• Journal of Korean Society for Atmospheric Environment
• /
• v.1 no.1
• /
• pp.93-98
• /
• 1985

Mass size distribution of atmospheric particulates were measured using an Andersen using an Andersen sampler in urban air. The atmospheric particulates were fractionated in eight stages of an Andersen sampler operating at 28.4$\ell/min$ and collected on polyester sheets. A quartz filter was placed behind the last stage collect permeated partculates. The size distribution of atmospheric particulates were divided around 1-2 $\mu$m into two groups, coarse and fine particulates regardless of sampling times. The variation of course particulates concentration was higher than fine particulates among sampling times. Different meterorological conditions and natural phenomena brought high variation of course particulates' concentration. The rain caused removal of coarse particulates seriously and the yellow and may take part in a increase of the course particulates in spring. The average concentration of atmospheric particulates to be collected by Andersen sampler was 170.8 $\mug/m^3$ during 3 times of sampling. Among them the average concentration of atmospheric particulates which could penetrated under a bronchi and alveoli were 70.4$\mug/m^3$ and 36.6$\mug/m^3$ respectively.

• Journal of Preventive Medicine and Public Health
• /
• v.19 no.1 s.19
• /
• pp.130-136
• /
• 1986

The particle size of suspended particulates was measured by a Anderson air sampler from Mar. 1982 to Feb. 1984 in a part of Seoul. It was concluded as follows : 1) The arithmetic concentration of suspended particulates was $147.8{\mu}g/m^3$ in Spring, 136.9 in Summer, 131.9 in Autumn and 158.1 in Winter respectively. 2) The cumulative distribution of suspended particulates size in logarithmic diagram showed similar to normal log distribution. 3) The atmospheric particulate matters showed a bimodal size distribution on the base of unit particle concentrations, which divided at approximately $2{\mu}m$ in the diameter. 4) While the fine particulates less than $2.1{\mu}m\;was\;35.4{\sim}45.0%$, the coarse particulates was $55.0{\sim}64.5%$. 5) The higher the concentration of suspended particulates, the more increased the ratio of fine particulates. The higher the concentration of suspended particulates, the lower median size of suspended particulate as well. 6) The respirable dust particulates less than $4.7{\mu}m\;was\;52.2{\sim}62.9%$ in seasonal average through the 2 year samples. With the above result, air pollution concerned with public health could be evaluated and the control measures also are suggested.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2001.05a
• /
• pp.29-33
• /
• 2001

In the present study, AZ91Mg/$\textrm{Al}_2\textrm{O}_3$ short fiber+SiC particulates hybrid metal matrix composites(MMCs) were fabricated by squeeze casting method. Different particulate sizes of 45, 29 and $9\mu\textrm{m}$ were hybridized with 5% volume fraction to investigate the effect of SiC particulates size on microstructure, mechanical and thermal properties such as hardness, flexural strength, wear resistance and thermal expansion. Results show that the microstructure of the hybrid composites were quite satisfactory, namely revealing relatively uniform distribution of reinforcements. Some aggregation of SiC particulates caused by particle pushing was observed especially in the hybrid composites containing in fine particulates($9\mu\textrm{m}$). The hardness and flexural strength were improved by decreasing particulates size, whereas wear resistance improved by increasing particulates size because of large particulates restricting matrix wear from contacted stress. Regardless of particulates size, thermal expansion of composites was the same. This may be because the content of particulates was in all cases 5 volume fraction.1

• Environmental Mutagens and Carcinogens
• /
• v.15 no.2
• /
• pp.131-139
• /
• 1995

Air suspedned particulates are the most serious factor among air pollutants in Seoul and their extracts have been revealed to be pulmonary carcinogenes. Air particulates were collected at a site representative of the high traffic area of Seoul from December 1993 to May 1994. Polycyclic aromatic hydrocarbons (PAHs) and nitroarenes in organic extracts of air particulates were determined by gas chromatography and mutagenicity of particle extracts was evaluated by the pre-incubation procedure with Salmonella typhirnurium TA98 and TA 98NR. The average concentration of total suspended particulates and inhalable (less than 10 $\mu$m) particulates were 169.63 $\mu g/m^3$, 141.92 $\mu g/m^3$, respectively. The relative contribution of organic matters was highest in neutral fraction and was lowest in basic fraction. Among identified 20 PAHs, the level of PAHs with 4-benzen ring i.e., pyrene, benzo(a)anthracene and chrysene were much higher than the PAHs with higher ring numbers. The mutagenicity of air particulates was much higher in the presence of rat liver microsomai fraction (S9 mixture) than that observed in its absence, which indicates that air particulates contained both direct and indirect mutagens. Nitroarenes in this study were not almost detected but mutagenicity of their fraction was higher. These results are represent to research for the identification of nitroarenes in the forward study.

• Proceedings of the Korean Environmental Sciences Society Conference
• /
• 2003.11a
• /
• pp.19-26
• /
• 2003

The dispersion of recycled particulates in the complex coastal terrain containing Kangnung city, Korea was investigated using a three-dimensional non-hydrostatic numerical model and lagrangian particle model (or random walk model). The results show that particulates at the surface of the city that float to the top of thermal internal boundary layer (TIBL) are then transported along the eastern slope of the mountains with the passage of sea breeze and nearly reach the top of the mountains. Those particulates then disperse eastward at this upper level over the coastal sea and finally spread out over the open sea. Total suspended particulate (TSP) concentration near the surface of Kangnung city is very low. At night, synoptic scale westerly winds intensify due to the combined effect of the synoptic scale wind and land breeze descending the eastern slope of the mountains toward the coast and further seaward. This increase in speed causes development of internal gravity waves and a hydraulic jump up to a height of about 1km above the surface over the city. Particulate matter near the top of the mountains also descends the eastern slope of the mountains during the day, reaching the central city area and merges near the surface inside the nocturnal surface inversion layer (NSIL) with a maximum ground level concentration of TSP occurring at 0300 LST. Some particulates were dispersed following the propagation area of internal gravity waves and others in the NSIL are transported eastward to the coastal sea surface, aided by the land breeze. The following morning, particulates dispersed over the coastal sea from the previous night, tend to return to the coastal city of Kangnung with the sea breeze, developing a recycling process and combine with emitted surface particulates during the morning. These processes result in much higher TSP concentration. In the late morning, those particulates float to the top of the TIBL by the intrusion of the sea breeze and the ground level TSP concentration in the city subsequently decreases.

• Asian Journal of Atmospheric Environment
• /
• v.12 no.3
• /
• pp.215-231
• /
• 2018

In order to understand the variation of air quality and the concentration of atmospheric particulates in Chengdu Second Ring Road renovation project, this paper starts to investigate the surrounding residents' opinions on the influenced environment and their daily lives via questionnaires. Then the study numerically simulates the change rule of atmospheric particulates in terms of time and space by using the Gaussian dispersion-deposition model and the compartment model. The optimized scientific scheme is selected by the improved fuzzy analytical hierarchy process(FAHP) to help decision making for the future urban reconstructions. Finally, the reduced emissions of atmospheric particulates are measured when the improvement scheme is provided. According to the study, it can be concluded that the concentration of atmospheric particulates increases rapidly in central Chengdu city during the renovation project, which results in worsening air quality in Chengdu during March 2012 to March 2013. Taking related measures on energy saving and emission reduction can effectively reduce the concentration of atmospheric particulates and promote economic, environmental and social coordination.

• Elastomers and Composites
• /
• v.54 no.4
• /
• pp.330-334
• /
• 2019

Cryogenic crushing techniques have been employed for recycling waste rubber articles and for extracting residual organic additives present in rubber samples. Rubber particulate derived from tire tread abrasion is one of the key components of road dust. Therefore, in this work, we prepared rubber particulates using a cryogenic crusher and characterized their shapes as well as size distributions according to the type of rubber. The rubber particulates exhibited uneven surfaces with the presence of some small pieces. The order of the particle size distribution was observed to be: NR > BR > SBR. Subsequently, carbon black was added; this led to a decrease in the particle size and the shape becoming rougher. The crushed particulates of the carbon black-filled samples comprised agglomerated shapes of small pieces, which were similar in shape to that of wear debris in tire tread. It was discovered that crosslink density was one of the principal factors that led to the formation of small crushed particulates. The small particulates obtained by cryogenic crushing can be utilized as model rubber particulates for researching micro dust.

• Journal of Korean Society for Atmospheric Environment
• /
• v.19 no.3
• /
• pp.297-306
• /
• 2003

Works were focused on back pressure characteristics of ceramic fiber filter on DPF (Diesel Particulate Filter) system and experiments were performed to select appropriate filter which can filter particulates. Filters were installed on metal -support tube which has openings for exhaust gas flow. Ceramic fiber filters with high specific surface area and adequate high temperature strength are commercially available for filtration of diesel particulates and in -situ hot regeneration. Thus, ceramic blanket and ceramic board which are used as insulating media were applied to filter and filtration apparatus was installed on exhaust gas line connected to 2.0 L diesel engine. Alternating filter structure to adapt DPF system, collection efficiency test of diesel particulates was measured. In case of ceramic blanket, pressure drop was low, caused by the destruction of soft structures. Also, particulate collection efficiency was decreased depending on loading time. In case of ceramic board, structure design was altered to reduce back pressure on DPF system. Structure design was altered to induce Z-flow by making 10 mm and 5 mm holes on the surface of media. Alteration of 5 mm hole showed that media have low back pressure but particulate collection efficiency was 77%, while 10 mm hole showed that of 90%.

• Journal of Korean Society for Atmospheric Environment
• /
• v.2 no.2
• /
• pp.60-65
• /
• 1986

Atmospheric particulates were collected at a site near the front gate of the Yonsei University using nine stages Andersen air sampler and the distribution of seasonal particle size was investigated. Rubber, Pb and Zn contents of the collected particulates in each stage were determined. Particle size distribution of atmospheric particulate, which was made by concentration distribution curve method, was usually divided into two groups, course (particles larger than 1 - 2 $\mu m in diameter$) and fine (particles smaller than 1 - 2 \mu m in diameter$) groups, regardless of sampling period. More than 80 percent of the total rubber contents in atmospheric particulates were larger than $5 \mu m$ in diameter, meaning that most of rubber particles were originated from tire tread. After benzene extraction for 4 hrs, the extracts were analyzed by Curie-point pyrolysis gas chromatography for rubber content. Pb and Zn contents were determined by atomic absorption spectroscopy. The annual average concentration of rubber particles was $4.2 \mu g/m^3$, which corresponded to 2.2% of the annual average total suspended particulates. Average concentration of styrene brtadiene rubber was about five times that of natural rubber. Annual average concentrations of Pb and Zn were $1.2 \mu g/m^3 and 0.4 \mu g/m^3$ respectively, which corresponded to about 0.7% and 0.2% of the annual average total suspended particulates.

• Journal of the Korean Solar Energy Society
• /
• v.25 no.4
• /
• pp.133-139
• /
• 2005

In this paper, the ventilation performance of suspended particulates in indoor side was investigated by step-down method. Experiments were performed in function of mechanical ventilation types and locations of supply and extract air. The type 2 ventilation system shows the highest removal characteristics rather than other 2 types. It means that the displacement ventilation has also good decay rates of concentration compared to mixing ventilation.