Concentration Of Aerosol Particles Research Articles

Understanding atmospheric aerosol particles with improved particle identification and quantification by single-particle mass spectrometry

Abstract. Single-particle mass spectrometry (SPMS) is a widely used tool to determine chemical composition and mixing state of aerosol particles in the atmosphere. During a 6-week field campaign in summer 2016 at a rural site in the upper Rhine valley, near the city of Karlsruhe in southwest Germany, ∼3.7×105 single particles were analysed using a laser ablation aerosol particle time-of-flight mass spectrometer (LAAPTOF). Combining fuzzy classification, marker peaks, typical peak ratios, and laboratory-based reference spectra, seven major particle classes were identified. With the precise particle identification and well-characterized laboratory-derived overall detection efficiency (ODE) for this instrument, particle similarity can be transferred into corrected number and mass fractions without the need of a reference instrument in the field. Considering the entire measurement period, aged-biomass-burning and soil-dust-like particles dominated the particle number (45.0 % number fraction) and mass (31.8 % mass fraction); sodium-salt-like particles were the second lowest in number (3.4 %) but the second dominating class in terms of particle mass (30.1 %). This difference demonstrates the crucial role of particle number counts' correction for mass quantification using SPMS data. Using corrections for size-resolved and chemically resolved ODE, the total mass of the particles measured by LAAPTOF accounts for 23 %–68 % of the total mass measured by an aerosol mass spectrometer (AMS) depending on the measurement periods. These two mass spectrometers show a good correlation (Pearson's correlation coefficient γ>0.6) regarding total mass for more than 85 % of the measurement time, indicating non-refractory species measured by AMS may originate from particles consisting of internally mixed non-refractory and refractory components. In addition, specific relationships of LAAPTOF ion intensities and AMS mass concentrations for non-refractory compounds were found for specific measurement periods, especially for the fraction of org ∕ (org + nitrate). Furthermore, our approach allows the non-refractory compounds measured by AMS to be assigned to different particle classes. Overall AMS nitrate mainly arose from sodium-salt-like particles, while aged-biomass-burning particles were dominant during events with high organic aerosol particle concentrations.

Impacts of exhaled aerosol from the usage of the tobacco heating system to indoor air quality: A chamber study

Aerosol particle, carbonyl, and nicotine concentrations were analysed as pollutants affecting indoor air quality during the usage of electrically-heated tobacco product - the Tobacco Heating System (THS). Quantitative experimental variables included THS use intensity as number of parallel users (1, 3, or 5), distance to the bystander (0.5, 1, or 2 m), as well as environmental conditions in a chamber: ventilation intensity as air changes per hour (0.2, 0.5, or 1 h−1), and relative humidity (RH, 30, 50 or 70%). The real-time particle number (PNC), CO and CO2 concentration, as well as off-line acetaldehyde, formaldehyde, nicotine, and 3-ethenylpyridine concentration was measured during and after the active usage. Use of THS resulted in a statistically significant increase of several analytes including nicotine, acetaldehyde, PM2.5, and PNC as compared to the background. The obtained levels were significantly lower (approximately 16, 8, 8 and 28 times for nicotine, acetaldehyde, PNC and PM2.5, respectively) compared to the levels resulting from conventional cigarette (CC) smoking under identical conditions. The maximum 30 min concentration of PNC (4.8 × 105 #/cm3), as well as maximum concentration of PNC (9.3 × 106 #/cm3) suggest that the intensive use of THS in a confined space with limited ventilation might cause substantially elevated aerosol concentrations, although these particles appeared as highly volatile ones and evaporated within seconds. Generally, the usage intensity (number of simultaneous users) prevailed as the most important factor positively affecting pollutant variations; another important factor was the distance to bystander.

Temporal variations of the conduction current density during fair weather days in Israel

Ground-based measurements of the atmospheric conduction current density were conducted on Mount Hermon in northern Israel (33°18′N 35°47.2′E, 2050 m a.s.l). The aim was to measure the conduction current diurnal behavior during days that are defined meteorologically as fair weather days. Results from 86 selected fair weather days show an average value of 0.9 pA/m2 downward, and a double oscillation behavior of the conduction current density with two maxima – a morning peak due to local effect and an evening peak due to global effect, with lower values in between. Fourier transform analysis applied to the continuous data shows the two maxima peaks under the daily background level. The conduction current density, together with the fair weather vertical electric field was used to calculate the fair weather mean conductivity behavior (based on Ohm's law). The conductivity shows minimum values during local noon hours when the station is assumed to be within the boundary layer and high conductivity values during the night hours when the station is above the boundary layer. This is likely due to the respective diurnal changes in concentrations of aerosol particles. A WRF simulation of a single fair weather day was conducted in order to determine the meteorological regime and the boundary layer height and is presented to support the hypothesis that conductivity values depend, at least in part, on the height of the boundary layer relative to the station.

Aliphatic amines at the Cape Verde Atmospheric Observatory: Abundance, origins and sea-air fluxes

Aliphatic amines are important constituents of the marine environment. However, their biogenic origins, formation processes and roles in atmospheric chemistry are still not well understood. Here we present measurements of monomethylamine (MMA), dimethylamine (DMA) and diethylamine (DEA) from two intensive sampling campaigns at the Cape Verde Atmospheric Observatory (CVAO), a remote marine station in the tropical Atlantic Ocean. The amines were measured in the sea surface microlayer (SML), in bulk seawater, in the gas and the submicron particulate aerosol phase. Additionally, a 24-month record of amine concentrations in aerosol particles, together with other particle constituents and biological and meteorological parameters, is presented. In the SML, mean amine concentrations were in the range 20–50 nmol L−1. The correlation of the amines to chlorophyll-a (R2 = 0.52) and the abundance of the diatom pigment fucoxanthin may indicate that amines were formed via algal production. Amine concentrations in the gas and particulate aerosol phases were dominated by DMA, with average concentrations of 4.5 ng m−3 and 5.6 ng m−3, respectively. Average MMA concentrations were 0.8 ng m−3 in the gas phase and 0.2 ng m−3 in the particle phase. DEA was present in the particle phase with an average concentration of 3.9 ng m−3, but was not detected in the gas phase. Sea to air fluxes for MMA and DMA were calculated from the seawater and gaseous amine concentrations; these varied from −8.7 E−14 to +4.0 E−13 mol m−2 s−1 and from −1.9 E−12 to +2.17 E−12 mol m−2 s−1, respectively. While the flux for MMA was mainly positive, suggesting an oceanic source for this analyte, the flux for DMA could be both positive and negative, indicating that 2-way transport may be occurring. Principal component analysis of the 24-month dataset of amines in aerosol particles revealed that the particulate amines were not directly linked to the identified sources. It seems that the transfer of amines was being determined by gas to particle conversion rather than via primary processes. The correlation of both seawater- and gas phase-amines with biological indicators suggests that they were partly linked and that the amine abundance in the atmosphere (gas phase) reflected biological processes in seawater. In contrast, particulate amine concentrations did not show such a direct response and might have other significant sources and environmental drivers.

Experimental study of electrostatic hazard inside scrubber column using response surface methodology

Electrostatic ignition has triggered significant fire/explosion incidents in liquid processing industries including chemical, oil/gas, food, pharmaceutical and transportation. In this work, the impact of gas-velocity and temperature on the electrostatic energy accumulation in a scrubber column was studied. An in-situ charge measurement apparatus combined with a particle scattering laser function was installed inside a pilot-scale column filled with water through which nitrogen was sparged; the formed aerosol particle size distribution, concentration, mass and charge were measured simultaneously. Response surface methodology was employed to construct a quadratic model correlating the electrostatic energy response with the gas velocity and column temperature. Four scenarios were considered and their capacity to provoke ignition was evaluated. Temperature was found affect the charged aerosol droplet size but also to facilitate the charge relaxation in the liquid phase. The faster the gas velocity the higher the electrostatic energy accumulation and the probability of ignition. In the presence of non-grounded conductors, the maximum electrostatic energy from spark discharge was found above the minimum ignition energy of some flammable chemicals and poses as significant fires or explosion risk. In contrast, if there is no ungrounded conductor, the corona discharge was found not sufficient for electrostatic ignition in the range of temperature and gas velocity in this study. To reduce the electrostatic hazards, it is recommended to remove ungrounded conductors within the column. And the gas flow should be maintained at minimum if ungrounded conductors are present.

Personal exposure to air pollutants in a Bus Rapid Transit System: Impact of fleet age and emission standard

This work documents the extremely high concentrations of fine aerosol particles (PM2.5), equivalent black carbon (eBC) and carbon monoxide (CO) experienced by commuters in one of the world largest Bus Rapid Transit (BRT) systems, located in Bogotá, Colombia. A strong relationship between vehicle emissions standard and in-vehicle concentrations was established. Extensive measurements of PM2.5, eBC, and CO were carried out inside the system buses and stations. Measurements were performed during eleven months covering all the system lanes and a significant fraction of the bus fleet and stations. Based on the observed in-bus and in-station concentrations, travel times, and urban ambient levels, the contribution of a typical round trip in the BRT system to the daily inhaled dose was estimated to be 60% for PM2.5, and between 79% and 90% for eBC. The mean PM2.5 dose inhaled by commuters in a typical round trip in the system is 1.2 times the dose a subject would inhale over 24 h exposed to WHO guideline of 25 μgm−3. In 52 out of 180 buses sampled the mean in-cabin concentration of eBC was in excess of 100 μgm−3. Measurements show that mean ratio of in-bus to urban ambient concentration is 8:1 for PM2.5 and 4:1 for CO. These ratios were observed to be much larger when traveling inside the older fraction of the BRT fleet, reaching 11:1 and 7:1 for PM2.5 and CO respectively. These older buses consist exclusively of Euro II and Euro III nominal emission standard vehicles. Average exposure levels inside Euro II and III buses was twice as large as those measured inside vehicles with stricter emission standards, Euro IV or superior. Overall, the measurements suggest that the entrainment of polluted pockets of air to the semi enclosed micro-environments in the system, namely, buses and stations, explains the extreme observed exposure concentrations. Measurements inside an underground bus-station where traffic is restricted to only BRT buses, and on-board a zero emission fully electric BRT bus suggested most of the pollution in the system comes from entrainment of the exhaust of the diesel-powered BRT buses. The significantly lower exposure and inhaled dose of PM2.5, eBC, and CO observed for commuters in newer vehicles suggests that a fleet renewal could have a disproportionately large impact on reducing population exposure to air pollutants. The extent of the reduction in exposure and inhaled dose through fleet renewal is proportional to the gradient of in-bus to urban ambient air pollution levels.

CCN measurements at the Princess Elisabeth Antarctica research station during three austral summers

Abstract. For three austral summer seasons (2013–2016, each from December to February) aerosol particles arriving at the Belgian Antarctic research station Princess Elisabeth (PE) in Dronning Maud Land in East Antarctica were characterized. This included number concentrations of total aerosol particles (NCN) and cloud condensation nuclei (NCCN), the particle number size distribution (PNSD), the aerosol particle hygroscopicity, and the influence of the air mass origin on NCN and NCCN. In general NCN was found to range from 40 to 6700 cm−3, with a median of 333 cm−3, while NCCN was found to cover a range between less than 10 and 1300 cm−3 for supersaturations (SSs) between 0.1 % and 0.7 %. It is shown that the aerosol is dominated by the Aitken mode, being characterized by a significant amount of small, and therefore likely secondarily formed, aerosol particles, with 94 % and 36 % of the aerosol particles smaller than 90 and ≈35 nm, respectively. Measurements of the basic meteorological parameters as well as the history of the air masses arriving at the measurement station indicate that the station is influenced by both marine air masses originating from the Southern Ocean and coastal areas around Antarctica (marine events – MEs) and continental air masses (continental events – CEs). CEs, which were defined as instances when the air masses spent at least 90 % of the time over the Antarctic continent during the last 10 days prior to arrival at the measurements station, occurred during 61 % of the time during which measurements were done. CEs came along with rather constant NCN and NCCN values, which we denote as Antarctic continental background concentrations. MEs, however, cause large fluctuations in NCN and NCCN, with low concentrations likely caused by scavenging due to precipitation and high concentrations likely originating from new particle formation (NPF) based on marine precursors. The application of HYSPLIT back trajectories in form of the potential source contribution function (PSCF) analysis indicate that the region of the Southern Ocean is a potential source of Aitken mode particles. On the basis of PNSDs, together with NCCN measured at an SS of 0.1 %, median values for the critical diameter for cloud droplet activation and the aerosol particle hygroscopicity parameter κ were determined to be 110 nm and 1, respectively. For particles larger than ≈110 nm the Southern Ocean together with parts of the Antarctic ice shelf regions were found to be potential source regions. While the former may contribute sea spray particles directly, the contribution of the latter may be due to the emission of sea salt aerosol particles, released from snow particles from surface snow layers, e.g., during periods of high wind speed, leading to drifting or blowing snow. The region of the Antarctic inland plateau, however, was not found to feature a significant source region for aerosol particles in general or for cloud condensation nuclei measured at the PE station in the austral summer.

Relationships Between Aerosol Particles and Airborne Bacteria and their Dependence on Environmental Factors in a Dairy Calf House

Abstract. The quality of indoor air dramatically affects the health of animals and humans. An investigation was conducted into the relationships among the total number of aerosol particles and different types of airborne bacteria and their dependence on indoor and outdoor environmental factors, including air temperature and relative humidity (RH), in the indoor air of a dairy calf house in Tochigi, Japan, during the summer season. The concentrations of aerosol particles, the concentrations of airborne total aerobic bacteria (, , and spp.) in the indoor air, and the indoor and outdoor temperature and RH were evaluated from 14 weekly measurements. The mean concentration of small aerosol particles (0.3 to 2.0 µm) was higher than the mean concentration of large aerosol particles (2.0 to 10.0 µm) in the summer season. The mean concentration of airborne total aerobic bacteria was higher than the concentrations of airborne , , and spp. Airborne and were positively correlated with the number of 2.0 to 10.0 µm aerosol particles, i.e., high concentrations of 2.0 to 10.0 µm particles were correlated with high concentrations of airborne and . Airborne total aerobic bacteria did not correlate with the number of aerosol particles of any size, but spp. was negatively correlated with the number of 1.0 to 2.0 µm aerosol particles, i.e., high concentrations of 1.0 to 2.0 µm particles were correlated with low concentrations of airborne spp. The indoor temperature and indoor and outdoor RH did not correlate with any airborne bacteria. The outdoor temperature was negatively correlated with spp., i.e., high outdoor temperature was correlated with a low concentration of spp. in the indoor air of the dairy calf house. Both indoor and outdoor temperatures were positively correlated with the number of 0.5 to 5.0 µm aerosol particles, and indoor RH was negatively correlated with the number of 5.0 to 10.0 µm aerosol particles. These findings will be important for elucidating the role of aerosol particles in the transmission of airborne bacteria and ultimately for the mitigation of aerosol particles and airborne bacteria in dairy houses. HighlightsThe number of fine aerosol particles increased with increasing temperatures.Environmental factors had a less critical effect on airborne bacteria than aerosol particles.Airborne E. coli strongly positively correlated with 5.0 to 10.0 µm aerosol particles.Airborne Salmonella spp. negatively correlated with 1.0 to 2.0 µm aerosol particles.Relative humidity did not affect any airborne bacteria. Keywords: Aerosol particle number, Airborne bacteria, Dairy calf, Indoor air, Relationship, Summer season.

Overview of HOMEChem: House Observations of Microbial and Environmental Chemistry.

The House Observations of Microbial and Environmental Chemistry (HOMEChem) study is a collaborative field investigation designed to probe how everyday activities influence the emissions, chemical transformations and removal of trace gases and particles in indoor air. Sequential and layered experiments in a research house included cooking, cleaning, variable occupancy, and window-opening. This paper describes the overall design of HOMEChem and presents preliminary case studies investigating the concentrations of reactive trace gases, aerosol particles, and surface films. Cooking was a large source of VOCs, CO2, NOx, and particles. By number, cooking particles were predominantly in the ultrafine mode. Organic aerosol dominated the submicron mass, and, while variable between meals and throughout the cooking process, was dominated by components of hydrocarbon character and low oxygen content, similar to cooking oil. Air exchange in the house ensured that cooking particles were present for only short periods. During unoccupied background intervals, particle concentrations were lower indoors than outdoors. The cooling coils of the house ventilation system induced cyclic changes in water soluble gases. Even during unoccupied periods, concentrations of many organic trace gases were higher indoors than outdoors, consistent with housing materials being potential sources of these compounds to the outdoor environment. Organic material accumulated on indoor surfaces, and exhibited chemical signatures similar to indoor organic aerosol.

Trends of Fog and Visibility in Taiwan: Climate Change or Air Quality Improvement?

ABSTRACT This study provides insight into how the visibility in Taiwan has varied over time and what the main drivers of these visibility changes are. From 1985 to 2016, urban inland sites showed increases in visibility and decreases in the frequency of hazy and/or foggy days, whereas urbanized and rural coastal regions either showed no clear trend or even an overall decrease in visibility. Over the most recent 5 to 10 years, a consistent increase in the visibility and decrease in the haze frequency has been found for most of the stations, except for the rural to suburban regions. In general, visibility is driven by the relative humidity (rH) and the mass concentration of aerosol particles (PM). On the one hand, the combination of climate change and urbanization, resulting in a rise in temperature (on average, +0.035°C y–1) and an associated overall decrease in rH (on average, –0.125% y–1), has had a positive influence on long-term visibility in the cities of Taiwan. On the other hand, improvements in air quality supported the increase in visibility during the late 2000s and early 2010s. Our results show an almost exponential relationship between visibility and PM10. At lower PM10 levels, the visibility is more sensitive to changes in the PM10. Thus, the influence of the long-term PM10 on visibility becomes weaker at high PM10 levels. Consequently, over the long term, the PM10 more strongly influenced the visibility trends at the northern urban stations, which had lower PM10 concentrations to begin with. At the southern urban stations, the PM10 concentrations were generally higher and hence were less of a factor in variations in visibility. Therefore, the visibility trends at these sites were more related to changes in rH until about 2011, at which time these regions reached a lower level of pollution.

14-Years Aerosol Fingerprint Impact and Implications Over Daloa in Western Ivory Coast

This study reports the trend and impact of aerosol loading over Duola from 2000 – 2013 using aerosol optical depth (AOD) data obtained for particulate matter in the region. The dataset was obtained from the Multi-angle Imaging Spectro-Radiometer (MISR). The secondary datasets that were generated from the primary data were aerosol loading, particles sizes, Angstrom parameter and the statistics of the primary dataset. We observed from the primary dataset that the aerosol loading values for the years under consideration varied but higher values were recorded in the years 2000 and 2007-2013. These high aerosol depths informed high aerosol concentrations over Duola from October through May. Years of high aerosol concentrations in the atmosphere were potential threats to human health; with high concentration of aerosol particles, the government should adopt and implement stricter environmental policies to reduce the industrial and human contributions to these air pollution. The Angstrom values calculations over the years were less than 1, thus, the aerosol particle size indicates size distributions dominated by coarse mode aerosols.

Experimental Studies of Aerosols in the Atmosphere of Semiarid Landscapes of Kalmykia: 1. Microphysical Parameters and Mass Concentration of Aerosol Particles

This paper summarizes the results of long-term (2004–2016) comprehensive experimental studies of microphysical parameters and the mass concentration of aerosol particles in the atmospheric surface layer of semiarid regions of Kalmykia arranged by the Obukhov Institute of Atmospheric Physics of the Russian Academy of Sciences. Characteristic values of the mass and number concentrations of aerosol particles in the summer have been determined for different velocities. A significant decrease in the concentration of surface submicron- and micron-sized aerosols in comparison with their values observed in desert areas of Kalmykia in the 1990s has been found. Mass concentration distributions over aerosol particle fractions have been obtained. The diurnal course of the particle number concentration has been studied taking the meteorological conditions (air temperature, velocity, and humidity) and the underlying surface into consideration. The particle-size distribution functions characteristic of atmospheric aerosols in Kalmykia have been determined. The removal of particles has been coupled with the main meteorological parameters in the atmospheric near-surface layer. A large number of submicron-sized particles have been found to persist in the atmospheric surface layer of semiarid landscapes, confirming that they are the main sources of transport of fine mineral aerosol particles, which are most dangerous to human health and actively engaged in biospheric and climate change processes.

Novel instrument to generate representative e-cigarette vapors for physicochemical particle characterization and in-vitro toxicity

The use of “electronic cigarettes” (e-cigs) has exponentially increased during the last decade. This drastic growth has been observed in smokers and never smokers, women and teenagers, with indicators for adverse effects related to nicotine, but also to e-liquid and vapor components. The aerosol characteristics depend on the e-cig features. Therefore, the introduction of many different e-cig types on the market leads to concerns regarding their potential health effects. Our study aims to develop an instrument to generate representative vapors from e-cigarette devices, characterize the physicochemical properties of the aerosols and elucidate the adverse effects of inhaled vapors on normal human airway epithelia. E-cig vapors were produced using a specially developed aerosol generation instrument mimicking user puffing behavior. Aerosol particle size distribution and concentration were characterized with a Scanning Mobility Particle Sizer. Air-liquid interface cultures of differentiated human bronchial epithelial cells were exposed to 1 puff topography, i.e. to 21 puffs of 3 s with 22-second puff intervals using the Nano-Aerosol Chamber for In-Vitro Toxicity, which simulates particle deposition in the respiratory tract. Cell morphology was evaluated by light microcopy and induction of cell death by release of lactate dehydrogenase at 4 and 24 h after aerosol exposure. Particle size in e-cig generated aerosols ranged from 20 to 430 nm and concentrations exceeded 1 × 106 particles/cm3. Deposited particle doses were 0.9–3 μg/cm2, depending on e-device type and number of puffs. A single exposure to e-cig vapors caused changes in epithelial cell shape but no massive cell death. We successfully developed an aerosol generation system to produce and deposit realistic vapors from e-cigs. The results obtained indicate that a single exposure to e-cig aerosols affects epithelial morphology and slightly increases cell death. Our interdisciplinary approach combining aerosol technology and biology allows identifying adverse effects of e-cigs to the respiratory tract in vitro.

Aerosol synthesis of germanium nanoparticles supported by external seeding: Theoretical and experimental analysis

In this work we present a detailed study of the effect of heterogeneous nucleation on the formation of germanium nanoparticles (Ge NPs) produced from monogermane (GeH4) in a hot wall reactor gas phase synthesis. As external seeding unit we use a hot wire generator (HWG) which produces a stable concentration of aerosol particles. The particle concentration and size of the seeds is easily controllable via the applied voltage and used metal. We demonstrate the importance of seed particles for the production of narrowly distributed Ge NPs with geometrical standard deviations (GSD) < 1.1 in our setup. Thereby, molybdenum and tungsten as wire metal show the best seeding results. The size of the final Ge NPs can be precisely controlled in the range of 20–60 nm. The expansion of Ge lattice seen in XRD and tiny amount of Mo probed by high-resolution STEM-EDXS analysis indicate that the Mo seed particles are most likely dissolved and incorporated in the Ge lattice during growth. Furthermore, we demonstrate an approach to investigate the effect of heterogeneous nucleation on the particle formation by population balance modeling. The results are in good agreement with experimental data. The seed concentration is the key parameter and has a major influence on the nucleation rate.

Calibration of a particle mass spectrometer using polydispersed aerosol particles

Routine calibrations of online aerosol chemical composition analyzers are important for assessing data quality during field measurements. The combination of a differential mobility analyzer (DMA) and condensation particle counter (CPC) is a reliable, conventional method for calibrations. However, some logistical issues arise, including the use of radioactive material, quality control, and deployment costs. Herein, we propose a new, simple calibration method for a particle mass spectrometer using polydispersed aerosol particles combined with an optical particle sizer. We used a laser-induced incandescence–mass spectrometric analyzer (LII-MS) to test the new method. Polydispersed aerosol particles of selected chemical compounds (ammonium sulfate and potassium nitrate) were generated by an aerosol atomizer. The LII section was used as an optical particle sizer for measuring number/volume size distributions of polydispersed aerosol particles. The calibration of the MS section was performed based on the mass concentrations of polydispersed aerosol particles estimated from the integration of the volume size distributions. The accuracy of the particle sizing for each compound is a key issue and was evaluated by measuring optical pulse height distributions for monodispersed ammonium sulfate and potassium nitrate particles as well as polystyrene latex particles. A comparison of the proposed method with the conventional DMA-CPC method and its potential uncertainties are discussed.Copyright © 2018 American Association for Aerosol Research

Study of interaction between cloud microphysics and chemistry using coupled bin microphysics and bin aqueous chemistry scheme

A bin chemistry scheme was developed to study sulfate production and the effect of aqueous chemistry on cloud microphysics in precipitating stratocumulus cloud using a 2D kinematical model. The impact of air pollution on aerosol processing was investigated by a comprehensive sensitivity study. The numerical simulations were carried out at different concentrations of condensation nuclei and trace gases of SO2, H2O2, O3 and NH3. The results show: (i) Significant amount of sulfate formed due to cloud chemistry even in less polluted atmosphere. The amount of sulfate formed due to the oxidation of S(IV) was affected less by the initial condensation nuclei (hereinafter: CN) concentration and more by the initial mixing ratio of gases in the atmosphere. The amount of sulfate staying in the atmosphere was affected by the initial CN concentration, because it impacted the efficiency of washout. (ii) The aqueous sulfate production impacts the characteristics of aerosol size distribution by increasing mean size and by increasing the concentration of the micron size aerosol particles. The change of aerosol size distribution due to sulfate production has no effect on the amount of surface precipitation if the CN concentration is low (100 cm−3), and significantly reduces accumulated surface precipitation if CN concentration is large (540 cm−3). (iii) Compared to the bin chemistry scheme the bulk chemistry scheme underestimates the sulfate production and overestimates the role of O3 in the sulfate production.

Precision measurements of the particle size distribution of powder materials based on state primary standard for the units of disperse parameters of aerosols, suspensions and powder materials GET-163

In this article the problem of lack of specialized reference base and national standards in the sphere of additive technologies, particularly for the equipment and methods used in production, control of properties and the quality of powder materials is designated. The existing methods and instruments for measurement of particle size distribution and morphology of powders are considered and also the solution of this problem with use of the technical realization applied in the State primary standard for the units of disperse parameters of aerosols, suspensions and the powder materials GET-163 is proposed. Get-163 provides reproduction, storage and transmission of particle size units in aerosols, suspensions and powdery materials in the range from 0.001 to 2000 μm, counting concentration of particles in aerosols and suspensions in the range from 103 to 1012 m-3, mass concentration of aerosol particles in the range from 0.001 to 10,000 mg/m3, electrophoretic mobility of particles in the range from - 2⋅10-7 to + 2⋅10-7 m2/(V⋅s), zeta potential of particles in the range from -150 to + 150 mV.

Atmospheric humidity and particle charging state on agglomeration of aerosol particles

Formation of haze is a phenomenon dependent on the relative atmospheric humidity and concentration of aerosol particles. The physical and chemical reactions on particle surfaces would lead to variations in particle sizes. This paper focuses on the physical behaviour of aerosol particles under the influence of atmospheric humidity, which produces liquid bridging forces and electrostatic interactions among particles. By water absorption experiment, a correlation between relative humidity (RH) and water content on particles was obtained. Through theoretical derivation, a relationship between the relative humidity and humidity ratio was established for calculating liquid bridging forces. The findings from experiments on atmospheric particles charging, showed most aerosols were negatively or positively charged and the average charges on these particles was more than one. An extended soft-sphere discrete element method (DEM) was used to simulate the evolution of aerosol particles, encapsulated in water vapour by considering liquid bridging forces, electrostatic interactions and Brownian forces. Results suggest that the agglomeration rate of particles would increase with a rise in the atmospheric humidity due to the increased liquid bridging forces that enhance the agglomeration velocity. The higher humidity would enhance the ionization on particle surfaces, which could affect electrostatic interactions. This paper provides an insight of a mechanism for formation of haze in atmosphere.

CHARACTERISING SEASONAL VARIATIONS AND SPATIAL DISTRIBUTION OF AMBIENT PM2.5 CONCENTRATION BASED ON SHORT-TERM MONITORING IN DARKHAN CITY

The purpose of this study was to survey the seasonal variation of fine particulate matter (PM2.5) concentration and determine spatial distribution in Darkhan city. Air pollution research and reports have been few and far between in most of parts in Mongolia, especially in Darkhan with respect to quantitative aerosol particle concentration. In this study, we utilized “PM2.5sensor” to measure spatial and seasonal variation of particulate matter concentrations in the study area. The monitoring points were chosen by basing on their specific features and set up directly at ambience outdoor. In each season, we carried out measurement at 3 points, which covered the ger district and apartment district areas for one day. Whereas, at one point the ger district was sampled for 4 days in summer. Fine particulate matter concentrations were the highest in the ger district area because there are many households that use coal for their daily heating and cooking, and at the bared surface. As for seasonal variation, in winter pollution reached 400 times higher than other seasons. Furthermore, at the ger district area, PM2.5 concentration was as much as 20 times greater than other points and it was observed that this too had its impact on the apartment district as well. As regards the air quality index, the level of particulate matter in the ger district area is extremely unhealthy to hazardous in winter. While, good and moderate indexes were mostly identified at monitoring points during the springtime.

Exploring non-linear associations between atmospheric new-particle formation and ambient variables: a mutual information approach

Abstract. Atmospheric new-particle formation (NPF) is a very non-linear process that includes atmospheric chemistry of precursors and clustering physics as well as subsequent growth before NPF can be observed. Thanks to ongoing efforts, now there exists a tremendous amount of atmospheric data, obtained through continuous measurements directly from the atmosphere. This fact makes the analysis by human brains difficult but, on the other hand, enables the usage of modern data science techniques. Here, we calculate and explore the mutual information (MI) between observed NPF events (measured at Hyytiälä, Finland) and a wide variety of simultaneously monitored ambient variables: trace gas and aerosol particle concentrations, meteorology, radiation and a few derived quantities. The purpose of the investigations is to identify key factors contributing to the NPF. The applied mutual information method finds that the formation events are strongly linked to sulfuric acid concentration and water content, ultraviolet radiation, condensation sink (CS) and temperature. Previously, these quantities have been well-established to be important players in the phenomenon via dedicated field, laboratory and theoretical research. The novelty of this work is to demonstrate that the same results are now obtained by a data analysis method which operates without supervision and without the need of understanding the physics deeply. This suggests that the method is suitable to be implemented widely in the atmospheric field to discover other interesting phenomena and their relevant variables.