Submicron Particle Size Distribution Research Articles

Chemical synthesis, structural and magnetic properties of Al-doped neodymium orthoferrite

Crystalline and single phase of Al doped orthoferrite with stoichiometry NdFe1-xAlxO3 was synthesized by a hydrothermal method. The effect of Al doping on the structure features was investigated by powder X-ray diffraction (PXRD) technique. In this sense, Rietveld refinement was applied in refining the PXRD data. Scanning electron microscopy (SEM) was used to characterize the morphology. And from image analyses show a sub-micron particle size distributions for all samples. Using hydrothermal synthesis method, a micro-sized particle distribution is reached. Measurement of magnetic hysteresis loops showed that the highest coercivity (Hc) obtained was 5.2 kOe for the sample with x=2. Compared to previous results using sol-gel synthesis, the hydrothermal method used in this study showed improved magnetization properties.

The Variability of the Size Distributions of Submicron Particles in the Oceans

AbstractThe size distribution of submicron particles is essential for understanding their biogeochemical and optical roles, but it has seldom been measured. This study utilizes ViewSizer 3000, an instrument that tracks Brownian motions of particles, to measure the particle size distributions (PSD) from 250 to 1,050 nm in the North Pacific Ocean (NP) and the North Atlantic Ocean (NA) at depths from 5 to 500 m. The concentration of particles varies over one order of magnitude at any given size bin, with greater variations up to two orders of magnitude at sizes >600 nm. In both locations, concentrations decrease with depth. Bacterioplankton are a dominant component, accounting for 65%–90% of the submicron particles in the surface waters (<100 m) and approximately 30%–40% at depths >150 m at both sites. In the NP, the volume mean diameter increased approximately 5% from the morning to noon at the surface, probably resulting from the diurnal growth of bacterioplankton. In the NA, the concentration and mean size increased by >60% and ∼10% respectively after one storm that introduced a different particle population into the study area.

Comparing novel small-angle x-ray scattering approaches for absolute size and number concentration measurements of spherical SiO2 particles to established methods

Biomedical analytical applications, as well as the industrial production of high-quality nano- and sub-micrometre particles, require accurate methods to quantify the absolute number concentration of particles. In this context, small-angle x-ray scattering (SAXS) is a powerful tool to determine the particle size and concentration traceable to the Système international d’unités (SI). Therefore, absolute measurements of the scattering cross-section must be performed, which require precise knowledge of all experimental parameters, such as the electron density of solvent and particles, whereas the latter is often unknown. Within the present study, novel SAXS-based approaches to determine the size distribution, density and number concentrations of sub-micron spherical silica particles with narrow size distributions and mean diameters between 160 nm and 430 nm are presented. For the first-time traceable density and number concentration measurements of silica particles are presented and current challenges in SAXS measurements such as beam-smearing, poorly known electron densities and moderately polydisperse samples are addressed. In addition, and for comparison purpose, atomic force microscopy has been used for traceable measurements of the size distribution and single particle inductively coupled plasma mass spectrometry with the dynamic mass flow approach for the accurate quantification of the number concentrations of silica particles. The possibilities and limitations of the current approaches are critically discussed in this study.

Past progress in environmental nanoanalysis and a future trajectory for atomic mass-spectrometry methods

The development of engineered nanotechnology has necessitated a commensurate maturation of nanoanalysis capabilities. Building off a legacy established by electron microscopy and light-scattering, environmental nanoanalysis has now benefited from ongoing advancements in instrumentation and data analysis, which enable a deeper understanding of nanomaterial properties, behavior, and impacts. Where once environmental nanoparticles and colloids were grouped into broad ‘dissolved or particulate’ classes that are dependent on a filter size cut-off, now size distributions of submicron particles can be separated and characterized providing a more comprehensive examination of the nanoscale. Inductively coupled plasma-quadrupole mass spectrometry (ICP-QMS), directly coupled to field flow fractionation (FFF-ICP-QMS) or operated in single particle mode (spICP-MS) have spearheaded a revolution in nanoanalysis, enabling research into nanomaterial behavior in environmental and biological systems at expected release concentrations. However, the complexity of the nanoparticle population drives a need to characterize and quantify the multi-element composition of nanoparticles, which has begun to be realized through the application of time-of-flight MS (spICP-TOFMS). Despite its relative infancy, this technique has begun to make significant strides in more fully characterizing particulate systems and expanding our understanding of nanoparticle behavior. Though there is still more work to be done with regards to improving instrumentation and data processing, it is possible we are on the cusp of a new nanoanalysis revolution, capable of broadening our understanding of the size regime between dissolved and bulk particulate compartments of the environment.

Measurement of Submicron Particle Size Using Scattering Angle-Corrected Polarization Difference with High Angular Resolution

The particle size of submicron particles significantly affects their properties; thus, the accurate measurement of submicron particle size is essential to ensure its excellent properties. Polarized light scattering is an important tool for measuring the particle size of the ensemble of particles in suspension. However, in the existing measurement systems, the polarized scattered light is detected using a CCD detector or an array of single-point detectors. The CCD detector misses a large part of the polarized scattered light due to its narrow detection range of scattering angles, and the array of single-point detectors has the problem of low angular resolution due to the limited number of detectors. According to the above problems, this paper designs a submicron particle size measurement method based on the polarization difference in polarized scattered light with high angular resolution. The vertically and horizontally polarized scattered light was acquired with high angular resolution (angular separation = 2°) over a scattering angle range of 50°–110° using a photomultiplier coupled with a turntable. The scattering angle of the acquired vertically and horizontally polarized scattered light were corrected to eliminate the scattering angle deviations caused by obliquely incident light, and then the polarization difference in the vertically and horizontally polarized scattered light was computed, from which the submicron particle size distribution was inverted subsequently. Experiments were performed using polystyrene microsphere standard particles with particle sizes of 350 nm, 200 nm, and 100 nm. The experimental results show that (1) the Pearson correlation coefficient of the linearly fitted curve of the corrected polarization difference to the theoretical polarization difference is larger than 0.997, and the slope and intercept of the linearly fitted curve are, respectively, close to 1 and 0, indicating that the corrected polarization difference is highly consistent with the theoretical polarization difference; (2) the mean relative error and coefficient of variation of the particle size distribution parameter D50 obtained from the polarization difference with high angular resolution (angular separation = 2°) are better than those of the parameter D50 obtained from the polarization difference with low angular resolution (angular separation = 12°), indicating better accuracy and repeatability of the particle size distribution inverted from the polarization difference with high angular resolution; and (3) for the particle size distribution parameters D10, D50, and D90 obtained from the scattering angle-corrected polarization difference with high angular resolution, the deviation of the measured values from the average value are all smaller than the thresholds given in the international standard, indicating a good repeatability of the proposed method.

Analysis of particle size distribution and electro-kinetics of submicron particles in shear-thinning liquids

Analysis of particle size distribution and electro-kinetics of submicron particles in shear-thinning liquids

Characterization of volatile organic compounds and submicron organic aerosol in a traffic environment

Abstract. Urban air consists of a complex mixture of gaseous and particulate species from anthropogenic and biogenic sources that are further processed in the atmosphere. This study investigated the characteristics and sources of volatile organic compounds (VOCs) and submicron organic aerosol (OA) in a traffic environment in Helsinki, Finland, in late summer. The anthropogenic VOCs (aVOCs; aromatic hydrocarbons) and biogenic VOCs (bVOCs; terpenoids) relevant for secondary-organic-aerosol formation were analyzed with an online gas chromatograph mass spectrometer, whereas the composition and size distribution of submicron particles was measured with a soot particle aerosol mass spectrometer. This study showed that aVOC concentrations were significantly higher than bVOC concentrations in the traffic environment. The largest aVOC concentrations were measured for toluene (campaign average of 1630 ng m−3) and p/m xylene (campaign average of 1070 ng m−3), while the dominating bVOC was α-pinene (campaign average of 200 ng m−3). For particle-phase organics, the campaign-average OA concentration was 2.4 µg m−3. The source apportionment analysis extracted six factors for OA. Three OA factors were related to primary OA sources – traffic (24 % of OA, two OA types) and a coffee roastery (7 % of OA) – whereas the largest fraction of OA (69 %) consisted of oxygenated OA (OOA). OOA was divided into less oxidized semi-volatile OA (SV-OOA; 40 % of OA) and two types of low-volatility OA (LV-OOA; 30 %). The focus of this research was also on the oxidation potential of the measured VOCs and the association between VOCs and OA in ambient air. Production rates of the oxidized compounds (OxPR) from the VOC reactions revealed that the main local sources of the oxidation products were O3 oxidation of bVOCs (66 % of total OxPR) and OH radical oxidation of aVOCs and bVOCs (25 % of total OxPR). Overall, aVOCs produced a much smaller portion of the oxidation products (18 %) than bVOCs (82 %). In terms of OA factors, SV-OOA was likely to originate from biogenic sources since it correlated with an oxidation product of monoterpene, nopinone. LV-OOA consisted of highly oxygenated long-range or regionally transported OA that had no correlation with local oxidant concentrations as it had already spent several days in the atmosphere before reaching the measurement site. In general, the main sources were different for VOCs and OA in the traffic environment. Vehicle emissions impacted both VOC and OA concentrations. Due to the specific VOCs attributed to biogenic emissions, the influence of biogenic emissions was more clearly detected in the VOC concentrations than in OA. In contrast, the emissions from the local coffee roastery had a distinctive mass spectrum for OA, but they could not be seen in the VOC measurements due to the measurement limitations for the large VOC compounds. Long-range transport increased the OA concentration and oxidation state considerably, while its effect was observed less clearly in the VOC measurements due to the oxidation of most VOC in the atmosphere during the transport. Overall, this study revealed that in order to properly characterize the impact of different emission sources on air quality, health, and climate, it is of importance to describe both gaseous and particulate emissions and understand how they interact as well as their phase transfers in the atmosphere during the aging process.

Retrieval of the sea spray aerosol mode from submicron particle size distributions and supermicron scattering during LASIC

Abstract. Improved quantification of sea spray aerosol concentration and size is important for determining aerosol effects on clouds and the climate, though attempts to accurately capture the size distribution of the sea spray mode remain limited by the availability of supermicron size distributions. In this work, we introduce a new approach to retrieving lognormal mode fit parameters for a sea spray aerosol mode by combining submicron size distributions with supermicron scattering measurements using a Mie inversion. Submicron size distributions were measured by an ultra-high-sensitivity aerosol spectrometer (UHSAS), and supermicron scattering was taken as the difference between <10 µm and <1 µm three-wavelength integrating nephelometer measurements (NEPH). This UHSAS-NEPH method was applied during background marine periods of the Department of Energy Atmospheric Radiation Measurement Layered Atlantic Smoke Interactions with Clouds (LASIC) campaign on Ascension Island (November 2016–May 2017), when the contribution of sea spray aerosol was expected to represent a large fraction of the aerosol mass and total scattering. Lognormal sea spray modal parameters were retrieved from comparisons between nephelometer measurements and a lookup table of Mie theory-simulated scattering coefficients for low-error solutions that minimized the 0.4–1 µm residual in the UHSAS size distribution. We evaluated the UHSAS-NEPH method with a set of clean marine measurements in the North Atlantic that included supermicron size and chemical measurements, showing that measured supermicron size distributions are needed to constrain the sea spray number concentration but that mass concentration was reasonably characterized using supermicron scattering. For LASIC, the UHSAS-NEPH method retrieved sea spray mode properties for approximately 88 % of the background marine times when the scattering variability and total particle concentration were low (<± 5 Mm−1 and <400 cm−3, respectively), with mass mean diameter ranging from 0.6 to 1.9 µm (1.47 ± 0.17 µm), modal width ranging from 1.1 to 3.97 (2.4±0.3), and mass concentration ranging from 0.18 to 23.0 µg m−3 (8.37. ± 4.1 µg m−3). The measured nephelometer scattering at three wavelengths was found to constrain the mode width marginally at the largest particle sizes in the absence of additional size and chemical measurements for defining parameters for the Mie solutions. Comparing UHSAS-NEPH retrievals to those of a fitting algorithm applied only to the submicron UHSAS number size distribution showed that correlations between retrieved mass concentration and the available mass-based sea spray tracers (coarse scattering, wind speed, and chloride) are low when supermicron measurements are not considered. This work demonstrates the added value of supermicron scattering measurements for retrieving reasonable sea spray mass concentrations, providing the best-available observationally constrained estimate of the sea spray mode properties when supermicron size distribution measurements are not available.

A method for tracking the Brownian motion to estimate the size distribution of submicron particles in seawater.

Because the diffusivity of particles undergoing the Brownian motion is inversely proportional to their sizes, the size distribution of submicron particles can be estimated by tracking their movement. This particle tracking analysis (PTA) has been applied in various fields, but mainly focused on resolving monodispersed particle populations and is rarely used for measuring oceanic particles that are naturally polydispersed. We demonstrated using Monte Carlo simulation that, in principle, PTA can be used to size natural, oceanic particles. We conducted a series of lab experiments using microbeads of NIST‐traceable sizes to evaluate the performance of ViewSizer 3000, a PTA‐based commercial instrument, and found two major uncertainties: (1) the sample volume varies with the size of particles and (2) the signal‐to‐noise ratio for particles of sizes < 200–250 nm was reduced and hence their concentration was underestimated with the presence of larger particles. After applying the volume correction, we found the instrument can resolve oceanic submicron particles of sizes greater than 250 nm with a mean absolute error of 3.9% in size and 38% in concentration.

Size distribution of primary submicron particles and larger aggregates in solvent-induced asphaltene precipitation in a model oil system

Asphaltene precipitation is a crucial phase separation phenomenon in the oil industry, especially in paraffinic froth treatment to extract bitumen from oil sands ores. This work reveals the ubiquitous presence of particles at 0.2 to 0.4 μm in radius, defined as primary sub-micron particles (PSMPs) at early stage asphaltene precipitation from diffusive mixing with solvents. We observed PSMPs in a quasi-2D chamber where asphaltene solution (the model oil) is displaced by 3 paraffinic solvents, the blends of solvents, and solvents containing inhibitor at low concentrations. The yield and size distribution of asphaltene particles are affected not only by the Hildebrand solubility parameter of the precipitants but also by the diffusion coefficients of the asphaltene solution and the precipitant. Even though n-pentane is a stronger solvent than n-heptane, the yield of asphaltene in the diffusive mixing chamber is close because of the difference in the diffusion coefficient between n-pentane and n-heptane in asphaltene solution. The results of n-heptane and n-decane blends reveal that the increase of the ratio of PSMPs compared with pure n-heptane or n-decane. The inhibitors significantly decrease the aggregation rate of PSMPs, displayed as a higher ratio of PSMPs compared to a non-inhibitor group. The population balance model (PBM) with the Hildebrand solubility parameter has been used to model particle size distribution. Good agreement has been achieved between numerical predictions and the experimental data. It indicates that the colloid theory can describe the size distribution of PSMPs and larger aggregates in early stage of asphaltene precipitation. This study illustrates the importance of mixing dynamics on the size distribution in asphaltene precipitation. The findings can be useful for accurate modeling of the hydrocarbon separation or asphaltene precipitation.

Submicron particle formation from co-firing of coal and municipal sewage sludge

With the increasing production of municipal sewage sludge (MSS) in China every year, the co-firing of MSS and pulverized coal is getting more and more widely applied in large coal-fired power plants. The co-firing of MSS and pulverized coal will produce a large amount of particulate matter (PM) emissions, especially submicron particles. In this paper, the formation characteristics of submicron particles in the co-firing process of coal and MSS were studied in a drop tube furnace. The influence of the furnace temperature and the addition ratio of sludge on the particle size distribution and element composition of submicron particles in MSS, pulverized coal combustion and co-firing was mainly studied. The experimental results show that the furnace temperature has an influence on the formation of PM0.4. For sludge combustion, increasing the furnace temperature will promote the formation of PM0.4. The main reason is that increasing the furnace temperature promotes the gasification of Si, S, Fe, and P to form the precursor of PM0.4 or PM0.4. At same furnace temperature, the volume concentration and mass concentration of PM0.4 produced from pulverized coal combustion are less than that of sludge. Different from sludge combustion, co-firing of pulverized coal and sludge has a synergistic effect on eliminating PM0.4 formation. Increasing the addition ratio of sludge can decrease the volume concentration and mass concentration of PM0.4. This is because that aluminosilicates formed during co-firing promotes the scavenge Si, Ca, Fe, thereby reducing the precursors of PM0.4 and the mass yield of PM0.4. Increasing the furnace temperature in co-firing can inhibit the formation of PM0.4. When the furnace temperature is between 1100 °C and 1300 °C, increasing the furnace temperature will reduce the Fe content and increase the content of Si, Ca, Na, K, and P in PM0.4. However, the reduction of Fe and the increase of Si, Ca, Na, K, and P in PM0.4 offset each other, resulting in an insensitive relationship between the mass yield of PM0.4 and the furnace temperature.

Particulate matter emission during municipal solid waste combustion: Submicron particulates formation mechanism

This paper presents an information on size distribution, inorganic composition and formation mechanism of submicron particles generated from MSW combustion. The XRD and CCSEM analysis results clearly showed that NaCl, KCl, K3Na(SO4)2, and SiO2 are the major inorganic mineral components in submicron particles. Submicron particles are mainly composed of organic components, alkali chlorides, alkali sulfates, and refractory inorganic minerals, but they account for different proportions in PM0.2 and PM0.2-1. There are five formation modes of submicron particles in MSW combustion: “condensation”, “nucleation”, “accumulation”, “crystallization” and “fragmentation”. The “condensation” mechanism mainly seen in PM0.2 composed of gas components, the “crystallization” and “fragmentation” modes formed by alkali salts and char particles are mainly present in PM0.2-1, the “nucleation” and “accumulation” modes coexist in PM0.2 and PM0.2-1. As the combustion temperature increased, the alkali chlorides and sulfates in the “crystallization” form decreased, and the inorganic mineral components in the “nucleation” form increased, which results in the variation of size distribution of submicron particles. In addition, volatile alkali salt nucleation experiments show that when alkali chloride and sulfate coexist in high-temperature flue gas, heterogeneous nucleation and agglomeration can significantly enhance the accumulation of particles in the range of 0.2–0.5 μm.

Physical and chemical properties of urban aerosols in São Paulo, Brazil: links between composition and size distribution of submicron particles

Abstract. In this work, the relationships between size and composition of submicron particles (PM1) were analyzed at an urban site in the Metropolitan Area of São Paulo (MASP), a megacity with about 21 million inhabitants. The measurements were carried out from 20 December 2016 to 15 March 2017. The chemical composition was measured with an Aerodyne Aerosol Chemical Speciation Monitor and size distribution with a TSI Scanning Mobility Particle Sizer 3082. PM1 mass concentrations in the MASP had an average mass concentration of 11.4 µg m−3. Organic aerosol (OA) dominated the PM1 composition (56 %), followed by sulfate (15 %) and equivalent black carbon (eBC, 13 %). Four OA classes were identified using positive matrix factorization: oxygenated organic aerosol (OOA, 40 % of OA), biomass burning organic aerosol (BBOA, 13 %), and two hydrocarbon-like OA components (a typical HOA related to vehicular emissions (16 %) and a second HOA (21 %) representing a mix of anthropogenic sources). Particle number concentrations averaged 12 100±6900 cm−3, dominated by the Aitken mode. The accumulation mode increased under relatively high-PM1 conditions, suggesting an enhancement of secondary organic aerosol (SOA) production. Conversely, the contribution of nucleation-mode particles was less dependent on PM1 levels, consistent with vehicular emissions. The relationship between aerosol size modes and PM1 composition was assessed by multilinear regression (MLR) models. Secondary inorganic aerosols were partitioned between Aitken and accumulation modes, related to condensation particle growth processes. Submicron mass loading in the accumulation mode was mostly associated with highly oxidized OOA and also traffic-related emissions. To the authors' knowledge, this is the first work that uses the MLR methodology to estimate the chemical composition of the different aerosol size modes. The chemical composition with size-dependent PM provides innovative information on the properties of both primary and secondary organic aerosols, as well as inorganic aerosols in a complex urban environment. The results emphasize the relevance of vehicular emissions to the air quality at MASP and highlight the key role of secondary processes on the PM1 ambient concentrations in the region since 56 % of PM1 mass loading was attributed to SOA and secondary inorganic aerosol.

Standardized procedure to measure the size distribution of extracellular vesicles together with other particles in biofluids with microfluidic resistive pulse sensing.

The particle size distribution (PSD) of extracellular vesicles (EVs) and other submicron particles in biofluids is commonly measured by nanoparticle tracking analysis (NTA) and tunable resistive pulse sensing (TRPS). A new technique for measuring the PSD is microfluidic resistive pulse sensing (MRPS). Because specific guidelines for measuring EVs together with other particles in biofluids with MRPS are lacking, we developed an operating procedure to reproducibly measure the PSD. The PSDs of particles in human plasma, conditioned medium of PC3 prostate cancer cell line (PC3 CM), and human urine were measured with MRPS (nCS1, Spectradyne LLC) to investigate: (i) the optimal diluent that reduces the interfacial tension of the sample while keeping EVs intact, (ii) the lower limit of detection (LoD) of particle size, (iii) the reproducibility of the PSD, (iv) the optimal dilution for measuring the PSD, and (v) the agreement in measured concentration between microfluidic cartridges with overlapping detection ranges. We found that the optimal diluent is 0.1% bovine serum albumin (w/v) in Dulbecco’s phosphate-buffered saline. Based on the shape of the PSD, which is expected to follow a power-law function within the full detection range, we obtained a lower LoD of 75 nm for plasma and PC3 CM and 65 nm for urine. Normalized PSDs are reproducible (R2 > 0.950) at dilutions between 10–100x for plasma, 5–20x for PC3 CM, and 2–4x for urine. Furthermore, sample dilution does not impact the dilution-corrected concentration when the microfluidic cartridges are operated within their specified concentration ranges. PSDs from microfluidic cartridges with overlapping detection ranges agreed well (R2 > 0.936) and when combined the overall PSD spanned 5 orders of magnitude of measured concentration. Based on these findings, we have developed operating guidelines to reproducibly measure the PSD of EVs together with other particles in biofluids with MRPS.

Corrigendum to “Capabilities and limitations of the single-particle extinction and scattering method for estimating the complex refractive index and size-distribution of spherical and non-spherical submicron particles” [JQSRT 243 (2020) 106811

Corrigendum to “Capabilities and limitations of the single-particle extinction and scattering method for estimating the complex refractive index and size-distribution of spherical and non-spherical submicron particles” [JQSRT 243 (2020) 106811

Multiphase materials based on the Fe73.9Si15.5Cu1Nb3B6.6 alloy obtained by dry and wet high-energy ball milling processes

Novel hybrid materials based on the soft nanocrystalline Fe73.9Si15.5Cu1Nb3B6.6 alloy are designed in this work with the purpose of reducing its particle size and developing different compositional, structural, and magnetic properties depending on the high-energy ball milling time and route employed. Innovative processes combining mixer, vibratory and planetary motions at the same time are carried out under a dry and a wet route, obtaining reduced sub-micron particle size distributions after 2 h of milling. The established approach takes advantage of the nature of amorphous materials to promote the formation of different hybrid compounds and it is supported by the high virulence of the milling process performed at 2000 rpm. On the one hand, the results obtained by the dry route show a structural and magnetic evolution dominated by the presence of ferromagnetic α-Fe3Si nanocrystals. On the other hand, the wet approach that is supported by glycerol evidences the destruction of the α-Fe3Si with the milling time in favor of the non-magnetic β-FeSi2 phase, obtaining a new functionality for the Fe73.9Si15.5Cu1Nb3B6.6 alloy. Their properties as soft magnetic alloys are evaluated and compared depending on the followed route, opening up a new physicochemical method in the development of multiphase compounds with potential applications. With this work, a controlled formation of different hybrid compounds is achieved, revealing an effective mechanism to introduce functional materials with different properties embedded in an amorphous ferromagnetic matrix.

Role of semi-volatile particulate matter in gas-particle partitioning leading to change in oxidative potential.

Atmospheric semi-volatile organic compounds (SVOCs) are complex in their chemical and toxicological characteristics with sources from both primary combustion emissions and secondary oxygenated aerosol formation processes. In this study, thermal desorption of PM2.5 in association with online measurement of reactive oxygen species (ROS) was carried out to study the role of SVOCs in its gas-particle partitioning. The mass concentrations of PM2.5, black carbon (BC) and p-PAHs downstream of a thermodenuder were measured online at different temperature settings (25, 50, 100, and 200°C) to characterize PM physico-chemical properties. While the mass concentrations of PM2.5 and p-PAHs reduced to ∼34% at 200°C compared to that in ambient temperature, BC mass concentration has decreased by 30% at the highest temperature. Furthermore, the submicron particle size distribution showed reduced particle number concentration in Aitken mode at 200°C heating. The ROS, measured by Particle-into-Nitroxide-Quencher, also showed reduction and followed a similar trend with PM measurements, where the total ROS decreased by 12%, 31%, and 53% at 50°C, 100°C, and 200°C, respectively, compared to the ambient sample. When a HEPA filter was included in the upstream of samples, 39% of gas phase ROS reduction was observed at 200°C. This provided a good estimate of the contribution of SVOCs in ROS production in PM2.5, where decreased SVOCs concentration at 200°C increased the percentage of particle surface area. This concludes that the surface chemistry of these organic coatings on the particles is important for assessing the health impacts of PM.

Relationship between submicron particle formation and air mass history observed in the Asian continental outflow at Gosan, Korea, during 2008–2018

We investigated the impact of air mass origin on submicron particle size distributions and new particle formation (NPF) events using 10-year measurements at Gosan, Korea, in the Asian continental outflow. NPF events were identified on approximately 27.1% of total observation days, and 123 and 381 days of them were classified as strong and weak NPF days, respectively, based on the first-mode loading vectors and corresponding principal components in the cyclostationary empirical orthogonal function analysis. NPF events occurred less than 15% of the total observation days for the South China (SC), Pacific Ocean, and stagnation (ST) air mass sectors, whereas 33.1% (243 days out of total 734 observation days) were identified as NPF events for the air mass traveling from the North China (NC) sector. Consistently, the lowest mode diameter (50.5 nm), highest formation rate, and the lowest growth rate were found in the NC air mass sector. The highest mode diameter (89.8 nm) was observed at the SC air mass sector because of the coagulation of newly formed aerosols under relatively humid conditions during the transport in summer. The condensation sink for SC (10.70 ± 2.35 × 10−3 s−1) and ST (10.80 ± 4.24 × 10−3 s−1) was approximately 25% higher than that for the NC air mass sector.

Evolution of particulate matter in the post-combustion zone of Zhundong lignite

Understanding the conversion of particulate matter (PM) in the post-combustion zone is important for controlling the emissions and ash deposition from coal combustion. In this study, the evolution of PM in the post-combustion zone of coal was investigated experimentally and numerically. The air combustion of three Zhundong lignite was performed in a drop tube furnace. PM was sampled at different flue gas temperature from 473K to 1273K. Low pressure impactor, X-ray fluorescence, scanning electron microscope, and scanning mobility particle sizer were applied to analyze mass-based particle size distribution (MPSD), elemental compositions, morphology, and number-based particle size distribution (NPSD) of PM. The results show that when the flue gas temperature decreases from 1273K to 473K, the MPSD and compositions of PM0.4-10 remain stable, while PM0.4 moves towards larger particle size. The reduction of NaCl concentration in the flue gas between 1073K and 1273K may be due to the sulfation of NaCl. The critical condensation temperature of NaCl in flue gas is between 843K and 902K. When the flue gas was sampled beyond the critical condensation temperature, NaCl vapors is converted to PM0.4 through nucleation and condensation during the cooling of the sampling system. The particle size distribution of submicron particles in the post-combustion zone is well described by an aerosol dynamics model with moment method. In the post-combustion zone of Zhundong lignite, coagulation is the dominate mechanism controlling the evolution of PM0.4 from 1273K to 473K.

Calibration of polyvinylidene fluoride based dust detectors in response to varying grain density and incidence angle.

Permanently polarized Polyvinylidene Fluoride (PVDF) films have been used on a variety of spacecraft as in situ dust detectors to measure the size and spatial distributions of micron and sub-micron dust particles. The detectors produce a short electric pulse when impacted by a hypervelocity dust particle. The pulse amplitude depends on the mass and relative speed of the dust grain. This relationship has been studied both empirically and numerically to better understand the film's principle of operation, as well as the effects of film thickness, film temperature, and particle penetration depth. However, little work has been done to constrain the effects of varying particle density and incidence angle despite the frequent occurrence of such configurations in most space-based applications. We present calibrations of non-penetrating impacts on 28 μm thick films at varying incidence angles ranging from 0° to 75° for iron and aluminum particles in the mass and speed range of 10-12 ≤ m ≤ 10-8 g and 0.5 ≤ v ≤ 7 km/s, respectively. The study was carried out at the 3 MV dust accelerator laboratory at the University of Colorado at Boulder. The results show that PVDF signals are largely independent of particle density and incidence angle up to 75° for non-penetrating impacts.