate and air quality after newly formed particles grow above ∼50 nm. In polluted urban atmospheres with 1-3 orders of magnitude higher new particle formation rates than those in clean atmospheres, particle growth rates are comparable or even lower for reasons that were previously unclear. Here, we address the slow growth in urban Beijing with advanced measurements of the size-resolved molecular composition of nanoparticles using the thermal desorption chemical ionization mass spectrometer and the gas precursors using the nitrate CI-APi-ToF. A particle growth model combining condensational growth and particle-phase acid-base chemistry was developed to explore the growth mechanisms. The composition of 8-40 nm particles during new particle formation events in urban Beijing is dominated by organics (∼80%) and sulfate (∼13%), and the remainder is from base compounds, nitrate, and chloride. With the increase in particle sizes, the fraction of sulfate decreases, while that of the slow-desorbed organics, organic acids, and nitrate increases. The simulated size-resolved composition and growth rates are consistent with the measured results in most cases, and they both indicate that the condensational growth of organic vapors and H2SO4 is the major growth pathway and the particle-phase acid-base reactions play a minor role. In comparison to the high concentrations of gaseous sulfuric acid and amines that cause high formation rates, the concentration of condensable organic vapors is comparably lower under the high NOx levels, while those of the relatively high-volatility nitrogen-containing oxidation products are higher. The insufficient condensable organic vapors lead to slow growth, which further causes low survival of the newly formed particles in urban environments. Thus, the low growth rates, to some extent, counteract the impact of the high formation rates on air quality and global climate in urban environments.},
 bibtype = {article},
 author = {Li, Xiaoxiao and Li, Yuyang and Cai, Runlong and Yan, Chao and Qiao, Xiaohui and Guo, Yishuo and Deng, Chenjuan and Yin, Rujing and Chen, Yijing and Li, Yiran and Yao, Lei and Sarnela, Nina and Zhang, Yusheng and Petäjä, Tuukka and Bianchi, Federico and Liu, Yongchun and Kulmala, Markku and Hao, Jiming and Smith, James N. and Jiang, Jingkun},
 doi = {10.1021/acs.est.2c01566},
 journal = {Environmental Science and Technology},
 number = {14}
}

Atmospheric new particle formation significantly affects global climate and air quality after newly formed particles grow above ∼50 nm. In polluted urban atmospheres with 1-3 orders of magnitude higher new particle formation rates than those in clean atmospheres, particle growth rates are comparable or even lower for reasons that were previously unclear. Here, we address the slow growth in urban Beijing with advanced measurements of the size-resolved molecular composition of nanoparticles using the thermal desorption chemical ionization mass spectrometer and the gas precursors using the nitrate CI-APi-ToF. A particle growth model combining condensational growth and particle-phase acid-base chemistry was developed to explore the growth mechanisms. The composition of 8-40 nm particles during new particle formation events in urban Beijing is dominated by organics (∼80%) and sulfate (∼13%), and the remainder is from base compounds, nitrate, and chloride. With the increase in particle sizes, the fraction of sulfate decreases, while that of the slow-desorbed organics, organic acids, and nitrate increases. The simulated size-resolved composition and growth rates are consistent with the measured results in most cases, and they both indicate that the condensational growth of organic vapors and H2SO4 is the major growth pathway and the particle-phase acid-base reactions play a minor role. In comparison to the high concentrations of gaseous sulfuric acid and amines that cause high formation rates, the concentration of condensable organic vapors is comparably lower under the high NOx levels, while those of the relatively high-volatility nitrogen-containing oxidation products are higher. The insufficient condensable organic vapors lead to slow growth, which further causes low survival of the newly formed particles in urban environments. Thus, the low growth rates, to some extent, counteract the impact of the high formation rates on air quality and global climate in urban environments.

@article{
 title = {Chemical Composition of an Ultrafine Sea Spray Aerosol during the Sea Spray Chemistry and Particle Evolution Experiment},
 type = {article},
 year = {2022},
 keywords = {inorganic mass fraction,organic mass fraction,phytoplankton bloom,sea spray aerosol,ultrafine},
 pages = {1914-1923},
 volume = {6},
 id = {6c098847-d3ca-3cf9-a3c2-3942772da89d},
 created = {2023-01-11T22:50:18.500Z},
 file_attached = {false},
 profile_id = {2e2b0bf1-6573-3fd8-8628-55d1dc39fe31},
 last_modified = {2023-01-31T22:46:17.588Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 source_type = {JOUR},
 private_publication = {false},
 abstract = {Sea spray is a significant global aerosol source with impacts on marine cloud formation and climate. The physical properties and atmospheric fate of the sea spray aerosol (SSA) depend on its chemical composition, but the current understanding of the sources and composition of the marine aerosol or SSA remains limited particularly for the smallest aerosol. The composition of ultrafine (<100 nm diameter) SSA particles controls the critical diameter for activation to cloud droplets. This study presents online measurements of sea salt and organic mass fractions in an ultrafine SSA measured during the Sea Spray Chemistry and Particle Evolution experiment conducted in summer 2019 at the Scripps Institution of Oceanography. Primary SSA particles were generated in a wave flume mesocosm study with coastal seawater obtained from the Scripps Pier in San Diego, CA. Ultrafine particle composition measurements were performed using the thermal desorption chemical ionization mass spectrometer (TDCIMS). Trends in inorganic and organic fractions show dependence on the biological activity of the ocean water, where heterotrophic bacterium concentrations were correlated with organic mass fractions of the ultrafine SSA. At low phytoplankton concentrations, ultrafine sea spray particles were mainly composed of inorganic salts. Characteristic positive ion fragments indicate influence from polysaccharides and fatty acids likely of bacterial origin in the smallest sizes. In contrast, polysaccharide and fatty acid species were below detection levels in TDCIMS measurements of the larger SSA (∼100-200 nm). Comparisons with the submicron aerosol composition measured by an aerosol mass spectrometer (AMS) showed high correlation between AMS and general TDCIMS organic fractions but anticorrelation between measured, individual TDCIMS organics. These results suggest biological drivers for inorganic and organic aerosol compositions and a strong size dependence on the organic composition of nascent sea spray, consistent with previous findings.},
 bibtype = {article},
 author = {Glicker, Hayley S. and Lawler, Michael J. and Chee, Sabrina and Resch, Julian and Garofalo, Lauren A. and Mayer, Kathryn J. and Prather, Kimberly A. and Farmer, Delphine K. and Smith, James N.},
 doi = {10.1021/acsearthspacechem.2c00127},
 journal = {ACS Earth and Space Chemistry},
 number = {7}
}

Sea spray is a significant global aerosol source with impacts on marine cloud formation and climate. The physical properties and atmospheric fate of the sea spray aerosol (SSA) depend on its chemical composition, but the current understanding of the sources and composition of the marine aerosol or SSA remains limited particularly for the smallest aerosol. The composition of ultrafine (<100 nm diameter) SSA particles controls the critical diameter for activation to cloud droplets. This study presents online measurements of sea salt and organic mass fractions in an ultrafine SSA measured during the Sea Spray Chemistry and Particle Evolution experiment conducted in summer 2019 at the Scripps Institution of Oceanography. Primary SSA particles were generated in a wave flume mesocosm study with coastal seawater obtained from the Scripps Pier in San Diego, CA. Ultrafine particle composition measurements were performed using the thermal desorption chemical ionization mass spectrometer (TDCIMS). Trends in inorganic and organic fractions show dependence on the biological activity of the ocean water, where heterotrophic bacterium concentrations were correlated with organic mass fractions of the ultrafine SSA. At low phytoplankton concentrations, ultrafine sea spray particles were mainly composed of inorganic salts. Characteristic positive ion fragments indicate influence from polysaccharides and fatty acids likely of bacterial origin in the smallest sizes. In contrast, polysaccharide and fatty acid species were below detection levels in TDCIMS measurements of the larger SSA (∼100-200 nm). Comparisons with the submicron aerosol composition measured by an aerosol mass spectrometer (AMS) showed high correlation between AMS and general TDCIMS organic fractions but anticorrelation between measured, individual TDCIMS organics. These results suggest biological drivers for inorganic and organic aerosol compositions and a strong size dependence on the organic composition of nascent sea spray, consistent with previous findings.

@article{
 title = {Tropical and Boreal Forest - Atmosphere Interactions: A Review},
 type = {article},
 year = {2022},
 pages = {24-163},
 volume = {74},
 websites = {https://doi.org/10.16993%2Ftellusb.34},
 month = {3},
 publisher = {Stockholm University Press},
 id = {27e739a1-cd9e-3bd2-a15c-2f2562a9b54b},
 created = {2023-01-31T22:46:11.579Z},
 file_attached = {false},
 profile_id = {2e2b0bf1-6573-3fd8-8628-55d1dc39fe31},
 last_modified = {2023-01-31T22:46:11.579Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Artaxo_2022},
 source_type = {article},
 private_publication = {false},
 abstract = {This review presents how the boreal and the tropical forests affect the atmosphere, its chemical composition, its function, and further how that affects the climate and, in return, the ecosystems through feedback processes. Observations from key tower sites standing out due to their long-term comprehensive observations: The Amazon Tall Tower Observatory in Central Amazonia, the Zotino Tall Tower Observatory in Siberia, and the Station to Measure Ecosystem-Atmosphere Relations at Hyytiäla in Finland. The review is complemented by short-term observations from networks and large experiments. The review discusses atmospheric chemistry observations, aerosol formation and processing, physiochemical aerosol, and cloud condensation nuclei properties and finds surprising similarities and important differences in the two ecosystems. The aerosol concentrations and chemistry are similar, particularly concerning the main chemical components, both dominated by an organic fraction, while the boreal ecosystem has generally higher concentrations of inorganics, due to higher influence of long-range transported air pollution. The emissions of biogenic volatile organic compounds are dominated by isoprene and monoterpene in the tropical and boreal regions, respectively, being the main precursors of the organic aerosol fraction. Observations and modeling studies show that climate change and deforestation affect the ecosystems such that the carbon and hydrological cycles in Amazonia are changing to carbon neutrality and affect precipitation downwind. In Africa, the tropical forests are so far maintaining their carbon sink. It is urgent to better understand the interaction between these major ecosystems, the atmosphere, and climate, which calls for more observation sites, providing long-term data on water, carbon, and other biogeochemical cycles. This is essential in finding a sustainable balance between forest preservation and reforestation versus a potential increase in food production and biofuels, which are critical in maintaining ecosystem services and global climate stability. Reducing global warming and deforestation is vital for tropical forests.},
 bibtype = {article},
 author = {Artaxo, Paulo and Hansson, Hans Christen and Andreae, Meinrat O. and Bäck, Jaana and Alves, Eliane Gomes and Barbosa, Henrique M.J. and Bender, Frida and Bourtsoukidis, Efstratios and Carbone, Samara and Chi, Jinshu and Decesari, Stefano and Després, Viviane R. and Ditas, Florian and Ezhova, Ekaterina and Fuzzi, Sandro and Hasselquist, Niles J. and Heintzenberg, Jost and Holanda, Bruna A. and Guenther, Alex and Hakola, Hannele and Heikkinen, Liine and Kerminen, Veli Matti and Kontkanen, Jenni and Krejci, Radovan and Kulmala, Markku and Lavric, Jost V. and De Leeuw, Gerrit and Lehtipalo, Katrianne and Machado, Luiz Augusto T. and McFiggans, Gordon and Franco, Marco Aurelio M. and Meller, Bruno Backes and Morais, Fernando G. and Mohr, Claudia and Morgan, William and Nilsson, Mats B. and Peichl, Matthias and Petäjä, Tuukka and Praß, Maria and Pöhlker, Christopher and Pöhlker, Mira L. and Pöschl, Ulrich and Von Randow, Celso and Riipinen, Ilona and Rinne, Janne and Rizzo, Luciana V. and Rosenfeld, Daniel and Dias, Maria A.F.Silva and Sogacheva, Larisa and Stier, Philip and Swietlicki, Erik and Sörgel, Matthias and Tunved, Peter and Virkkula, Aki and Wang, Jian and Weber, Bettina and Yáñez-Serrano, Ana Maria and Zieger, Paul and Mikhailov, Eugene and Smith, James N. and Kesselmeier, Jürgen},
 doi = {10.16993/tellusb.34},
 journal = {Tellus, Series B: Chemical and Physical Meteorology},
 number = {1}
}

This review presents how the boreal and the tropical forests affect the atmosphere, its chemical composition, its function, and further how that affects the climate and, in return, the ecosystems through feedback processes. Observations from key tower sites standing out due to their long-term comprehensive observations: The Amazon Tall Tower Observatory in Central Amazonia, the Zotino Tall Tower Observatory in Siberia, and the Station to Measure Ecosystem-Atmosphere Relations at Hyytiäla in Finland. The review is complemented by short-term observations from networks and large experiments. The review discusses atmospheric chemistry observations, aerosol formation and processing, physiochemical aerosol, and cloud condensation nuclei properties and finds surprising similarities and important differences in the two ecosystems. The aerosol concentrations and chemistry are similar, particularly concerning the main chemical components, both dominated by an organic fraction, while the boreal ecosystem has generally higher concentrations of inorganics, due to higher influence of long-range transported air pollution. The emissions of biogenic volatile organic compounds are dominated by isoprene and monoterpene in the tropical and boreal regions, respectively, being the main precursors of the organic aerosol fraction. Observations and modeling studies show that climate change and deforestation affect the ecosystems such that the carbon and hydrological cycles in Amazonia are changing to carbon neutrality and affect precipitation downwind. In Africa, the tropical forests are so far maintaining their carbon sink. It is urgent to better understand the interaction between these major ecosystems, the atmosphere, and climate, which calls for more observation sites, providing long-term data on water, carbon, and other biogeochemical cycles. This is essential in finding a sustainable balance between forest preservation and reforestation versus a potential increase in food production and biofuels, which are critical in maintaining ecosystem services and global climate stability. Reducing global warming and deforestation is vital for tropical forests.

@article{
 title = {Sulfuric acid in the Amazon basin: measurements and evaluation of existing sulfuric acid proxies},
 type = {article},
 year = {2022},
 pages = {10061-10076},
 volume = {22},
 id = {8495573c-4d42-3fdd-aadf-60e53859a523},
 created = {2023-01-31T22:46:13.028Z},
 file_attached = {false},
 profile_id = {2e2b0bf1-6573-3fd8-8628-55d1dc39fe31},
 last_modified = {2023-01-31T22:46:13.028Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 source_type = {JOUR},
 private_publication = {false},
 abstract = {Sulfuric acid is a key contributor to new particle formation, though measurements of its gaseous concentrations are difficult to make. Several parameterizations to estimate sulfuric acid exist, all of which were constructed using measurements from the Northern Hemisphere. In this work, we report the first measurements of sulfuric acid from the Amazon basin. These measurements are consistent with concentrations measured in Hyytiälä, Finland, though, unlike Hyytiälä, there is no clear correlation of sulfuric acid with global radiation. There was a minimal difference in sulfuric acid observed between the wet and dry seasons in the Amazon basin. We also test the efficacy of existing proxies to estimate sulfuric acid in this region. Our results suggest that nighttime sulfuric acid production is due to both a stabilized Criegee intermediate pathway and oxidation of SO2 by OH, the latter of which is not currently accounted for in existing proxies. These results also illustrate the drawbacks of the common substitution of radiation for OH concentrations. None of the tested proxies effectively estimate sulfuric acid measurements at night. For estimates at all times of day, a recently published proxy based on data from the boreal forest should be used. If only daytime estimates are needed, several recent proxies that do not include the Criegee pathway are sufficient. More investigation of nighttime sulfuric acid production pathways is necessary to close the gap between measurements and estimates with existing proxies.},
 bibtype = {article},
 author = {Myers, Deanna C. and Kim, Saewung and Sjostedt, Steven and Guenther, Alex B. and Seco, Roger and Vega Bustillos, Oscar and Tota, Julio and Souza, Rodrigo A.F. and Smith, James N.},
 doi = {10.5194/acp-22-10061-2022},
 journal = {Atmospheric Chemistry and Physics},
 number = {15}
}

Sulfuric acid is a key contributor to new particle formation, though measurements of its gaseous concentrations are difficult to make. Several parameterizations to estimate sulfuric acid exist, all of which were constructed using measurements from the Northern Hemisphere. In this work, we report the first measurements of sulfuric acid from the Amazon basin. These measurements are consistent with concentrations measured in Hyytiälä, Finland, though, unlike Hyytiälä, there is no clear correlation of sulfuric acid with global radiation. There was a minimal difference in sulfuric acid observed between the wet and dry seasons in the Amazon basin. We also test the efficacy of existing proxies to estimate sulfuric acid in this region. Our results suggest that nighttime sulfuric acid production is due to both a stabilized Criegee intermediate pathway and oxidation of SO2 by OH, the latter of which is not currently accounted for in existing proxies. These results also illustrate the drawbacks of the common substitution of radiation for OH concentrations. None of the tested proxies effectively estimate sulfuric acid measurements at night. For estimates at all times of day, a recently published proxy based on data from the boreal forest should be used. If only daytime estimates are needed, several recent proxies that do not include the Criegee pathway are sufficient. More investigation of nighttime sulfuric acid production pathways is necessary to close the gap between measurements and estimates with existing proxies.

@article{
 title = {The missing base molecules in atmospheric acid–base nucleation},
 type = {article},
 year = {2022},
 volume = {9},
 websites = {https://doi.org/10.1093%2Fnsr%2Fnwac137},
 month = {7},
 publisher = {Oxford University Press (OUP)},
 id = {f5e8c919-f79a-30ad-823b-7d505028fd4e},
 created = {2023-01-31T22:46:13.525Z},
 file_attached = {false},
 profile_id = {2e2b0bf1-6573-3fd8-8628-55d1dc39fe31},
 last_modified = {2023-01-31T22:46:13.525Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Cai_2022},
 source_type = {article},
 private_publication = {false},
 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.},
 bibtype = {article},
 author = {Cai, Runlong and Yin, Rujing and Yan, Chao and Yang, Dongsen and Deng, Chenjuan and Dada, Lubna and Kangasluoma, Juha and Kontkanen, Jenni and Halonen, Roope and Ma, Yan and Zhang, Xiuhui and Paasonen, Pauli and Petäjä, Tuukka and Kerminen, Veli-Matti and Liu, Yongchun and Bianchi, Federico and Zheng, Jun and Wang, Lin and Hao, Jiming and Smith, James N and Donahue, Neil M and Kulmala, Markku and Worsnop, Douglas R and Jiang, Jingkun},
 doi = {10.1093/nsr/nwac137},
 journal = {National Science Review},
 number = {10}
}

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