Aerosol Mixtures Research Articles

The Mathematical Modeling of the Charging and Deposition of Aerosol Particles in a Corona Field

In this study, we derive some mathematical expressions that allow us to determine the proportion of charged aerosol particles in the corona, as well as analyzed the conditions of deposition of charged particles uniformly distributed in the space between the discharge and collecting electrodes. The numerical implementation of this method confirms its acceptable accuracy compared to known methods in the literature. The obtained results indicate that, under suitable conditions, use of a corona field can be an alternative technique for cleaning and refining impure aerosol mixtures for desired purposes.

A predictive thermodynamic framework of cloud droplet activation for chemically unresolved aerosol mixtures, including surface tension, non-ideality, and bulk–surface partitioning

Abstract. This work presents a thermodynamically consistent framework that enables self-contained, predictive Köhler calculations of droplet growth and activation with considerations of surface adsorption, surface tension reduction, and non-ideal water activity for chemically complex and unresolved surface-active aerosol mixtures. The common presence of surface-active species in atmospheric aerosols is now well-established. However, the impacts of different effects driven by surface activity, in particular bulk–surface partitioning and resulting bulk depletion and/or surface tension reduction, on aerosol hygroscopic growth and cloud droplet activation remain to be generally established. Because specific characterization of key properties, including water activity and surface tension, remains exceedingly challenging for finite-sized activating droplets, a self-contained and thermodynamically consistent model framework is needed to resolve the individual effects of surface activity during droplet growth and activation. Previous frameworks have achieved this for simple aerosol mixtures, comprising at most a few well-defined chemical species. However, atmospheric aerosol mixtures and more realistic laboratory systems are typically chemically more complex and not well-defined (unresolved). Therefore, frameworks which require specific knowledge of the concentrations of all chemical species in the mixture and their composition-dependent interactions cannot be applied. For mixtures which are unresolved or where specific interactions between components are unknown, analytical models based on retrofitting can be applied, or the mixture can be represented by a proxy compound or mixture with well-known properties. However, the surface activity effects evaluated by such models cannot be independently verified. The presented model couples Köhler theory with the Gibbs adsorption and Szyszkowski-type surface tension equations. Contrary to previous thermodynamic frameworks, it is formulated on a mass basis to obtain a quantitative description of composition-dependent properties for chemically unresolved mixtures. Application of the model is illustrated by calculating cloud condensation nuclei (CCN) activity of aerosol particles comprising Nordic aquatic fulvic acid (NAFA), a chemically unresolved and strongly surface-active model atmospheric humic-like substance (HULIS), and NaCl, with dry diameters of 30–230 nm and compositions spanning the full range of relative NAFA and NaCl mixing ratios. For comparison with the model presented, several other predictive Köhler frameworks, with simplified treatments of surface-active NAFA, are also applied. Effects of NAFA surface activity are gauged via a suite of properties evaluated for growing and activating droplets. The presented framework predicts a similar influence of surface activity of the chemically complex NAFA on CCN activation as was previously shown for single, strong surfactants. Comparison to experimental CCN data shows that NAFA bulk–surface partitioning is well-represented by Gibbs adsorption thermodynamics. Contrary to several recent studies, no evidence of significantly reduced droplet surface tension at the point of activation was found. Calculations with the presented thermodynamic model show that throughout droplet growth and activation, the finite amounts of NAFA in microscopic and submicron droplets are strongly depleted from the bulk, due to bulk–surface partitioning, because surface areas for a given bulk volume are very large. As a result, both the effective hygroscopicity and ability of NAFA to reduce droplet surface tension are significantly lower in finite-sized activating droplets than in macroscopic aqueous solutions of the same overall composition. The presented framework enables the influence of surface activity on CCN activation for other chemically complex and unresolved aerosol mixtures, including actual atmospheric samples, to be systematically explored. Thermodynamic input parameters can be independently constrained from measurements, instead of being either approximated by a proxy or determined by retrofitting, potentially confounding several mechanisms influenced by surface activity.

Calibration and evaluation of a broad supersaturation scanning (BS2) cloud condensation nuclei counter for rapid measurement of particle hygroscopicity and cloud condensation nuclei (CCN) activity

Abstract. For understanding and assessing aerosol–cloud interactions and their impact on climate, reliable measurement data on aerosol particle hygroscopicity and cloud condensation nuclei (CCN) activity are required. The CCN activity of aerosol particles can be determined by scanning particle size and supersaturation (S) in CCN measurements. Compared to an existing differential mobility analyzer (DMA) with CCN activity measurement, a broad supersaturation scanning CCN (BS2-CCN) system, in which particles are exposed to a range of S simultaneously, can measure the CCN activity with a high time resolution. Based on a monotonic relation between the activation supersaturation of aerosol particles (Saerosol) and the activated fraction (Fact) of the BS2-CCN measurement, we can derive κ, a single hygroscopicity parameter, directly. Here, we describe how the BS2-CCN system can be effectively calibrated and which factors can affect the calibration curve (Fact−Saerosol). For calibration, size-resolved CCN measurements with ammonium sulfate and sodium chloride particles are performed under three different thermal gradient (dT) conditions (dT=6, 8, and 10 K). We point out key processes that can affect the calibration curve and thereby need to be considered as follows: first, the shape of the calibration curve is primarily influenced by Smax, the maximum S in the activation tube. We need to determine appropriate Smax depending on the particle size and κ to be investigated. To minimize the effect of multiply charged particles, a small geometric mean diameter (Dg) and geometric standard deviation (σg) in number size distribution are recommended when generating the calibration aerosols. Last, Fact is affected by particle number concentration and has a decreasing rate of 0.02 per 100 cm−3 due to the water consumption in the activation tube. For evaluating the BS2-CCN system, intercomparison experiments between typical DMA-CCN and BS2-CCN measurements were performed with a laboratory-generated aerosol mixture and ambient aerosols. Good agreement of κ values between DMA-CCN and BS2-CCN measurements for both experiments shows that the BS2-CCN system can measure CCN activity well compared to the existing measurement method and can measure a broad range of hygroscopicity distributions with a high time resolution (∼1 s vs. a few minutes for a standard CCN activity measurement). As the hygroscopicity can be used as a proxy for the chemical composition, our method can also serve as a complementary approach for fast and size-resolved detection and estimation of aerosol chemical composition.

Metals in Cannabis Vaporizer Aerosols: Sources, Possible Mechanisms, and Exposure Profiles.

In recent years, cannabis vaporizer cartridges have increased in popularity and availability, and there are concerns regarding exposure to heavy-metal compounds from their use. The physical components of the cartridge devices themselves have been implicated as a potential source of metal exposure, but it is not known if these metals migrate into the inhalable vapor. This study analyzes the components of vaporizer cartridges for 10 different metals and also collects aerosol mixtures from 13 randomly purchased commercially available cannabis cartridges from Washington State to compare their elemental profiles. Results indicate that chromium, copper, nickel, as well as smaller amounts of lead, manganese, and tin migrate into the cannabis oil and inhaled vapor phase, resulting in a possible acute intake of an amount of inhaled metals above the regulatory standard of multiple governmental bodies. Noncartridge heating methods of cannabis flower and concentrate were compared, and results indicate that the heating device itself is a source of metal contamination. As safety and compliance testing regulations evolve, it will be important to include more than the standard As, Cd, Hg, and Pb to the list of regulated metals.

E-cigarette aerosol mixtures inhibit biomaterial-induced osseointegrative cell phenotypes

ObjectivesSmoking is a known contributor to the failure of dental implants. Despite a decline in cigarette use, the popularity of e-cigarettes has exploded. However, little is known about how e-cigarettes affect the biologic response to implants. This study examines the effect of e-cigarette aerosol mixtures (ecig-AM) on macrophage activation and osteoblastogenesis of mesenchymal stem cells (MSCs) in response to titanium (Ti) implant surfaces. MethodsEcig-AMs were prepared by bubbling aerosol through PBS. Human-derived MSCs or murine-derived macrophages were plated on smooth, rough-hydrophobic, or rough-hydrophilic Ti surfaces in media supplemented with ecig-AM. In macrophages, expression of inflammatory markers was measured by qPCR and macrophage immunophenotype characterized by flow cytometry after 24 h of exposure. In MSCs, expression of osteogenic markers and inflammatory cytokines was measured by qPCR and ELISA, while alkaline phosphatase activity (ALP) was determined by colorimetric assay. ResultsEcig-AM polarized primary macrophages into a pro-inflammatory state with higher effect on ecig-AM with flavorants and nicotine. Metabolic activity of MSCs decreased in a concentration dependent fashion and was stronger in ecig-AM containing nicotine. MSCs reduced expression of osteogenic markers in response to ecig-AM, but increased RANKL secretion, particularly at the highest ecig-AM concentrations. The effect of ecig-AM exposure was lessened when macrophages or MSCs were cultured on rough-hydrophilic substrates. SignificanceEcig-AM activated macrophages into a pro-inflammatory phenotype and impaired MSC-to-osteoblast differentiation in response to Ti implant surfaces. These effects were potentiated by flavorants and nicotine, suggesting that e-cigarette use may compromise the osseointegration of dental implants.

Southern Ocean latitudinal gradients of cloud condensation nuclei

Abstract. The Southern Ocean region is one of the most pristine in the world and serves as an important proxy for the pre-industrial atmosphere. Improving our understanding of the natural processes in this region is likely to result in the largest reductions in the uncertainty of climate and earth system models. While remoteness from anthropogenic and continental sources is responsible for its clean atmosphere, this also results in the dearth of atmospheric observations in the region. Here we present a statistical summary of the latitudinal gradient of aerosol (condensation nuclei larger than 10 nm, CN10) and cloud condensation nuclei (CCN at various supersaturations) concentrations obtained from five voyages spanning the Southern Ocean between Australia and Antarctica from late spring to early autumn (October to March) of the 2017/18 austral seasons. Three main regions of influence were identified: the northern sector (40–45∘ S), where continental and anthropogenic sources coexisted with background marine aerosol populations; the mid-latitude sector (45–65∘ S), where the aerosol populations reflected a mixture of biogenic and sea-salt aerosol; and the southern sector (65–70∘ S), south of the atmospheric polar front, where sea-salt aerosol concentrations were greatly reduced and aerosol populations were primarily biologically derived sulfur species with a significant history in the Antarctic free troposphere. The northern sector showed the highest number concentrations with median (25th to 75th percentiles) CN10 and CCN0.5 concentrations of 681 (388–839) cm−3 and 322 (105–443) cm−3, respectively. Concentrations in the mid-latitudes were typically around 350 cm−3 and 160 cm−3 for CN10 and CCN0.5, respectively. In the southern sector, concentrations rose markedly, reaching 447 (298–446) cm−3 and 232 (186–271) cm−3 for CN10 and CCN0.5, respectively. The aerosol composition in this sector was marked by a distinct drop in sea salt and increase in both sulfate fraction and absolute concentrations, resulting in a substantially higher CCN0.5/CN10 activation ratio of 0.8 compared to around 0.4 for mid-latitudes. Long-term measurements at land-based research stations surrounding the Southern Ocean were found to be good representations at their respective latitudes; however this study highlighted the need for more long-term measurements in the region. CCN observations at Cape Grim (40∘39′ S) corresponded with CCN measurements from northern and mid-latitude sectors, while CN10 observations only corresponded with observations from the northern sector. Measurements from a simultaneous 2-year campaign at Macquarie Island (54∘30′ S) were found to represent all aerosol species well. The southernmost latitudes differed significantly from both of these stations, and previous work suggests that Antarctic stations on the East Antarctic coastline do not represent the East Antarctic sea-ice latitudes well. Further measurements are needed to capture the long-term, seasonal and longitudinal variability in aerosol processes across the Southern Ocean.

Mie–Raman–fluorescence lidar observations of aerosols during pollen season in the north of France

Abstract. The multiwavelength Mie–Raman–fluorescence lidar of the University of Lille has the capability to measure three aerosol backscattering coefficients, two extinction coefficients and three linear depolarization ratios, together with fluorescence backscattering at 466 nm. It was used to characterize aerosols during the pollen season in the north of France for the period March–June 2020. The results of observations demonstrate that the presence of pollen grains in aerosol mixture leads to an increase in the depolarization ratio. Moreover, the depolarization ratio exhibits a strong spectral dependence increasing with wavelength, which is expected for the mixture containing fine background aerosols with low depolarization and strongly depolarizing pollen grains. A high depolarization ratio correlates with the enhancement of the fluorescence backscattering, corroborating the presence of pollen grains. Obtained results demonstrate that simultaneous measurements of particle depolarization and fluorescence allows for the separation of dust, smoke particles and aerosol mixtures containing the pollen grains.

Strategies for Nonpolar Aerosol Collection and Heavy Metals Analysis of Inhaled Cannabis Products.

The rapid growth of inhalable cannabis concentrates raises questions about the safety of acute and chronic exposure to these aerosol mixtures. Due to the nonpolar nature of the aerosol mixture created from cannabis vapor cartridges, traditional aqueous-based capture methods used in e-cigarette or tobacco cigarette studies for analysis of metals are insufficient. Moreover, hydrophobic cannabis concentrates are not miscible with dilute aqueous acids and therefore not ideal for metal spiking unlike electronic nicotine delivery systems. This study describes a method of spiking nonaqueous matrices with aqueous metals standards to investigate aerosolization and recovery of the metals. It also compares various methods for nonpolar aerosol capture and subsequent analysis of 10 metals (As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, and Sn) in two model cannabis matrices, flower and concentrate. Spiked cannabis concentrates were vaped in commercially available cartridges, and their aerosol mixtures were investigated for recovery of heavy metals via ICP-MS. Spiked flower samples were also combusted to compare collection rates of the 10 metals. Results show that not all metals that are present in the concentrate or flower can be fully recovered in the aerosol capture processes at standard voltage settings or combustion temperatures. These studies also demonstrate the importance of a nonpolar solvent as part of the aerosol collection to increase the recovery of some metals. The high concentration of some metals seen in the concentrate suggests that the devices themselves are potential routes of exposure. The ICP-MS analysis method was further validated by evaluating different parameters including linearity, matrix effect, limit of detection, limit of quantitation, and repeatability.

Effects of Aerosols and Clouds on the Levels of Surface Solar Radiation and Solar Energy in Cyprus

Cyprus plans to drastically increase the share of renewable energy sources from 13.9% in 2020 to 22.9% in 2030. Solar energy can play a key role in the effort to fulfil this goal. The potential for production of solar energy over the island is much higher than most of European territory because of the low latitude of the island and the nearly cloudless summers. In this study, high quality and fine resolution satellite retrievals of aerosols and dust, from the newly developed MIDAS climatology, and information for clouds from CM SAF are used in order to quantify the effects of aerosols, dust, and clouds on the levels of surface solar radiation for 2004–2017 and the corresponding financial loss for different types of installations for the production of solar energy. Surface solar radiation climatology has also been developed based on the above information. Ground-based measurements were also incorporated to study the contribution of different species to the aerosol mixture and the effects of day-to-day variability of aerosols on SSR. Aerosols attenuate 5–10% of the annual global horizontal irradiation and 15–35% of the annual direct normal irradiation, while clouds attenuate 25–30% and 35–50% respectively. Dust is responsible for 30–50% of the overall attenuation by aerosols and is the main regulator of the variability of total aerosol. All-sky annual global horizontal irradiation increased significantly in the period of study by 2%, which was mainly attributed to changes in cloudiness.

Quantify the Contribution of Dust and Anthropogenic Sources to Aerosols in North China by Lidar and Validated with CALIPSO

Persistent heavy haze episodes have repeatedly shrouded North China in recent years. Besides anthropogenic emissions, natural dust also contributes to the aerosols in this region. Through continuous observation by a dual-wavelength Raman lidar, the primary aerosol types and their contributions to air pollution in North China were determined. The following three aerosol types can be classified: natural dust, anthropogenic aerosols, and the mixture of anthropogenic aerosols and dust (polluted dust). The classification results are basically consistent with the classification results from the cloud–aerosol lidar and infrared pathfinder satellite observations (CALIPSO) satellite measurements. The relative bias of the lidar ratio between the Raman lidar and CALIPSO is less than 25% over 90% of the cases, indicating that the CALIPSO lidar ratio selection algorithm is reasonable. The classification results show that approximately 45% of aerosols below 1.8 km are contributed by polluted dust during our one year observations. The contribution of dust increased with height, from 6% at 500 m to 28% at 1,800 m, while the contribution of anthropogenic aerosols decreased from 49% to 25%. In addition, polluted dust is the major aerosol subtype below 1.0 km in spring (over 60%) and autumn (over 70%). Anthropogenic aerosols contribute more than 75% of air pollution in summer. In winter, anthropogenic aerosols prevailed (over 80%) in the lower layer, while polluted dust (around 60%) dominated the upper layer. Our results identified the primarily aerosol types to assess the contributions of anthropogenic and natural sources to air pollution in North China, and highlight that natural dust plays a crucial role in lower-layer air pollution in spring and autumn, while controlling anthropogenic aerosols will significantly improve air quality in winter.

Ice‐Nucleating Particle Concentrations and Sources in Rainwater Over the Third Pole, Tibetan Plateau

AbstractThe ice‐nucleating particles (INPs) modulate the microphysics and radiative properties of clouds. However, less is known concerning their abundance and sources in the most pristine and climatic sensitive regions, such as the Tibetan Plateau (TP). Here, to our best knowledge, we conduct the first investigation on INPs in rainwater collected in the TP region under mixed‐phase cloud conditions. The value of INP concentrations varies from 0.002 to 0.675 L−1 air over the temperature range from −7.1 to −27.5°C. This is within the INP spectra derived from precipitation under worldwide geophysical conditions and is also comparable with INP concentrations in the Arctic regions. The heat‐sensitive INPs account for 57% ± 30% of the observed INPs at −20°C and become increasingly important at higher temperatures, indicating biological particles as major contributors to INPs at temperatures above −20°C over the TP, especially on the day with additional input of biogenic materials carried by dust particles. Chemical analysis demonstrates that the rainwater components are mixture of dust particles, marine aerosol, and anthropogenic pollutants. Combined with the backward trajectory analysis, we show that dust particles transported from the surrounding deserts and originated from ground surface of TP may contribute to the heat‐resistant INPs at temperatures below −20°C.

Coexistence of three liquid phases in individual atmospheric aerosol particles

Individual atmospheric particles can contain mixtures of primary organic aerosol (POA), secondary organic aerosol (SOA), and secondary inorganic aerosol (SIA). To predict the role of such complex multicomponent particles in air quality and climate, information on the number and types of phases present in the particles is needed. However, the phase behavior of such particles has not been studied in the laboratory, and as a result, remains poorly constrained. Here, we show that POA+SOA+SIA particles can contain three distinct liquid phases: a low-polarity organic-rich phase, a higher-polarity organic-rich phase, and an aqueous inorganic-rich phase. Based on our results, when the elemental oxygen-to-carbon (O:C) ratio of the SOA is less than 0.8, three liquid phases can coexist within the same particle over a wide relative humidity range. In contrast, when the O:C ratio of the SOA is greater than 0.8, three phases will not form. We also demonstrate, using thermodynamic and kinetic modeling, that the presence of three liquid phases in such particles impacts their equilibration timescale with the surrounding gas phase. Three phases will likely also impact their ability to act as nuclei for liquid cloud droplets, the reactivity of these particles, and the mechanism of SOA formation and growth in the atmosphere. These observations provide fundamental information necessary for improved predictions of air quality and aerosol indirect effects on climate.

A Two-phase mixture model of Atmospheric Aerosols in the channel with an applied electric and magnetic field

Objectives: A mathematical model is constructed to investigate the concentration of aerosol mixture in the atmosphere. Aerosol is the significant constituent of the atmosphere, as it is playing a key role in environmental effects including air quality degradation, smoke-fog related accidents, acid rain formation, and visibility issues. The objective of this paper is to formulate the effects of aerosol mixture, and it is monitored through its concentration in the presence and absence of chemical reaction. The effects of concentration of aerosol mixture has to be reduced so as to enhance visibility. Methodology: A two-dimensional schematic geometry is considered which comprises the channel extended to infinity in the x-axis bounded by porous layers, also electric and magnetic field are applied transversely. A general exact solution of the dimensionless governing partial differential equations are obtained using perturbation technique with appropriate boundary conditions. Findings: Detailed results of velocity and concentration of the aerosol mixture were presented graphically. The graphical representation validated the accuracy of attained results with an encouraging level of agreement. As a measure to enhance the effects of air visibility, significant conclusions are specified using the obtained results. Keywords: atmospheric fluid; coagulation; concentration; porous layers; mixture theory

Hygroscopicity and mass transfer limit of mixed glutaric acid/MgSO4/water particles

Tropospheric aerosols are usually complex mixtures of inorganic and organic components, which show non-ideal behavior in hygroscopicity, mass transfer, and partitioning between gas and aerosols. In this study, we applied a novel approach based on a combination of a pulse RH controlling system and a rapid scan vacuum FTIR spectrometer to investigate the mass transfer limit of magnesium sulfate/glutaric acid (GA) mixture aerosol particles. The liquid water band area of the aerosols is used to reveal the mass transfer limit during the rapid pulse RH downward and upward processes. Partitioning equilibrium between the aerosol particles and water gas phase is observed at the higher RH range (73–50%). When the RH is lower than 40%, there is a hysteresis for the liquid water content changing with the RH, indicating the limited water mass transfer in the aerosols.

Study of nicotine content in the aerosols of ENDS of various designs

The aim of the research is to study the features of aerosol mixture on various types of electronic nicotine delivery systems (ENDS) on a laboratory linear smoking machine to develop requirements both for the devices themselves and for the nicotine content in aerosol of liquids for ENDS. The analysis of data on aerosol collection on various types of nicotine-containing products (NCP) is relevant and in the future will allow to develop recommendations and proposals for establishing safety requirements for such devices and the composition of the aerosol produced. Since manufacturers position ENDS (e-cigarettes) as low-risk for health devices, the study of ENDS is an urgent task. The principle of operation of the devices is not associated with the combustion of tobacco as when smoking cigarettes. The article presents the results of the analysis of the nicotine content in the solid-liquid phase of the aerosol of ENDS devices. The issues of assessing the content of nicotine in the aerosol of the solid-liquid phase of innovative nicotine-containing products of such brands as «LUXLITE», «Von Erl My» and «eGo AIO» have been considered. Currently, a unified approach to the regulation of NCP and control of the content of toxic substances in the aerosol has not been developed, which leads to the use of various modes of aerosol collection on laboratory smoking machines. The article presents the aerosol collection parameters, since there are no regulatory measures to control the safety of electronic nicotine delivery systems. To determine the nicotine content in ENDS aerosol, it is recommended to use the ISO 20768 method, since when using ISO 20768exp, the stable operation of ENDS devices decreases. It has been found that different devices produce different amounts of nicotine according to the ISO 20768: 2018 aerosol collection regime. The nicotine content in the solid-liquid phase of the ENDS aerosol is influenced by the duration of the puff, and the nicotine content in the aerosol of the ENDS solid-liquid phase depends on the individual characteristics of the device operation.

Method for estimating the volatility of aerosols using the piezobalance: Examples from vaping e-cigarette and marijuana liquids

We present a new method to estimate the fraction of an aerosol mixture that is volatile, as well as the time required for evaporation from a collecting surface. The method depends on an instrument (the Piezobalance) designed to measure the accumulated mass on a quartz crystal that can also measure the subsequent loss of mass due to evaporation. Commercially available e-liquids or marijuana liquids were heated using an e-cigarette device or a vapor pen, inhaled, and exhaled into a closed unventilated room (volume = 43 and 33 m3) in each of two residences. From a set of 88 measurements on an e-liquid containing 99.7% “vegetable glycerin” (VG), we estimate the fraction of the e-cigarette aerosol that is volatile to be 88% (95% confidence interval (CI) 77–99%). We also estimate the time to reach 95% of the total loss of the volatile material from the crystal to be 47 min (CI 33–60 min). For pure propylene glycol (PG) liquid, we measured extremely high rates of evaporation, finding that 8–16 rapid-fire puffs were required to reach a high concentration at just 0.65 m distance. From 124 experiments on three types of marijuana cartridges, the corresponding estimates of the volatile fraction of exhaled marijuana aerosol were normally 5–7% for liquids heated to moderate temperatures (N = 106), but 25–34% for liquids heated to high temperatures (N = 18). In the latter case, the time to reach 95% of the total loss of volatile material was on the order of 5–10 h. This indicates the importance of volatility considerations in affecting exposure to indoor aerosols from these two common sources. Secondhand exposures to PM2.5 from e-cigarette aerosols are likely to be short-lived for most scenarios, whereas we show that secondhand PM2.5 exposures from marijuana vaping aerosols can be substantial and long-lived after a single puff. Practical implicationsThe method presented here is general and can be used on almost any aerosol mixtures. It has the advantage of requiring a single instrument that can measure both the source strength and decay rates of the aerosol created by the source and also the fraction of collected material that is volatile. The method identified a major difference in the expected exposure to e-cigarette aerosols vs. marijuana aerosols from vaping. The method should be of interest to investigators who study particulate air pollution and to companies that manufacture air monitoring systems. A number of important sources of indoor aerosol mixtures (e.g., cooking, candle use, incense, etc.) remain to be investigated for volatility effects using this method.

Air Quality in East Asia during the heavy haze event period of 10 to 15 January 2013

A prolonged heavy haze event that has caused for the Environmental Protection Bureau (EPB) in Beijing to take emergency measures for the protection of the public health and the reduction of air pollution damages in China has been analyzed with the use of the Aerosol modeling System (AMS) to identify causes of this event. It is found that the heavy haze event is associated with high aerosols and water droplets concentrations. These high aerosol concentrations are mainly composed of anthropogenic aerosols, especially secondary inorganic aerosols formed by gas-to-particle conversion of gaseous pollutants in the eastern part of China whereas those in the northeastern parts of China are composed of the mixture of the anthropogenic aerosols and the Asian dust aerosol originated from the dust source regions of northern China and Mongolia. These high aerosol concentrations are found to be subsequently transported to the downwind regions of the Korean Peninsula and Japan causing a prolonged haze event there. It is also found that the Asian dust aerosol originated from northern China and Mongolia and the anthropogenic aerosols produced by chemical reactions of pollutants in the high emissions region of eastern China can cause significantly adverse environmental impacts in the whole Asian region by increased atmospheric aerosol loadings that may cause respiration diseases and visibility reduction and by excess deposition of aerosols causing adverse impacts on terrestrial and marine eco-systems.

Profiling Dust Mass Concentration in Northwest China Using a Joint Lidar and Sun-Photometer Setting

The satellite-based estimation of the dust mass concentration (DMC) is essential for accurately evaluating the global biogeochemical cycle of the dust aerosols. As for the uncertainties in estimating DMC caused by mixing dust and pollutants and assuming a fixed value for the mass extinction efficiency (MEE), a classic lidar-photometer method is employed to identify and separate the dust from pollutants, obtain the dust MEE, and evaluate the effect of the above uncertainties, during five dust field experiments in Northwest China. Our results show that this method is effective for continental aerosol mixtures consisting of dust and pollutants. It is also seen that the dust loading mainly occurred in the free troposphere (<6 km), with the average mass loading of 905 ± 635 µg m−2 trapped in the planetary boundary layer. The dust MEE ranges from 0.30 to 0.60 m2 g−1 and has a significantly negative relationship with the size of dust particles. With the assumption of the dust MEE of 0.37 (0.60) m2 g−1, the DMC is shown to be overestimated (underestimated) by 20–40% (15–30%). In other words, our results suggest that the change of MEE with the size of dust particles should be considered in the estimation of DMC.

Aerosol type classification analysis using EARLINET multiwavelength and depolarization lidar observations

Abstract. We introduce an automated aerosol type classification method, called Source Classification Analysis (SCAN). SCAN is based on predefined and characterized aerosol source regions, the time that the air parcel spends above each geographical region, and a number of additional criteria. The output of SCAN is compared with two independent aerosol classification methods, which use the intensive optical parameters from lidar data: (1) the Mahalanobis distance automatic aerosol type classification (MD) and (2) a neural network aerosol typing algorithm (NATALI). In this paper, data from the European Aerosol Research Lidar Network (EARLINET) have been used. A total of 97 free tropospheric aerosol layers from four typical EARLINET stations (i.e., Bucharest, Kuopio, Leipzig, and Potenza) in the period 2014–2018 were classified based on a 3β+2α+1δ lidar configuration. We found that SCAN, as a method independent of optical properties, is not affected by overlapping optical values of different aerosol types. Furthermore, SCAN has no limitations concerning its ability to classify different aerosol mixtures. Additionally, it is a valuable tool to classify aerosol layers based on even single (elastic) lidar signals in the case of lidar stations that cannot provide a full data set (3β+2α+1δ) of aerosol optical properties; therefore, it can work independently of the capabilities of a lidar system. Finally, our results show that NATALI has a lower percentage of unclassified layers (4 %), while MD has a higher percentage of unclassified layers (50 %) and a lower percentage of cases classified as aerosol mixtures (5 %).

Characterization of Aerosol Sources and Optical Properties in Siberia Using Airborne and Spaceborne Observations

Airborne backscatter lidar at 532 nm and in-situ measurements of black carbon (BC), carbon monoxide excess above background (ΔCO), and aerosol size distribution were carried out over Siberia in July 2013 and June 2017 in order to sample several kinds of aerosol sources. Aerosol types are derived using the Lagrangian FLEXible PARTicle dispersion model (FLEXPART) simulations and satellite observations. Six aerosol types could be identified in this work: (i) dusty aerosol mixture, (ii) Ob valley gas flaring emission, (iii) fresh forest fire, (iv) aged forest fire, (v) urban emissions over the Tomsk/Novosibirsk region (vi) long range transport of Northern China urban emission. The altitude range of aerosol layers is discussed for each aerosol type, showing transport above the boundary layer for long range transport of Northern China emissions or fresh forest fire. Comparisons of aerosol optical properties, BC and ΔCO are made between aged and fresh plumes for both the urban and forest fire emissions. An increase of aerosol optical depth at 532 nm (AOD532), aerosol particle size and ΔCO is found for aged forest fire plumes. Similar results are obtained when comparing the aged urban plume from Northern China with fresh urban emissions from Siberian cities. A flight above gas flaring emissions corresponds to the largest AOD532 and provides a possible range of 50–60 sr for the lidar ratio of these aerosol plumes often encountered in Siberia. Black carbon concentrations are relatively higher for the flaring plume (0.4–0.5 μμg.m−3) than for the urban plume (0.2 μμg.m−3). The largest BC concentrations are found for the fresh forest fire plume. The aerosol type identification and AOD532 provided by CALIOP Version 4.2 data products in air masses with similar origin generally agree with the results obtained from our detailed analysis of the aerosol plume origins.