• 한국대기환경학회:학술대회논문집
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• 한국대기환경학회 2010년도 춘계학술대회 논문집
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• pp.506-507
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• 2010

• 대한원격탐사학회지
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• 제39권5_3호
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• pp.891-907
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• 2023

Compact Advanced Satellite 500-4 (CAS500-4) is scheduled to be launched to collect high spatial resolution data focusing on vegetation applications. To achieve this goal, accurate surface reflectance retrieval through atmospheric correction is crucial. Therefore, a machine learning-based atmospheric correction algorithm was developed to simulate atmospheric correction from a radiative transfer model using Sentinel-2 data that have similarspectral characteristics as CAS500-4. The algorithm was then evaluated mainly for forest areas. Utilizing the atmospheric correction parameters extracted from Sentinel-2 and GEOKOMPSAT-2A (GK-2A), the atmospheric correction algorithm was developed based on Random Forest and Light Gradient Boosting Machine (LGBM). Between the two machine learning techniques, LGBM performed better when considering both accuracy and efficiency. Except for one station, the results had a correlation coefficient of more than 0.91 and well-reflected temporal variations of the Normalized Difference Vegetation Index (i.e., vegetation phenology). GK-2A provides Aerosol Optical Depth (AOD) and water vapor, which are essential parameters for atmospheric correction, but additional processing should be required in the future to mitigate the problem caused by their many missing values. This study provided the basis for the atmospheric correction of CAS500-4 by developing a machine learning-based atmospheric correction simulation algorithm.

• Asian Journal of Atmospheric Environment
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• 제6권2호
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• pp.96-103
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• 2012

Ambient particulate matter (PM) and particle-bound polycyclic aromatic hydrocarbon (PAH) concentrations were measured continuously for 70 days at a Korean elementary school located near a highway. The $PM_{10}$, $PM_{2.5}$, and $PM_1$ values were measured with a light-scattering, multi-channel, aerosol spectrometer (Grimm, Model 1.107). The number concentrations of the particles were measured using a scanning mobility particle sizer and counter (SMPS+C) which counted particles from 11.1 to 1083.3 nm classified in 44 channels. Particle-bound PAHs were measured with a direct reading, photoelectric aerosol sensor. The daily $NO_2$, $SO_2$, and CO concentrations were obtained from a national air-monitoring station located near the school. The average concentrations of $PM_{10}$, $PM_{2.5}$, and $PM_1$ were 75.3, 59.3, and $52.1{\mu}g/m^3$, respectively. The average number concentration of the ultrafine particles (UFPs) was $46,307/cm^3$, and the averaged particle-bound PAHs concentration was $17.9ng/cm^3$ during the study period. The ambient UFP variation was strongly associated with traffic intensity, particularly peak concentrations during the traffic rush hours. Particles <100 nm corresponded to traffic-related pollutants, including PAHs. Additional longterm monitoring of ambient UFPs and high-resolution traffic measurements should be carried out in future studies. In addition, transient variations in the ambient particle concentration should be taken into consideration in epidemiology studies in order to examine the short-term health effects of urban UFPs.

• 한국입자에어로졸학회지
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• 제10권3호
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• pp.119-130
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• 2014

Home is a major living environment of children. In urban area, indoor air at home could be severely influenced by combustion sources such as vehicle exhaust and cooking. In this work, the air quality of a high-rise apartment was investigated by monitoring combustion-related air pollutants at both indoor and outdoor in winter of 2014. From 48-h continuous monitoring data, large amount of $NO_x$ was observed at the balcony of the high-rise apartment during the morning traffic hours. It deteriorated indoor air quality of the apartment. During the cooking activity, high peak episodes of ultrafine particles were seen. It was concluded that effects of vehicle exhaust and cooking activity on the indoor air of the high-rise apartment could be easily checked by $NO_x$ and ultrafine particle indicators, respectively.

• 한국입자에어로졸학회지
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• 제9권3호
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• pp.149-161
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• 2013

Experiments on photochemical reactions of purified air alone in an indoor smog chamber were carried out after flushing Teflon bags with purified air for many hours in order to check the level of contamination on the chamber wall. Ozone concentrations were linearly increased from <4 ppb up to about 8 ppb with irradiation time for four hours. Outgassing of NOx from the chamber wall was found to be less than 1 ppb. New ultrafine particles were formed and grown up to about 70 nm during the photochemical reactions, and then total number and mass concentrations of particles were increased from <10 particles/$cm^3$ up to about 4,000 particles/$cm^3$ and $1.3{\mu}g/m^3$, respectively. The wall conditions of these Teflon bags flushed with purified air might not severly affect the chamber experimental results for photochemical reactions of polluted urban ambient air. The difference of gaseous species between two chambers was 2.4 ppb of ozone at most, indicating that the wall cleaning performance of two chambers was nearly similar.

• 한국환경보건학회지
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• 제13권2호
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• pp.25-33
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• 1987

This study was carried out to evaluate student exposures to dust in classroom of middle schools. A total of four schools, such as two in an urban and two in a rural area, were selected for this study. In this study, airborne dust concentrations were measured during a period from July 8 to July 18, 1986. Additional measurements of dust concentrations were conducted from November 4 to 7, 1986 to compare the results by seasonal variation. The results of this study were as follows. 1. Respirable dust concentrations were measured by both filtration method (C mg/m$^3$) and Digital Aerosol Monitor (cpm) to calculate anexchange factor K. K- value was 0.159 as follows. $K=\frac{c}{cpm} = \frac{2.71}{17.09} = 0.159$ 2. In summer when windows were opened, the concentrations of airborne respirable dusts measured by filter sampling method were 0.54-1.37 mg/m$^3$ in the morning and 0.79-1.75 mg/m$^3$ in the afternoon. Thus, higher levels were indicated in the afternoon. Meanwhile, the concentrations of airborne respirable dusts measured in winter were approximately twice as high as those in summer. 3. The highest dust concentrations were determined in School D which is a coeducational school with classroom of concrete floor. Walking roads in School D were not paved and students did not wear indoor-shoes. Dust levels in School D were approximately twice as high as levels in School B. All of the measured dust levels in four schools exceeded Korean Standard for outdoor air, 0.3 mg/m$^3$ for 24 hours. Results by Digital Aerosol Monitor indicated that there was no significant difference in dust levels among grades. The concentration of airborne dusts in the classroom was 1.5-3.0 times higher than that in the hall way. The concentration of airborne dusts during recess was 1.3-1.6 times higher than that during class. In winter, the dust concentrations during clean-up exceeded the permissible exposure limit, 10 mg/m$^3$ (as total dusts), for occupational exposures. 4. The concentrations of total dusts measured in winter were 1.5-2.4 times higher than those of respirable dusts measured simultaneously.

• 한국환경과학회지
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• 제12권2호
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• pp.217-225
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• 2003

Samples of size-fractionated PM10 (airborne particulate matter with aerodynamic diameter less than $10\mu\textrm{m}$) were collected at an urban site in Jeju city from May to September 2002. The mass concentration and chemical composition of the samples were measured. The data sets were then applied to the CMB receptor model to estimate the source contribution of PM10 in Jeju area. The average PM10 mass concentration was 28.80$\mu\textrm{g}/m^3$ ($24.6~33.49\mu\textrm{g}/m^3$), and the FP (fine particle with aerodynamic diameter less than $2.l\mu\textrm{m}$ fraction in PM10 was approximately 8% higher than the CP (coarse particle with aerodynamic diameter greater than $2.l\mu\textrm{m}$ and less than $10\mu\textrm{m}$ fraction in PM10. The CP composition was obviously different from the FP composition, that is, the most abundant water soluble species was nitrate ion in the FP, but sulfate ion in the CP. Also sulfur was the most dominant element in the FP, however, sodium was that in the CP. From CMB receptor model results, it was found that road dust was the largest contributor to the CP mass concentration (45% of the CP) and ammonium nitrate, domestic boiler, and marine aerosol were major sources to the CP mass. However, the secondary aerosol was the most significant contributor to the FP mass concentration (45% of the FP). In this study, it was suggested that the contributions of soil dust and gasoline vehicle became very low due to collinearity with road dust and diesel vehicle, respectively.

• 대기
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• 제16권2호
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• pp.85-96
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• 2006

The six-year (2000~2005) record of aerosol optical thickness (AOT or $\tau$) data from the Moderate Resolution Imaging Spectroradiometer (MODIS) was analyzed over the Northeast Asia. The MODIS AOT standard products (MOD04_L2) over both ocean and land were collected to evaluate the spatial and temporal variability of the atmospheric aerosols over the study region ($32^{\circ}N{\sim}42^{\circ}N$ and $115^{\circ}E{\sim}133^{\circ}E$). The monthly averaged AOT result revealed slight changes(${\pm}0.002{\tau}/month$), which was almost unchangeable, over Korea. In contrast, the large AOT values (> 0.6) and a significant AOT increase (> 0.004 ${\tau}/month$) over East China were observed. For the analysis of spatio-temporal variability of AOT values, study area was divided by six sectors (I: North-East China, II: East China, III: Yellow Sea, IV: Korea Peninsular, V: East Sea, and VI: South Sea and Western part of Japan). The considerable result showed that particularly high AOT contribution was observed over sector I (32.5%) and II (25.5%) where some major urban and industrialized areas and agricultural fields are located and other cases were observed 13.2%, 14.6%, 7.1%, 7.0% over sector III, IV, V, and VI, respectively. In addition, yearly AOT changes based on seasons are observed differently at each sector but increasing trends reveal in summer and fall over all sectors.

• 한국농림기상학회지
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• 제11권4호
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• pp.185-191
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• 2009

여름을 제외한 다른 계절의 온난화 혹은 일 최저기온에 대한 온실효과와 도시열섬효과에 관한 연구가 활발히 수행되었던 것에 비하면 여름철의 기온상승, 특히 일 최고기온의 상승에 대한 연구는 미흡하다. 최근 25년간 전국 18개 지점에서 관측된 우리나라의 여름철(6-8월) 일 최고기온 변화를 조사하고 그 변화에 미친 일사량의 영향을 분석한 결과, 평년(1971-2000)에 비해 하루 평균 일사량은 $0.61MJ\;m^{-2}$ 증가하였으며 같은 기간 일 최고기온은 $0.1^{\circ}C$ 상승한 것으로 확인된다. 이 기간 중 일사량의 연차변이는 여름 최고기온 연차변이의 65%를 설명할 수 있었다. 일사량의 증가는 대기투과율의 증가에 기인하며 대기투과율의 증가는 에어로졸 농도 특히 아황산가스 농도 감소 때문인 것으로 판단된다. 1999년부터 2007년까지 여름철 아황산가스 농도가 계속 감소해왔는데 이와 같은 경향이 앞으로도 지속된다면 대기투과율 증가 및 이에 따른 일사량 증가와 증가된 일사량으로 인한 최고기온 상승을 예상할 수 있다.

• 한국대기환경학회지
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• 제31권3호
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• pp.239-254
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• 2015

Little information on HUmic-Like Substances (HULIS) in ambient particulate matter has been reported yet in Korea. HULIS makes up a significant fraction of the water-soluble organic mass in the atmospheric aerosols and influence their water uptake properties. In this study 24-hr $PM_{2.5}$ samples were collected between December 2013 and October 2014 at an urban site in Gwangju and analyzed for organic carbon (OC), elemental carbon (EC), water-soluble OC (WSOC), HULIS, and ionic species, to investigate possible sources and formation processes of HULIS. HULIS was separated using solid phase extraction method and quantified by total organic carbon analyzer. During the study period, HULIS concentration ranged from 0.19 to $5.65{\mu}gC/m^3$ with an average of $1.83{\pm}1.22{\mu}gC/m^3$, accounting for on average 45% of the WSOC (12~ 73%), with higher in cold season than in warm season. Strong correlation of WSOC with HULIS ($R^2=0.91$) indicates their similar chemical characteristics. On the basis of the relationships between HULIS and a variety of chemical species (EC, $K^+$, $NO_3{^-}$, $SO_4{^{2-}}$, and oxalate), it was postulated that HULIS observed during summer and winter were likely attributed to secondary formation and primary emissions from biomass burning (BB) and traffics. Stronger correlation of HULIS with $K^+$, which is a BB tracer, in winter ($R^2=0.81$) than in summer ($R^2=0.66$), suggests more significant contribution of BB emissions in winter to the observed HULIS. It is interesting to note that BB emissions may also have an influence on the HULIS in summer, but further study using levoglucosan that is a unique organic marker of BB emissions is required during summer. Higher correlation between HULIS and oxalate, which is mainly formed through cloud processing and/or photochemical oxidation processes, was found in the summer ($R^2=0.76$) than in the winter ($R^2=0.63$), reflecting a high fraction of secondary organic aerosol in the summer.