Particle Mass Concentration Research Articles

Effect of mixed magnetic field on physical properties of atmospheric suspended fine particles

In recent years, the fine particles suspended in the atmosphere, especially the particle size less than 10 μm, have caused very adverse effects on the climate environment and human health. However, the current research on the causes of air pollution mainly focuses on human activities and weather conditions. Considering the weak magnetism and chargeability of atmospheric fine particles, this study proposed a new view that space electromagnetic radiation may affect the physical properties of fine particles. We first analyzed the dynamic characteristics of magnetic micro-particle in the electromagnetic environment, and built a simulation model in the COMSOL simulation software. Finally, based on the theoretical analysis and simulation results, we built an experimental verification system to evaluate the effects of electromagnetic radiation on the physical properties of micro-particle, and carried out a 30-day control experiment. The experimental results showed that the physical properties such as particle size distribution, mass concentration, and morphology of suspended fine particles in the atmosphere under electromagnetic radiation are significantly different from those under non-electromagnetic radiation environment. It can be inferred that the aggregation, fusion, and deposition of suspended particles in the atmosphere are closely related to the complex electromagnetic environment in space.

Study on the real-world emission characteristics of gaseous and particulate pollutants from an inland ship using a portable emission measurement system.

The emissions of pollutants from inland ships endanger the urban environment and human health, deserving quantitative study to make reduction measurements to achieve clean emissions. In this study, the real-world gaseous emissions (CO, THC, SO2, NOx) and particulate emissions including particle mass (PM) and particle number (PN) as well as the particle size distribution and particle compositions from an inland ship were investigated using a portable emission measurement system (PEMS) method. The results showed that the emission concentrations of CO, THC, PM and PN at departure and idling conditions were significantly higher than those at other conditions, while the emission concentrations of NOx and SO2 at cruising condition were the highest. The particle size distribution always presented a bimodal distribution ranged at 40nm and 200nm respectively at different conditions and engine loads. The proportion of nucleation mode particles was the highest at departure condition, and a larger engine load resulted in a declined proportion of nucleation mode particles. The anions of the emitted particles mainly included nitrite ion (NO2-), nitrate ion (NO3-), sulfate ion (SO42-), and cations mainly included ammonium ion (NH4+), sodium ion (Na+) and potassium ion (K+). The main components of organic carbon (OC) in soot were OC1 and OC2, accounting for more than 80%, while the main component of elemental carbon (EC) was EC2, accounting for 83.9%. The emission factors based on fuel consumption of CO and THC were significantly higher at idling conditions than other conditions, and the emission factor of NOx was higher at cruising conditions, while the emission factors of PM and PN were higher at departure and idling conditions than other conditions.

Analysis of Mass Concentration and Morphology of Fume Particles during ECDM of CFRP Composites

Electrochemical discharge machining (ECDM) is a hybrid method used to generate micro-features in hard and brittle materials (glass, ceramics, and composites) in aerospace, microelectromechanical systems (MEMS), and microfluidic applications. A significant improvement was observed in ECDM process but the effect of the process on the health of working operator are rarely investigated. Sustainability in manufacturing is a major concern for a better environment and safety of human operators. In this paper, analysis of fumes mass concentration (FMC), size and morphology of fume particles, and composition of fume particles along with their biological effects are studied during ECDM of CFRP composites. FMC was calculated by varying the concentration of electrolyte from 20 to 50% and duty cycle from 60 to 90% for a fixed sampling duration of 30 minutes. SEM images indicated the presence of spherical, irregular, and loosely packed fumes particles in the fumes generated during machining. EDS was also performed to study the chemical composition of fumes particles.

Aerosol emissions from a marine diesel engine running on different fuels and effects of exhaust gas cleaning measures

The emissions of marine diesel engines have gained both global and regional attentions because of their impact on human health and climate change. To reduce ship emissions, the International Maritime Organization capped the fuel sulfur content of marine fuels. Consequently, either low-sulfur fuels or additional exhaust gas cleaning devices for the reduction in sulfur dioxide (SO2) emissions became mandatory. Although a wet scrubber reduces the amount of SO2 significantly, there is still a need to consider the reduction in particle emissions directly.We present data on the particle removal efficiency of a scrubber regarding particle number and mass concentration with different marine fuel types, marine gas oil, and two heavy fuel oils (HFOs). An open-loop sulfur scrubber was installed in the exhaust line of a marine diesel test engine. Fine particulate matter was comprehensively characterized in terms of its physical and chemical properties. The wet scrubber led up to a 40% reduction in particle number, whereas a reduction in particle mass emissions was not generally determined. We observed a shift in the size distribution by the scrubber to larger particle diameters when the engine was operated on conventional HFOs.The reduction in particle number concentrations and shift in particle size were caused by the coagulation of soot particles and formation/growing of sulfur-containing particles. Combining the scrubber with a wet electrostatic precipitator as an additional abatement system showed a reduction in particle number and mass emission factors by >98%.Therefore, the application of a wet scrubber for the after-treatment of marine fuel oil combustion will reduce SO2 emissions, but it does not substantially affect the number and mass concentration of respirable particulate matters. To reduce particle emission, the scrubber should be combined with additional abatement systems.

Assessment of the exposure to PM2.5 in different Lebanese microenvironments at different temporal scales.

The weak potential of using the sole outdoor concentrations to represent personal exposure to PM2.5 is confirmed by the literature; therefore, it is important to account for a person’s movements over time when estimating the short-term personal air pollution exposure within different microenvironments (MEs). This study is an example of applying an assessment method of the exposure to PM2.5 in different microenvironments at different temporal scales. A low-cost particle counter (the Dylos 1700) was used; its performance was validated in comparison with equivalent instruments such the SidePak AM520 Personal Aerosol Monitor (R2 = 0.89). This validation also provided a function to convert measured particle number concentrations (PNCs) into calculated particle mass concentrations. The 150 profiles that was collected on a minute-by-minute basis regarding PM2.5 concentration from December 2018 to May 2021 highlight the influence of individual activities and contextual factors on the air quality, so that Lebanon’s annual PM2.5 mean (24.2 µg⁄m3) is 142% higher than the World Health Organization (WHO) annual mean guideline (10 µg⁄m3). Winter is the most polluted period due to the increased application of space heating devices. Additionally, the occurrence of dusty winds during the spring period leads to the elevated levels of dispersed PM2.5. Simultaneously, the rural zones are more polluted than urban ones due to the usage of more traditional heating equipment, in addition to the usage of chemical products like pesticides and fertilizers in agricultural activities in such areas. Furthermore, the (outdoor–indoor–transport) MEs indicate that the transport and indoor MEs have similar levels of suspended fine particulates, while outdoor MEs are less polluted. Studies based on the personal exposure to PM2.5 were generally applied on specific and limited places such as schools, workplaces, or residences. The study aims to shed light on the modern method in an attempt to estimate the personal exposure to PM2.5 and to inspire similar studies to achieve the maximum efficiency.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10661-022-10607-6.

Characteristics of fine and ultrafine aerosols in the London underground

Underground railway systems are recognised spaces of increased personal pollution exposure. We studied the number-size distribution and physico-chemical characteristics of ultrafine (PM0.1), fine (PM0.1–2.5) and coarse (PM2.5–10) particles collected on a London underground platform. Particle number concentrations gradually increased throughout the day, with a maximum concentration between 18:00 h and 21:00 h (local time). There was a maximum decrease in mass for the PM2.5, PM2.5–10 and black carbon of 3.9, 4.5 and ~ 21-times, respectively, between operable (OpHrs) and non-operable (N-OpHrs) hours. Average PM10 (52 μg m−3) and PM2.5 (34 μg m−3) concentrations over the full data showed levels above the World Health Organization Air Quality Guidelines. Respiratory deposition doses of particle number and mass concentrations were calculated and found to be two- and four-times higher during OpHrs compared with N-OpHrs, reflecting events such as train arrival/departure during OpHrs. Organic compounds were composed of aromatic hydrocarbons and polycyclic aromatic hydrocarbons (PAHs) which are known to be harmful to health. Specific ratios of PAHs were identified for underground transport that may reflect an interaction between PAHs and fine particles. Scanning transmission electron microscopy (STEM) chemical maps of fine and ultrafine fractions show they are composed of Fe and O in the form of magnetite and nanosized mixtures of metals including Cr, Al, Ni and Mn. These findings, and the low air change rate (0.17 to 0.46 h−1), highlight the need to improve the ventilation conditions.

Impact of Sterilization on the Colloidal Stability of Ligand-Free Gold Nanoparticles for Biomedical Applications.

Sterilization is a major prerequisite for the utilization of nanoparticle colloids in biomedicine, a process well examined for particles derived from chemical synthesis although highly underexplored for electrostatically stabilized ligand-free gold nanoparticles (AuNPs). Hence, in this work, we comprehensively examined and compared the physicochemical characteristics of laser-generated ligand-free colloidal AuNPs exposed to steam sterilization and sterile filtration as a function of particle size and mass concentration and obtained physicochemical insight into particle growth processes. These particles exhibit long-term colloidal stability (up to 3 months) derived from electrostatic stabilization without using any ligands or surfactants. We show that particle growth attributed to cluster-based ripening occurs in smaller AuNPs (∼5 nm) following autoclaving, while larger particles (∼10 and ∼30 nm) remain stable. Sterile filtration, as an alternative effective sterilizing approach, has no substantial impact on the colloidal stability of AuNPs, regardless of particle size, although a mass loss of 5-10% is observed. Finally, we evaluated the impact of the sterilization procedures on potential particle functionality in proton therapy, using the formation of reactive oxygen species (ROS) as a readout. In particular, 5 nm AuNPs exhibit a significant loss in activity upon autoclaving, probably dedicated to specific surface area reduction and surface restructuring during particle growth. The filtered analog enhanced the ROS release by up to a factor of ∼2.0, at 30 ppm gold concentration. Our findings highlight the need for carefully adapting the sterilization procedure of ligand-free NPs to the desired biomedical application with special emphasis on particle size and concentration.

Effects of doping on the thermophysical properties of Ag and Cu doped TiO2 nanoparticles and their nanofluids

A widely accepted method to improve the thermal performance of nanofluids is adding more particles to the fluid, which often causes higher viscosity and sedimentation risk. Therefore, alternative methods are required to create complex structures and improve the properties of particles to acquire similar or even better performance with a smaller amount. Doping is one of the promising methods, and this study examined the effects of doping rates (0.1 and 0.3 %) and materials (Ag and Cu) on the thermophysical properties of ethylene glycol-water-based nanofluids. Nanofluids were prepared with pure and Ag/Cu doped TiO2 nanoparticles at various concentrations (0.3 %, 0.5 %, 1 %, and 2) by mass. The synthesized nanoparticles were characterized by X-ray diffraction (XRD), particle size distribution (PSD), Brunauer, Emmett, and Teller (BET) surface area analysis, and transmission electron microscopy (TEM). Thermophysical property measurements were carried out at a temperature range of 40 and 60 °C. Based on the results, all particles were spherical and had an anatase structure with an average particle size ranging from 6 nm to 8 nm. There was also a monodisperse distribution in the base fluid. At the highest doping rate (0.3 %) and lowest mass concentration (0.3 %) of Ag-doped particles, the maximum specific heat (3051.31 J/kgK) of the study was observed. Increasing concentration resulted in a maximum 48.2 % decrease in specific heat for nanofluids containing 0.1 % Cu particles. The thermal conductivity increased by 2.40 % with doping but by only 1.89 % with concentration. The highest increase in viscosity was determined as 75.21 % at 40 °C, depending on the concentration increase. Thus, the doping method presents better heat transfer performance without an undesirable increase in viscosity compared to increasing the concentration.

Changes in heart rate variability of healthy subjects shortly exposed to printing shop particles and the effect of air purifier intervention

Particulate matter (PM) released by printers may cause airway inflammation and cardiac electrophysiological changes. We conducted a two-stage crossover study to examine the association between short-term exposure to printing shop particles (PSPs) and the heart rate variability (HRV) among healthy volunteers, as well as to evaluate the effect of air purifier intervention. The on-site assessments of PSPs and individual HRV parameters of the volunteers were used to analyze the influence of size-fractionated PSPs and air purifier intervention on HRV at different lag times after PSPs exposure (0 min, 5 min, 15 min, and 30 min) by using the linear mixed-effects models. We observed that changes in 6 HRV parameters were associated with particle mass concentration (PMC) of PSPs, and changes in 8 HRV parameters were associated with particle number concentration (PNC) of PSPs. The sensitive HRV parameters were the square root of the mean of the sum of the squares of differences between adjacent NN intervals (rMSSD), NN50 count divided by the total number of all NN intervals (pNN50), normalized high frequency power (nHF), very high frequency power (VHF), normalized low frequency power (nLF), and the ratio of low frequency power to high frequency power (LF/HF). Most HRV parameters exhibited the strongest effect associated with PMC and PNC at a lag time of 30 min. The air purifier intervention markedly reduced the PNC and PMC of size-fractionated PSPs, enhanced 5 HRV parameters, and decreased the nLF and LF/HF. Our study suggests that short-term exposure to PSPs can affect HRV parameters, reflecting changes in cardiac autonomic nervous activity, and the use of an air purifier can reduce the concentration of PSPs and improve the autonomic nervous system activity of the exposed individuals.

Study on mass concentration and morphology of SMAW fume particles with a new covered electrode using nano-CaTiO3 as an arc stabilizer

Advances in manufacturing emphasize on the development of sustainable and green manufacturing processes. Welding is a popular manufacturing process practiced worldwide. The paper presented here describes a new covered electrode for a shielded metal arc welding (SMAW) process wherein nano-sized calcium titanate (CaTiO3) powder was used as an arc stabilizer, replacing the conventional micro sized CaTiO3 in the flux. The effect of this flux modification on the mass concentration and morphology of welding fume particulates was systematically investigated. The mass concentration of coarse, fine and sub-micron sized fume particulates was measured by segregating the fumes in a four-stage personal cascade impactor. The particle mass distribution was estimated from the mass median aerodynamic diameter (MMAD) and geometric standard deviation (GSD) of the fume particulates. The morphology of fumes at each impactor stage was analysed using scanning electron microscopy and its count median diameter (CMD) was determined. The results indicated as much as 48 % reduction in total fumes and 54 % reduction in the breathing zone concentration of fumes when the entire CaTiO3 in the electrode flux was substituted with nano-CaTiO3. Morphological analysis indicated that a large fraction of the fumes from the conventional electrode were polydispersed particles, while the new electrodes predominantly contained monodispersed particles which have a relatively faster rate of removal from the lungs. Overall, the present work indicated that introducing nano sized CaTiO3 as an arc stabilizer to the flux covering of SMAW electrode could not only reduce the hazardous fume emissions but also reduce its biological activity and toxicity, thus making the process more sustainable and environment friendly.

Effects of emission sources on the particle number size distribution of ambient air in the residential area

Particle size distribution is a major factor in the health and climate effects of ambient aerosols, and it shows a large variation depending on the prevailing atmospheric emission sources. In this work, the particle number size distributions of ambient air were investigated at a suburban detached housing area in northern Helsinki, Finland, during a half-year period from winter to summer of 2020. The measurements were conducted with a scanning mobility particle sizer (SMPS) with a particle size range of 16–698 nm (mobility diameter), and the events with a dominant particle source were identified systematically from the data based on the time of the day and different particle physical and chemical properties. During the measurement period, four different types of events with a dominant contribution from either wood-burning (WB), traffic (TRA), secondary biogenic (BIO), or long-range transported (LRT) aerosol were observed. The particle size was the largest for the LRT events followed by BIO, WB, and TRA events with the geometric mean diameters of 72, 62, 57, and 41 nm, respectively. BIO and LRT produced the largest particle mode sizes followed by WB, and TRA with the modes of 69, 69, 46, and 25 nm, respectively. Each event type had also a noticeably different shape of the average number size distribution (NSD). In addition to the evaluation of NSDs representing different particle sources, also the effects of COVID-19 lockdown on specific aerosol properties were studied as during the measurement period the COVID-19 restrictions took place greatly reducing the traffic volumes in the Helsinki area in the spring of 2020. These restrictions had a significant contribution to reducing the concentrations of NOx and black carbon originating from fossil fuel combustion concentration, but insignificant effects on other studied variables such as number concentration and size distribution or particle mass concentrations (PM1, PM2.5, or PM10).

Mass quantification of microplastic at wastewater treatment plants by pyrolysis-gas chromatography–mass spectrometry

Municipal wastewater treatment plants (WWTPs) are a central point of collection of plastic particles from households and industry and for their re-distribution into the environment. Existing studies evaluating levels of plastics in WWTPs, and their removal rates have reported and used data on polymer type, size, shape, colour, and number of plastic particles, while the total mass concentration of plastic particles (especially >1 μm) remains unclear and unknown. To address this knowledge gap, raw influent, effluent, and reference water samples from three WWTPs in Australia were collected to analyse the mass concentrations and removal rates of seven common plastics (>1 μm in size) across the treatment schemes. Quantitative analysis was performed by pressurized liquid extraction followed by pyrolysis coupled to gas chromatography mass spectrometry. Results showed that the total plastic content in the WWTPs raw influent samples was between 840 and 3116 μg/L, resulting in an inflow of between about 2.1 and 196.4 kg/day of the total measured plastics. Overall, >99 % by mass of the plastics entering the three WWTPs from the raw influent was removed during the pre-treatment stages, presumably ending up in the sewage sludge, which means emissions (via treated effluent) from the treatment plants are low. Compared with the raw influent, the plastic mass concentrations in the treated effluents (i.e., Class C, A, and final effluent) from the three WWTPs, as well as the reference water samples within their catchments were below the limits of reporting. Of the five quantified plastic types, polyethylene (PE, 76.4 %), and polyvinylchloride (PVC, 21 %) dominated by mass, while polyethylene terephthalate (PET, 1.9 %), polypropylene (PP, 0.4 %) and polymethyl methacrylate (PMMA, 0.3 %) accounted for a small proportion of the total. Overall, this study investigated the mass concentrations of plastic particles above 1 μm in wastewater and their removal, which provided valuable information regarding the pollution level and distribution characteristics of plastic polymers in Australian WWTPs.

Aerosol concentrations and size distributions during clinical dental procedures

BackgroundSuspected aerosol-generating dental instruments may cause risks for operators by transmitting pathogens, such as the SARS-CoV-2 virus. The aim of our study was to measure aerosol generation in various dental procedures in clinical settings. MethodsThe study population comprised of 84 patients who underwent 253 different dental procedures measured with Optical Particle Sizer in a dental office setting. Aerosol particles from 0.3 to 10 μm in diameter were measured. Dental procedures included oral examinations (N = 52), restorative procedures with air turbine handpiece (N = 8), high-speed (N = 6) and low-speed (N = 30) handpieces, ultrasonic scaling (N = 31), periodontal treatment using hand instruments (N = 60), endodontic treatment (N = 12), intraoral radiographs (N = 24), and dental local anesthesia (N = 31). ResultsAir turbine handpieces significantly elevated <1 μm particle median (p = 0.013) and maximum (p = 0.016) aerosol number concentrations as well as aerosol particle mass concentrations (p = 0.046 and p = 0.006) compared to the background aerosol levels preceding the operation. Low-speed dental handpieces elevated >5 μm median (p = 0.023), maximum (p = 0.013) particle number concentrations,> 5 μm particle mass concentrations (p = 0.021) and maximum total particle mass concentrations (p = 0.022). High-speed dental handpieces elevated aerosol concentration levels compared to the levels produced during oral examination. ConclusionsAir turbine handpieces produced the highest levels of <1 μm aerosols and total particle number concentrations when compared to the other commonly used instruments. In addition, high- and low-speed dental handpieces and ultrasonic scalers elevated the aerosol concentration levels compared to the aerosol levels measured during oral examination. These aerosol-generating procedures, involving air turbine, high- and low-speed handpiece, and ultrasonic scaler, should be performed with caution. Clinical significanceAerosol generating dental instruments, especially air turbine, should be used with adequate precautions (rubber dam, high-volume evacuation, FFP-respirators), because aerosols can cause a potential risk for operators and substitution of air turbine for high-speed dental handpiece in poor epidemic situations should be considered to reduce the risk of aerosol transmission.

Attenuation of blast waves from an intense explosion in dusty gases: a case study

An intense explosion in dusty gas is analyzed considering the Beirut ammonium nitrate explosion of 2020 as a case study. The data available from various sources for the Beirut explosion are used to determine the energy released and the possible reduction in damage radius if there were additional dust particles in the atmosphere. The relationship derived in our previous article ( Proc. R. Soc. A 476 , 2020) between the blast radius and the time of arrival of the shock seems quite accurate, and here the energy released by the explosion and the mass of trinitrotoluene (TNT) equivalent based on energy considerations and blast damage are estimated for dusty gases. These estimates depend on Γ , the ratio of specific heats of the dusty gas mixture. The hydrostatic overpressure and dynamic pressure are calculated from previous results by using the data available. The variation of the three dust parameters in the atmosphere, i.e. (i) mass concentration of dust particles ( k p ) , (ii) specific heat ratio ( β ) , and (iii) density ratio ( G ) , gives the estimated TNT equivalence as ≈ 0.1 kt to 2.5 kt up to a distance of 500 m. Enhanced decay and reduced pressure is evident for dusty gases with appropriate dust parameters.

Applying negative ions to reduce surgical smoke in operation room

Long-term exposure to surgical smoke generated from electrocautery can increase health risks for medical personnel. Surgical smoke contains high concentrations of nanoparticles (NP, diameter ≤200 nm) and particulate matters with diameter less than 2.5 μm (PM 2.5 ), which can cause respiratory illnesses in medical personnel. Currently, local exhaust ventilation (LEV) is often used to reduce particles levels. However, LEV generates extra noise and can be easily blocked by blood clots formed during surgery. In this study, we added an ionizer to an electrosurgical pencil to help increase NP removal efficiency and compared the removal efficiency with that of a smoke evacuation pencil. The experiments were performed in an animal surgical facility in which air change rate, relative humidity, and temperature were controlled. We measured the PM 2.5 and NP concentrations near the source and in the breathing zone. The ionizer alone, wall suction, smoke evacuation pencil, and wall suction plus ionizer reduce NP number concentrations by 80.1%, 84.5%, 90.3%, and 92.4%, respectively in the breathing zone. The respective reductions in PM 2.5 were 86.5%, 92.9%, 93.0%, and 97.2%. Similar PM 2.5 and NP removal efficiency was seen near the source. Wall suction plus ionizer shows the highest removal efficiency for NP and PM 2.5 , but the removal efficiency is not significantly higher ( p > 0.05) than the commercial smoke evacuation pencil and wall suction. Moreover, excess lifetime carcinogenic risk also decreased by 79.1%, 90.7%, 93.0%, and 95.6% for the negative ions (NI), wall suction, smoke evacuation pencil, and NI + wall suction, respectively. The newly developed surgical smoke removal devices help reduce particle concentrations and thus can help protect the health of medical personnel. • Negative ions can help reduce surgical smoke concentrations without generating additional noise. • Adding negative ions to wall suction proves to be the most efficient method for reducing the particle number and mass concentrations in surgical smoke. • Negative ions can be used in clinical practice or other workplaces that requires silence and efficient removal rates of nanoparticles.

Particulate Matter Characterization in a Hospital’s Underground Car Park

The air quality in a hospital’s underground car park is a concern because diesel fumes from cars impact upon vulnerable people attending medical consultations. This research aims to quantify the potential health risk associated with a particular hospital car park. Particulate matter was evaluated in the area with direct reading devices for particle numbers and mass concentrations (CPC 3007, EEPS 3090, Trolex Air XD, Nanozen, and Grimm 1109). Elemental and total carbon concentrations were measured following the NIOSH 5040 method, while volatile organic compounds (VOCs), and polycyclic aromatic hydrocarbons (PAHs) were measured through laboratory analysis and Scanning Electron Microscopy and Energy Dispersive using X-Ray Analysis SEM-EDX microscopy. The nanoparticle levels reached over 80,000 nanoparticles/cm3 (double the German Institut für Arbeitsschutz (IFA) benchmark levels). Diesel particulate matter levels measured as elemental carbon were around 35% of the occupational limit, and from the 49 VOCs analyzed only 13 were detected in quantities below the 0.1% of the occupational limit, while levels of the 13 PAHs analyzed, were below the laboratory limit of quantification. The study concludes that particulate matter in the underground car park can easily exceed nanoparticles benchmark levels and could be harmful, mainly to vulnerable people. It is therefore recommended that they use the outdoor car park or minimize their time in the underground one.

Kinetic and Products Study of the Atmospheric Degradation of trans-2-Hexenal with Cl Atoms.

The gas-phase reaction between trans-2-hexenal (T2H) and chlorine atoms (Cl) was studied using three complementary experimental setups at atmospheric pressure and room temperature. In this work, we studied the rate constant for the titled oxidation reaction as well as the formation of the gas-phase products and secondary organic aerosols (SOAs). The rate constant of the T2H + Cl reaction was determined using the relative method in a simulation chamber using proton-transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS) to monitor the loss of T2H and the reference compound. An average reaction rate constant of (3.17 ± 0.72) × 10–10 cm3 molecule–1 s–1 was obtained. From this, the atmospheric lifetime of T2H due to Cl reaction was estimated to be 9 h for coastal regions. HCl, CO, and butanal were identified as primary products using Fourier transform infrared spectroscopy (FTIR). The molar yield of butanal was (6.4 ± 0.3)%. Formic acid was identified as a secondary product by FTIR. In addition, butanal, 2-chlorohexenal, and 2-hexenoic acid were identified as products by gas chromatography coupled to mass spectrometry but not quantified. A reaction mechanism is proposed based on the observed products. SOA formation was observed by using a fast mobility particle sizer spectrometer. The measured SOA yields reached maximum values of about 38% at high particle mass concentrations. This work exhibits for the first time that T2H can be a source of SOA in coastal atmospheres, where Cl concentrations can be high at dawn, or in industrial areas, such as ceramic industries, where Cl precursors may be present.

Gas-Particle Uptake and Hygroscopic Growth by Organosulfate Particles

Organosulfate compounds make up a substantial fraction of the particle mass concentration in some regions of the Earth’s atmosphere, and organosulfate particles can have sufficiently high viscosity to limit rates of gas-particle interactions. Viscosity varies with relative humidity (RH). Herein, organosulfate particles were exposed to the gas-phase products of α-pinene photooxidation. The gas-particle partitioning of these species was studied from 15 to 70% RH and <1 to 16 ppb NO at 299 K. The uptake of the α-pinene oxidation products increased with the increase in RH, and higher gas-phase NO concentrations resulted in increased particle-phase concentrations of nitrogen compounds. Particle hygroscopicity was examined by optical microscopy. Hygroscopic growth at elevated RH was sufficient to explain the RH-dependent uptake measurements, and kinetic limitations tied to particle viscosity were not observed. The lack of kinetic limitations combined with the Stokes–Einstein equation implied a viscosity much less than 1 × 106 Pa s. This value is consistent with estimated viscosities based on literature parameterizations for water mass fractions in the particles of at least 0.05 at 15% RH. Overall, these results suggest that organosulfate hygroscopicity plays a key role in their viscosity and hence in regulating gas-particle partitioning, thereby simplifying the treatment of atmospheric chemistry and transport of pollutants in models of the Earth’s atmosphere. The role of organosulfates is expected to take on increasing importance for projected future emission trends.

The effect of clouds and precipitation on the aerosol concentrations and composition in a boreal forest environment

Abstract. Atmospheric aerosol particle concentrations are strongly affected by various wet processes, including below and in-cloud wet scavenging and in-cloud aqueous-phase oxidation. We studied how wet scavenging and cloud processes affect particle concentrations and composition during transport to a rural boreal forest site in northern Europe. For this investigation, we employed air mass history analysis and observational data. Long-term particle number size distribution (∼15 years) and composition measurements (∼8 years) were combined with air mass trajectories with relevant variables from reanalysis data. Some such variables were rainfall rate, relative humidity, and mixing layer height. Additional observational datasets, such as temperature and trace gases, helped further evaluate wet processes along trajectories with mixed effects models. All chemical species investigated (sulfate, black carbon, and organics) exponentially decreased in particle mass concentration as a function of accumulated precipitation along the air mass route. In sulfate (SO4) aerosols, clear seasonal differences in wet removal emerged, whereas organics (Org) and equivalent black carbon (eBC) exhibited only minor differences. The removal efficiency varied slightly among the different reanalysis datasets (ERA-Interim and Global Data Assimilation System; GDAS) used for the trajectory calculations due to the difference in the average occurrence of precipitation events along the air mass trajectories between the reanalysis datasets. Aqueous-phase processes were investigated by using a proxy for air masses travelling inside clouds. We compared air masses with no experience of approximated in-cloud conditions or precipitation during the past 24 h to air masses recently inside non-precipitating clouds before they entered SMEAR II (Station for Measuring Ecosystem–Atmosphere Relations). Significant increases in SO4 mass concentration were observed for the latter air masses (recently experienced non-precipitating clouds). Our mixed effects model considered other contributing factors affecting particle mass concentrations in SMEAR II: examples were trace gases, local meteorology, and diurnal variation. This model also indicated in-cloud SO4 production. Despite the reanalysis dataset used in the trajectory calculations, aqueous-phase SO4 formation was observed. Particle number size distribution measurements revealed that most of the in-cloud SO4 formed can be attributed to particle sizes larger than 200 nm (electrical mobility diameter). Aqueous-phase secondary organic aerosol (aqSOA) formation was non-significant.

Properties and Atmospheric Oxidation of Norpinic Acid Aerosol

Norpinic acid is a major semi-volatile oxidation product of α-pinene and β-pinene, two of the most important biogenic atmospheric volatile organic compounds. In this study we characterized the physicochemical properties of norpinic acid aerosol using a variety of techniques, and we investigated its reaction with OH radicals. The Aerosol Mass Spectrometer (AMS) spectrum of norpinic acid was characterized by a pronounced peak at m/z 82 (C5H6O+), which can be used as its chemical signature. The measured density of norpinic acid particles was 1.3 g cm−3. Its saturation concentration at 298 K was estimated to be equal to 8.9 μg m−3 using thermodenuder measurements and 12.8 μg m−3 using isothermal dilution. Its vaporization enthalpy was equal to 71 kJ mol−1. After reaction with OH radicals for an equivalent atmospheric period of 0.6–5 days under UV radiation and low RH, there were no noticeable changes in the AMS spectrum of the particles, while the wall-loss corrected mass concentration slightly decreased. This suggests that the atmospheric aging products of norpinic acid particles are quite similar to the parent molecule when measured by the AMS, and the aging reactions lead to a small change in particle mass concentration.