Overview of ICARUS-A Curated, Open Access, Online Repository for Atmospheric Simulation Chamber Data.

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 not been available in the United States and many parts of the world.

Reactive Chlorine Emissions from Cleaning and Reactive Nitrogen Chemistry in an Indoor Athletic Facility.

Indoor gas-phase radical sources are poorly understood but expected to be much different from outdoors. Several potential radical sources were measured in a windowless, light-emitting diode (LED)-lit room in a college athletic facility over a 2 week period. Alternating measurements between the room air and the supply air of the heating, ventilation, and air-conditioning system allowed an assessment of sources.

Chemistry of Secondary Organic Aerosol Formation from Reactions of Monoterpenes with OH Radicals in the Presence of NO.

The oxidation of volatile organic compounds (VOCs), which are emitted to the atmosphere from natural and anthropogenic sources, leads to the formation of ozone and secondary organic aerosol (SOA) particles that impact air quality and climate. In the study reported here, we investigated the products of the reactions of five biogenic monoterpenes with OH radicals (an important daytime oxidant) under conditions that mimic the chemistry that occurs in polluted air, and developed mechanisms to explain their formation. Experiments were conducted in an environmental chamber, and information on the identity of gas-phase molecular products was obtained using online mass spectrometry, while liquid chromatography and two methods of functional group analysis were used to characterize the SOA composition.

Secondary Organic Aerosol Mass Yields from NO Oxidation of α-Pinene and Δ-Carene: Effect of RO Radical Fate.

Dark chamber experiments were conducted to study the SOA formed from the oxidation of α-pinene and Δ-carene under different peroxy radical (RO) fate regimes: RO + NO, RO + RO, and RO + HO. SOA mass yields from α-pinene oxidation were <1 to ∼25% and strongly dependent on available OA mass up to ∼100 μg m. The strong yield dependence of α-pinene oxidation is driven by absorptive partitioning to OA and not by available surface area for condensation.

Kinetics of oligomer-forming reactions involving the major functional groups present in atmospheric secondary organic aerosol particles.

Atmospheric organic aerosol particles impact climate as well as human and environmental health. Secondary organic aerosol (SOA), which is formed by the gas-to-particle partitioning of products of the oxidation of volatile organic compounds (VOCs) emitted from biogenic or anthropogenic sources, contributes a large fraction of this material. In the particle phase, these products can undergo accretion reactions to form oligomers that impact the formation, composition, and chemical-physical properties of aerosols.

Gas- and Particle-Phase Products and Their Mechanisms of Formation from the Reaction of Δ-3-Carene with NO Radicals.

Monoterpenes are a major component of the large quantities of biogenic volatile organic compounds that are emitted to the atmosphere each year. They have a variety of structures, which influences their subsequent reactions with OH radicals, O, or NO radicals and the tendency for these reactions to form secondary organic aerosol (SOA). Here we report the results of an environmental chamber study of the reaction of Δ-3-carene, an abundant unsaturated C bicyclic monoterpene, with NO radicals, a major nighttime oxidant.

Comprehensive Analysis of Products and the Development of a Quantitative Mechanism for the OH Radical-Initiated Oxidation of 1-Alkenes in the Presence of NO.

The reactions of 1-tetradecene and 1-pentadecene, the C and C linear 1-alkenes, with OH radicals in the presence of NO were investigated in a series of environmental chamber experiments. Particle-phase β-hydroxynitrates, dihydroxynitrates, dihydroxycarbonyls, and 1,4-hydroxynitrates and gas-phase aldehydes were sampled and then identified and quantified using a suite of offline analytical techniques that included derivatization, gas and liquid chromatography, and multiple types of mass spectrometry. Measured molar yields of products formed by OH radical addition to the C═C double bond, including β-hydroxynitrates, dihydroxynitrates, dihydroxycarbonyls (which have not been previously directly quantified with high accuracy), and aldehydes were 0.

Quantification and source characterization of volatile organic compounds from exercising and application of chlorine-based cleaning products in a university athletic center.

Humans spend approximately 90% of their time indoors, impacting their own air quality through occupancy and activities. Human VOC emissions indoors from exercise are still relatively uncertain, and questions remain about emissions from chlorine-based cleaners. To investigate these and other issues, the ATHLETic center study of Indoor Chemistry (ATHLETIC) campaign was conducted in the weight room of the Dal Ward Athletic Center at the University of Colorado Boulder.

Quantification of alkenes on indoor surfaces and implications for chemical sources and sinks.

Indoor surfaces are known to support organic films, but their thickness, composition, and variability between environments remain poorly characterized. Alkenes are expected to be a significant component of these films, with the reaction with O being a major sink for O and source of airborne chemicals. Here, we present a sensitive, microscale, nanospectrophotometric method for quantifying the alkene (C=C bond) content of surface films and demonstrate its applicability in five studies relevant to indoor air chemistry.

Measurements and modeling of absorptive partitioning of volatile organic compounds to painted surfaces.

Partitioning to surfaces is an important sink for volatile organic compounds (VOCs) indoors, but the mechanisms are not well understood or quantified. Here, a mass spectrometer was coupled to a portable surface reactor and a flow tube to measure partitioning of VOCs into paint films coated onto glass or wallboard, and their subsequent diffusion. A model was developed to extract values of the effective absorbing organic mass concentration of the film, C , which is a measure of absorption capacity, and VOC diffusion coefficients, D , from VOC time profiles measured during film passivation and depassivation.

Budgets of Organic Carbon Composition and Oxidation in Indoor Air.

The chemical composition of indoor air at the University of Colorado, Boulder art museum was measured by a suite of gas- and particle-phase instruments. Over 80% of the total observed organic carbon (TOOC) mass (100 μg m) consisted of reduced compounds (carbon oxidation state, OS < -0.5) with high volatility (log * > 7) and low carbon number ( < 6).

Branching Ratios and Rate Constants for Decomposition and Isomerization of β-Hydroxyalkoxy Radicals Formed from OH Radical-Initiated Reactions of C-C 2-Methyl-1-Alkenes in the Presence of NO.

A series of C-C 2-methyl-1-alkenes were reacted with OH radicals in the presence of NO in a Teflon environmental chamber, and molar yields of the 2-ketone products were measured using gas chromatography. Yields were corrected for secondary reactions with OH radicals and for gas-wall partitioning of the 2-methyl-1-alkene and 2-ketone, with the latter correction being determined from measurements of gas-wall partitioning of 2-ketone standards. Molar yields of 2-ketones decreased with increasing 2-methyl-1-alkene carbon number from a maximum of 0.

Time-Resolved Measurements of Indoor Chemical Emissions, Deposition, and Reactions in a University Art Museum.

A 6-week study was conducted at the University of Colorado Art Museum, during which volatile organic compounds (VOCs), carbon dioxide (CO), ozone (O), nitric oxide (NO), nitrogen dioxide (NO), other trace gases, and submicron aerosol were measured continuously. These measurements were then analyzed using a box model to quantify the rates of major processes that transformed the composition of the air. VOC emission factors were quantified for museum occupants and their activities.

Nanoporous silicon nitride-based membranes of controlled pore size, shape and areal density: Fabrication as well as electrophoretic and molecular filtering characterization.

A new route will be presented for an all-parallel fabrication of highly flexible, freestanding membranes with well-defined porosity. This fabrication is based on arrays of well-defined Au nanoparticles (NPs) exhibiting a high degree of hexagonal order as obtained in a first step by a proven micellar approach. These NP arrays serve as masks in a second reactive ion etching (RIE) step optimized for etching Si and some important Si compounds (silicon oxide, silicon nitride) on the nanoscale.

Electrochemically-Driven Insertion of Biological Nanodiscs into Solid State Membrane Pores as a Basis for "Pore-In-Pore" Membranes.

Nanoporous membranes are of increasing interest for many applications, such as molecular filters, biosensors, nanofluidic logic and energy conversion devices. To meet high-quality standards, e.g.

Identification and Quantitation of Aerosol Products of the Reaction of β-Pinene with NO Radicals and Implications for Gas- and Particle-Phase Reaction Mechanisms.

Substantial amounts of gas- and particle-phase organic nitrates have been reported in field studies of atmospheric chemistry conducted around the world, and it has been proposed that a significant fraction of these may be formed from the nighttime reaction of monoterpenes with NO radicals. In the study presented here, β-pinene (a major global monoterpene emission) was reacted with NO radicals in an environmental chamber and the molecular and functional group composition of the resulting secondary organic aerosol (SOA) was determined using a variety of methods. Eight products, which comprised ∼95% of the SOA mass, were identified and quantified.

Identification and Quantification of 4-Nitrocatechol Formed from OH and NO Radical-Initiated Reactions of Catechol in Air in the Presence of NO: Implications for Secondary Organic Aerosol Formation from Biomass Burning.

Catechol (1,2-benzenediol) is emitted from biomass burning and produced from a reaction of phenol with OH radicals. It has been suggested as an important secondary organic aerosol (SOA) precursor, but the mechanisms of gas-phase oxidation and SOA formation have not been investigated in detail. In this study, catechol was reacted with OH and NO radicals in the presence of NO in an environmental chamber to simulate daytime and nighttime chemistry.

Regional Similarities and NO-related Increases in Biogenic Secondary Organic Aerosol in Summertime Southeastern U.S.

During the 2013 Southern Oxidant and Aerosol Study, Fourier Transform Infrared Spectroscopy (FTIR) and Aerosol Mass Spectrometer (AMS) measurements of submicron mass were collected at Look Rock (LRK), Tennessee, and Centreville (CTR), Alabama. Carbon monoxide and submicron sulfate and organic mass concentrations were 15-60% higher at CTR than at LRK but their time series had moderate correlations (r~0.5).

Direct Measurements of Gas/Particle Partitioning and Mass Accommodation Coefficients in Environmental Chambers.

Secondary organic aerosols (SOA) are a major contributor to fine particulate mass and wield substantial influences on the Earth's climate and human health. Despite extensive research in recent years, many of the fundamental processes of SOA formation and evolution remain poorly understood. Most atmospheric aerosol models use gas/particle equilibrium partitioning theory as a default treatment of gas-aerosol transfer, despite questions about potentially large kinetic effects.

Hygroscopicity of Organic Compounds as a Function of Carbon Chain Length and Carboxyl, Hydroperoxy, and Carbonyl Functional Groups.

The albedo and microphysical properties of clouds are controlled in part by the hygroscopicity of particles serving as cloud condensation nuclei (CCN). Hygroscopicity of complex organic mixtures in the atmosphere varies widely and remains challenging to predict. Here we present new measurements characterizing the CCN activity of pure compounds in which carbon chain length and the numbers of hydroperoxy, carboxyl, and carbonyl functional groups were systematically varied to establish the contributions of these groups to organic aerosol apparent hygroscopicity.

Gas-Phase Carboxylic Acids in a University Classroom: Abundance, Variability, and Sources.

Gas-phase carboxylic acids are ubiquitous in ambient air, yet their indoor occurrence and abundance are poorly characterized. To fill this gap, we measured gas-phase carboxylic acids in real-time inside and outside of a university classroom using a high-resolution time-of-flight chemical ionization mass spectrometer (HRToF-CIMS) equipped with an acetate ion source. A wide variety of carboxylic acids were identified indoors and outdoors, including monoacids, diacids, hydroxy acids, carbonyl acids, and aromatic acids.

The Essential Role for Laboratory Studies in Atmospheric Chemistry.

Laboratory studies of atmospheric chemistry characterize the nature of atmospherically relevant processes down to the molecular level, providing fundamental information used to assess how human activities drive environmental phenomena such as climate change, urban air pollution, ecosystem health, indoor air quality, and stratospheric ozone depletion. Laboratory studies have a central role in addressing the incomplete fundamental knowledge of atmospheric chemistry. This article highlights the evolving science needs for this community and emphasizes how our knowledge is far from complete, hindering our ability to predict the future state of our atmosphere and to respond to emerging global environmental change issues.

Effect of the Keto Group on Yields and Composition of Organic Aerosol Formed from OH Radical-Initiated Reactions of Ketones in the Presence of NOx.

Yields of secondary organic aerosol (SOA) were measured for OH radical-initiated reactions of the 2- through 6-dodecanone positional isomers and also n-dodecane and n-tetradecane in the presence of NOx. Yields decreased in the order n-tetradecane > dodecanone isomer average > n-dodecane, and the dodecanone isomer yields decreased as the keto group moved toward the center of the molecule, with 6-dodecanone being an exception. Trends in the yields can be explained by the effect of carbon number and keto group presence and position on product vapor pressures, and by the isomer-specific effects of the keto group on branching ratios for keto alkoxy radical isomerization, decomposition, and reaction with O2.

Magnetic switching of nanoscale antidot lattices.

We investigate the rich magnetic switching properties of nanoscale antidot lattices in the 200 nm regime. In-plane magnetized Fe, Co, and Permalloy (Py) as well as out-of-plane magnetized GdFe antidot films are prepared by a modified nanosphere lithography allowing for non-close packed voids in a magnetic film. We present a magnetometry protocol based on magneto-optical Kerr microscopy elucidating the switching modes using first-order reversal curves.