Size Distribution Of Ultrafine Particles Research Articles

Size-classified aerosol-bound heavy metals and their effects on human health risks in industrial and remote areas in Japan

Airborne aerosols were collected in six size classes (PM<0.1, PM0.1–0.5, PM0.5–1, PM1–2.5, PM2.5–10 and PM>10) to investigate aerosol health risks in remote and industrial areas in Japan. We focused on heavy metals and their water-dispersed fractions. The average concentration of heavy metals was 18 ± 25–86 ± 48 ngm−3 for PM<0.1, 46 ± 19–154 ± 80 for PM0.5–1 ngm−3, 98 ± 49–422 ± 186 ngm−3 for PM1–2.5, 321 ± 305–1288 ± 727 ngm−3 for PM2.5–10 and 65 ± 52–914 ± 339 ngm−3 or PM>10, and these concentrations were higher in industrial areas. Heavy metals emitted from domestic anthropogenic sources were added to the long-range transport component of the aerosols. The water-dispersed fraction of heavy metals contained 3.3–40.1% of the total heavy metals in each size class. The relative contribution of Zn and other species (As, Cd, Cr, Ni, Pb, Mn, V and Cu) increased in the water-dispersed fraction. Smaller particles contained greater proportions of the water-dispersed heavy metal fraction. Carcinogenic risk (CR) and the hazard index (HI) were estimated for each size class. The CR of carcinogens was at acceptable levels (<1 ×10−6) for five particle size fractions. The HI values for carcinogens and noncarcinogens were also below acceptable levels (<1) for the same five size fractions. The estimated CR and HI values were dominated by contributions from the inhalation process.

A methodology for occupational exposure assessment of organic pollutants emitted through aerosols from recycling of e‐waste

AbstractEmission of airborne particulate matter is produced by the industrial processes of metal extraction from electronic waste (e‐waste). These aerosols can transport organic contaminants, such as polyaromatic hydrocarbons (PAHs) and polybrominated biphenyls. These pollutants are proven to have long‐term effects on workers' health. In this work, we characterize aerosol particles and dust deposited from a recycling process of printed circuit boards in a recycling plant. This study also explores the significance of the secondary aerosol sources, and their importance, as an additional burden compared to primary sources. A Scanning Mobility Particles Counter and Sizer (SMPCS) was used to measure the size distributions of ultrafine particles. A Micro‐Orifice Uniform Deposition Impactor (MOUDI) collected aerosol particle samples for chemical analysis. All plant compartments checked are subject to high particulate matter concentrations during work hours. Concentrations of organic pollutants in the machinery compartments do not pose a short or long‐term health risk according to US Occupational Safety and Health Administration (OHSA). The application of the model presented in this work revealed that the accumulation of contaminants in other compartments should be considered in an occupational exposure assessment because it can present an equally important burden to workers’ health.

Catalytic conversion of polysulfides by atomic layer deposition derived titanium nitride for high‐performance lithium‐sulfur batteries

AbstractLithium‐Sulfur (Li‐S) batteries as the next‐generation battery system have an ultrahigh theoretical energy density. However, the limited conversion of polysulfides in sulfur cathodes deteriorates the performance of Li‐S batteries. In this study, we develop a novel titanium nitride (TiN) catalyst for sulfur cathodes via atomic layer deposition (ALD). The synthesized ALD‐TiN catalyst shows controllable ultrafine particle size (&lt;2 nm) and uniform distribution at the nanoscale in the carbon matrix. Combined with electrochemical analysis and multiple post‐characterization techniques, ALD‐TiN demonstrates an excellent catalytic effect to facilitate the nucleation and deposition of Li2S, which effectively suppresses the dissolution and shuttle of polysulfides. The as‐prepared sulfur cathodes, with the assistance of TiN catalyst, exhibit excellent cycling performance at a high rate (4 C) and deliver 200% higher discharge capacity than the pristine Sulfur‐pristine porous carbon composite cathodes.

Phenomenology of ultrafine particle concentrations and size distribution across urban Europe

The 2017–2019 hourly particle number size distributions (PNSD) from 26 sites in Europe and 1 in the US were evaluated focusing on 16 urban background (UB) and 6 traffic (TR) sites in the framework of Research Infrastructures services reinforcing air quality monitoring capacities in European URBAN & industrial areaS (RI-URBANS) project. The main objective was to describe the phenomenology of urban ultrafine particles (UFP) in Europe with a significant air quality focus.The varying lower size detection limits made it difficult to compare PN concentrations (PNC), particularly PN10-25, from different cities. PNCs follow a TR > UB > Suburban (SUB) order. PNC and Black Carbon (BC) progressively increase from Northern Europe to Southern Europe and from Western to Eastern Europe. At the UB sites, typical traffic rush hour PNC peaks are evident, many also showing midday-morning PNC peaks anti-correlated with BC. These peaks result from increased PN10-25, suggesting significant PNC contributions from nucleation, fumigation and shipping.Site types to be identified by daily and seasonal PNC and BC patterns are: (i) PNC mainly driven by traffic emissions, with marked correlations with BC on different time scales; (ii) marked midday/morning PNC peaks and a seasonal anti-correlation with PNC/BC; (iii) both traffic peaks and midday peaks without marked seasonal patterns. Groups (ii) and (iii) included cities with high insolation.PNC, especially PN25-800, was positively correlated with BC, NO2, CO and PM for several sites. The variable correlation of PNSD with different urban pollutants demonstrates that these do not reflect the variability of UFP in urban environments. Specific monitoring of PNSD is needed if nanoparticles and their associated health impacts are to be assessed. Implementation of the CEN-ACTRIS recommendations for PNSD measurements would provide comparable measurements, and measurements of <10 nm PNC are needed for full evaluation of the health effects of this size fraction.

Simulation of the effects of low-volatility organic compounds on aerosol number concentrations in Europe

Abstract. PMCAMx-UF, a three-dimensional chemical transport model focusing on the simulation of the ultrafine particle size distribution and composition has been extended with the addition of reactions of chemical aging of semivolatile anthropogenic organic vapors, the emissions and chemical aging of intermediate-volatility organic compounds (IVOCs), and the production of extremely low-volatility organic compounds (ELVOCs) by monoterpenes. The model is applied in Europe to quantify the effect of these processes on particle number concentrations. The model predictions are evaluated against both ground measurements collected during the PEGASOS 2012 summer campaign across many stations in Europe and airborne observations by a zeppelin measuring above Po Valley, Italy. PMCAMx-UF reproduces the ground level daily average concentrations of particles with a diameter larger than 100 nm (N100) with normalized mean error (NME) of 45 % and normalized mean bias (NMB) close to 10 %. For the same simulation, PMCAMx-UF tends to overestimate the concentration of particles with a diameter larger than 10 nm (N10) with a daily NMB of 23 % and a daily NME of 63 %. The model was able to reproduce more than 75 % of the N10 and N100 airborne observations (zeppelin) within a factor of 2. According to the PMCAMx-UF predictions, the ELVOC production by monoterpenes leads to surprisingly small changes of the average number concentrations over Europe. The total number concentration decreased due to the ELVOC formation by 0.2 %, N10 decreased by 1.1 %, N50 (particles with a diameter larger than 50 nm) increased by 3 %, and N100 increased by 4 % due to this new secondary organic aerosol (SOA) source. This small change is due to the nonlinearity of the system, with increases predicted in some areas and decreases in others, but also the cancelation of the effects of the various processes like accelerated growth and accelerated coagulation. Locally, the effects can be significant. For example, an increase in N100 by 20 %–50 % is predicted over Scandinavia and significant increases (10 %–20 %) are predicted over some parts of central Europe. The ELVOCs contributed on average around 0.5 µg m−3 and accounted for 10 %–15 % of the PM2.5 OA. The addition of IVOC emissions and their aging reactions led to a surprising reduction of the total number of particles (Ntot) and N10 by 10 %–15 % and 5 %–10 %, respectively, and to an increase in the concentration of N100 by 5 %–10 %. These were due to the accelerated coagulation and reduced nucleation rates.

Reduce and concentrate graphene quantum dot size via scissors: vacancy, pentagon-heptagon and interstitial defects in graphite by gamma rays

Graphene quantum dots (GQDs) with ultrafine particle size and centralized distribution have advantages of small size, narrow size distribution and large specific surface area, which make it be better applied in bioimaging, drug delivery and so on. In our research, we used graphite irradiated by γ-rays to successfully prepare GQDs with ultrafine particle size, narrow size distribution and high quantum yields through solvothermal method. Vacancy defects, pentagon–heptagon defects and interstitial defects were introduced to graphite structure after irradiation, which caused the abundance and concentrated distribution of defects. The defects generated by irradiation could damage the lattice structure of graphite to make it easy for introduction of C–O–C inside graphite sheets. The oxygen-containing functional groups in graphene oxide (GO) increased and centrally distributed after irradiation in graphite, especially for C–O–C group, which were beneficial for cutting of GO and grafting of functional groups in GQDs. Therefore, average size of GQDs was successfully reduced to 1.43 nm and concentrated to 0.6–2.4 nm. After irradiation in graphite, the content of carbonyl and C–N in GQDs had a promotion, which suppressed non-radiative recombination and upgraded the quantum yields to 13.9%.

Contributions of traffic emissions and new particle formation to the ultrafine particle size distribution in the megacity of Beijing

The important role of traffic emissions in air pollution has been widely recognized. However, the corresponding contributions to the ultrafine particle distribution and new particle formation (NPF) are poorly understood due to the mixed influences of various sources. Measurements of particle evolution and NPF were made at a heavy traffic site near the 5th Ring Road of Beijing from August 2017 to October 2019. A positive matrix factorization receptor model (version 5.0) consisting of the log-normal fit method and the k-means clustering method was used to identify and quantify the major sources of particle number concentrations. Based on the characteristics of NPF, additional analyses were performed to identify formation sources, including back-trajectory clustering and correlations between auxiliary variables and the relative contributions of all resolved factors. Traffic emissions mainly influenced Aitken mode (25–100 nm) particles (>60%), and NPF significantly contributed to the ultrafine particle distribution (47.2%). Additionally, regional transport notably affected the occurrence of NPF at the observation site, with northwest airmass transport influencing the nucleation mode the most and southeast airmass transport influencing the Aitken mode the most.

Synthesis and characterization of bacterial cellulose/graphene oxide nano‐biocomposites

AbstractBacterial cellulose/graphene oxide (BC/GO) nano‐biocomposites constructed using two methods of in situ and immersion. Scanning electron microscopy showed that a lower amount of GO formed a stronger composite with smaller pores. The in situ method formed a nanostructured composite with an ultrafine particle size distribution. X‐ray diffraction peaks indicated that GO embedded in BC network uniformly. The Young's modulus of the fabricated composites for both methods increased compared to pure BC. DSC analysis showed that the prepared samples were endothermic and in the 350–370°C, the BC/GO sample experienced a 46.9% weight loss. The immersion method formed a composite with higher thermal stability.

Relationship between Indoor High Frequency Size Distribution of Ultrafine Particles and Their Metrics in a University Site

Exposure to ultrafine particles (UFPs size &lt; 100 nm) in life and work environments can contribute to adverse health effects also in terms of health burden of related diseases over time. The choice of parameters which better characterize UFPs is challenging, due to their physical-chemical properties and their variable size. It is also strictly related to the availability of different instrumental techniques. In the present study we focus on real time high frequency (1 Hz) UFPs particle size distribution (PSD) and their relationship with total particle number concentration (TPNC) and mean particle diameter (Davg) as a contribution characterizing by size the human exposure to UFPs in an indoor site of the University of Rome “Sapienza” (Italy). Further considerations about UFPs contribution to nucleation mode (NM) and accumulation mode (AM) have been highlighted, also in order to investigate the contribution of polycyclic aromatic hydrocarbons (PAHs) surface-adsorbed on indoor air particles (pPAHs). High indoor TPNC values were registered during the rush hours (early morning and mid/late afternoon) according to the outdoor influences originated from anthropogenic activities. AM mainly contribute to the indoor TPNC during working days showing high correlation with pPAHs. These findings may provide useful indications in terms of occupational exposure to UFPs since there are many evidences that indoor exposures to such pollutants may be associated with adverse health effects also in working environments.

Observations of new particle formation, modal growth rates, and direct emissions of sub-10 nm particles in an urban environment.

Ultrafine particles with diameters less than 100 nm suspended in the air are a topic of interest in air quality and climate sciences. Sub-10 nm particles are of additional interest due to their health effects and contribution to particle growth processes. Ambient measurements were carried out at North Carolina State University in Raleigh, NC between April to June 2019 and November 2019 to May 2020 to investigate the temporal variability of size distribution and number concentration of ultrafine particles. A mobile lab was deployed between March and May 2020 to characterize the spatial distribution of sub-10 nm particle number concentration. New particle formation and growth events were observed regularly. Also observed were direct emissions of sub-10 nm particles. Analysis against meteorological variables, gas-phase species, and particle concentrations show that the sub-10nm particles dominated number concentration during periods of low planetary boundary layer height, low solar radiation, and northeast winds. The spatial patterns observed during mobile deployments suggest that multiple temporally stable and spatially confined point sources of sub-10 nm particles are present within the city. These sources likely include the campus utility plants and the Raleigh-Durham International Airport. Additionally, the timing of data collection allowed for investigation of variations in the urban aerosol number size distribution due to reduced economic activity during the COVID-19 pandemic.

Fabrication of Fe-Ni Ultrafine Particles Epoxy Composite Film Using the LbL Assisted Composite Plating Method

Magnetic ultrafine particles-insulator composite films including Fe-Ni ultrafine particles and insulating epoxy films used for electromagnetic wave absorbing films were synthesized by a newly developed electrochemical method termed the “LbL assisted composite plating method”.The reaction solution containing 40 ml / L water-solve epoxy resin prepared by NIPPON PAINT Co., LTD and 0-3 g / L Fe-Ni ultrafine particles 60 nm in diameter manufactured by the Nilaco corporation were used for film fabrication. Cu substrates and Ti / Pt plates were used as the cathode and anode, respectively.Epoxy films were deposited by the following schemes:O2 + 2H2O +4e- → 4OH- (Resin)3NH+ + OH- → (Resin)3N + H2OIn LbL assisted composite plating, charged Fe-Ni ultrafine particles are attracted to the cathode by electrostatic force simultaneously with insulator epoxy film electrodeposition. LbL treatment was performed using 1 wt.% PSS (Poly (sodium 4-styrenesulfonate)) and 0.5 mM NaCl solution, and 1 wt.% PDDA (poly (diallyl dimethyl ammonium chloride)) and 0.5 mM NaCl solution. Fe-Ni ultrafine particles were alternately immersed in PSS solution and PDDA solution.In water Fe-Ni ultrafine particles before LbL treatment have 20 mV zeta potential. After immersion in PSS solution, Fe-Ni ultrafine particles have -40 mV zeta potential, and after immersion in PDDA solution, Fe-Ni zeta potential increases to 60 mV. This increase of zeta potential means that the amount of charged electrons on the ultrafine particles surface were increased through a layer by layer structure of cationic and anionic polyelectrolytes formed on the particles. The Fe-Ni ultrafine particles not treated with LbL precipitated in the reaction solution within 30 minutes, while the particles subjected to the LbL treatment were stable in the reaction solution over 16 days. Figure 1 shows the particle size distribution of Fe-Ni ultrafine particles with LbL treatment and without LbL treatment in water. The peak diameters of the distribution curves with LbL treatment and without LbL treatment were 35 nm and 52 nm, respectively. LbL treatment using PSS and PDDA were effective for increasing the charging electrons on Fe-Ni ultrafine particles and for enhancing the dispersibility of ultrafine particles in the reaction solution.At electrophoresis of only Fe-Ni ultrafine particles without epoxy film on Cu substrate, the 4.3-fold increase in the mass of deposited particles with LbL treatment was observed compared with no LbL treatment, as a result of the increase of charging electrons on Fe-Ni particles.Electrodeposition of Fe-Ni ultrafine particle-epoxy composite films was conducted under a constant current density of 4 mA / cm2, and 5-minute deposition time using the LbL assisted composite plating method. The film thickness was measured from the cross-section SEM image of the films. The film thickness of the deposited film prepared from the reaction solution containing 3 g / L Fe-Ni fine particles without LbL treatment is about 30μm, whereas that prepared from the reaction solution containing 3 g / L Fe-Ni particles with LbL treatment is about 80 μm. From the EDX mapping image of the film prepared using Fe-Ni particles without LbL treatment, the agglomerates of Fe-Ni particles were observed. On the other hand, there are no agglomerates in the film prepared using Fe-Ni particles with LbL treatment.These aggregates of Fe-Ni particles not treated with LbL were generated due to less electron charging on the particle surface than particles having LbL treatment, and act as the growth inhibiter of the epoxy film. Therefore, the film thickness of the films prepared using Fe-Ni particles not treated with LbL was less than that of the film prepared using Fe-Ni particles having LbL treatment.Figure 2 shows the Fe-Ni content in the films dependence on the concentration of Fe-Ni ultrafine particles in the reaction solution. The Fe-Ni content in the films increased in proportion to the Fe-Ni concentration in the reaction solution. Using LbL treatment, the Fe-Ni content in the films increased 1.6 times compared to that without LbL treatment. Over 22 vol. % Fe-Ni ultrafine particles included in epoxy films were successfully obtained using LbL assisted composite plating from the 3 g / L Fe-Ni content reaction solution.The experimental results clearly show the dispersibility in the reaction solution could be greatly improved using LbL treatment for Fe-Ni ultrafine particles, and Fe-Ni ultrafine particles uniformly dispersed in epoxy film could be fabricated using our newly developed electrochemical method. Figure 1

A Cost-effective, Miniature Electrical Ultrafine Particle Sizer (mini-eUPS) for Ultrafine Particle (UFP) Monitoring Network

ABSTRACT A cost-effective, miniature electrical ultrafine particle sizer (mini-eUPS) has been developed for future UFP (ultrafine particle) monitoring networks in cities with high traffic density and in communities close to freeways, airports or stationary combustion sources. The mini-eUPS mainly consists of a mini-plate unipolar particle charger, a mini-plate differential mobility classifier and a mini-particle Faraday cage with a sensitive electrometer. A custom-made circuit board was designed for operating the mini-eUPS. In addition to the primary function of measuring the UFP size distribution, the mini-eUPS records the temperature, relative humidity, pressure, altitude, timing and location for each measured data set. The operational status of the mini-eUPS is also registered for data quality assurance. Due to the built-in features of self-diagnosis, malfunction reporting and wireless networking, this particle sizer is suitable for UFP monitoring network. The prototype, which possesses overall dimensions of 6.5′′ (L) × 5.0′′ (W) × 4′′ (H) and a total weight of ~1.0 kg, measures particles ranging in size from 5 to 200 nm. To evaluate the performance of the mini-eUPS, size distribution measurements of lab-generated particles in both unimodal and bimodal distributions and of UFPs emitted from a low-cost 3D printer and diesel engine were compared with those taken by a Scanning Mobility Particle Sizer (SMPS; TSI Inc.). A reasonably good agreement between the mini-eUPS and SMPS data was found.

Evaluation of Second-Hand Exposure to Electronic Cigarette Vaping under a Real Scenario: Measurements of Ultrafine Particle Number Concentration and Size Distribution and Comparison with Traditional Tobacco Smoke.

The present study aims to evaluate the impact of e-cig second-hand aerosol on indoor air quality in terms of ultrafine particles (UFPs) and potential inhalation exposure levels of passive bystanders. E-cig second-hand aerosol characteristics in terms of UFPs number concentration and size distribution exhaled by two volunteers vaping 15 different e-liquids inside a 49 m3 room and comparison with tobacco smoke are discussed. High temporal resolution measurements were performed under natural ventilation conditions to simulate a realistic exposure scenario. Results showed a systematic increase in UFPs number concentration (part cm−3) related to a 20-min vaping session (from 6.56 × 103 to 4.01 × 104 part cm−3), although this was one up to two order of magnitude lower than that produced by one tobacco cigarette consumption (from 1.12 × 105 to 1.46 × 105 part cm−3). E-cig second-hand aerosol size distribution exhibits a bimodal behavior with modes at 10.8 and 29.4 nm in contrast with the unimodal typical size distribution of tobacco smoke with peak mode at 100 nm. In the size range 6–26 nm, particles concentration in e-cig second-hand aerosol were from 2- (Dp = 25.5 nm) to 3800-fold (Dp = 9.31 nm) higher than in tobacco smoke highlighting that particles exhaled by users and potentially inhaled by bystanders are nano-sized with high penetration capacity into human airways.

Evaluation of ultrafine particle concentrations and size distributions at London Heathrow Airport

A study to monitor UFP at Heathrow Airport was undertaken in the autumn of 2016. The objective was to assess the context of measurements at the airport compared to measurements at “typical” traffic, background and rural locations in the south east of England. Measurements were made at two airport locations (called LHR2 and Oaks Road) at opposite ends of the airfield, to further understand the contribution of the airport to local air quality. Average concentrations showed that total particle number concentrations at the airport are typically lower than a traffic location and higher than an urban background location in London, matching the trends seen for NOx, PM10, PM2.5 and BC pollutants. However, the size distribution of the submicrometre particles at the airport is completely different to the London monitoring stations, with the airport PSD dominated by particles with a mode of 20 nm. In contrast, measurements of PN in London have a significantly larger mode of 30 nm. This study demonstrated that measurements of particle number from within the airport perimeter are dominated by the smallest particles and are closely associated with aircraft. Analysis of the operating modes at the airport showed that aircraft departing from the airport emit particles in much higher numbers than those arriving. Nucleation mode particles are commonly associated with emissions from combustion processes. However, measurement of these particles at the airport are not strongly correlated with Black Carbon. There does appear to be some correlation of nucleation mode particles with UV active BC particles (brown carbon, typically associated with biomass combustion or wood smoke) at the Heathrow airside monitoring station, LHR2. There is also modest association between nucleation mode particles and NO2. The study showed that the classical air pollutants measured at Heathrow are very similar in concentration to typical urban environments in London and south east England, but particle numbers in the sub 30 nm size range are markedly different to those measured in London.

Size-dependent efficiencies of ultrafine particle removal of various filter media

Ultrafine particles (UFPs) are hazardous air pollutants produced by human activities in outdoor and indoor environments. Filtration in mechanical ventilation systems or air purifiers is an effective technology for removal of outdoor- or indoor-originated particles, to reduce human exposure to UFPs in indoor environments, where people spend most of their time. The filtration efficiency of filter media is critical to performance, and the efficiency significantly depends on particle diameter. Thus, the size-dependent efficiencies of 47 commercial filter media with 17 filter classes were measured at typical air flow velocities. The pressure drops at different velocities were also measured to obtain the ratios of pressure drops to media velocities. Total efficiencies of UFP removal were estimated based on the size-dependent efficiencies and size distributions of UFPs in three typical cases. The average efficiency of the UFP removal of coarse filters, fine filters, high-efficiency particulate air filters, and ultra-low particulate air filters in typical cases were 10.85%, 76.87%, 99.37%, and 99.92%, respectively. The maximum range of the total efficiency was 18.17%, which was significantly smaller than that of size-dependent efficiency (45.15%). The efficiencies for particles with the mean diameter and mean value of the total efficiency of the UFPs were similar, with absolute differences of less than 5%. These results can provide guidance for selection of filter media under the comprehensive consideration of air quality and energy consumption and offer reference values for the evaluation of new filter media as well as basic data for the assessment of human exposure to UFPs.

Simulation of the size-composition distribution of atmospheric nanoparticles over Europe

Abstract. PMCAMx-UF, a three-dimensional chemical transport model focusing on the simulation of the ultrafine particle size distribution and composition has been extended with the addition of the volatility basis set (VBS) approach for the simulation of organic aerosol (OA). The model was applied in Europe to quantify the effect of secondary semi-volatile organic vapors on particle number concentrations. The model predictions were evaluated against field observations collected during the PEGASOS 2012 campaign. The measurements included both ground and airborne measurements, from stations across Europe and a zeppelin measuring above Po Valley. The ground level concentrations of particles with a diameter larger than 100 nm (N100) were reproduced with a daily normalized mean error of 40 % and a daily normalized mean bias of −20 %. PMCAMx-UF tended to overestimate the concentration of particles with a diameter larger than 10 nm (N10) with a daily normalized mean bias of 75 %. The model was able to reproduce, within a factor of 2, 85 % of the N10 and 75 % of the N100 zeppelin measurements above ground. The condensation of organics led to an increase (50 %–120 %) in the N100 concentration mainly in central and northern Europe, while the N10 concentration decreased by 10 %–30 %. Including the VBS in PMCAMx-UF improved its ability to simulate aerosol number concentration compared to simulations neglecting organic condensation on ultrafine particles.

Effect of prolonged dry grinding on size distribution, crystal structure and thermal decomposition of ultrafine particles of dolostone

The effect of ultrafine dry grinding for up to 1920 min in a planetary ball mill at 300 rpm on size distribution, particle agglomeration and bulk structural changes in a dolomite-rich (CaMg(CO3)2) rock was studied. The size and shape of the ground particles were characterized by laser scattering and scanning electron microscopy (SEM) respectively. The uniformity index of the size distribution evaluated using the Rosin-Rammler equation showed that the apparent grinding limit was reached after 480 min. Differential- and thermo-gravimetric (DTA-TG) analyses showed that the decomposition temperature of magnesite (MgCO3) was affected to a far greater extent by the input energy of grinding than that of calcite (CaCO3). The activation energy of the total decomposition decreased for the aliquots ground above 480 min. This behavior was explained by the storage of extensive lattice distortions in dolomite crystal structure evaluated by X ray line profile analysis of major diffracting peaks. The infrared (IR) bands related to the bending (877 cm−1) and stretching (1418 cm−1) vibrations of the anionic CO32– groups increased with the particle size decreasing as well as being sensitive to particle coarsening caused by agglomeration. Coupled to morphological and Rosin-Rammler size distribution analyses, IR data confirmed extensive agglomeration above 480 min. The transformation between calcite and aragonite polymorphs was also noticed in those aliquots ground for periods ≥480 min. The bulk structural changes documented here were useful to show that the inversion from the breakage to the agglomeration regime observed in dolostone powder system is directly associated with the change in the energy relaxation mechanism inside the dolomite grains.

Role of anthropogenic emissions and meteorology on ultrafine particle bursts over a high altitude site in Western Ghats during pre-monsoon

The ultrafine particle number concentration and size distribution during pre-monsoon (spring) over a high altitude location, Ooty (11.3 °N, 74.4 °E, 2240 m amsl) in Western Ghats, the highest peak in South India, are examined using campaign based ground observations. The total number concentrations are in the range ∼1000–3000 cm−3 with significant increase (2–4 folds) during the periods of ultrafine particle (UFP) (diameter < 100 nm) bursts. The UFP burst happens mostly during afternoon/evening with significant enhancement in number concentrations of nucleation (Nnuc) and Aitken (NAitk) mode particles. Examination of the association of these events with prevailing meteorology and trace gas concentrations revealed weaker dependence in general. However, the association between NOX and the UFP concentration indicates the possibility of common source for both. During the high concentrations of UFP, local winds originated predominantly from south/south west directions of the study location where the valley region with significant anthropogenic activities is located. Time of occurrence of the UFP bursts, trace gas concentrations and direction of the winds points towards the role of valley winds in transporting plume of pollutants to the mountain top observatory during the daytime.

Composition of Metallic Elements and Size Distribution of Fine and Ultrafine Particles in a Steelmaking Factory.

Background: The characteristics of aerosol, in particular particle size and chemical composition, can have an impact on human health. Particle size distribution and chemical composition is a necessary parameter in occupational exposure assessment conducted in order to understand possible health effects. The aim of this study was to characterize workplace airborne particulate matter in a metallurgical setting by synergistically using two different approaches; Methodology: Analysis of inhalable fraction concentrations through traditional sampling equipment and ultrafine particles (UFP) concentrations and size distribution was conducted by an Electric Low-Pressure Impactor (ELPI+™). The determination of metallic elements (ME) in particles was carried out by inductively coupled plasma mass spectrometry; Results: Inhalable fraction and ME concentrations were below the limits set by Italian legislation and the American Conference of Governmental Industrial Hygienists (ACGIH, 2017). The median of UFP was between 4.00 × 104 and 2.92 × 105 particles/cm3. ME concentrations determined in the particles collected by ELPI show differences in size range distribution; Conclusions: The adopted synergistic approach enabled a qualitative and quantitative assessment of the particles in steelmaking factories. The results could lead to a better knowledge of occupational exposure characterization, in turn affording a better understanding of occupational health issues due to metal fumes exposure.

Airborne ultrafine particles in a naturally ventilated metro station: Dominant sources and mixing state determined by particle size distribution and volatility measurements

Ultrafine particle number concentrations and size distributions were measured on the platform of a metro station in Athens, Greece, and compared with those recorded at an urban background station. The volatility of the sampled particles was measured in parallel, providing further insights on the mixing state and composition of the sampled particles. Particle concentration exhibited a mean value of 1.2 × 104 # cm−3 and showed a weak correlation with train passage frequency, but exhibited a strong correlation with urban background particle concentrations. The size distribution appears to be strongly influenced by outdoor conditions, such as the morning traffic rush hour and new particle formation events observed at noon. The aerosol in the metro was externally mixed throughout the day, with particle populations being identified (1) as fully refractory particles being more dominant during the morning traffic rush hours, (2) as core-shell structure particles having a non-volatile core coated with volatile material, and (3) fully volatile particles. The evolution of particle volatility and size throughout the day provide additional support that most nanoparticles in the metro station originate from outdoor urban air.