Scanning Mobility Particle Sizer Research Articles

Source apportionment of marine atmospheric aerosols in northern South China Sea during summertime 2018

Marine atmospheric aerosols play important roles in the global radiation balance and climate change. Hence, measuring physiochemical aerosol properties is essential to better understand their formation, aging processes, and source origins. However, high temporal resolution measurements of submicron particles are currently scarce in the northern South China Sea (SCS). In this study, we conducted a ship-based cruise campaign with a scanning mobility particle sizer and an online time of flight aerosol chemical speciation monitor to measure the particle number size distribution (PNSD) and the chemical composition of submicron particles over the northern SCS during summer 2018. The mean concentration of non-refractory submicron particulate matter (NR-PM1) was generally 9.11 ± 4.86 μg m−3; sulfate was the most abundant component, followed by organics, ammonium, nitrate, and chloride. Positive matrix factorization (PMF) analysis was applied to the PNSD (size PMF) and organic aerosols (OA PMF) and further investigated the source apportionment of the submicron particles. The size PMF identified four factors, including ship exhaust, ship influencing marine primary, continent affected marine secondary, and mixed accumulation aerosols. The most abundant particles in the number concentration were associated with ship emissions, which accounted for approximately 44 %. The submicron organic aerosols were highly oxidized and composed of low-volatility oxygenated OA (LV-OOA, 68 %), semi-volatile OOA (SV-OOA, 21 %), and hydrocarbon-like OA (HOA, 11 %). The backward trajectory of air masses showed that the northern SCS was most frequently (64.7 %) influenced by air masses from the Indo-Chinese Peninsula (ICP) during the campaign, implying that pollutants from ICP have a significant impact on the atmosphere of the northern SCS during summer. Thus, in situ ship-based cruise measurements can provide valuable data on the physiochemical characteristics of marine atmospheric aerosols to better understand their source origins.

Nasal endoscopy, room filtration, and aerosol concentrations during live outpatient encounters: a prospective, case-control study.

BackgroundThe coronavirus disease 2019 (COVID‐19) pandemic has highlighted safety concerns surrounding possible aerosol‐generating procedures, but comparative data on the smallest particles capable of transmitting this virus remain limited. We evaluated the effect of nasal endoscopy on aerosol concentration and the role of a high‐efficiency particulate air (HEPA) filter in reducing aerosol concentration.MethodsOtolaryngology patients were prospectively enrolled in an outpatient, cross‐sectional study. Demographic information and clinic room characteristics were recorded. A scanning mobility particle sizer and GRIMM aerosol monitor measured aerosols 14.3 nm to 34 μm in diameter (i.e., particles smaller than those currently examined in the literature) during (1) nasal endoscopy (± debridement) and (2) no nasal endoscopy encounters. One‐way analysis of variance (ANOVA) and Student's t test were performed to compare aerosol concentrations and impact of HEPA filtration.ResultsSixty‐two patients met inclusion criteria (25 nasal endoscopy without debridement; 18 nasal endoscopy with debridement; 19 no nasal endoscopy). There was no significant difference in age or gender across cohorts. Aerosol concentration in the nasal endoscopy cohort (± debridement) was not greater than the no nasal endoscopy cohort (p = 0.36; confidence interval [95% CI], −1.76 to 0.17 μg/m3; and p = 0.12; 95% CI, −0.11 to 2.14 μg/m3, respectively). Aerosol concentrations returned to baseline after 8.76 min without a HEPA filter versus 4.75 min with a HEPA filter (p = 0.001; 95% CI, 1.73–6.3 min).ConclusionUsing advanced instrumentation and a comparative study design, aerosol concentration was shown to be no greater during nasal endoscopy versus no endoscopy encounters. HEPA filter utilization reduced aerosol concentrations significantly faster than no HEPA filter.

Comprehensive characterization of sooting butane jet flames, Part 2: Temperature and soot particle size

The present work investigates the effect of jet-exit Reynolds number (Re) on soot particle size and flame temperature in n-butane jet flames. Correlation of temperature with soot volume fraction (fv), soot precursor (polycyclic aromatic hydrocarbons or PAH), and reaction zone (OH) is also examined. The investigated flames (Re=5000–21,500) are identical as of the companion work (Part 1). The temperature was measured in a low-sooting region using a fine-wire thermocouple. The soot particle size distribution was obtained using a scanning mobility particle sizer (SMPS). Temporal evolution (with 0.1s resolution) of fv in the extracted aerosol sample was monitored with a Pegasor particle sensor (PPS). fv from LII and PPS are compared, and the reasons for differences are discussed in detail. The radial location of peak temperature is biased towards the fuel-rich side. At Re5000, peak-PAH occurs at 650K, whereas in lifted turbulent flame (Re21,500), peak-PAH shifts to 940K. PAH formation temperature is influenced by air/fuel mixing. Despite the variation of turbulence level (Re=5000−21,500), peak-fv in the soot inception region occurs at a nearly identical temperature of 1400K. Peak-fv shifts towards lower temperature with increasing height, likely due to oxidation by diffused OH. The soot mode diameter (Dm) was measured along the axis. Dm increases with height and reaches a maximum near peak-fv region. Dm at moderate Re (5000−7200), varies between 12 and 28 nm along the flame axis. At high Re (21,500), Dm range decreases to 12−24nm. The decrease in peak-Dm with Re is likely due to reduced residence time and enhanced reactant mixing. The comprehensive database containing a wide range of parameters from the present and companion (Part 1) papers will aid in the development and validation of turbulence and soot chemistry models, especially for fuels of practical relevance.

Source apportionment of atmospheric particle number concentrations with wide size range by nonnegative matrix factorization (NMF)

Quantifying the sources of atmospheric particles is essential to air quality control but remains challenging, especially for the source apportionment of particles based on number concentration with wide size range. Here, particle number concentrations (PNC) with size range 19–20,000 nm involving four modes Nucleation, Aitken, Accumulation, and Coarse are used to do source apportionment of PNC at the Guangdong Atmospheric Supersite (Heshan) during July–October 2015 by nonnegative matrix factorization (NMF) with 6 factors. For July 2015, separated source apportionments for three different size ranges from collocated instruments nano scanning mobility particle sizer (NSMPS), SMPS, and aerodynamic particle sizer (APS) and for two different size ranges (below and above 100 nm) show similar quantitative source information with that for the one whole size range. The mean absolute difference of contribution percentages of total particle number concentrations (TPNC) based on 5 unique apportioned sources is 5.6 % (4.3–7.6 %) for the instrument segregated apportionment and 4.2 % (0–5.3 %) for the size range segregated apportionment respectively, relative to the one whole apportionment. Moreover, the contribution percentages of TPNC are close to the weighted sum of contribution percentages of all size bins, with a mean absolute difference of 1.1 % (0–3.4 %). In both these two aspects, the consistency among different technical paths proves the matrix factorization by NMF is practically desirable and the simplicity of reducing some steps or calculations saves time. Besides, dust can be identified with the wide size range including larger than 3000 nm. Six apportioned sources in the 4 months are Accumulation (32.4 %), Nucleation (20.0 %), Aitken (15.2 %), traffic (14.6 %), dust (10.6 %), and Coarse (7.1 %). Therefore, NMF would serve as a promising tool for PNC source apportionment with wide size range and conducting the apportionment with the whole size range in one matrix factorization procedure and using the single TPNC contribution percentage are feasible.

Production of ibuprofen-magnetite nanocomposites by pulsed laser ablation

We investigated the application of pulsed laser ablation (PLA) for the production of magnetic nanoparticles (MNPs)/drug nanocomposites. Magnetic drug delivery vehicles can provide a multifunctional theranostic platform and allow for a combination of diagnostics, monitoring and therapeutics. We applied nanosecond laser pulses at two different wavelengths (Nd:YAG laser, λ 1 = 532 nm/λ 2 = 1064 nm, FWHM = 6 ns) for the ablation of target tablets consisting of a mixture of ibuprofen (as a model drug) and magnetite NPs in various mass ratios. Fourier-transform infrared and Raman spectroscopy investigations of the ablated particles revealed that PLA induced no chemical changes in the pharmaceutical compound. The size distributions of the composite particles were established using a particle size analyzer (scanning mobility particle sizer), and 100–150 nm mean particle size values were obtained. SEM, energy dispersive x-ray spectroscopy and fast photography studies provided morphological and compositional information about the ablated particles. We demonstrated that PLA offers a simple and chemical free method for producing MNPs/drug nanocomposites, and it can be applied for the future development of new theranostic nanosystems.

Chemical Composition of Gas and Particle Phase Products of Toluene Photooxidation Reaction under High OH Exposure Condition

In the current study, the photooxidation reaction of toluene (C7H8) was investigated in a Potential Aerosol Mass Oxidation Flow Reactor (PAM OFR). The hydroxyl radical (OH) exposure of toluene in the PAM OFR ranged from 0.4 to 1.4 × 1012 molec cm−3 s, which is equivalent to 3 to 12 days of atmospheric oxidation. A proton transfer reaction-mass spectrometer (PTR-MS) and a scanning mobility particle sizer (SMPS) were used to study the gas-phase products formed and particle number changes of the oxidation reaction in PAM OFR. The secondary organic aerosol (SOA) formed in the PAM OFR was also collected for off-line chemical analysis. Key gas-phase reaction products of toluene, including glyoxal, methyl glyoxal, unsaturated carbonyl compounds, and benzaldehyde, were identified by the PTR-MS. Second generation products, including acetic acid, formaldehyde, formic acid, and acetaldehyde, were also detected. By comparing the mass spectrums obtained under different OH exposures and relative humidity (RH), changes in the two parameters have minimal effects on the composition of gas-phase products formed, expect for the spectrum obtained at OH exposure of 0.4 × 1012 cm−3 s and RH = 17%, which is slightly different from other spectrums. SMPS results showed that particle mass concentration increases with increasing OH exposure, while particle number concentration first increases and then decreases with increasing OH exposure. This result probably suggests the formation of oligomers at high OH exposure conditions. Off-line chemical analysis of the SOA sample was dominated by C4 diacids, including malic acid, citramalic acid, and tartaric acid. The well-known toluene SOA marker 2,3-Dihydroxy-4-oxopentanoic acid, as well as 2,3-dihydroxyglutaric acid, which has not been identified in previous toluene photooxidation experiments, were also detected in the SOA sample. Our results showed good agreements with the results of previous smog chamber studies of toluene photooxidation reaction, and they suggested that using PAM OFR for studies of oxidation reaction of different VOCs can be atmospherically relevant.

On-line study of the influence of seed particle acidity on ozonation reaction of pyrene

Acid-catalyzed heterogeneous reaction can lead to potentially multifold increase in secondary organic aerosol (SOA) generation, which may have a greater impact on climate forcing effects. In this study, single particle aerosol mass spectrometry (SPAMS) and scanning mobility particle sizer (SMPS) were applied to perform an online study of the chemical and physical characteristics of the pyrene-coated inorganic seed particle ozonation in a smog chamber to examine the influence of seed acidity on pyrene-SOA formation. Acidic seed particles are made of ammonium sulfate, ammonium bisulfate and sulfuric acid in different proportions. Fs, the inorganic seed composition number, is defined as a ratio of the molar concentration of SO42− to the total molar concentration of SO42− and NH4+ in this study. Suspended pyrene-coated acidic seed particles were generated by the vaporization-condensation method. Homogeneous and heterogeneous reaction products were identified and assigned. The results show that the seed particle acidity can enhance the mass yield, as well as the chemical diversity of pyrene-SOAs, and also dramatically increase the formation of new smaller particles. Kinetic analysis revealed that the first-order reaction rate constant (K) of acidic seed particles was much higher than that of neutral seed particles, with K values for Fs = 0.77 being 1.47 times that of Fs = 0.50 and 2.58 times that of Fs = 0.33. A mechanism for pyrene-SOA formation was also proposed based on real-time monitoring. For neutral seeds, the pyrene ozonation preferred ‘atom attack’ and mainly formed 1-hydroxypyrene; while for acidic seeds, the pyrene ozonation preferred ‘bond attack’ and formed a Criegee intermediate, followed by broken C–O and C–C bonds, thereby resulting in a variety of semi- and low-volatile products. This study presents a rapid analytical method for the combined use of smog chamber, SPAMS, and SMPS to immediately characterize the effect of seed particle acidity on the formation of polycyclic aromatic hydrocarbon SOA, which may deepen our understanding of new particle formation and particle growth in the atmosphere. Therefore, the present study provides a new insight for an in-depth understanding of haze pollution in China.

Formation of secondary organic aerosols from the reaction of γ-terpinene with ozone: yields and morphology

Atmospheric secondary organic aerosols (SOAs), formed from condensable oxidation products of anthropogenic and biogenic volatile organic compounds (VOCs), are important constituents of the atmosphere accounting for a significant fraction of ambient tropospheric aerosol. In this study, the formation of SOAs from the gas-phase ozonolysis of γ-terpinene (1-isopropyl-4-methyl-1,4-cyclohexadiene), a monoterpene emitted by many different trees (elm, cypress, water hickory, maple trees …) has been studied in an indoor atmospheric simulation chamber (CHARME), at 294 ± 2 K, atmospheric pressure, under dry conditions (relative humidity, RH < 2%) and in absence of seed particles. The concentration of γ-terpinene was measured by a proton Transfer Reaction - Time of Flight - Mass Spectrometer (PTR-ToF-MS), that of ozone by an UV photometric analyzer and the aerosol mass concentration was monitored using a scanning mobility particle sizer (SMPS). Scanning electronic microscopy (SEM) observations were performed to characterize the physical state and morphology of the formed SOAs. They show the formation of spherical particles in a viscous state.The overall organic aerosol yield (Y) was determined as the ratio of the suspended aerosol mass concentration corrected for wall losses (Mo) to the total reacted γ-terpinene concentration, assuming a particle density of 1 g cm−3. The aerosol formation yield increases as the initial γ-terpinene concentration raises. The presence of an OH radical scavenger (cyclohexane) leads to a decrease in the SOA yields (they varied from 0.11 to 0.54 and from 0.16 to 0.49, without and with, an OH radical scavenger, respectively). Y is a strong function of Mo and the organic aerosol formation can be expressed by a one-product gas/particle partitioning absorption model.

Effects of NH3 on secondary aerosol formation from toluene/NOx photo-oxidation in different O3 formation regimes

Ammonia (NH3) is an important base gas in the atmosphere and has received extensive research interest due to its role on secondary aerosol formation. However, the effects of NH3 on the photochemical smog oxidants formation including ozone and secondary aerosol did not attract much attention. In this study, a set of smog chamber experiments was conducted under toluene/NOx photo-oxidation base condition and adding NH3 in the following photochemical regimes referred as hydrocarbon, NOx-limited and transitional regimes. Dedicated instruments including gas analysers, scanning mobility particle sizer (SMPS), aerosol mass spectrometry (HR-ToF-AMS) were used to measure the gaseous compounds, aerosol mass concentration and chemical composition. It was found that the presence of NH3 did not affect the O3 formation rate. However, the particle number concentration increased dramatically after NH3 was injected in any photochemical regimes. This effect has been mainly attributed to the rapid formation of organic ammonium and ammonium nitrate. The mass spectra of organic aerosols from AMS showed that the most abundant fragments were at m/z 28, 29, 43 and 44, which became higher after the addition of NH3 in the transition and NOx-limited regimes, indicating that NH3 could enhance the formation of the compounds containing carbonyl and carboxylic acid functional groups. Compared to hydrocarbon-limited regime, higher atomic nitrogen-to-carbon (N:C) ratios were observed when NH3 were injected into transition and NOx-limited regimes, and this is mainly due to more organic nitrate formation. Four factors, which were assigned to inorganic nitrate aerosols, carboxylic acid compounds, carbonyl compounds and N-containing organic compounds (NOC), were identified and interpreted by applying the positive matrix factorization (PMF) to the AMS dataset. These results provide new insights into the complex chemistry of toluene/NOx/NH3 during different O3 formation regimes, and imply the benefit of controlling NH3 to mitigate PM2.5 when O3 formation is under VOC-limited regime.

Application of Acoustic Agglomeration Technology to Improve the Removal of Submicron Particles from Vehicle Exhaust

The natural processes of interactions between aerosol particles in the ambient air through which they agglomerate is a vast area of chamber research and are inherent to many industries and are often inter-connected with transport engineering. Further improvement of symmetric methods for aerosol particle number and mass concentration reduction made it possible to create various synergic techniques. The study used a 1.9 TDI diesel internal combustion engine, which was supplied with diesel (D100) and second-generation biofuels (NExBTL100) with the EGR exhaust system on and off. Measurements were performed using a Bruel and Kjær “Type 9727” system for measurement of vibrations, a scanning mobility particle sizer (SMPS) and an original agglomeration chamber. The three modes of particle size distributions were observed in the size range from 10 to 470 nm for both D100 and NExBTL100 fuels with and without the use of the EGR system. The application of 21.3 kHz frequency sound with SPL 144.1 dB changed the NExBTL100 generated aerosol particle number concentration but did not sufficiently affect the concentration of D100 emitted particles. The greatest agglomeration effect (21.7 ± 10.0%) was observed in the range of extremely small NExBTL100 derived particles (10–70 nm) when used in combination with an EGR system.

Overview of the SLOPE I and II campaigns: aerosol properties retrieved with lidar and sun–sky photometer measurements

Abstract. The Sierra Nevada Lidar aerOsol Profiling Experiment I and II (SLOPE I and II) campaigns were intended to determine the vertical structure of aerosols by remote sensing instruments and test the various retrieval schemes for obtaining aerosol microphysical and optical properties with in situ measurements. The SLOPE I and II campaigns were developed during the summers of 2016 and 2017, respectively, combining active and passive remote sensing with in situ measurements at stations belonging to the AGORA observatory (Andalusian Global ObseRvatory of the Atmosphere) in the Granada area (Spain). In this work, we use the in situ measurements of these campaigns to evaluate aerosol properties retrieved by the GRASP code (Generalized Retrieval of Atmosphere and Surface Properties) combining lidar and sun–sky photometer measurements. We show an overview of aerosol properties retrieved by GRASP during the SLOPE I and II campaigns. In addition, we evaluate the GRASP retrievals of total aerosol volume concentration (discerning between fine and coarse modes), extinction and scattering coefficients, and for the first time we present an evaluation of the absorption coefficient. The statistical analysis of aerosol optical and microphysical properties, both column-integrated and vertically resolved, from May to July 2016 and 2017 shows a large variability in aerosol load and types. The results show a strong predominance of desert dust particles due to North African intrusions. The vertically resolved analysis denotes a decay of the atmospheric aerosols with an altitude up to 5 km a.s.l. Finally, desert dust and biomass burning events were chosen to show the high potential of GRASP to retrieve vertical profiles of aerosol properties (e.g. absorption coefficient and single scattering albedo) for different aerosol types. The aerosol properties retrieved by GRASP show good agreement with simultaneous in situ measurements (nephelometer, aethalometer, scanning mobility particle sizer, and aerodynamic particle sizer) performed at the Sierra Nevada Station (SNS) in Granada. In general, GRASP overestimates the in situ data at the SNS with a mean difference lower than 6 µm3 cm−3 for volume concentration, and 11 and 2 Mm−1 for the scattering and absorption coefficients. On the other hand, the comparison of GRASP with airborne measurements also shows an overestimation with mean absolute differences of 14 ± 10 and 1.2 ± 1.2 Mm−1 for the scattering and absorption coefficients, showing a better agreement for the absorption (scattering) coefficient with higher (lower) aerosol optical depth. The potential of GRASP shown in this study will contribute to enhancing the representativeness of the aerosol vertical distribution and provide information for satellite and global model evaluation.

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.

Assessing the sources of particles at an urban background site using both regulatory instruments and low-cost sensors – a comparative study

Abstract. Measurement and source apportionment of atmospheric pollutants are crucial for the assessment of air quality and the implementation of policies for their improvement. In most cases, such measurements use expensive regulatory-grade instruments, which makes it difficult to achieve wide spatial coverage. Low-cost sensors may provide a more affordable alternative, but their capability and reliability in separating distinct sources of particles have not been tested extensively yet. The present study examines the ability of a low-cost optical particle counter (OPC) to identify the sources of particles and conditions that affect particle concentrations at an urban background site in Birmingham, UK. To help evaluate the results, the same analysis is performed on data from a regulatory-grade instrument (SMPS, scanning mobility particle sizer) and compared to the outcomes from the OPC analysis. The analysis of the low-cost sensor data manages to separate periods and atmospheric conditions according to the level of pollution at the site. It also successfully identifies a number of sources for the observed particles, which were also identified using the regulatory-grade instruments. The low-cost sensor, due to the particle size range measured (0.35 to 40 µm), performed rather well in differentiating sources of particles with sizes greater than 1 µm, though its ability to distinguish their diurnal variation, as well as to separate sources of smaller particles, at the site was limited. The current level of source identification demonstrated makes the technique useful for background site studies, where larger particles with smaller temporal variations are of significant importance. This study highlights the current capability of low-cost sensors in source identification and differentiation using clustering approaches. Future directions towards particulate matter source apportionment using low-cost OPCs are highlighted.

The important roles of surface tension and growth rate in the contribution of new particle formation (NPF) to cloud condensation nuclei (CCN) number concentration: evidence from field measurements in southern China

Abstract. The contribution of new particle formation (NPF) to cloud condensation nuclei (CCN) number concentration (NCCN) varies largely under different environments and depends on several key factors such as formation rate (J), growth rate (GR), distribution of preexisting particles, and properties of new particles during NPF events. This study investigates the contribution of NPF to the NCCN and its controlling factors based on measurements conducted at the Heshan supersite, in the Pearl River Delta (PRD) region of China during fall 2019. The size-resolved cloud condensation nuclei activity and size-resolved particle hygroscopicity were measured by a cloud condensation nuclei counter (CCNc) and a hygroscopic tandem differential mobility analyzer (HTDMA), respectively, along with a scanning mobility particle sizer (SMPS) and a diethylene glycol scanning mobility particle sizer (DEG-SMPS) for particle number size distribution (PNSD). A typical NPF event on 29 October was chosen to investigate the contribution of the NPF to NCCN under several supersaturation (SS) ratios. Two particle properties (hygroscopicity and surface tension) affect CCN activation with the latter being more important in terms of the CCN concentration (NCCN). A lower value of surface tension (i.e., 0.06 N m−1) than the pure-water assumption (0.073 N m−1) could increase the NCCN at SS = 1.0 % by about 20 % during the nonevent period and by about 40 % during the event. In addition, an earlier peak time corresponding to a lower critical diameter (D50) was also observed. The results show that high formation rate, growth rate, and low background particle concentration lead to high number concentrations of newly formed particles. The high growth rate was found to have the most significant impact on the NCCN, which can be attributed to the fact that a higher growth rate can grow particles to the CCN size in a shorter time before they are scavenged by preexisting particles. Two other NPF events (an event on 18 October in this campaign and an event on 12 December 2014 in Panyu) were chosen to perform sensitivity tests under different scenarios (growth rate, formation rate, and background particle concentration). The calculated NCCN at SS = 1.0 % on 12 December 2014 was significantly lower than that from the other two events. The event on 12 December was re-simulated using the growth rate taken from the event on 18 October which resulted in similar CCN concentrations between the two events (12 December and 18 October), implying that the growth rate is the major impact factor for CCN activation. Our results highlight the importance of growth rate and surface tension when evaluating the contribution of NPF to the NCCN.

Using particle effective density to determine SMPS-based aerosol mass concentration: application to airborne carbon and titanium nanoparticles

To avoid multiple instruments to be deployed in field measurement campaigns based on airborne nanoparticles characterization, this study aims at investigating the capability of a Scanning Mobility Particle Sizer (SMPS) to provide accurate data relative to the mass concentration. Two series of test nanoaerosols were produced using a spark-discharge generator equipped with carbon or titanium electrodes (modal number diameters between ~ 50 and ~ 170 nm). The mass concentration was monitored by means of a personal AM520 photometer operated in parallel with the SMPS and closed-face cassette sampling for further off-line analysis: gravimetric analysis, and chemical analysis (thermo-optical analysis for carbon, ICP-OES for titanium). For each operating condition, the average number size distribution stemming from the SMPS was converted into mass size distribution accounting for particle effective density and integrated over the whole range of particle diameters to determine the corresponding mass concentration. Results highlight correlations (R2 ~ 0.9) between SMPS-based and chemical analysis or gravimetric mass concentrations below 1 mg/m3, with relative discrepancies lower than ~ 15% and ~ 25%, respectively. The AM520 photometric response remains dependent on particle physical and light scattering properties, which differ with the test dust used for factory calibration.

Applicate Tangential Flow Filtration System to Improve Post CMP-Cleaning Performance

Chemical mechanical polishing (CMP) is one of the important process steps in semiconductor manufacturing. Several types of abrasives are used in the CMP process, among these, ceria slurry is commonly used through its excellent polishing performance in terms of oxide MRR. However, ceria particles remain on the wafer surface after polishing process as contaminants, and small ceria particles are difficult to remove from wafer surface [1].In this respect, we focused to treat small ceria particles that interfere with the cleaning process and we applicate the tangential flow filtration (TFF) system before the CMP process. TFF system is a system for separation of particles by Brownian motion, shear-induced diffusion and the mechanism shown in Fig. In this experiment, separation of small ceria particles successfully and it was evaluated by scanning mobility particle sizer (SMPS) analysis. Furthermore, TFF system did not affect the slurry properties of particle mean diameter, pH value, and zeta potential.In this study, concentration of ceria particles on the wafer surface after CMP process were evaluated by ICP-MS analysis. We calculated the cleaning efficiency with and without TFF separation system. As a result, cleaning efficiency was improved by using TFF system. In addition, the removal rate of SiO2 was almost maintained and the deviation decreased.

Scavenging of submicron aerosol particles in a suburban atmosphere: The raindrop size factor

This paper studies the below-cloud scavenging caused by precipitation on ultrafine and accumulation modes, as well as the role of the different raindrop sizes in an urban environment. The equipment used to measure aerosol particles and raindrop variables includes a scanning mobility particle sizer spectrometer-SMPS and a Laser Precipitation Monitor (LPM), respectively. An analysis of the scavenging efficiency and the scavenging coefficient (λ) by modes and rain intensities was carried out. The main results observed have been: i) the nucleation (between 14 and 30 nm), Aitken (between 30 and 100 nm), accumulation 1 (between 100 and 300) and accumulation 2 (between 300 and 1000 nm) modes presented a scavenging efficiency of 15, 4, 22 and 21%, respectively; ii) events with rain intensities between 1 and 3 mm h−1 caused less scavenging in all modes; iii) raindrop sizes between 1.25 and 3.5 mm scavenged mainly particle sizes between 70 and 250 nm. Lower scavenging was observed on particle sizes >300 nm, and particle sizes >600 nm were only scavenged by raindrop sizes >4.75 mm; iv) the respirable fraction before and after the rain events presented a statically significant decrease of −35%. The combination in this study of SMPS and disdrometer measurements has resulted in a more detailed characterization of the influence of this process on the submicrometer aerosol fraction, noting that below-cloud scavenging is one of the main removal pathways for submicrometer aerosol particles. This study thus contributes to improving the current state of knowledge of below-cloud scavenging.

New Particle Formation Events in Summer and Winter in the Coastal Atmosphere in Qingdao, China

Atmospheric particle number size distributions were measured by a wide-range particle size spectrometer and a scanning mobility particle size spectrometer in the summertime and wintertime in the coastal area of Qingdao (China). The inorganic and organic gaseous precursors and particulate chemical composition were measured to characterize new particle formation (NPF) events by combining meteorological parameters and backward trajectories. In summer, the occurrence frequency of NPF events was 18% lower. However, the atmospheric particle number concentration increased by approximately 1-4 times during the NPF events compared with those without NPF. The apparent formation rates and growth rates were (5.2±4.3) cm-3·s-1 and (6.5±2.2) nm·h-1, respectively, except for a special NPF event on July 20. The correlation analysis results implied that biogenic volatile organic compounds (BVOCs) seemingly favor NPF, and the reverse is true for anthropogenic volatile organic compounds (AVOCs). The occurrence frequency of NPF events of 27% in winter was clearly higher than that in summer. The apparent formation rates and growth rates, i.e., (3.3±3.1) cm-3·s-1 and (5.3±3.3) nm·h-1, decreased, although the decreases were not significant (P>0.05). The correlation analyses implied that AVOCs favored NPF. However, BVOCs had no correlation with NPF. For the cases in which new particles could grow to CCN sizes (>50 nm), the particle growth characteristics showed significant seasonal differences, i.e., in summer, new particles could grow to CCN sizes via photochemical reactions, whereas in winter, second-stage growth driven by the formation of nitrate aerosols was needed to grow new particles to CCN sizes.

Monitoring of Indoor Ultrafine Particulate Matter at the Sites of the Czech Armed Forces

Ultrafine particles and nanoparticles in the air are evaluated as a risk factor for the development of respiratory and other healthsymptoms due to their inhalation from the ambient air. The Czech Army professionals are expected to have frequent presence in apolluted environment and regular exposure to air with increased concentration of airborne pollutants. The report evaluates the presenceof ultra-fine particles (in the range of about 7.6–299.6 nm) in rooms often used by soldiers during their working hours whenthey are not deployed. The purpose is to assess whether the presence of troops in these workplaces is safe and does not pose a riskof adverse health effects in itself. Testing took place in three military rooms (classroom 1, classroom 2 and exercise flight simulatorroom). Seven samples of air were analysed in time by the scanning mobility particle sizer in succession. Mean particle concentrationswere found at 1.79×104, 7.53×103 and 8.39×103 N·cm-3 for the classroom 1, classroom 2 and exercise flight simulator room.Conclusions of the research have shown that particle concentrations in the places of the Czech Army can reach values that borderthe immission limits stated by the World Health Organisation.

Fabrication of Submicrometer-Sized Meloxicam Particles Using Femtosecond Laser Ablation in Gas and Liquid Environments.

In pharmaceutical development, more and more drugs are classified as poorly water-soluble or insoluble. Particle size reduction is a common way to fight this trend by improving dissolution rate, transport characteristics and bioavailability. Pulsed laser ablation is a ground-breaking technique of drug particle generation in the nano- and micrometer size range. Meloxicam, a commonly used nonsteroidal anti-inflammatory drug with poor water solubility, was chosen as the model drug. The pastille pressed meloxicam targets were irradiated by a Ti:sapphire laser (τ = 135 fs, λc = 800 nm) in air and in distilled water. Fourier transform infrared and Raman spectroscopies were used for chemical characterization and scanning electron microscopy to determine morphology and size. Additional particle size studies were performed using a scanning mobility particle sizer. Our experiments demonstrated that significant particle size reduction can be achieved with laser ablation both in air and in distilled water without any chemical change of meloxicam. The size of the ablated particles (~50 nm to a few microns) is approximately at least one-tenth of the size (~10–50 micron) of commercially available meloxicam crystals. Furthermore, nanoaggregate formation was described during pulsed laser ablation in air, which was scarcely studied for drug/organic molecules before.