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 d_(p50) of 100 nm with steepness d_(p84)/d_(p16) = 1.7, e.g., was obtained at ΔP ~12 kPa while d_(p84)/d_(p16) = 2.4 at ~16 kPa was found for the previous type.
Polyphenylene sulfide (PPS) is known as a material resistant to high temperature and chemicals; however, there are arguments on the durability of PPS non-woven fabrics to chemicals, such as nitric ...acid (HNO
3), sulfuric acid (H
2SO
4), and hydrochloric acid (HCl). Therefore, this work aims at investigating the degradation of PPS non-woven fabrics in HNO
3, H
2SO
4 and HCl, and at confirming acid durability of PPS non-woven fabrics. In addition, this paper also studies the interaction among these three acids by measuring the retention of strength in binary or tertiary mixtures of these three acids. A discussion has been made on the acceleration/retardation of PPS degradation by the interactive effects, and also on the chemistry related to the degradation by these acids. Furthermore, there is a linear relationship between the nitric acid concentration and the proportion of carbon in the remaining PPS structures after 100
h of acid exposure. Also, this proportion of carbon is a good indicator of the retained strength in PPS fabrics.
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 NH^(4+), NO^(3-) and SO_4^(2-) 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.
Mixed crude palm oil （MCPO）, the mixture of palm fiber oil and palm kernel oil, has become of great interest as a renewable energy source. It can be easily extracted from whole dried palm fruits. In ...the present work, the degummed, deacidified MCPO was blended in petroleum diesel at portions of 30% and 40% by volume and then tested in agricultural diesel engines for long term usage. The particulates from the exhaust of the engines were collected every 500 hr using a four-stage cascade air sampler. The 50% cut-off aerodynamic diameters for the first three stages were 10, 2.5 and 1μm, while the last stage collected all particles smaller than 1 μm. Sixteen particle bounded polycyclic aromatic hydrocarbons （PAHs） were analyzed using a high performance liquid chromatography. The results indicated that the size distribution of particulate matter was in the accmnulation mode and the pattern of total PAHs associated with fine-particles （〈 1 μm） showed a dominance of larger molecular weight PAHs （4--6 aromatic rings）, especially pyrene. The mass median diameter, PM and total PAH concentrations decreased when increasing the palm oil content, but increased when the running hours of the engine were increased. In addition, Commercial petroleum diesel （PB0） gave the highest value of carcinogenic potency equivalent （BaPeq） for all particle size ranges. As the palm oil was increased, the; BaPeq decreased gradually. Therefore the degununed-deacidified MCPO blends are recommended for diesel substitute.
The workplace environment in factories producing ribbed smoked sheet rubber (RSS), the interiors which are heavily contaminated by wood burning smoke, was evaluated with a focus on the concentration ...of suspended particulates and particle-bound PAHs as well as workers' exposure in the breathing zone during the period January, 2006-February, 2008 in Thailand. Seasonal changes in particulate and PAH concentrations are discussed in relation to the amount of RSS produced, wind direction, ventilation type and the geometry of the factory building. The concentration of particulate matter in the workplace was shown to increase nearly linearly with RSS production while being influenced by the wind direction to the open sides of the building and wind speed. Particulate concentrations in the workplace and in the worker's breathing zone were lower than those for other common occupational exposure limits. However, rather high PAH concentrations of 97.4 c 129 ng/m super(3) and 142 c 184 ng/m super(3) were found in the workplace and in the breathing zone, respectively. BaP sub(TEQ) concentrations in the workplace ranging from 21.4 to 91.0 ng/m super(3) were similar to those in a sinter plant. The workers' exposure to PAHs was similar to that in a sinter plant, a metal recycling plant, a paving bitumen manufacturing plant and a carbon black manufacturing plant. The mass fraction of PAHs in particles in the RSS factory was as high as 0.30 BaP sub(TEQ)ng/kg, much higher than that in a carbon black plant (0.004-0.01 BaP sub(TEQ)ng/kg). The results reported herein suggest that the workers in the RSS factory have a somewhat high health risk from exposure to PAHs. Natural ventilation by the addition of roof turbines was insufficient in terms of reducing PAHs levels in the workplace although a roof ridge vent was functional and had a positive effect.
Daily PM2.5 samples were collected at a rural site in Fukui City, Japan, over two months from September to November 2019, covering the rice harvest and postharvest periods, to understand the changes ...in levels of combustion of various types of biomass during the autumn season. Four organic tracer components of biomass combustion—levoglucosan, mannosan, vanillic acid, and dehydroabietic acid—were analyzed from the PM2.5 samples to reveal their relationships with different types of biomass, such as plants and forests. The ratio of levoglucosan-to-mannosan, a typical organic tracer component of biomass combustion, changed from an average value of 36 ± 17 during the rice harvest season to a value of 13 ± 4 after the rice harvest season, indicating a shift in the primary combustibles from crop residues such as rice straw to other combustibles. The concentration and proportion of mannosan and dehydroabietic acid increased after the rice harvest season, indicating an increase in the proportion of conifers among biomass-burning species. Our new analysis of multiple organic biomass burning (BB) traces indicated the availability of the elucidation of compositional changes in different BB types.
•Organic tracers revealed changes in biomass burning species in the fall season.•The ratio of levoglucosan to mannosan (L/M) increased during the rice harvest season.•L/M decreases as dehydroabietic acid increases after the rice harvest season.•The main biomass burning species shifted from rice residues to softwood.
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