A5072221729- Atmospheric chemistry and aerosols
- Atmospheric aerosols and clouds
- Atmospheric Ozone and Climate
- Air Quality Monitoring and Forecasting
- Air Quality and Health Impacts
- nanoparticles nucleation surface interactions
- Arctic and Antarctic ice dynamics
- Icing and De-icing Technologies
- Oil Spill Detection and Mitigation
- Atmospheric and Environmental Gas Dynamics
- Marine and coastal ecosystems
- Advanced Aircraft Design and Technologies
- Catalytic Processes in Materials Science
- Aeolian processes and effects
- Cryospheric studies and observations
- Particle Dynamics in Fluid Flows
- Vehicle emissions and performance
- Methane Hydrates and Related Phenomena
- Climate change and permafrost
- Cyclone Separators and Fluid Dynamics
- Meteorological Phenomena and Simulations
- Indoor Air Quality and Microbial Exposure
- Infection Control and Ventilation
- Freezing and Crystallization Processes
- SARS-CoV-2 detection and testing
Paul Scherrer Institute
2017-2024
Vifor Pharma (Switzerland)
2024
Stony Brook University
2010-2022
Université Claude Bernard Lyon 1
2015-2017
Forum Réfugiés - Cosi
2017
Centre National de la Recherche Scientifique
2016-2017
Institut de Recherches sur la Catalyse et l'Environnement de Lyon
2015-2017
Stony Brook Medicine
2017
Catalytic Materials (United States)
2015-2016
State University of New York
2016
Immersion freezing of water and aqueous solutions by particles acting as ice nuclei (IN) is a common process heterogeneous nucleation which occurs in many environments, especially the atmosphere where it results glaciation clouds. Here we experimentally show, using variety IN types suspended various solutions, that immersion temperatures kinetics can be described solely temperature, T, solution activity, a(w), ratio vapour pressure saturation under same conditions and, equilibrium,...
Abstract. Ice formation in the atmosphere by homogeneous and heterogeneous nucleation is one of least understood processes cloud microphysics climate. Here we describe our investigation marine environment as a potential source atmospheric IN experimentally observing ice from aqueous NaCl droplets comparing against containing intact fragmented diatoms. Homogeneous are studied function temperature water activity, aw. Additional analyses presented on dependence diatom surface area volume...
There has been increasing interest in ice nucleation research the last decade. To identify important gaps our knowledge of processes and their impacts, two international workshops on were held Vienna, Austria 2015 2016. Experts from these identified following needs: (1) uncovering molecular identity active sites for nucleation; (2) importance modeling understanding heterogeneous (3) identifying quantifying contributions biological nuclei natural managed environments; (4) examining role aging...
Atmospheric aerosol particles may contain light absorbing (brown carbon, BrC), triplet forming organic compounds that can sustain catalytic radical reactions and thus contribute to oxidative aging. We quantify UVA induced production initiated by imidazole-2-carboxaldehyde (IC), benzophenone (BPh). 4-benzoylbenzoic acid (BBA) in the presence of nonabsorbing organics citric (CA), shikimic (SA), syringol (Syr) at varying mixing ratios. observed a maximum HO2 release 1013 molecules min–1 cm–2...
Abstract In viscous, organic-rich aerosol particles containing iron, sunlight may induce anoxic conditions that stabilize reactive oxygen species (ROS) and carbon-centered radicals (CCRs). laboratory experiments, we show mass loss, iron oxidation radical formation release from photoactive organic iron. Our results reveal a range of temperature relative humidity, including ambient conditions, control ROS build up CCR persistence in photochemically active, viscous particles. We find can attain...
Abstract Prediction of ice formation in clouds presents one the grand challenges atmospheric sciences. Immersion freezing initiated by ice-nucleating particles (INPs) is dominant pathway primary crystal mixed-phase clouds, where supercooled water droplets and crystals coexist, with important implications for hydrological cycle climate. However, derivation INP number concentrations from an ambient aerosol population cloud-resolving climate models remains highly uncertain. We conducted...
Optical confinement (OC) structures the optical field and amplifies light intensity inside atmospheric aerosol particles, with major consequences for sunlight-driven chemistry. Although theorized, OC-induced spatial structuring has so far defied experimental observation. Here, x-ray spectromicroscopic imaging complemented by modeling provides direct evidence patterning photoactive particles. Single iron(III)-citrate particles were probed using iron oxidation state as a photochemical marker....
Sea spray aerosol (SSA) is a widely recognized important source of ice-nucleating particles (INPs) in the atmosphere. However, composition-specific identification, nucleation processes, and ice rates SSA-INPs have not been well constrained. Microspectroscopic characterization ambient laboratory-generated SSA confirms that water-borne exudates from planktonic microorganisms composed mixture proteinaceous polysaccharidic compounds act as agents (INAs). These data previously published mesocosm...
Biogenic particles have the potential to affect formation of ice crystals in atmosphere with subsequent consequences for hydrological cycle and climate. We present laboratory observations heterogeneous nucleation immersion deposition modes under atmospherically relevant conditions initiated by Nannochloris atomus Emiliania huxleyi, marine phytoplankton structurally chemically distinct cell walls. Temperatures at which freezing, melting, water uptake occur are observed using optical...
Abstract The effect of anthropogenic and biogenic organic particles on atmospheric glaciation processes is poorly understood. We use an optical microscopy setup to identify the ice nuclei (IN) active in immersion freezing (IMF) deposition nucleation within a large population collected substrate from ambient environment central California dominated by urban marine aerosols. Multimodal microspectroscopy methods are applied characterize physicochemical properties mixing state individual IN...
Abstract Long‐range transported free tropospheric particles can play a significant role on heterogeneous ice nucleation. Using optical and electron microscopy we examine the physicochemical characteristics of nucleating (INPs). Particles were collected substrates from troposphere at remote Pico Mountain Observatory in Azores Islands, after long‐range transport aging over Atlantic Ocean. We investigate four specific events to study formation potential by with different ages patterns. use...
Abstract. Immersion freezing is an important ice nucleation pathway involved in the formation of cirrus and mixed-phase clouds. Laboratory immersion experiments are necessary to determine range temperature, T, relative humidity, RH, at which occurs quantify associated kinetics. Typically, isothermal (applying a constant temperature) cooling-rate-dependent conducted. In these it usually assumed that droplets containing nucleating particles (INPs) all have same INP surface area (ISA); however,...
Anthropogenic and biogenic gas emissions contribute to the formation of secondary organic aerosol (SOA). When present, soot particles from fossil fuel combustion can acquire a coating SOA. We investigate SOA–soot biogenic–anthropogenic interactions their impact on ice nucleation in relation particles’ phase state. SOA were generated OH oxidation naphthalene, α-pinene, longifolene, or isoprene, with without presence sulfate particles. Corresponding particle glass transition...
Abstract. Aerosol absorption is strongly dependent on the internal heterogeneity (mixing state) and morphology of individual particles containing black carbon (BC) other non-absorbing species. Here, we examine an extensive microscopic data set collected in California Central Valley during CARES 2010 field campaign. During a period high photochemical activity pollution buildup, particle mixing state were characterized using scanning transmission X-ray microscopy (STXM) at K-edge. Observations...
Abstract Atmospheric immersion freezing (IF), a heterogeneous ice nucleation process where an nucleating particle (INP) is immersed in supercooled water, dominant formation pathway impacting the hydrological cycle and climate. Implementation of IF derived from field laboratory data cloud climate models difficult due to high variability spatio-temporal scales, INP composition, morphological complexity. We demonstrate that can be consistently described by stochastic accounting for...
Abstract A new parameterization for quantifying the mixing state of aerosol populations has been applied first time to samples ambient particles analyzed using spectro‐microscopy techniques. Scanning transmission X‐ray microscopy/near edge absorption fine structure (STXM/NEXAFS) and computer‐controlled scanning electron microscopy/energy dispersive spectroscopy (CCSEM/EDX) were used probe composition organic inorganic fraction individual collected on 27 28 June during 2010 Carbonaceous...
Abstract. Immersion freezing of water and aqueous (NH4)2SO4 droplets containing leonardite (LEO) Pahokee peat (PP) serving as surrogates for humic-like substances (HULIS) has been investigated. Organic aerosol HULIS are ubiquitous in the atmosphere; however, their potential ice cloud formation is uncertain. studied temperatures low 215 K solution activity, aw, from 0.85 to 1.0. The LEO PP 5–15 warmer than homogeneous nucleation temperatures. Heterogeneous can be represented by a horizontal...
Films of biogenic compounds exposed to the atmosphere are ubiquitously found on surfaces cloud droplets, aerosol particles, buildings, plants, soils and ocean. These air/water interfaces host countless amphiphilic concentrated there with respect in bulk water, leading a unique chemical environment. Here, photochemical processes at interface biofilm-containing solutions were studied, demonstrating abiotic VOC production from authentic surfactants under ambient conditions. Using combination...
Abstract The oceans cover most of the Earth's surface, contain nearly half total global primary biomass productivity, and are a major source atmospheric aerosol particles. Here we experimentally investigate links between biological activity in seawater sea spray (SSA) flux, relationship potential significance for organic loading cloud formation over thus climate globally. Bubbles were generated laboratory mesocosm experiments either by recirculating impinging water jets or glass frits....
Organic interfaces that exist at the sea surface microlayer or as surfactant coatings on cloud droplets are highly concentrated and chemically distinct from underlying bulk overlying gas phase. Therefore, they may be potentially unique locations for chemical photochemical reactions. Recently, production of volatile organic compounds (VOCs) was reported a nonanoic acid interface however, subsequent secondary aerosol (SOA) particle incapable being observed. We investigated SOA formation due to...