Search

Atmospheric nanoparticles (PM0.1 µm) are a major cause of environmental problems and also affect health risk. To control and reduce these problems, sources identification of atmospheric particulates is necessary. Combustion of bituminous coal and biomass including rubber wood, palm kernel, palm fiber, rice stubble, rice straw, maize residue, sugarcane leaves and sugarcane bagasse, which are considered as sources of air quality problems in many countries, was performed. Emissions of particle-bound chemical components including organic carbon (OC), elemental carbon (EC), water-soluble ions (NH

Rapid economic growth has led to increasing air pollution in Southeast Asia (SEA). Urbanization, industrialization and open biomass burning all lead to deteriorating air quality. Recent advances allow recording, sampling and analyzing ultrafine particles, or nanoparticles, finer than the already extensively reported PM2.5 particles; these nanoparticles have been shown to be a potentially more significant health hazard – causing cardiovascular and respiratory diseases, since they can penetrate further into our bodies. Analysis of the collected particles allows, in turn, identifying sources. Although vehicle emissions generally dominate nanoparticles, biomass generates a significant proportion in the burning seasons. In Malaysia, the number of particles smaller than 50 nm dominate, but, by mass, PM0.1 accounts for ∼15% of PM2.5 in upper SEA, and ∼18% in lower SEA. Sampling compared normal periods, where ratios of organic to elemental carbon and char to soot elemental carbon indicated that vehicle exhaust dominates. However, in haze periods, increased char to soot elemental carbon ratios indicate strong contributions from biomass burning. In lower SEA severe haze periods, polycyclic aromatic hydrocarbon levels are 3–8 times higher than in normal periods, confirming the sources as peatland fires in Indonesia. Open biomass burning clearly contributes a significant portion of PM0.1 during SEA haze periods. Further PM0.1 studies are needed to better understand sources, transport and influences on human health to identify suitable measures to solve the problem sustainably.

Size-segregated of particulate matter (PM) including PM0.1 at two different sites, i.e., educational (EA) and residential (RA) areas in Padang city, Indonesia were sampled by using a cascade type air sampler for 24 hours with the average flowrate 40 l/m throughout three weeks (March, 08th-25th 2018). Carbonaceous components were analyses by a carbon analyzer following the IMPROVE_TOR protocol. Average PM2.5 and PM10 concentrations in RA were higher than those in EA while being below the NAAQS of Indonesia. However, it was much higher compared to the WHO limit for 24 hours in RA. OC was the dominant fraction in TC. OC/EC ratio ranging from 2.4 to 33.0 was similar at both sites, suggesting the OC was emitted from various sources. Char-EC and soot-EC ratio were founded to be minimized for PM0.1 (0.40 ± 0.27 and 0.39 ± 0.39, respectively at each site), indicating a more influence of burning of fossil fuel as vehicles exhaust and coal combustion. The transboundary influence of open biomass burning was not so significant although it cannot be ignored.

Transboundary haze from biomass burning is one of the most important air pollutions in Southeast Asia. The most recent serious haze episode occurred in 2015. Southern Thailand was affected by the haze during September to October when the particulate matter concentration hit a record high. We investigated physical and chemical characteristics of aerosols, including concentration and aerosol size distribution down to sub-micron sizes during haze episodes in 2013 and 2015 and, for reference, an insignificant haze period in 2017. The highest total suspended particulates and PM10 levels in Hat Yai city were 340.1 and 322.5 µg/m3. The mass fractions were nanoparticles (< 100 nm) 3.1%-14.8% and fine particles (< 1 µm) 54.6%-59.1%. Polycyclic aromatic hydrocarbon size distributions in haze periods peaked at 0.75 µm and the concentrations are 2-30 times higher than the normal period. High molecular weight (4-6 ring) PAHs during the haze episode contribute to about 56.7%-88.0% for nanoparticles. The average values of benzo(a)pyrene toxic equivalency quotient were 3.34±2.54ng/m3 in the 2015 haze period but only 0.89±0.17 ng/m3 in 2017. It is clear that particles smaller than 1 µm, were highly toxic. Nanoparticles contributed 19.4%-26.0% of total BaP-TEQ, whereas the mass fraction is 13.1%-14.8%. Thus the nanoparticles were more carcinogenic and can cause greater health effect than larger particles. The fraction of BaP-TEQ for nanoparticles during 2017 non-haze period was nearly the same, while the mass fraction was lower. This indicates that nanoparticles are the significant source of carcinogenic aerosols both during haze and non-haze periods.

The health risk of schoolchildren who were exposed to airborne fine and ultrafine particles (PM0.1) during the COVID-19 pandemic in the Jambi City (a medium-sized city in Sumatra Island), Indonesia was examined. A questionnaire survey was used to collect information on schoolchildren from selected schools and involved information on personal profiles; living conditions; daily activities and health status. Size-segregated ambient particulate matter (PM) in school environments was collected over a period of 24 h on weekdays and the weekend. The personal exposure of PM of eight selected schoolchildren from five schools was evaluated for a 12-h period during the daytime using a personal air sampler for PM0.1 particles. The schoolchildren spent their time mostly indoors (~88%), while the remaining ~12% was spent in traveling and outdoor activities. The average exposure level was 1.5~7.6 times higher than the outdoor level and it was particularly high for the PM0.1 fraction (4.8~7.6 times). Cooking was shown to be a key parameter that explains such a large increase in the exposure level. The PM0.1 had the largest total respiratory deposition doses (RDDs), particularly during light exercise. The high level of PM0.1 exposure by indoor sources potentially associated with health risks was shown to be important.

OBJECTIVES Gas sampling tubes are essential tools for the evaluation of air quality in work environments. It adsorbs toxic gaseous matters onto the surface of various granular adsorbents, such as silica gel or activated carbon packed in a thin glass tube, for quantitative analysis by gas chromatography. Currently, most of the semi-volatile matters are evaluated via aerosol filtration or solid-phase gas adsorption depending on the main phase of the substances; however, only a few substances have a sampling protocol regarding both solid and gaseous phases. Therefore, semi-volatile components evaluated by the solid-phase adsorption may result in the underestimation of the component concentrations due to particulate components passing through and remaining in the adsorbent. To highlight issues on sampling of semi-volatile matters by the solid-phase adsorption method, the collection efficiency of aerosol particles by 17 commercial gas sampling tubes were measured via pressure drop. METHODS To measure the particle collection efficiency of the gas collection tubes, precise control and dilution of the aerosol particle monitors are essential. However, we cannot apply typical filter test methods at a lower filtration flow rate than that of the aerosol particles monitors. Therefore, we developed a new experimental method that considers flow adjustment between the aerosol monitors. By assuming two specific particle size distributions and five inlet conditions, the collection efficiencies of total mass particles are estimated. From the gas-particle partitioning ratio of 16 polycyclic aromatic hydrocarbons (PAHs) in a coal tar pitch manufacturing industry, the underestimation of the concentration of semi-volatile matters using the gas collection tubes has been discussed. RESULTS The aerosol particles were collected in all kinds of layers in the gas sampling tubes, such as in the glass wool cap, gas adsorbent granular bed, and polyurethane foam. Furthermore, the collection efficiency curve of all 17 gas sampling tubes tested showed similar trends; a valley around particle sizes ranging from 0.2-0.3 μm between high collection zones below 0.1 μm and above 1 μm was observed. The observations suggested granular bed filters collection mechanisms such as inertial impaction, Brownian diffusion, gravity, and interception as same as air filters. CONCLUSIONS Solid-phase collection can underestimate the concentrations of multi-phase matters. Thus, we wish to highlight the importance of solid-phase collection methods along with filtration collection methods to collect all phases of semi-volatile matters.

PM0.1 (particles diameter ≤ 0.1 µm), nanoparticles (NPs), and ultrafine particles (UFPs), were interchangeably used in the scientific communities. PM0.1 originated from both natural and human sources. However, investigations of PM0.1 and its effects on the environment, visibility, and human health risk to understand the levels of air pollution, sources, and impacts in South East Asia (SEA) countries continue to be lacking. The concentration of PM0.1 in most SEA countries are much worse than those in western countries environment. A further motivation of this reviewed article is to provide a critical synthesis of the current knowledge and study of ambient PM0.1 in SEA cities. The main influence of characteristics of PM0.1 appears to be local sources including biomass burning and motor vehicles. Continuous monitoring of PM0.1 in terms of both mass and number concentration should be further understood. A critical review is of great importance to facilitating air pollution control policies and predicting the behavior of PM0.1 in SEA.

Size-segregated ambient particles down to particles smaller than 0.1 μm (PM0.1) were collected during the year 2014–2015 using cascade air samplers with a PM0.1 stage, at two cities in Thailand, Bangkok and Chiang Mai. Their characteristics and seasonal behavior were evaluated based on the thermal/optical reflectance (IMPROVE_TOR) method. Diagnostic indices for their emission sources and the black carbon (BC) concentration were assessed using an aethalometer and related to the monthly emission inventory (EI) of particle-bound BC and organic carbon (OC) in order to investigate the contribution of agricultural activities and forest fires as well as agro-industries in Thailand. Monthly provincial EIs were evaluated based on the number of agricultural crops produced corresponding to field residue burning and the use of residues as fuel in agro-industries, and also on the number of hot spots from satellite images corresponding to the areas burned by forest fires. The ratio of char-EC/soot-EC describing the relative influence of biomass combustion to diesel emission was found to be in agreement with the EI of BC from biomass burning in the size range

Ribbed Smoked Sheet (RSS) is one of the leading primary rubber products and is used as a raw material for tire production. An emission inventory (EI) analysis was conducted for the production and transportation of RSS in Thailand following the Life Cycle Inventory (LCI) methodology in order to highlight improvements needed to render the processes more environmentally friendly. The air emission inventory focussed on CO2, NOx, SOx, particulate matters (PM) and particle-bound polycyclic aromatic hydrocarbons (PAHs) using available databases, reports and previously published papers. Data was also obtained from a small-scale RSS factory, known as a cooperative, in Songkhla province, Thailand. Upstream para-rubber industries start from RSS in Thailand. Instead, downstream industries operate under tire production in Japan. There are high exported of RSS from Thailand to tire production in Japan. The material flow during the production and export of the amount of RSS produced and transported and the distances travelled were investigated. The results suggest that the tire production in Japan contributes more than 80% of the CO2 and 90% of the SOx emissions arising during the period from latex tapping to tire production. Conversely, 60% of PM and more than 90% of the PAHs were released from the drying process involving the wood-fuel burning without any pollution control devices. These results indicate that the environmental load due to hazardous air pollutants such as PAHs and smoke particles is serious in Thailand and has to be reduced to achieve environmentally sustainable tire production.

PM0.1 (particles with a diameter ≤ 0.1 µm), nanoparticles (NPs), or ultrafine particles (UFPs) were interchangeably used in the scientific communities. PM0.1 originated from both natural and human sources; however, PM0.1 and its effects on the environment, visibility, and human health to understanding air pollution levels, sources, and impacts in Southeast Asia (SEA) countries continue to be challenging. The concentrations of PM0.1 in most SEA countries are much worse than in western countries’ environments. A further motivation of this reviewed article is to provide a critical synthesis of the current knowledge and study of ambient PM0.1 in SEA cities. The primary influence of characteristics of PM0.1 appears to be local sources, including biomass burning and motor vehicles. Continuous monitoring of PM0.1 in mass and number concentration should be further understood. A critical review is of great importance to facilitating air pollution control policies and predicting the behavior of PM0.1 in SEA.

Distribution of PM

Ambient nanoparticles, or PM

Atmospheric size-classified particles in sizes ranging from small to nanoparticles (PM0.1) are reported for Rangsit City in the Bangkok Metropolitan Region (BMR) of Thailand, for October 2019 (wet season) and January–February 2020 (dry season). The sampling involved the use of a PM0.1 cascade air sampler to determine the mass concentration. The PMs consisted of six stages including TSP–PM10, PM2.5-10, PM1.0-2.5, PM0.5-1.0, PM0.5-1.0 and PM0.1. Elemental carbon (EC) and organic carbon (OC) were evaluated by a carbon analyzer following the IMPROVE_TOR protocol. The average PM0.1 mass concentrations were found to be 13.47 ± 0.79 (wet season) and 18.88 ± 3.99 (dry season) μg/m3, respectively. The average OC/EC ratio for the rainy season was lower than that in the dry season. The char-EC/soot-EC ratios were consistently below 1 for the PM0.1 fraction in both seasons indicating that vehicular traffic appeared to be the main emission source. However, the influence of open biomass burning on fine and coarse PM particles on local air pollution was found to be an important issue during the wet season. In addition, long-range transport from other countries may also contribute to the carbon content in the Bangkok Metropolitan Region (BMR) atmosphere during the dry season. The higher secondary organic carbon to organic carbon (SOC/OC) ratio in the dry season is indicative of the contribution of secondary sources to the formation of PM, especially finer particles. A strong correlation between OC and EC in nanoparticles was found, indicating that they are derived from sources of constant emission, likely the diesel engines. Conversely, the OC and EC correlation for other size-specific PMs decreased during the dry season, indicating that these emission sources were more varied.

We applied a 3-nozzle geometry to the inertial filter unit of a previously developed cascade air sampler, which originally consisted of a 4-stage (PM10/2.5/1/0.5) impactor, and an inertial filter unit embedded in a single circular nozzle (for PM0.1), and compared its performance against that of a single-nozzle inertial filter unit. The multi-nozzle design enabled the collection of multiple samples and the analysis of multi-chemical particle components in the size range of 0.1–0.5 µm. The total carbon was analyzed to determine the uniformity of the PM0.1 collected on a filter downstream from the inertial filter unit in both samplers, and the differences between the individual nozzles of the 3-nozzle unit as well as those between the 1- and 3-nozzle units were identified based on the chemical composition. After adjusting the quantity of the fibers in each inertial filter (one per nozzle) of the 3-nozzle sampler with care on the fiber packing uniformity , the 3-nozzle and 1-nozzle units exhibited similar separation performance, with approximately a 5% lower pressure drop for the former. The differences in the collected particle mass and the total carbon between the individual nozzles of the multi-nozzle unit and between the single- and multi-nozzle units were found to be less than 10%. However, the 3-nozzle unit uniformly collected particles regardless of the loaded particle mass, whereas its 1-nozzle counterpart exhibited non-uniform collection with higher loads. These data, together with the lower pressure drop, show that the multi-nozzle design has practical applicability, thus opening possibilities for chemically analyzing PM0.1.

Data for source apportionment estimation was obtained from combustion of 11 types of biomass (rubber wood, palm kernel, palm fiber, sugarcane bagasse, sugarcane leaves, maize residue, rice stubble, rice straw, Xylocarpus moluccensis, Avicennia alba Blume and Rhizophora mucronata) and bituminous coal. Combustion was carried out in a tube furnace and emitted particulate matter (PM) was collected using a nanosampler that segregated particle sizes down to 0.1 μm. Emission factors of PM 0.1 μm were in the range of 0.11-0.28 g kg

This research aims to investigate the effects of irradiation energy and residence time of soft X-ray irradiation in the decomposition of sixteen polycyclic aromatic hydrocarbons (PAHs) in smoke particles emitted from the Para rubber wood burning. The burning process was carried out in a tube furnace and the soft X-ray radiation used had a wave length of 0.13-0.41 nm. The irradiated (IR) and non irradiated (N-IR) smoke particles were collected simultaneously using a 10-stage Andersen sampler equipped with an inertial-filter stage (ANIF), in order to determine the physicochemical characteristic of both IR and N-IR smoke particles, including particle size distribution and concentration, and particle-bound PAHs concentration. Results show that the nano-size smoke particles contained the highest amount of PAHs and of carcinogenic potency equivalent (BaP-TEQ). About 75% of PAH compounds on the total smoke particles were decomposed at the highest irradiation energy. Moreover, 4-6 ring PAHs in nanoparticles (

Size-segregated particulate matter (PM) including the PM0.1 fraction, particles ≤0.1 µm, was monitored during the rainy and dry seasons at three different cities in Sumatra island, Indonesia in 2018. In order to identify possible emission sources, carbonaceous components in the particles collected by a cascade air sampler that is capable of collecting PM0.1 particles were analyzed by applying a thermal/optical reflectance (IMPROVE-TOR) protocol. The PM0.1 levels in the Jambi and Pekanbaru areas were similar to those in large cities in East Asia, such as Bangkok and Hanoi. During the rainy season, local emissions in the form of vehicle combustion were the main sources of PM. The influence of peatland fires in the dry season was more significant in cities that are located on the east coast of Sumatra island because of the larger number of hotspots and air mass trajectories along the coast. A clear increase in the carbonaceous profiles as OC, TC, and OC/EC ratios in the dry season from the rainy season was observed, particularly in fine fractions such as PM0.5–1. In both seasons, EC vs. OC/EC correlations and soot-EC/TC ratios showed that the PM0.1 fraction in Sumatra island was heavily influenced by vehicle emissions, while the effect of biomass burning was more sensitive with respect to the PM0.5–1 fraction, particularly in Jambi and Pekanbaru sites during the dry season.

Household fuel combustion for cooking is a major source of hazardous pollutants, including polycyclic aromatic hydrocarbons (PAHs) and their nitro derivatives (NPAHs). These pollutants impact indoor air quality and human health. In this study of two rural households in Chiang Mai, Thailand, PM2.5 samples were collected both inside and outside the houses during cooking and noncooking periods. Real-time monitoring of indoor PM2.5 was also conducted. The concentrations of PAHs, NPAHs, levoglucosan (LG), and carbon fractions in the PM2.5 fractions were quantified. The most severe contamination was observed inside the house during cooking with mean concentrations of 9980 ng/m3 and 18,700 pg/m3 for PAHs and NPAHs, respectively. The composition profiles of PAHs and NPAHs showed that benz[a]anthracene, benzo[k]fluoranthrene, and benzo[a]pyrene made the greatest contribution to total PAHs, while 9-nitroanthracene made the greatest contribution to total NPAHs. The correlation coefficient (p

We examined particulate matter (PM), polycyclic aromatic hydrocarbons (PAHs), and carcinogenic potencies of benzo[a]pyrene equivalent (BaP eq ) emissions from an indirect injection (IDI-turbo) diesel engine fueled by commercial diesel (PB0) and palm oil blends with portions of 40 and 50 vol.% (PB40 and PB50). The engine was in operation over long-term test cycles. A four-stage cascade impactor air sampler was used to collect particles emitted from the engine. The PM and PAHs were predominantly fine particles ( eq were reduced as the fraction ratio of palm oil was increased because palm oil blends have a high amount of oxygen, which enhances combustion compared to PB0. Although PM, PAHs, and BaP eq emissions of PB50 were less than those of PB0 and PB40, PB50 is not an appropriate fuel for the long-term running of this engine.

Aims To provide information on the time-dependent behaviour of microbe staining by fluorescent dyes in the order of seconds, which is important in terms of the recent rapid and online techniques for microbe measurements and/or environmental microbe analysis. Methods and results For combinations of yeast (Saccharomyces cerevisiae) and typical dyes, including DAPI (4',6-diamidino-2-phenylindole) and Auramine-O, a suspension of yeast cells in ultrapure water was injected into a dye solution in a micro cuvette placed inside a spectrofluorometer and the fluorescence intensity of the resulting solution was measured at 1 s intervals, starting immediately after the mixing and continued until the time for the maximum intensity using various concentrations of yeast and dyes. The relaxation time τ, which corresponds to ~63·2% of the maximum fluorescence intensity, was shown to decrease to below 1 s with increasing DAPI concentration, whereas it remained constant for 2-3 s with increasing Auramine-O concentration, for example at a yeast concentration of 100 µg ml-1 . Conclusions For the conditions of yeast >10 µg ml-1 , DAPI >1 µg ml-1 and Auramine-O >0·1 µg ml-1 , τ could be adjusted to below 5 s to achieve a rapid and stable staining. Significance and impact of the study Design and operating conditions for rapid and online measurements of microbes can be optimized.

In this study, size-fractionated particulate matters (PM) down to ultrafine (PM

In this study, as the first step in mitigating contamination by PM0.1, particles with diameters less than 0.1 μm, the current air pollution situation in Indonesia was investigated with respect to particulate matter (PM), especially regarding the status and characteristics of PM0.1. Air sampling in different size ranges down to PM0.1 was conducted at roadsides, at a school adjacent to a road, an industrial area and an area near a volcano in North Sumatera Province. Analyses were conducted for carbonous components (OC, EC, TC, WSOC and WISOC), and ions including oxalate in the PM0.1 fraction. We identified PM2.5 and PM10 mass concentrations in the area of the city that exceeded WHO guidelines. From the chemical components in the PM0.1 fraction, we found that WISOC, NO3− and soot-EC were the most common components, suggesting that local traffic is a contributor and another group consisting of K+, SO42− and WSOC suggesting the occurrence of biomass burning related to local industrial and rural sources.

The international regulation of persistent organic pollutants (POPs) according to the Stockholm convention started in May 2001, and is intended to regulate the production and use of hazardous chemicals on a global scale. PFOS is one of the newly listed emerging POPs and only one of a diverse huge group of perfluoroalkyl substances (PFASs), which are known as a “super set” of chemical tracers that include more than ninety related chemicals. The comprehensive monitoring of PFASs is necessary to develop a reliable understanding of environmental kinetics related to these pollutants. However, the extent of atmospheric pollution by PFASs is still unclear because their distribution and sources are not fully understood. Hence, a reliable analytical method for precisely measuring the levels of PFASs in particulate matter is needed. In this study, in order to investigate the levels of PFASs in atmospheric particles including PM2.5, the use of new sampling equipment was evaluated by obtaining multiple samples of air from a stable meeting room environment. Meanwhile, by simultaneously obtaining samples from a roadside environment, the characteristics of PFASs from two different types of air samples were compared.

Seasonal and local characteristics of perfluorinated alkylated substances (PFASs) were examined using size-segregated particles including an ultrafine range. The examination included sampling and analysis of ambient particles collected at four sites located in different environments in three different countries, Japan (Kanazawa and Okinawa), Hong Kong and India. To minimize the evaporation artefacts derived from PFASs during the sampling, an air sampler that permitted particles smaller than 0.1 μm (PM0.1) to be separated at a moderate pressure drop (

A layered mesh inertial filter that was previously developed by the authors, was combined with an impactor, in which the collection efficiency curve overlaps that of the inertial filter, in order to provide a sharp-cut separation tool for aerosol nanoparticles operating at a moderate pressure drop of less than 10–15 kPa. The separation performance of the proposed “hybrid inertial filter” of the inertial filter and an impactor, such as cut-off size, steepness of the collection efficiency curve and pressure drop ΔP, was evaluated for a single nozzle type in order to confirm the proposed system. The performance of the single nozzle type, which can be used as a unit of a multi nozzle type, was compared with that of the previous type layered mesh inertial filter with a stainless steel fiber mat. The hybrid inertial filter was found to have a collection efficiency curve with a much better steepness at less ΔP compared to those of the previous type for particles with the same cut-off size: a cut-off size dp50 of 100 nm with steepness dp84/dp16 = 1.7, e.g., was obtained at ΔP ~12 kPa while dp84/dp16 = 2.4 at ~16 kPa was found for the previous type.

The particle size distribution of chlorinated polycyclic aromatic hydrocarbons (ClPAHs) in particulate matter (PM) in Japan is examined for the first time. PM was collected using a PM0.1 air sampler with a six-stage filter. PM was collected in October 2014 and January 2015 to observe potential seasonal variation in the atmospheric behavior and size of PM, including polycyclic aromatic hydrocarbons (PAHs) and ClPAHs. We found that the concentration of PAHs and ClPAHs between 0.5–1.0 μm and 1.0–2.5 μm markedly increase in January (i.e., the winter season). Among the ClPAHs, 1-ClPyrene and 6-ClBenzo[a]Pyrene were the most commonly occurring compounds; further, approximately 15% of ClPAHs were in the nanoparticle phase (

Northern Thailand has long been severely affected by haze from biomass burning containing fine and ultrafine aerosols in the dry period. The carbonaceous PM0.1 comprising elemental carbon (EC) and organic carbon (OC) collected during the haze and non-haze periods in Chiang Mai, Thailand was investigated. The PM0.1 levels during the haze periods were about 3 times higher than the non-haze periods, a significant increase. PM0.1 concentration was strongly correlated with atmospheric relative humidity and the number of forest fire hotspots. Carbonaceous aerosol characteristics in PM0.1 were analyzed with the thermal/optical transmittance (TOT) method following the IMPROVE protocol. The concentrations of OC and EC, distribution of OC and EC and OC/EC ratios in PM0.1 were evaluated. Average OC and EC mass concentrations in PM0.1 were 6.8 ± 2.7 and 1.4 ± 0.5 µg m–3 during the haze periods, significantly higher than those during the non-haze periods; 1.9 ± 0.9 and 0.5 ± 0.2 µg m–3. The OC/EC ratio increased linearly with the number of hotspots. This indicated significant contribution from biomass burning to the PM0.1. This was strongly supported by the 48-hr backward trajectory simulation, that indicated both domestic and transboundary aerosol transports. Because both organic and elemental carbon are the light-absorbing carbonaceous aerosols, the increase during the haze periods contributed to regional air quality and climate. This study enhances the understanding of PM0.1 behavior in Chiang Mai, Thailand, during the haze periods in upper southeast Asia.

For the appropriate hygienic management of workplaces where workers handled nano-TiO2 products, the status of the personal exposure of workers to respirable dust (PM4) and nanoparticles (PM0.1) was investigated. Using a cyclone sampler for PM4 and a personal sampler for PM0.1, PM4 and PM0.1 exposure levels were evaluated to discuss them in relation to worker’s duties. The number of particles of 0.01–10 µm was also monitored online in order to examine the short-term fluctuation in the concentration and size distribution of particles. The 8h-time-weighted average (TWA) and 95% upper limit for respirable dust exposure were below the occupational exposure limit specified by the Japan Society for Occupational Health and the recommended exposure limits for TWA by NIOSH. The action level was exceeded during the filling of a flexible container bag. More than 70% of particles in the breathing zone was coarse agglomerates of > 1 µm, while it may be influenced by powder properties and the handling process as well as the management of local ventilation. The maximum PM0.1 concentration (31.3 µg m–3) occurred in a powder filling booth without air ventilation. The operation of a gasoline powered forklift temporarily increased the concentration of ultrafine particles. Most of TiO2 powder was suspended as micron-order agglomerates in the breathing zone. However, since PM0.1 exposure was much larger than those in outdoor environment particularly under insufficient cares to aerosolized powder and air ventilation, PM0.1 exposure should also be monitored.

In this study, size-fractionated particulate matters (PM) down to ultrafine (PM0.1) particles were collected using a cascade air sampler with a PM0.1 stage, in Hat Yai city, Songkhla province, southern Thailand during the year 2018. The particle-bound carbonaceous aerosols (CA) as elemental carbon (EC) and organic carbon (OC) were quantified with the thermal/optical reflectance method following the IMPROVE_TOR protocol. The concentrations of different temperature carbon fractions (OC1-OC4, EC1-EC3 and PyO) in the size-fractionated PM were evaluated to discern OC and EC correlations as well as those between char-EC and soot-EC. The results showed that biomass burning, motor vehicle, and secondary organic aerosols (SOC) all contributed to the size-fractionated PM. The OC/EC ratios ranged from 2.90 to 4.30 over the year, with the ratios of PM2.5-10 being the highest, except during the open biomass burning period. The concentration of CA was found to increase during the pre-monsoon season and had its peak value in the PM0.5-1.0 fraction. The long-range transport of PMs from Indonesia, southwest of Thailand toward southern Thailand became more obvious during the pre-monsoon season. Transported plumes from biomass burning in Indonesia may increase the concentration of OC and EC both in the fine (PM0.5-1.0 and PM1.0-2.5) and coarse (PM2.5-10 and PM>10) fractions. The OC fraction in PM0.1 was also shown to be significantly affected by the transported plumes during the pre-monsoon season. Good OC and EC correlations (R2 = 0.824–0.915) in the fine particle fractions indicated that they had common sources such as fossil fuel combustion. However, the lower and moderate correlations (R2 = 0.093–0.678) among the coarser particles suggesting that they have a more complex pattern of emission sources during the dry and monsoon seasons. This indicates the importance of focusing emission control strategies on different PM particle sizes in southern Thailand.

Two artifacts were observed during collection of atmospheric ultrafine particles (UFPs; < 100 nm diameter) using an inertial filter (INF) sampler recently developed for this purpose. These artifacts were evaluated. First, the adsorption of organic and ionic gas onto a quartz fiber filter installed in the INF sampler was evaluated to provide information on the positive artifact; this information is important for accurate analysis of the UFP components. Gas adsorption by the INF sampler was similar to or less than that of other devices for collecting UFPs. The gas adsorption of organic carbon (OC) fractions, and ionic components of NH4+, NO3– and SO42– was confirmed, and the adsorption of OC1 and ionic components were highly dependent on the concentration of the gas and the UFP concentration under ambient conditions. These results suggest that it is necessary to know the concentration of the UFPs on the filter in order to evaluate the exact concentrations of UFP components under high flow rate conditions. Second, the efficiency of UFP collection on a polytetrafluoroethylene (PTFE) filter installed in the INF sampler was evaluated to clarify the negative artifact. The data confirmed that the efficiency of collection changed with changing structure such as pore size, porosity and thickness of the filter. The structure of these filters and UFPs collected on there were observed by a scanning electron microscopy. The highest particle collection efficiency (almost 100%) was obtained by installing two thick membrane PTFE filters. The collection of UFPs using a sampler comprising several filter stages is a convenient and useful method for evaluating positive and negative artifacts and for quantifying the concentration of components of UFPs.