Alla Zelenyuk

Clustering has become an unavoidable step in big data analysis. It may be used to arrange data into a compact format, making operations on big data manageable. However, clustering of big data requires not only the capability of handling data with large volume and high dimensionality, but also the ability to process streaming data, all of which are less developed in most current algorithms. Furthermore, big data processing is seldom interactive, which stands at conflict with users who seek answers immediately. The best one can do is to process incrementally, such that partial and, hopefully, accurate results can be available relatively quickly and are then progressively refined over time. We propose a clustering framework which uses Multi-Dimensional Scaling for layout and GPU acceleration to accomplish these goals. Our domain application is the clustering of mass spectral data of individual aerosol particles with 8 million data points of 450 dimensions each.

The Cloud, Aerosol, and Complex Terrain Interactions (CACTI) field campaign was designed to improve understanding of orographic cloud life cycles in relation to surrounding atmospheric thermodynamic, flow, and aerosol conditions. The deployment to the Sierras de Córdoba range in north-central Argentina was chosen because of very frequent cumulus congestus, deep convection initiation, and mesoscale convective organization uniquely observable from a fixed site. The C-band Scanning Atmospheric Radiation Measurement (ARM) Precipitation Radar was deployed for the first time with over 50 ARM Mobile Facility atmospheric state, surface, aerosol, radiation, cloud, and precipitation instruments between October 2018 and April 2019. An intensive observing period (IOP) coincident with the RELAMPAGO field campaign was held between 1 November and 15 December during which 22 flights were performed by the ARM Gulfstream-1 aircraft. A multitude of atmospheric processes and cloud conditions were obser...

We developed a parametrizable box model to empirically derive the yields of semivolatile products from VOC oxidation using chamber measurements, while explicitly accounting for the multigenerational chemical aging processes (such as the gas-phase fragmentation and functionalization and aerosol-phase oligomerization and photolysis) under different NO levels and the loss of particles and gases to chamber walls. Using the oxidation of isoprene as an example, we showed that the assumptions regarding the NO -sensitive, multigenerational aging processes of VOC oxidation products have large impacts on the parametrized product yields and SOA formation. We derived sets of semivolatile product yields from isoprene oxidation under different NO levels. However, we stress that these product yields must be used in conjunction with the corresponding multigenerational aging schemes in chemical transport models. As more mechanistic insights regarding SOA formation from VOC oxidation emerge, our box ...

Low bulk diffusivity inside viscous semisolid atmospheric secondary organic aerosol (SOA) can prolong equilibration timescale, but its broader impacts on aerosol growth and size distribution dynamics are poorly understood. Here we present quantitative insights into the effects of bulk diffusivity on the growth and evaporation kinetics of SOA formed under dry conditions from photooxidation of isoprene in the presence of a bimodal aerosol consisting of Aitken (ammonium sulfate) and accumulation (isoprene or -pinene SOA) mode particles. Aerosol composition measurements and evaporation kinetics indicate that isoprene SOA is composed of several semivolatile organic compounds (SVOCs), with some reversibly reacting to form oligomers. Model analysis shows that liquid-like bulk diffusivities can be used to fit the observed evaporation kinetics of accumulation mode particles, but fail to explain the growth kinetics of bimodal aerosol by significantly under-predicting the evolution of the Ait...

Polycyclic aromatic hydrocarbons (PAHs) have toxic impacts on humans and ecosystems. One of the most carcinogenic PAHs, benzo(a)pyrene (BaP), is efficiently bound to and transported with atmospheric particles. Laboratory measurements show that particle-bound BaP degrades in a few hours by heterogeneous reaction with ozone, yet field observations indicate BaP persists much longer in the atmosphere, and some previous chemical transport modeling studies have ignored heterogeneous oxidation of BaP to bring model predictions into better agreement with field observations. We attribute this unexplained discrepancy to the shielding of BaP from oxidation by coatings of viscous organic aerosol (OA). Accounting for this OA viscosity-dependent shielding, which varies with temperature and humidity, in a global climate/chemistry model brings model predictions into much better agreement with BaP measurements, and demonstrates stronger long-range transport, greater deposition fluxes, and substantia...

Multiphase chemistry of isomeric isoprene epoxydiols (IEPOX) has been shown to be the dominant source of isoprene-derived secondary organic aerosol (SOA). Recent studies have reported particles composed of ammonium bisulfate (ABS) mixed with model organics exhibit slower rates of IEPOX uptake. In the present study, we investigate the effect of atmospherically-relevant organic coatings of α-pinene (AP) SOA on the reactive uptake of trans-β-IEPOX onto ABS particles under different conditions and coating thicknesses. Single particle mass spectrometry was used to characterize in real-time particle size, shape, density, and quantitative composition before and after reaction with IEPOX. We find that IEPOX uptake by pure sulfate particles is a volume-controlled process, which results in particles with uniform concentration of IEPOX-derived SOA across a wide range of sizes. Aerosol acidity was shown to enhance IEPOX-derived SOA formation, consistent with recent studies. The presence of wate...

New gasoline engine technologies such as Spark Ignition Direct Injection (SIDI), Gasoline Direct Injection Compression Ignition (GDICI), and Reaction Controlled Compression Ignition (RCCI) offer the possibility of dramatically increasing the fuel efficiency of future vehicles. One drawback to these advanced engines is that they have the potential to produce higher levels of exhaust particulates than current Port Fuel Injection (PFI) engines. Regulation of engine particulate emissions in Europe is moving from mass-based standards toward number-based standards. Due to growing health concerns surrounding nano-aerosols, it is likely that similar standards will eventually be applied in the United States. This would place more emphasis on the reliable removal of smaller particles, which make up the vast majority of the particulates generated on a number basis. While Diesel Particulate Filters (DPF) have become standard, different filter systems would likely be required for advanced gasoline vehicles, due to factors such as differing particulate properties and higher exhaust temperatures. High exhaust temperatures can limit the accumulation of a soot cake, which performs most of the actual filtration in a typical DPF system.

We have developed the novel Aerosol Dynamics, gas- and particle-phase chemistry model for laboratory CHAMber studies (ADCHAM). The model combines the detailed gas-phase Master Chemical Mechanism version 3.2 (MCMv3.2), an aerosol dynamics and particle-phase chemistry module (which considers acid-catalysed oligomerization, heterogeneous oxidation reactions in the particle phase and non-ideal interactions between organic compounds, water and inorganic ions) and a kinetic multilayer module for diffusion-limited transport of compounds between the gas phase, particle surface and particle bulk phase. In this article we describe and use ADCHAM to study (1) the evaporation of liquid dioctyl phthalate (DOP) particles, (2) the slow and almost particle-size-independent evaporation of α-pinene ozonolysis secondary organic aerosol (SOA) particles, (3) the mass-transfer-limited uptake of ammonia (NH<sub>3</sub>) and formation of organic salts between ammonium (NH<sub>4</sub&gt...

A review of water uptake measurements conducted over the past 25 years using the Humidified Tandem Differential Mobility Analyzer (HTDMA) technique reveals that ambient Aitken and accumulation mode particles typically grow substantially less at a given relative humidity compared to pure ammonium sulfate. Multiple hygroscopic modes at a single particle size are routinely observed, revealing that ambient particles are externally mixed with respect to their chemical composition. The observed growth of the multiple hygroscopic modes is typically less than that for particles composed of purely soluble salts, indicating that the externally mixed populations are themselves internally mixed with more and less-water soluble species. Therefore, the HTDMA is a powerful tool for quantitative measurements of size-dependent hygroscopic growth factors and for qualitative observations of the complex chemical composition responsible for the observed growth. The strengths and limitations of the HTDMA...

Aerosol particles are ubiquitous in the atmosphere and have been shown to impact the Earth’s climate, reduce visibility, and adversely affect human health. Modeling the evolution of aerosol systems requires an understanding of the species and mechanisms involved in particle growth, including the complex interactions between particle- and gas-phase species. Here we report studies of displacement of amines (methylamine, dimethylamine, or trimethylamine) in methanesulfonate salt particles by exposure to a different gas-phase amine, using a single particle mass spectrometer, SPLAT II. The variation of the displacement with the nature of the amine suggests that behavior is dependent on water in or on the particles. Small clusters of methanesulfonic acid with amines are used as a model in quantum chemical calculations to identify key structural elements that are expected to influence water uptake, and hence the efficiency of displacement by gas-phase molecules in the aminium salts. Such molecular-level understa...

The three major atmospheric oxidants involved in SOA formation from biogenic volatile organic compounds are O3, OH and nitrate radical (NO3). While O3 and OH-initiated oxidation occur during the day, NO3 radical-initiated oxidation is recognized to be a major contributor to the night-time chemistry of volatile organic compounds in the troposphere. Specifically, the reaction of biogenic hydrocarbons with NO3 is

A unique, high-volume, low-flow, stainless steel aerosol flow system for the study of the formation and reactions of aerosols relevant to the troposphere has been constructed, modeled and experimentally tested. The total flow tube length is 7.3 m which includes a 1.2 m section used for mixing. The flow tube is equipped with ultraviolet lamps for photolysis. The diameter of

More stringent emissions regulations are continually being proposed to mitigate adverse human health and environmental impacts of internal combustion engines. With that in mind, it has been proposed that vehicular particulate matter (PM) emissions should be regulated based on particle number in addition to particle mass. One aspect of this project is to study different sample handling methods for number based aerosol measurements, specifically, two different methods for removing volatile organic compounds (VOCs). One method is a thermodenuder (TD) and the other is an evaporative chamber/diluter (EvCh). These sample handling methods have been implemented in an engine test cell with a spark ignited direct injection (SIDI) engine. The engine was designed for stoichiometric, homogeneous combustion. SIDI is of particular interest for improved fuel efficiency compared to other SI engines, however, the efficiency benefit comes with greater PM emissions and may therefore be subject to the proposed number based PM regulation. Another aspect of this project is to characterize PM from this engine in terms of particle number and composition.

Diesel engines offer higher fuel efficiency, but produce more exhaust particulate than conventional gasoline engines. Diesel particulate filters are presently the most efficient means to reduce these emissions. These filters typically trap particles in two basic modes: at the beginning of the ...

Previous focus+context techniques for radial dendrograms only allow users to either stretch the display along the radius or the angle. In this poster, we present an interactive, hardware-accel- erated rubbersheet-like technique that allows users to perform both operations simultaneously. 1 Introduction Dendrograms are a popular visualization method for illustrat- ing the outcome of decision tree-type clustering in statistics. Most commonly, dendrograms are drawn in a Cartesian layout, as an up- right tree. However, this layout does not make good use of space, it is sparse towards the root and crowded towards the leaf nodes (see Fig. 1). The spacing between nodes at different levels in the hierar- chy is not uniform, which is due to the shrinking number of nodes from bottom to top. For this reason, long, wide-spanning connect- ing lines are needed to merge nodes at higher levels. A better lay- out in this respect is the polar or radial layout, where leaf nodes are located on the outer ring and the root is located in the center, as a focal point. A more uniform node spacing results, leading to a bet- ter utilization of space and resulting in a better illustration of the class relationships. Recently, Barlow and Neville (1) presented an empirical user study for tree layouts (with less than 200 leaves) in which they compare some of the major schemes: organizational chart (a standard drawing of a tree), tree ring (basically a pie chart of circular segments), icicle plot (the cartesian version of the tree ring), and tree map. According to the measured performance within a group of 15 users, the three former methods yielded simi- lar results, with the icicle plot having a slight advantage. However, given the much larger number of leaves in our case (1000 and more) and the fact that the tree ring is the most compact of the three winning configurations, a radial layout seemed to be the most favorable one for our purposes (see Fig. 2). Radial graph layouts that illustrate hierarchical relationships are very popular, and for the special application of dendrograms, we know only of one other application using a radial layout, the recent one by Kreussler and Schumann (3). In their implementation, the radii of the circles onto which nodes can be placed are quantized into a number of levels. The radius at which a (non-leaf) node is placed is a measure of the dissimilarity among its child-nodes, and a linear mapping is used to relate dissimilarity to radius. Leaf nodes, on the other hand, are always placed onto the circle one level below that of the parent node, while the root node is always at the center of the radial lay- out. Context and focus is provided by mapping the radial dendro-

The importance of black carbon particles as heterogeneous ice nuclei is currently in question. While pure black carbon is hydrophobic, atmospheric processing or aging by condensation or heterogeneous oxidation may alter the surface, physical and chemical properties, likely causing the particle surface and perhaps the particle bulk to become more hydrophilic. The impact of such atmospheric processing on the ice

We will present results from two field programs where our Single Particle Laser Ablation Time of Flight Mass Spectrometer (SPLAT-MS) was deployed. SPLAT-MS provides size and chemical composition of individual aerosol particles obtained by real-time sampling directly from ambient air. An aerodynamic lens is used to focus between 50 and 90 percent of entrained particles in the 50nm to 3.5micron into an extremely narrow beam. Two-stages of optical detection placed along the well-defined particle beam are used to detect the presence of an incoming particle, measure its velocity from which its aerodynamic diameter can be obtained, and start a clock to generate a trigger to fire the excimer laser. The excimer laser pulse is timed to be coincident with the particles' arrival at the entrance to time of flight MS. When the laser pulse hits the particle it generates ions that are subsequently analyzed in the TOF-MS. At present the instrument is capable of characterizing ~20 particles per second in the 50nm to 3.5micron size range. The combination of the high efficiency inlet with a carefully designed photon counting based optical detection system result in an extremely sensitive instrument that make it possible to characterize particles as small as 50nm with high efficiency. Under most ambient conditions there is a need to dilute the aerosol flow to keep the number of detected particles near 20p/second. A second just as important aspect of SPLAT-MS is SpectraMiner, the data analysis and visualization software that we have developed jointly with SUNYSB. This software makes it extremely easy to cluster the data and then visualize through an interactive interface that is the gateway to data exploration. With a simple click of the mouse one can drill into the data to view individual particle spectra, or alternatively view the data on a coarse scale. The software makes it easy to investigate correlation between classes of aerosols and other observables such as gas phase concentrations, wind direction etc. During 2 weeks of the month of September 2000 SPLAT-MS was sited on the 62nd floor of the Williams Tower located west of the Houston downtown, and west northwest of the ship channel. The high altitude of this site provided a unique opportunity to study particles in the free troposphere and within the boundary layer. A total of 250000 particles were characterized during this period. The smallest particle detected was a 47nm organic nitrate particle. The data show episodic behavior in particle composition that can be correlated with wind direction and gas phase compositions. SPLAT-MS participated in the PMTACS-NY 2001 study during the month of July 2001. We will present data obtained during the period of 8 days when a total of 280000 particles were detected and characterized. Since this was a ground site located relatively close to intense sources much of the observed data is impacted very local sources such as a bus passing by. We will present a comparison between the observations made in Houston and in NY.

Field measurements of secondary organic aerosol (SOA) find significantly higher mass loads than predicted by models, sparking intense effort that is focused on finding additional SOA sources, but leaves many of the fundamental assumptions that are used by models unchallenged. Current air-quality models use absorptive partitioning theory assuming SOA particles are liquid droplets that form instantaneous reversible equilibrium with gas

Single particle mass spectrometers (SPMS) have been developed and deployed to characterize, in real-time the size and chemical compositions of individual ambient particles. SPMS have undeniably proven to be extremely valuable, improving our understanding of the properties and evolution of atmospheric aerosols. At the same time these instruments have also persistently been subject to criticism on a number of fronts. Recently we have completed the construction of our second generation single particle mass spectrometer - SPLAT II, in which we have made significant improvements that directly address the shortcomings that are often associated with SPMS. We will present the results of instrument characterization experiments demonstrating that considerable improvements in instrument performance have been accomplished. SPLAT II offers significantly improved detection sensitivity of small particles, such that 30% of all 100 nm particles that enter the instrument are detected and characterize...

During the month of April 2008 a single particle mass spectrometer, SPLAT II, was deployed on board the Canadian National Research Council Convair 580 aircraft for participation in the Indirect and Semi-Direct Aerosol Campaign (ISDAC). ISDAC's main scientific objective was to improve our understanding of the relationship between the properties of aerosol particles over the North Pole and their impact on the regional climate. During ISDAC SPLAT II participated in all 27 flights that lasted slightly over 100 hrs. It measured the size of more than 10 million particles and characterized the composition of over 3 million of them. When sampling in clear air SPLAT II measured a wide range of particle compositions, including sulfates mixed with organics, nitrates mixed with organic, processed and freshly emitted sea-salt, a few dust particles, and a significant number of biomass burning particles. Many of these particle types appeared in aerosol layers that had horizontal and vertical f...

In their role as CCN and IN, atmospheric aerosol particles significantly impact the Global climate. Since cloud activation is strongly related to particle size and composition, it is important to develop the knowledge that connects these particle properties to their activity as CCN and IN. At present, our understanding of the relationship between the IN properties and ice cloud formation is particularly lacking. Typical concentration of IN are very low (

Atmospheric loadings of secondary organic aerosols (SOA) are significantly under-predicted by climate models. In these models, SOA particles are assumed liquid-like droplets at equilibrium with the gas-phase. In sharp contrast, our recent laboratory and field measurements show that SOA particles are non-rigid, highly viscous, spherical, quasi-solids, and do not behave like liquid droplets. They evaporate at rates much lower than predicted by models, and are consequently not at equilibrium with the gas phase. In addition, our data show that SOA particles trap hydrophobic organics, whose presence further reduces evaporation rates, and that aging these particles nearly stops evaporation. Measurements of the evaporation kinetics of ambient SOA particles under vapor-free conditions at room temperature showed that less than 20 % of particle mass evaporates in 4 h. In this study, we examine, for the first time, these groundbreaking observations to present a new, experimentally based pictur...

A central objective of the Carbonaceous Aerosol and Radiative Effects Study (CARES) was to characterize unequivocally all aspects related to organics in aerosols. To this end, a range of instruments measured loadings, size distributions, compositions, densities, CCN activities, and optical properties of aerosol sampled in Sacramento, CA over the month of June 2010. We present the results of measurements conducted by our single particle mass spectrometer, SPLAT. SPLAT was used to measure the size, composition, and density of individual particles with diameters between 50 to 2000 nm. SPLAT measured the vacuum aerodynamic diameters (dva) of more than 2 million particles and the compositions of ~350,000 particles, each day. In addition, SPLAT was used in combination with a differential mobility analyzer to measure the density, or effective density of individual particles. These measurements were typically conducted twice per day: in the morning, and mid-afternoon. Preliminary analysis o...

The volcanic ash from the volcanic emissions can significantly contribute to the natural source of aerosols in the atmosphere. In the vicinity and downwind of eruption site, the transported ash might have a stronger impact on the aviation industry, regional air quality, and climate. Despite the environmental significance of ash, our understanding of ash particles reacting with other volcanic plume constituents is rudimentary. In particular, the complex interactions between the water vapor and ash particles under different meteorological conditions that lead to cloud hydrometeors are poorly understood. To improve our understanding, we focus on investigating the ice formation properties of ash particles collected from the recent volcanic eruption. It was observed that the ash particles are less efficient ice nuclei compared to the natural dust particles in the deposition nucleation regime, but have similar efficiencies in the condensation freezing mode. The ice nucleated ash particles...

We present results of measurements conducted by our Single Particle Mass Spectrometer, SPLAT II, in Sacramento, CA over the month of June 2010. SPLAT II measured the size of 195 million particles, and compositions of 10 million particles. In addition to size and composition, SPLAT II simultaneously measured size, density and composition of 121,000 individual particles. These measurements were conducted 2 - 3 times per day, depending on conditions. The data show that throughout the day particles were relatively small (<200 nm), and the vast majority were composed of oxygenated organics mixed with various amounts of sulfate. In addition, we characterized fresh and processed soot, biomass burning aerosol, organic amines, fresh and processed sea salt, and few dust particles. The data show a reproducible diurnal pattern in aerosol size distributions, number concentrations, and compositions. Early in the day, number concentrations were low, particles were very small, and the size distr...

Secondary organic aerosols (SOA) represent the largest and least understood fraction of atmospheric aerosols. Recent studies by our group demonstrated that these particles are in quasi-solid phase and that their evaporation rates are orders of magnitude slower than predicted. Similar measurements on ambient SOA particles mixed with small amount of sulfate reveal nearly identical results, providing direct evidence that SOA evaporation in the ambient atmosphere is negligible. These results demonstrate that assumptions used by all current models that SOA is liquid that can be modeled with Raoult's law, and that the particles are at equilibrium with the gas-phase at all times need to be significantly changed. To explore the interaction between SOA and different hydrophobic organics, representing typical anthropogenic emissions, we formed SOA by condensation on particles composed of hydrophobic organics and coated SOA seed particles with the same organics. We find that hydrophobic or...

Isoprene produced in forest ecosystems is the most abundantly emitted non-methane volatile organic compound in the Earth’s atmosphere. Recent laboratory and field studies suggest that photooxidation of isoprene forms appreciable amounts of secondary organic aerosol (SOA), which likely affects climate by scattering solar radiation and by acting as cloud condensation nuclei (CCN). As these climate effects depend on both aerosol size and number concentration, it is crucial to understand how SOA partitioning influences particle growth kinetics. Recent studies indicate that biogenic SOA becomes increasingly viscous as relative humidity decreases, with the theoretical implication that its reduced bulk diffusivity slows down further growth via condensation of semivolatile organic compounds. We present here evidences from chamber experiments and the CARES field campaign for such bulk diffusion-limited growth of isoprene SOA formed in the presence of pre-existing Aitken and accumulation mode...