
Sergey NizkorodovUniversity of California, Irvine | UCI · Department of Chemistry
Sergey Nizkorodov
PhD
About
252
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Introduction
Education
September 1993 - June 1997
September 1989 - June 1993
Publications
Publications (252)
Emission factors of 16 particle-bound polycyclic aromatic hydrocarbons (16 p-PAHs) from residential fuel combustion are highly variable, resulting in significant uncertainty with respect to the estimation of emissions of PAHs from this sector. Emissions of 16 p-PAHs were characterized during daily cooking activities for two traditional Indian cooks...
Free radicals play an important role in many chemical and biological processes, but due to their highly reactive and short-lived nature, they evade most analytical techniques, limiting our understanding of their formation and reactivity. Spin trapping molecules can react with free radicals to form radical adducts with lifetimes long enough for anal...
Fires at the wildland–urban interface (WUI) are increasing in magnitude and frequency, emitting organic aerosol (OA) with unknown composition and atmospheric impacts. In this study, we investigated the chemical composition of OA produced through the 600 °C pyrolysis of ten urban materials in nitrogen, which were subsequently aged under UV light for...
Primary biological aerosol particles (PBAPs) and secondary organic aerosol (SOA) both contain organic compounds that share similar chemical and optical properties. Fluorescence is often used to characterize PBAPs; however, this may be hindered due to interferences from fluorophores in SOA. Despite extensive efforts to understand the aging of SOA un...
The chemical composition and physical properties of secondary organic aerosol (SOA) generated through OH-initiated oxidation of mixtures containing β-myrcene, an acyclic monoterpene, and d-limonene, a cyclic monoterpene, were investigated to assess the extent of the chemical interactions between their oxidation products. The SOA samples were prepar...
Oxidation of indole by nitrate radical (NO3) was previously proposed to form nitroindole, largely responsible for the brown color of indole secondary organic aerosol (SOA). As there are seven known nitroindole isomers, we used chromatographic separation to show that a single nitroindole isomer is produced in the indole + NO3 reaction and definitive...
Electronic cigarette smoking (or vaping) is on the rise, presenting questions about the effects of secondhand exposure. The chemical composition of vape emissions was examined in the exhaled breath of eight human volunteers with the high chemical specificity of complementary online and offline techniques. Our study is the first to take multiple exh...
Sulfuric acid in the atmosphere can participate in acid-catalyzed and acid-driven reactions, including those within secondary organic aerosols (SOA). Previous studies have observed enhanced absorption at visible wavelengths and significant changes in the chemical composition when SOA was exposed to sulfuric acid. However, the specific chromophores...
Thermal desorption measurements, including thermal desorption mass spectrometry, are often used to determine the volatility and chemical composition of secondary organic aerosol (SOA). Accurately interpreting such measurements requires understanding the response of SOA to heat. Using optical microscopy, we monitored catechol + O₃ SOA during heating...
Emissions from large-scale fires significantly contribute to the atmospheric burden of primary organic aerosol (OA). The frequency of fires occurring at the wildland-urban interface (WUI) is increasing, with biomass and...
The photochemical aging of biomass-burning organic aerosols (BBOAs) by exposure to sunlight changes the chemical composition over its atmospheric lifetime, affecting the toxicological and climate-relevant properties of BBOA particles. This study used electron paramagnetic resonance (EPR) spectroscopy with a spin-trapping agent, 5-tert-butoxycarbony...
Atmospheric simulation chambers continue to be indispensable tools for research in the atmospheric sciences. Insights from chamber studies are integrated into atmospheric chemical transport models, which are used for science-informed policy decisions. However, a centralized data management and access infrastructure for their scientific products had...
Plant stress alters emissions of volatile organic compounds. However, little is known about how this could influence climate-relevant properties of secondary organic aerosol (SOA), particularly from complex mixtures such as real plant emissions. In this study, the chemical composition and viscosity were examined for SOA generated from real healthy...
Light-absorbing organic aerosols, commonly referred to as “brown carbon” (BrC), have important climate effects. The primary source of BrC is biomass burning, but additional BrC can be formed by less constrained secondary atmospheric reactions, such as photooxidation of aromatic volatile organic compounds (VOCs) and reactions of carbonyl compounds i...
Secondary organic aerosol (SOA) from indole was produced in a smog chamber under different relative humidity (RH = <2%, 25% and 50%) and with different oxidants (O3, OH, OH + NOx, and NO3). The mass absorption coefficients were measured by extracting SOA in methanol and taking absorption spectra in the 200-700 nm range. Chromophoric compounds were...
Hydroxyl radical (OH) is a key oxidant that triggers atmospheric oxidation chemistry in both gas and aqueous phases. The current understanding of its aqueous sources is mainly based on known bulk (photo)chemical processes, uptake from gaseous OH, or related to interfacial O3 and NO3 radical-driven chemistry. Here, we present experimental evidence t...
Wildfires, which have been occurring increasingly in the era of climate change, emit massive amounts of particulate matter (PM) into the atmosphere, strongly affecting air quality and public health. Biomass burning aerosols may contain environmentally persistent free radicals (EPFRs, such as semiquinone radicals) and redox-active compounds that can...
Previous studies have suggested that the photochemistry of nitroaromatics in organic solvents can vary significantly from the photochemistry in aqueous solutions. This work compares the photodegradation of 2-nitrophenol (2NP), 4-nitrophenol (4NP), 2,4-dinitrophenol (24DNP), and 2,4,6-trinitrophenol (246TNP) in 2-propanol and water to better underst...
Biomass burning organic aerosol (BBOA) is one of the largest sources of organics in the atmosphere.
Secondary organic aerosol (SOA) constitutes a large fraction of atmospheric aerosol. To assess its impacts on climate and air pollution, knowledge of the number of phases in internal mixtures of different SOA types is required. Atmospheric models often assume that different SOA types form a single phase when mixed. Here, we present visual observati...
Secondary organic aerosol (SOA) plays a critical, yet uncertain, role in air quality and climate. Once formed, SOA is transported throughout the atmosphere and is exposed to solar UV light. Information on the viscosity of SOA, and how it may change with solar UV exposure, is needed to accurately predict air quality and climate. However, the effect...
Reactive oxygen species (ROS) and environmentally persistent free radicals (EPFR) play an important role in chemical transformation of atmospheric aerosols and adverse aerosol health effects. This study investigated the effects of nitrogen oxides (NOx) during photooxidation of α-pinene and naphthalene on the EPFR content and ROS formation from seco...
The viscosity of secondary organic aerosol (SOA) is needed to improve predictions of air quality, climate, and atmospheric chemistry. Many techniques have been developed to measure the viscosity of micrometer-sized materials at room temperature; however, few techniques are able to measure viscosity as a function of temperature for these small sampl...
Secondary organic aerosol (SOA) generated from the photooxidation of aromatic compounds in the presence of oxides of nitrogen (NOx) is known to efficiently absorb ultraviolet and visible radiation. With exposure to sunlight, the photodegradation of chromophoric compounds in the SOA causes this type of SOA to slowly photobleach. These photodegradati...
Secondary organic aerosol (SOA) constitutes a large fraction of atmospheric aerosol. To assess its impacts on cli-mate and air pollution, knowledge of the number of phases in internal mixtures of different SOA types is required. Atmospheric models often assumed that different SOA types form a single phase when mixed. Here, we present visual observa...
The viscosity of secondary organic aerosols (SOA) is needed to predict their influence on air quality, climate, and atmospheric chemistry. Many techniques have been developed to measure the viscosity of micrometer-sized materials at room temperature, however, few techniques are able to measure viscosity as a function of temperature for these small...
In addition to the well-constrained inorganic acid-base chemistry of ammonia resulting in fine particulate matter (PM2.5) formation, ammonia also reacts with certain organic compounds in secondary organic aerosol (SOA) to produce less basic nitrogen-containing organic compounds. In this study, the potential meteorology and air quality impacts of th...
Transition metals are increasingly recognized as key drivers in the formation and aging of light-absorbing organic aerosols, known as brown carbon, which impact the energy flux in the atmosphere. Here the authors discuss somewhat overlooked condensed phase chemical processes and identify research needs to improve our fundamental understanding of at...
This study investigated the uptake of ammonia (NH3) by secondary organic aerosol (SOA) particles generated via limonene photooxidation or ozonolysis as well as the uptake of dimethylamine (DMA) by limonene ozonolysis, α-cedrene photooxidation, or toluene photooxidation SOA in an environmental chamber between 0–50% relative humidity. In addition to...
We investigated the photosensitizing properties of secondary organic aerosol (SOA) formed during the hydroxyl radical (OH) initiated oxidation of naphthalene. This SOA was injected into an aerosol flow tube and exposed to UV radiation and gaseous volatile organic compounds or sulfur dioxide (SO2). The aerosol particles were observed to grow in size...
Molecular composition, viscosity, and phase state were investigated for secondary organic aerosol derived from synthetic mixtures of volatile organic compounds representing emissions from healthy and aphid-stressed Scots pine trees.
A large concern with estimates of climate and health co-benefits of "clean" cookstoves from controlled emissions testing is whether results represent what actually happens in real homes during normal use. A growing body of evidence indicates that in-field emissions during daily cooking activities differ substantially from values obtained in laborat...
Our previous work demonstrated formation of highly insoluble and strongly light-absorbing organic particles in reactions between catechol or guaiacol with Fe( iii ) under pH = 3 conditions characteristic of aerosol liquid water.
Dust is the major source of iron in atmospheric aerosols but little is known about its role in catalyzing polymerization reactions of organics in particles. Using Arizona Test Dust (AZTD) and hematite nanoparticles as laboratory standards and proxies for hematite-rich natural dust, respectively, we show that their reactions with catechol in aqueous...
Secondary organic aerosol (SOA) is an important constituent of the atmosphere where SOA particles are formed chiefly by the condensation or reactive uptake of oxidation products of volatile organic compounds (VOCs). The mass yield in SOA particle formation, as well as the chemical composition and volatility of the particles, is determined by the id...
To better understand the effects of wildfires on air quality and climate, it is important to assess the occurrence of chromophoric compounds in smoke and characterize their optical properties. This study explores the molecular composition of light-absorbing organic aerosol, or brown carbon (BrC), sampled at the Missoula Fire Sciences laboratory as...
The effect of common atmospheric solutes on aqueous-phase aging of secondary organic aerosol (SOA) was explored under irradiated and dark conditions. SOA particles were produced from dark ozonolysis of α-pinene or α-humulene in a photochemical smog chamber, collected on filters, and extracted in either pure water or in aqueous solutions containing...
Abstract. Secondary organic aerosol (SOA) is an important constituent of the atmosphere where SOA particles are formed chiefly by the condensation or reactive uptake of oxidation products of volatile organic compounds (VOC). The mass yield in SOA particle formation, as well as the chemical composition and volatility of the particles are determined...
Information on liquid–liquid phase separation (LLPS) and viscosity (or diffusion) within secondary organic aerosol (SOA) is needed to improve predictions of particle size, mass, reactivity, and cloud nucleating properties in the atmosphere. Here we report on LLPS and viscosities within SOA generated by the photooxidation of diesel fuel vapors. Dies...
To better understand the effects of wildfires on air quality and climate, it is important to assess the occurrence of chromophoric compounds in smoke and characterize their optical properties. This study explores the molecular composition of light-absorbing organic aerosol, or brown carbon (BrC), sampled at the Missoula Fire Sciences laboratory as...
Approximately 3 billion people worldwide cook with solid fuels, such as wood, charcoal, and agricultural residues. These fuels, also used for residential heating, are often combusted in inefficient devices, producing carbonaceous emissions. Between 2.6 and 3.8 million premature deaths occur as a result of exposure to fine particulate matter from th...
Information on liquid-liquid phase separation (LLPS) and viscosity (or diffusion) within secondary organic aerosol (SOA) is needed to improve predictions of particle size, mass, reactivity, and cloud nucleating properties in the atmosphere. Here we report on LLPS and viscosities within SOA generated by the photooxidation of diesel fuel vapors. Dies...
The volatility of oxidation products of volatile organic compounds (VOCs) in the atmosphere is a key factor to determine if they partition into the particle phase contributing to secondary organic aerosol (SOA) mass. Thus, linking volatility and measured particle composition will provide insights into SOA formation and its fate in the atmosphere. W...
Viscosities and diffusion rates of organics within secondary organic aerosol (SOA) remain uncertain. Using the bead-mobility technique, we measured viscosities as a function of water activity (aw) of SOA generated by the ozonolysis of limonene followed by browning by exposure to NH3 (referred to as brown limonene SOA or brown LSOA). These measureme...
Ammonia-driven carbonyl-to-imine conversion is an important formation pathway to the nitrogen-containing organic compounds (NOCs) in secondary organic aerosols (SOAs). Previous studies have mainly focused on the dicarbonyl compounds as the precursors of light-absorbing NOCs. In this work, we investigated whether acrolein could also act as an NOC pr...
Approximately 3 billion people worldwide cook with solid fuels, such as wood, charcoal, and agricultural residues. These fuels are often combusted in inefficient cookstoves, producing carbonaceous emissions. Between 2.6 and 3.8 million premature deaths occur as a result to exposure to fine particulate matter from the resulting household air polluti...
The absorption of solar actinic radiation by atmospheric secondary organic aerosol (SOA) particles drives condensed-phase photochemical processes, which lead to particle mass loss by the production of CO, CO2, hydrocarbons, and various oxygenated volatile organic compounds (OVOCs). We examined the influence of relative humidity (RH) and Fe(III) con...
Secondary organic aerosol (SOA) produced by photooxidation of biogenic and anthropogenic volatile organic compounds (VOCs) represent a large fraction of fine atmospheric particulate matter (PM 2.5). The chemical composition of SOA particles is continuously changing as a result of various chemical and physical aging processes. One of the recently di...
The chapter outlines authors' view on the importance of multiphase chemistry in the atmosphere. The chapter starts with a short description of the development of atmospheric chemistry from gas-phase spectroscopy and kinetics into a highly interdisciplinary research on complex multiphase processes. Despite the impressive progress over the years in o...
Light-absorbing organic aerosol, commonly known as brown carbon (BrC), is a significant contributor to radiative forcing of the Earth's climate and also is of potential toxicological concern. Understanding the environmental effects of BrC, its sources, formation, and aging processes requires molecular-level speciation of its chromophores and charac...
Secondary organic aerosol (SOA) produced by photooxidation of biogenic and anthropogenic volatile organic compounds (VOCs) represent a large fraction of fine atmospheric particulate matter (PM2.5). The chemical composition of SOA particles is continuously changing as a result of various chemical and physical aging processes. One of the recently dis...
Air quality in rural India is impacted by residential cooking and heating with biomass fuels. In this study, emissions of CO, CO2, and 76 volatile organic compounds (VOCs) and fine particulate matter (PM2.5) were quantified to better understand the relationship between cook fire emissions and ambient ozone and secondary organic aerosol (SOA) format...
Light-absorbing components of atmospheric organic aerosols, which are collectively termed "brown carbon" (BrC) are ubiquitous in the atmosphere. They affect absorption of solar radiation by aerosols in the atmosphere and human health as some of them have been identified as potential toxins. Understanding the sources, formation, atmospheric evolutio...
Ammonia-driven carbonyl-to-imine conversion is an important formation pathway to the nitrogen-containing organic compounds (NOC) in secondary organic aerosols (SOA). Previous studies have mainly focused on the dicarbonyl compounds as the precursors of light-absorbing NOC. In this work, we investigated whether acrolein could also act as a NOC precur...
Viscosities and diffusion rates of organics within secondary organic aerosol (SOA) remain uncertain. Using the bead-mobility technique, we measured the viscosities as a function of water activity (aw) of SOA generated by the ozonolysis of limonene followed by browning by exposure to NH3 (referred to as brown limonene SOA or brown LSOA). These measu...
Environmental transmission electron microscopy was employed to probe transformations in the size, morphology, and composition of individual atmospheric particles as a function of temperature. Two different heating devices were used and calibrated in this work: a furnace heater and a Micro Electro Mechanical System heater. The temperature calibratio...
The photochemistry of carbonyl compounds is of considerable atmospheric importance, but the mechanisms and dynamics are often unknown. Here, we explore these topics for a system with adjacent keto and enol chromophoric groups. The photochemistry in the S1 and S2 states of the most stable tautomer of 1,2-cyclohexanedione, is studied theoretically us...
Air quality in rural India is impacted by residential cooking and heating with biomass fuels. In this study, emissions of CO, CO2, and 76 volatile organic compounds (VOCs) and fine particulate matter (PM2.5) were quantified to better understand the relationship between cook fire emissions and ambient ozone and secondary organic aerosol formation. C...
Reactions between ammonia (NH3) and organic compounds containing carbonyl functional groups in aerosol particles can form organic products that are less basic than NH3 and are thus unable to neutralize efficiently nitric and sulfuric acids. In this exploratory study, the University of California, Irvine - California Institute of Technology (UCI-CIT...
We used a quartz crystal microbalance (QCM) to quantify the mass loss resulting from exposure of secondary organic aerosol (SOA) particles deposited on the QCM crystal to 254, 305, and 365 nm radiation. We coupled the QCM setup to a Proton Transfer Reaction Time-of-Flight Mass Spectrometer (PTR-ToF-MS) to chemically resolve the photoproduced volati...