Volatile Particles Research Articles

Spheroidization of borosilicate glass powder by RF induction coupled plasma

The International Simple Glass (ISG) spherical particles were prepared by Ar–H2 radio-frequency (RF) plasma, the effect of experimental parameters on the volatilization and size distribution of spherical particles was studied. The results show that the spherical powders can be obtained by RF plasma. The spheroidized powders (112 μm) have a smaller diameter than starting particles (124 μm). The high spheroidization (98%) was achieved under low flow rate of carry gas and low feed rate. In addition, the volatilization of B2O3 and Na2O are 23.48% and 56.36%, respectively. The higher feed rate and flow rate of carry gas, the lower volatilization of B2O3 and Na2O and well-spheroidization rate. Meanwhile, the particle surface is not completely smooth at low flow rate of carry gas. The distribution of elements was studied by Electro-probe Microanalyzer (EPMA), which shows the distribution of element is nearly homogeneous that provides a possibility for subsequent research.

Rumen function and grazing behavior of early-lactation dairy cows supplemented with fodder beet

Fodder beet (FB) is a source of readily fermentable carbohydrate that can mitigate early spring herbage deficits and correct the negative energy balance experienced during early lactation in pastoral dairy systems of New Zealand. However, the low-fiber and high-soluble carbohydrate content of both FB bulb and spring herbage are factors that promote subacute ruminal acidosis, impairing rumen function and limiting the marginal milk production response to supplement. In a crossover experiment, 8 Holstein Friesian × Jersey early-lactation dairy cows were used to test the effect of supplementing 16 kg of dry matter (DM) of a grazed perennial ryegrass herbage with 6 kg of DM/d of FB bulb (FBH) versus herbage only (HO) on changes in rumen function and grazing behavior. Following 20 d of adaptation to diets, DM disappearance (%) of FB bulb (FBH cows only) and herbage were measured in sacco, separately. Cows were fasted overnight, and the ruminal contents were bailed the following morning (~0930 h) again to determine the pool size of volatile fatty acids, ammonia, and particle size of digesta, as well as to estimate the rate of ruminal outflow and degradation of neutral detergent fiber. The FBH diet did not alter DM intake, milk yield, or milk solid (fat + protein) production compared with HO. Supplementation of herbage with FB reduced ruminal pH compared with HO between ~0800 h and 1300 h each day. During each period, 1 cow experienced severe subacute ruminal acidosis (pH <5.6 for >180 min/d) during final adaptation to the target FB allocation. The FBH diet reduced the ruminal pool of acetate and ammonia, but increased the ruminal pool of butyrate and lactate compared with HO. When fed FB, rumination and grazing time increased and grazing intensity declined compared with cows fed HO. Despite increased rumination, the comminution of large particles declined 28% between the first and second rumen bailing when cows were fed FB, and in sacco DM disappearance of perennial ryegrass declined 18% compared with cows fed HO. These results indicate that grazing dairy cows supplemented with FB (40% of daily intake) increase rumination and mastication intensity to counteract reduced ruminal degradation of ryegrass herbage due to low ruminal fluid pH.

Evaluating a commercially available in-duct bipolar ionization device for pollutant removal and potential byproduct formation

We conducted a series of experiments to evaluate the gas and particle removal effectiveness and potential for byproduct formation resulting from the operation of a commercially available in-duct bipolar ionization device. Laboratory tests were conducted with the ionizer installed in a small air handler serving a large semi-furnished chamber. Chamber experiments were conducted under (i) normal operating conditions to characterize the impact of the ionizer on concentrations of particles (0.01–10 μm), ozone (O3), nitrogen dioxide (NO2), volatile organic compounds (VOCs), and aldehydes, and (ii) particle injection and decay conditions to characterize the impact of the ionizer operation on particle loss rates. The field test involved air sampling of particulates (0.01–10 μm), O3, and VOCs upstream and downstream of an operating ionizer device installed in an air handling unit serving an occupied office building. Both the chamber and field tests suggested that the use of the tested bipolar ionization unit led to a decrease in some hydrocarbons (e.g., xylenes) among the lists of compounds we were able to analyze, but an increase in others, most prominently oxygenated VOCs (e.g., acetone, ethanol) and toluene. Ionizer operation appeared to minimally impact particle, O3, and NO2 concentrations during normal operating conditions. Particle injection and decay experiments in the chamber suggest that operation of the ionizer unit led to a small increase in loss rates for ultrafine particles (<0.15 μm) and a small decrease in loss rates for larger particles (>0.3 μm), but with negligible net changes in estimated PM2.5 loss rates.

The Dynamics of Exhaled Aerosol Following the Usage of Heated Tobacco Product, Electronic Cigarette, and Conventional Cigarette

ABSTRACT Heated tobacco products (HTPs) and electronic cigarettes (ECs) represent a potentially less harmful alternative to traditional tobacco products, such as conventional cigarettes (CCs), with growing popularity amongst adult smokers worldwide. Their users exhale a very dynamic aerosol to indoor air which undergoes rapid transformations. In the present study, we assessed the dynamics of the generated exhaled aerosols following use of a new HTP (branded as “Pulze”, operating in eco and standard modes) and an e-cigarette (“myblu”) in a chamber environment by three volunteers, controlling for the distance to bystander, ventilation intensity and microclimate. The HTP and EC data was compared against conventional cigarette data. HTP generally resulted in lower aerosol number concentration during puffs reaching 1.66E+06 # cm–3 at 0.5 m from bystander, compared to EC (averaging 4.3E+06 # cm–3), and CC (1.47E+08 # cm–3). No significant difference was observed between “eco” and “standard” modes of HTP. At the same time, EC concentration decrease after puffs was also faster, indicating higher volatility of particles. EC also featured higher mode during puff (120 nm) compared to HTP (90 nm), which was significantly different from conventional cigarette (165–200 nm). The evaporation/shrinkage of particles has been observed within 10 s after puff with the HTP and EC. Distance to a bystander was shown to be as a significant factor affecting aerosol dynamics, however ventilation intensity and relative humidity did not have statistically significant effect.

Psychological And Physiological Benefits Of Plants In The Indoor Environment: A Mini And In-Depth Review

People tend to spend approximately 87% of their time in the indoor environment. There is a possibility that they are exposed to volatile organic compound (VOC) and particle pollution, and to experience stress related disorder. This has potential threaten the well-being of indoor occupants if left untreated. Hence, plants were introduced to alleviate these negative impacts. This paper reviews past literature from 1990 to 2010s, to examine the relationship of plants with indoor environment and identifies how they influence people, psychologically and physiologically, and how they promote indoor environment quality. Most studies suggest that the presence of plants is associated with positive feelings and able to enhance productivity. In addition, they also may help to promote general health such as reducing blood pressure, perceived stress, sick building syndrome, and increase pain tolerance of the patient. Moreover, plants also help in improving the indoor environment quality (IEQ), for instance, they can reduce carbon dioxide (CO2), indoor ozone (O3) level, VOC, and particulate matter accumulation through bioremediation process. Despite all the benefits that the plants could offer, several studies pointed out that factors such as gender, perceived attractiveness of the space, physical characteristics of plants, and methods of interaction with plants may lead to non-identical results. Hence, the selection of the right species of plant in an indoor environment becomes mandatory in order to improve the indoor environment quality; to provide restorative effect; to invoke positive feelings and comfort of the people. In conclusion, this review may provide notable insights to landscape architects, gardeners and even interior designers to choose the right species of plant in an indoor environment, to maximize their psychological and physiological benefits, at the same time, improving indoor environment quality.

Combustion and emission characteristics of solid waste from dioctyl phthalate production

AbstractBACKGROUNDA novel combustion process of solid waste from dioctyl phthalate (SWDOP) production was developed. The SWDOP is high in organic combustible components, has high calorific value, low ash content and no halogen element and is especially suitable for combustion treatment. The combustion and emission characteristics of SWDOP under various conditions in a tube furnace were investigated.RESULTSMajor pollution factors detected in flue gas include CO, volatile organic compounds (VOCs), particles and NO. The combustion of SWDOP happens in two stages. Most DOP escapes from activated carbon and oxidizes to VOCs between 150 and 270 °C, and the activated carbon burns together with the little residual DOP between 270 and 525 °C. Moreover, thermogravimetry was employed to study the effects of combustion of SWDOP. There are two strong and narrow peaks at around 250 and 420 °C in the differential thermogravimetry curve since DOP evaporates rapidly at 250 °C, and activated carbon burns intensely at 420 °C. The peak concentration of VOCs during combustion is 245.4 mg m−3 at 250 °C and 254.9 mg m−3 at 400 °C. Among all VOCs, toluene concentration is the largest, accounting for 70%. The generated CO concentration decreases with increasing air flow. Varied‐mesh screens were used to intercept and detect the particle matter from flue gas, while particle size distributions and scanning electron microscopy analyses were carried out. The amount of condensates from the flue gas is increased as the air flow increases. It was determined from Fourier transform infrared analysis that both the SWDOP sample and the flue gas contain DOP.CONCLUSIONSThe results obtained in this work suggest that temperature has a great effect on the combustion and emission of SWDOP. Owing to many advantages of this treatment process for SWDOP by combustion, it has great potential for commercial applications. © 2020 Society of Chemical Industry (SCI)

Effects of pyrolysis temperature on production and physicochemical characterization of biochar derived from coconut fiber biomass through slow pyrolysis process

The purposes of this research were to investigate the competence of coconut fiber to produce biochar by slow pyrolysis process and analyze the effects of different pyrolysis temperatures on the yield and physicochemical properties of biochars. Coconut fiber biomass was subjected to slow pyrolysis process using a laboratory scale fixed bed reactor at six different temperatures ranging from 350 to 600 °C (at an interval of 50 °C). The slow pyrolysis process was carried out in an inert environment for 1 (one) hour at a constant heating rate of 10 °C/min. The physicochemical properties of biomass and obtained biochars were characterized by proximate analysis (VM, FC, ash), ultimate analysis (CHNSO), higher heating value (HHV), bulk density, BET surface area, pH, and electrical conductivity (EC). Functional groups and particle sizes of biomass and biochars were identified by FTIR and particle size distribution respectively. Surface morphology and pore distribution of the biochars were observed by SEM images. The pyrolysis temperature had a negative effect on biochar yield and reduced from 48.13 to 29.34% as the pyrolysis temperature increased from 350 to 600 °C. Fixed carbon, ash content, pH, organic carbon, specific surface area, EC, degree of aromaticity, and porosity of the biochars enhanced as the pyrolysis temperature rose from 350 to 600 °C. However, the volatile matter, VM/FC ratio, H/C ratio, HHV, bulk density, and particle sizes of biochars were negatively correlated with the pyrolysis temperatures. Higher pyrolysis temperatures increased aromatic C groups and recalcitrant characteristics, yielded smaller particles, and formed elongated and porous structures. The physicochemical properties of high-temperature biochars (500–600 °C) showed the potential to be used as soil amendments and an efficient tool for C sequestration and retention of nutrients, and water. The porous structures of high-temperature biochars can accommodate suitable soil-microorganism activities, increase water sorption, and increase soil density. Moreover, the high alkalinity of the biochars can assist to neutralize acidic soil and increases soil fertility and plant growth. On the contrary, low-temperature biochars (350–450 °C) are promising tools for solid fuels.

Measuring Automotive Exhaust Particles Down to 10 nm

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;The latest generation of internal combustion engines may emit significant levels of sub-23 nm particles. The main objective of the Horizon 2020 “DownToTen” project was to develop a robust methodology and provide policy recommendations towards the particle number (PN) emissions measurements in the sub-23 nm region. In order to achieve this target, a new portable exhaust particle sampling system (PEPS) was developed, being capable of measuring exhaust particles down to at least 10 nm under real-world conditions. The main design target was to build a system that is compatible with current PMP requirements and is characterized by minimized losses in the sub-23 nm region, high robustness against artefacts and high flexibility in terms of different PN modes investigation, i.e. non-volatile, volatile and secondary particles. This measurement setup was used for the evaluation of particle emissions from the latest technology engine and powertrain technologies (including vehicles from other Horizon 2020 projects), different fuel types, and a wide range of exhaust aftertreatment systems. Results revealed that in most cases (non-volatile), PN emissions down to 10 nm (SPN&lt;sub&gt;10&lt;/sub&gt;) do not exceed the current SPN&lt;sub&gt;23&lt;/sub&gt; limit of 6×10&lt;sup&gt;11&lt;/sup&gt; p/km. However, there are some cases where SPN&lt;sub&gt;10&lt;/sub&gt; emissions exceeded the limit, although SPN&lt;sub&gt;23&lt;/sub&gt; were below that. An interesting finding was that even in the latter cases, the installation of a particle filter could significantly reduce PN emissions across a wide particle size range, fuels, and combustion technology. DownToTen results are being used to scientifically underpin the Euro 7/VII emission standard development in the EU. The method developed and the results obtained may be used to bring in the market clean and efficient vehicle technologies, improve engine and emission control performance with different fuels, and characterize size-fractionated particle chemistry to identify the formation mechanisms and control those in a targeted, cost-effective fashion.&lt;/div&gt;&lt;/div&gt;

Development of Measurement Methodology for Sub 23 nm Particle Number (PN) Measurements

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;A proposal for sub-23 nm Solid Particle Number (SPN) measurement method was developed by the Particle Measurement Programme (PMP) group, based on the current SPN measurement method. In the proposal, a Particle Number Counter (PNC) having (65 ± 15)% counting efficiency at 10 nm and &amp;gt;90% at 15 nm (PNC10) replaces the current regulation PNC efficiency of 50±12% at 23 nm and &amp;gt;90% at 41 nm. Additionally, a catalytically active evaporation tube (CS) is required for sub-23 nm measurement method instead of the non-reactive evaporation tube (ET) of the current regulation. Here experimental work carried out at the JRC to address the issues of sub-23 nm SPN-measurement method is presented. The PNC10 was shown to be less dependent on the particle material than the PNC23, thus soot-like particles are still allowed for PNC-calibration. The high charging probability of soot-like particles was shown to have a low effect on PNC calibration uncertainties. The new proposed linearity test which requires that the PNC readings need to be within ±5% of the slope was here shown to be applicable. The proposal requires that Particle Concentration Reduction Factor (PCRF) at 15 nm shall be at most 100% higher than the 100 nm PCRF for the Volatile Particle Remover (VPR). The allowed variability in VPR-losses and PNC10-efficiencies of the new proposal could cause differences up to 36% when a distribution with Geometric Mean Diameter at 15 nm was simulated. Yet, for the commercial CS and ET systems with experimentally determined PCRF 15 nm to 100 nm ratios of 80% and 50% respectively, the maximum difference was 19% using PNC10. The average PCRF in the proposal is calculated as in the current regulation, with an average of PCRFs at 30 nm, 50 nm and 100 nm in order to keep the comparability with the 23 nm regulation and because the addition of the PCRF at 15 nm did not improve the accuracy.&lt;/div&gt;&lt;/div&gt;

A Novel Link between Early Life Allergen Exposure and Neuroimmune Development in Children

As COVID-19 unprecedented situation significantly increased the time families spend indoors, the awareness of unhealthy living conditions negatively impacting immune system and early neurodevelopment of children is of crucial importance. We retrospectively reviewed unrelated cases of the children with confirmed multiple indoor allergen sensitization due to prolonged exposure to unhealthy indoor environment with infestation and water damage, who, in addition to multiple health problems related to allergy and asthma, also developed neuroimmune complications and growth delay. Documented early in life atypical neurologic and behavioral changes were common in all cases. Clinical analysis did not establish other causative reason aside from prenatal and early life exposure to unhealthy living conditions. Alternaria Alternara and Penicillium/Aspergillus molds were found in all homes and sensitization was confirmed in all cases. Significant similarities in the symptoms recorded in all three families led us to a hypothesis that, likely, a significant level of the immune response to external immunogenic pathological stimulus such as mold spore protein, mycotoxin protein, dust mite protein, decay-related volatile particles (VOC) skewed a balance of the neuroimmune interactions, and further affected neuronal network establishment. As all children exhibited significant spectrum of the systemic inflammatory conditions early in life, coupled with inability to follow normal neurodevelopment, we hypothesize that an overwhelming activation of the aggressive immune mechanisms by the epigenetic factors led to glia activation, cytokine storm and break of tolerance. We hypothesize that developing immune system exhibited aggressive responses due to environmental danger signals, subsequently TH-1 or TH-2 switch enables multiple clinical syndromes development with atypical presentation due to the described novel mechanism. An increased due to the COVID-19 lock-down may increase an amount of exposure of vulnerable people to indoor biological particles and volatile organic compounds present in unhealthy buildings. It is of crucial importance to identify and remediate indoor exposure factors that can decrease immune protection, especially against infectious pathogens such as novel coronavirus.

Non-Volatile Particle Number Emission Measurements with Catalytic Strippers: A Review

Vehicle regulations include limits for non-volatile particle number emissions with sizes larger than 23 nm. The measurements are conducted with systems that remove the volatile particles by means of dilution and heating. Recently, the option of measuring from 10 nm was included in the Global Technical Regulation (GTR 15) as an additional option to the current &gt;23 nm methodology. In order to avoid artefacts, i.e., measuring volatile particles that have nucleated downstream of the evaporation tube, a heated oxidation catalyst (i.e., catalytic stripper) is required. This review summarizes the studies with laboratory aerosols that assessed the volatile removal efficiency of evaporation tube and catalytic stripper-based systems using hydrocarbons, sulfuric acid, mixture of them, and ammonium sulfate. Special emphasis was given to distinguish between artefacts that happened in the 10–23 nm range or below. Furthermore, studies with vehicles’ aerosols that reported artefacts were collected to estimate critical concentration levels of volatiles. Maximum expected levels of volatiles for mopeds, motorcycles, light-duty and heavy-duty vehicles were also summarized. Both laboratory and vehicle studies confirmed the superiority of catalytic strippers in avoiding artefacts. Open issues that need attention are the sulfur storage capacity and the standardization of technical requirements for catalytic strippers.

Composition and volatility of secondary organic aerosol (SOA) formed from oxidation of real tree emissions compared to simplified volatile organic compound (VOC) systems

Abstract. Secondary organic aerosol (SOA) is an important constituent of the atmosphere where SOA particles are formed chiefly by the condensation or reactive uptake of oxidation products of volatile organic compounds (VOCs). The mass yield in SOA particle formation, as well as the chemical composition and volatility of the particles, is determined by the identity of the VOC precursor(s) and the oxidation conditions they experience. In this study, we used an oxidation flow reactor to generate biogenic SOA from the oxidation of Scots pine emissions. Mass yields, chemical composition and volatility of the SOA particles were characterized and compared with SOA particles formed from oxidation of α-pinene and from a mixture of acyclic–monocyclic sesquiterpenes (farnesenes and bisabolenes), which are significant components of the Scots pine emissions. SOA mass yields for Scots pine emissions dominated by farnesenes were lower than for α-pinene but higher than for the artificial mixture of farnesenes and bisabolenes. The reduction in the SOA yield in the farnesene- and bisabolene-dominated mixtures is due to exocyclic C=C bond scission in these acyclic–monocyclic sesquiterpenes during ozonolysis leading to smaller and generally more volatile products. SOA particles from the oxidation of Scots pine emissions had similar or lower volatility than SOA particles formed from either a single precursor or a simple mixture of VOCs. Applying physical stress to the Scots pine plants increased their monoterpene, especially monocyclic β-phellandrene, emissions, which further decreased SOA particle volatility and increased SOA mass yield. Our results highlight the need to account for the chemical complexity and structure of real-world biogenic VOC emissions and stress-induced changes to plant emissions when modelling SOA production and properties in the atmosphere. These results emphasize that a simple increase or decrease in relative monoterpene and sesquiterpene emissions should not be used as an indicator of SOA particle volatility.

Deposition of α-pinene oxidation products on plant surfaces affects plant VOC emission and herbivore feeding and oviposition

White cabbage, Brassica oleracea, plants and artificial leaves covered with B. oleracea epicuticular wax were exposed to α-pinene and α-pinene oxidation products formed through the oxidation of α-pinene by ozone (O3) and hydroxyl (OH) radicals. O3 and OH-induced oxidation of α-pinene led to the formation of oxygenated volatile organic compounds (OVOCs) and secondary organic aerosol particles (SOA), referred to together as oxidation products (OP). Exposure of cabbage plants to O3 and OH-induced α-pinene OP led to the deposition and re-emission of gas-phase OP by exposed cabbage plants. In a series of 2-choice bioassays, the specialist cruciferous herbivore, Plutella xylostella adults deposited less eggs on artificial leaves exposed to α-pinene OP than on control plants exposed to clean filtered air. P. xylostella larvae did not show a specific feeding preference when offered leaves from different exposure treatments. However, the generalist Indian stick insect, Carausius morosus, fed more on control filtered air-exposed plants than on those exposed to α-pinene OP. Taken together, our results show that exposure to α-pinene oxidation products affects VOC emissions of B. oleracea and alters P. xylostella oviposition and C. morosus feeding responses.

Association between diesel engine exhaust exposure and lung function in Australian gold miners.

Previous studies have reported that miners (and other workers) exposed to high levels of diesel engine exhaust (DEE) have an increased risk of lung function decline. The main objective of this study was to evaluate associations between exposure to different components associated with DEE in relation to lung function across a 12-h working shift. Eighty underground gold miners and twenty surface miners completed spirometry and questionnaires at the beginning and end of their 12h work shift. Personal exposure to elemental carbon (EC), volatile organic compounds (VOCs), nitrogen dioxide (NO2), particle size and particle number were monitored during their shift. Multiple regression models were used to examine the associations between DEE and lung function, adjusting for a range of covariates. Underground miners were exposed to higher levels of EC, VOCs, NO2, and particle number and larger mean particle size than surface miners. Cross-shift reduction in Z-score value of FEV1/FVC in underground miners was statistically significantly greater than those of surface miners. The cross-shift change in Z-score value of FEV1/FVC was associated with exposure to higher concentration of EC and particle number, but not with VOCs, NO2 and particle size. Occupational exposure to diesel engine exhaust in current Australian gold mines is substantial. Exposures were higher in underground miners and had a negative association with their lung function over a single 12-h shift.

A transition of atmospheric emissions of particles and gases from on-road heavy-duty trucks

Abstract. The transition, in extent and characteristics, of atmospheric emissions caused by the modernization of the heavy-duty on-road fleet was studied utilizing roadside measurements. Emissions of particle number (PN), particle mass (PM), black carbon (BC), nitrogen oxides (NOx), carbon monoxide (CO), hydrocarbon (HC), particle size distributions, and particle volatility were measured from 556 individual heavy-duty trucks (HDTs). Substantial reductions in PM, BC, NOx, CO, and to a lesser extent PN were observed from Euro III to Euro VI HDTs by 99 %, 98 %, 93 %, and 57 % for the average emission factors of PM, BC, NOx, and CO, respectively. Despite significant total reductions in NOx emissions, the fraction of NO2 in the NOx emissions increased continuously from Euro IV to Euro VI HDTs. Larger data scattering was evident for PN emissions in comparison to solid particle number (SPN) for Euro VI HDTs, indicating a highly variable fraction of volatile particle components. Particle size distributions of Euro III to enhanced environmentally friendly vehicle (EEV) HDTs were bimodal, whereas those of Euro VI HDTs were nucleation mode dominated. High emitters disproportionately contributed to a large fraction of the total emissions with the highest-emitting 10 % of HDTs in each pollutant category being responsible for 65 % of total PM, 70 % of total PN, and 44 % of total NOx emissions. Euro VI HDTs, which accounted for 53 % of total kilometres driven by Swedish HDTs, were estimated to only contribute to 2 %, 6 %, 12 %, and 47 % of PM, BC, NOx, and PN emissions, respectively. A shift to a fleet dominated by Euro VI HDTs would promote a transition of atmospheric emissions towards low PM, BC, NOx, and CO levels. Nonetheless, reducing PN, SPN, and NO2 emissions from Euro VI HDTs is still important to improve air quality in urban environments.

Development and evaluation of a catalytic stripper for the measurement of solid ultrafine particle emissions from internal combustion engines

Solid particle number vehicle exhaust measurements necessitate an aerosol conditioning system that removes efficiently volatile particles, does not create artifacts, and minimizes solid nucleation ...

Particulate emissions from L-Category vehicles towards Euro 5

The current experimental study presents particulate emissions from 30 Euro 1-4 L-category vehicles (i.e. 2-, 3- and 4-wheelers such as mopeds, motorcycles, quads and minicars, registered in Europe between 2009 and 2016) tested on a chassis dynamometer. The objectives were to identify those sub-categories with high emissions, to assess whether the measures prescribed in the Euro 5 legislation will effectively control particulate emissions and finally to investigate the need for additional measures. The results showed that 2-stroke (2S) mopeds and diesel minicars comprised the vehicles with the highest particulate mass (PM) and solid particle number above 23 nm (SPN23) emissions (up to 64 mg/km and 4.5 × 1013 km−1, respectively). It is uncertain whether the installation of diesel particulate filters (DPF) is a cost-effective measure for diesel mini-cars in order to comply with Euro 5 standard, while advanced emission controls will be required for 2S mopeds, if such vehicles remain competitive for Euro 5. Regarding 4-stroke mopeds, motorcycles and quads, PM emissions were one order of magnitude lower than 2S ones and already below the Euro 5 limit. Nevertheless, SPN23 emissions from these sub-categories were up to 5 times higher than the Euro 6 passenger cars limit (6 × 1011 km−1). Even recent Euro 4 motorcycles exceeded this limit by up to 3 times. These results indicate that L-category vehicles are a significant contributor to vehicular particulate emissions and should be further monitored during and after the introduction of the Euro 5 step. Moreover, including SPN in the range 10–23 nm increases emission levels by up to 2.4 times compared to SPN23, while volatile and semi-volatile particle numbers were even higher. Finally, cold engine operation was found to be a significant contributor on SPN23 emissions, especially for vehicles with lower overall emission levels. These results indicate that a specific particle number limit may be required for L-category to align emissions with passenger cars.

Interfacial Dimerization by Organic Radical Reactions during Heterogeneous Oxidative Aging of Oxygenated Organic Aerosols.

Oxidative aging of atmospheric organic aerosols (OA) substantially modifies their chemical compositions, physical properties, and hence the various environmental impacts. Here, we report observations of a previously unrecognized process leading to dimer formation during heterogeneous •OH-initiated oxidative aging of oxygenated OA. Isomer-resolved ion mobility mass spectrometry measurements and reaction-diffusion kinetic simulations are in good agreement, elucidating new mechanisms of dimerization by organic radical (i.e., peroxy and alkoxy radicals) cross reactions using glutaric acid as a surrogate oxygenated OA. These radical reactions are predicted to occur more prominently near the gas-particle interface following oxidation, especially in diffusion-limited viscous OA particles. Chemical structure analysis shows that esters dominate the detected dimers, followed by organic peroxides and ethers, highlighting the importance of acyl peroxy and acyloxy radicals. Simulations suggest that the reported dimer formation through the new interfacial mechanism could be appreciable under both laboratory and ambient conditions. Therefore, the dimers that are formed and enriched at the gas-particle interface are expected to play a crucial role in the effective reactivity, volatility, viscosity, and hygroscopicity of aged OA particles.

Effect of Decreased Temperature on the Evaporation of α-Pinene Secondary Organic Aerosol Particles

Interplay of volatility distribution and particle viscosity governs the gas-to-particle partitioning dynamics of atmospheric secondary organic aerosol (SOA) constituents. Temperature-induced shifts in both particle volatility distribution and viscosity can influence the evaporation behavior of atmospheric SOA particles. However, knowledge of the particle evaporation at low temperatures is still limited. Here, we combined the isothermal evaporation measurements and processes modelling to explore the evaporation of α-pinene ozonolysis (αpinO3) and photooxidation (αpinOH) SOA particles under a series of relative humidity (RH) at two different temperatures. Experimental results revealed that the particle evaporation was hindered at low temperature, in agreement with the temperature dependence of the effective saturation vapor concentration and the possible temperature impact on the particle viscosity. Both αpinO3 and αpinOH SOA particles showed similar evaporation rates at 80% RH when particles were in a liqu...

Season specificity in the cold-induced calcium signal and the volatile chemicals in the atmosphere.

Cold-induced Ca2+ signals in plants are widely accepted to be involved in cold acclimation. Surprisingly, despite using Arabidopsis plants grown in a growth chamber, we observed a clear seasonal change in cold-induced Ca2+ signals only in roots. Ca2+ signals were captured using Arabidopsis expressing Yellow Cameleon 3.60. In winter, two Ca2+ signal peaks were observed during a cooling treatment from 20 to 0°C, but in summer only one small peak was observed under the same cooling condition. In the spring and autumn seasons, an intermediate type of Ca2+ signal, which had a delayed first peak and smaller second peaks compared with the those of the winter type, was observed. Volatile chemicals and/or particles in the air from the outside may affect plants in the growth chamber. This idea is supported by the fact that incubation of plants with activated carbon changed the intermediate-type Ca2+ signal to the summer-type. The seasonality was also observed in the freezing tolerance of plants cold-acclimated in a low-temperature chamber. The solar radiation intensity was weakly correlated, not only with the seasonal characteristics of the Ca2+ signal but also with freezing tolerance. It has been reported that the ethylene concentration in the atmosphere seasonally changes depending on the solar radiation intensity. Ethylene gas and 1-aminocyclopropane-1-carboxylic acid treatment affected the Ca2+ signals, the shape of which became a shape close to, but not the same as, the winter type from the other types, indicating that ethylene may be one of several factors influencing the cold-induced Ca2+ signal.