Publications by authors named "Marcel Zauner-Wieczorek"
Aircraft observations have revealed ubiquitous new particle formation in the tropical upper troposphere over the Amazon and the Atlantic and Pacific oceans. Although the vapours involved remain unknown, recent satellite observations have revealed surprisingly high night-time isoprene mixing ratios of up to 1 part per billion by volume (ppbv) in the tropical upper troposphere. Here, in experiments performed with the CERN CLOUD (Cosmics Leaving Outdoor Droplets) chamber, we report new particle formation initiated by the reaction of hydroxyl radicals with isoprene at upper-tropospheric temperatures of -30 °C and -50 °C.
View Article and Find Full Text PDFNew particle formation (NPF) in the tropical upper troposphere is a globally important source of atmospheric aerosols. It is known to occur over the Amazon basin, but the nucleation mechanism and chemical precursors have yet to be identified. Here we present comprehensive in situ aircraft measurements showing that extremely low-volatile oxidation products of isoprene, particularly certain organonitrates, drive NPF in the Amazonian upper troposphere.
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- Ammonia emissions in Southeast Asia significantly impact air pollution and the development of the Asian Tropopause Aerosol Layer (ATAL), particularly during summer when the South Asian monsoon is active.
- The study utilizes the EMAC chemistry-climate model to analyze how ammonia influences particle formation, revealing a tenfold increase in particle creation during the day, especially within the monsoon's upper troposphere and lower stratosphere (UTLS).
- Findings indicate that while ammonia enhances cloud condensation nuclei (CCN) concentrations and aerosol optical depth (AOD), its effect on aerosol mass in the ATAL is comparatively limited, suggesting a complex relationship between ammonia, particle growth, and aerosol composition.
Article Synopsis
- * The study found that particle formation rates due to ion-induced processes are stable across temperature changes, while neutral particle formation rates increase significantly when temperatures drop from +10 °C to -10 °C.
- * Despite higher ionization rates, the formation of charged clusters is unlikely to be enhanced in upper tropospheric conditions; instead, neutral nucleation is expected to dominate, with humidity having little effect unless extremely low.
Article Synopsis
- Aerosols from gas-to-particle processes significantly contribute to urban smog and haze, particularly through the formation of ammonium nitrate, which can thrive in polluted city conditions.
- Urban areas face complex variations in temperature and gas concentrations, influencing how quickly aerosols can form and grow.
- Experimental results from CERN's CLOUD chamber reveal that rapid temperature fluctuations can enhance nanoparticle growth, highlighting the influence of inconsistent ammonia emissions in cities on aerosol dynamics.
Highly oxygenated organic molecules (HOMs) are a major source of new particles that affect the Earth's climate. HOM production from the oxidation of volatile organic compounds (VOCs) occurs during both the day and night and can lead to new particle formation (NPF). However, NPF involving organic vapors has been reported much more often during the daytime than during nighttime.
View Article and Find Full Text PDFThe main nucleating vapor in the atmosphere is thought to be sulfuric acid (HSO), stabilized by ammonia (NH). However, in marine and polar regions, NH is generally low, and HSO is frequently found together with iodine oxoacids [HIO, i.e.
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- The study investigates how high relative humidity (RH) influences the partitioning of biogenic oxidized organic molecules into secondary organic aerosols (SOA) using real-time measurements in a controlled lab setting.
- Results show significant increases in SOA mass (45%-85%) as RH rises from low to high levels, with semi-volatile compounds playing a key role in this process.
- The research explains that higher RH alters the chemical composition of aerosols, shifting toward more volatile species, and emphasizes the critical role of water content in promoting organic aerosol growth.
Iodine is a reactive trace element in atmospheric chemistry that destroys ozone and nucleates particles. Iodine emissions have tripled since 1950 and are projected to keep increasing with rising O surface concentrations. Although iodic acid (HIO) is widespread and forms particles more efficiently than sulfuric acid, its gas-phase formation mechanism remains unresolved.
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- Dimethyl sulfide (DMS) contributes to climate change by affecting cloud formation through its oxidation products, primarily methanesulfonic acid (MSA) and sulfuric acid (HSO), but predicting their levels accurately is difficult.
- Experiments conducted at CERN's CLOUD chamber showed that lowering the temperature significantly boosts the production of MSA from DMS oxidation, while HSO production remains relatively stable, resulting in a lower HSO/MSA ratio at cold temperatures.
- The research introduces a new DMS oxidation mechanism that increases MSA production estimates, significantly higher than previous models, revealing MSA's crucial role in the sulfur cycle and its impact on cloud condensation nuclei.
Article Synopsis
- New particle formation events occur frequently in polluted environments, despite high loss rates of tiny clusters, suggesting scavenging by larger particles or unknown growth mechanisms might be less effective than anticipated.
- Experiments in the CLOUD chamber at CERN showed that the creation of new particles from human-made vapors significantly drops when there are many pre-existing particles, proving they effectively scavenge smaller molecular clusters.
- In conditions with high levels of nitric acid and ammonia, newly formed particles can grow rapidly and maintain their numbers, even in heavily polluted air, which helps explain why these particles survive in haze-like situations.
New particle formation in the upper free troposphere is a major global source of cloud condensation nuclei (CCN). However, the precursor vapours that drive the process are not well understood. With experiments performed under upper tropospheric conditions in the CERN CLOUD chamber, we show that nitric acid, sulfuric acid and ammonia form particles synergistically, at rates that are orders of magnitude faster than those from any two of the three components.
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- - Iodic acid (HIO) can rapidly form aerosol particles in coastal areas, with nucleation rates surpassing those of sulfuric acid-ammonia under similar conditions.
- - Ion-induced nucleation involves the initial formation of IO followed by the addition of HIO, occurring efficiently at temperatures below +10°C, while neutral nucleation relies on a different process involving iodous acid.
- - Freshly formed HIO particles significantly contribute to fast particle growth and can effectively compete with sulfuric acid particle formation in unpolluted atmospheric regions.
Article Synopsis
- New-particle formation significantly contributes to urban smog, and researchers investigated how this process occurs in cities, particularly in colder temperatures.
- Experiments at CERN's CLOUD chamber revealed that below +5°C, nitric acid and ammonia vapors can rapidly condense onto new particles, stimulating high particle growth rates, especially below -15°C when they can nucleate directly into ammonium nitrate.
- These findings suggest that in urban environments, especially during winter, vertical mixing and high local emissions can create conditions where these particles grow quickly, enhancing their chances of survival against scavenging.