• Journal of Korean Society for Atmospheric Environment
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• v.17 no.5
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• pp.375-384
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• 2001

Optical remote sensing techniques are particularly advantageous over the conventional fixed point methods because with these methods large-area monitoring can be possible and sample preparation difficulties are avoidable. Instruments based on the differential optical absorption spectroscopy (DOAS) technique are widely used for monitoring air pollutants in urban areas in recent years. In this study, $O_3$, SO$_2$, NO$_2$, and VOCs (benzene, toluene, xylene, and styrene) are measured continuously at Sihwa industrial area using a DOAS from February to November. 1999. Intercomparison between the DOAS method and the conventional methods (filed point samplers for $O_3$, NO$_2$, and SO$_2$, and adsorbent sampling methods and gas chromatography for VOCs) are performed simultaneously at the same site. The time series of the DOAS data and that of fixed point method show good match at the view point of the tendency, but the absolute concentration values of these two methods differ quite a lot from each other; correlation coefficients shows 0.78 for $O_3$and 0.97 for SO$_2$. However, the results of VOCs measurements are not quite satisfactory ; the spectral interference with $O_2$and $O_3$appears to be the major cause of the errors for VOCs .

• Journal of the Optical Society of Korea
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• v.1 no.1
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• pp.15-18
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• 1997

Intensity dependent dynamics of photoinduced absorption in $CdS_{0.4}$/$Se_{0.6}$ semiconductor doped glasses below the band gap was investigated by using time-resolved differential transmittance spectroscopy. The carriers populated through ultrafast trapping at semiconductor-glass interfaces give rise to a broad photoinduced absorption below the band gap. The decay time of transient absorption depends strongly on the excitation intensity. Based on our results, the physical mechanism for photoinduced absorption processes was suggested.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.302-305
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• 2007

During the CareBeijing campaign in September 2006, Imaging Differential Optical Absorption Spectroscopy (IDOAS) measurements were made over the city of Beijing, China using a spatial resolution of 146 pixels horizontally and 61 pixels vertically, each with a field of view of $0.133^{\circ}$ and $0.072^{\circ}$ in the horizontal and vertical directions, respectively. Using Fraunhofer reference spectra (FRS) for the evaluation of data for two consecutive days, the diurnal variation of $NO_2$ distributions was determined from data measured every single hour from 08:00 until 16:00 on September 9 and 10. Both days presented a fairly clear sky with high visibility. The setup allowed detailed images of the low surface $NO_2$ distribution over Beijing. Images with less than a 30-min temporal resolution showed variation of plume dispersal in both horizontal and vertical directions. An in-situ measurement was also conducted. Results from both instruments are interpreted by considering local emission sources and wind conditions.

• Korean Journal of Remote Sensing
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• v.39 no.5_1
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• pp.551-561
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• 2023

In this study, we investigated the effects of the spectral fitting window and absorption cross-section on the retrieval of the formaldehyde (HCHO) slant column density (SCD) from the direct-sun measurement of pandora spectrometer system using differential optical absorption spectroscopy (DOAS). Pandora Level 1 data observed at Yonsei University in Seoul from October 12 to 31, 2022 were used. The HCHO column density was retrieved under eight ranges including the spectral fitting window used in the Second Cabauw Intercomparison campaign for Nitrogen Dioxide measuring Instruments (CINDI-2) and seven types of absorption cross-section composition. The spectral fitting window was selected from 336.5 to 359.0 nm with minimum residual and HCHO SCD error. When the nitrogen dioxide (NO2) absorption cross-section at 220 K was added to the cross-section composition used in the CINDI-2 campaign among seven types, the residual and HCHO SCD error were the smallest and the HCHO column density wasstably retrieved. The average HCHO SCD with the highest retrieval accuracy and the values retrieved under other conditions differed from a minimum of 4% to a maximum of 40%.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2008.04a
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• pp.432-433
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• 2008

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2007.10a
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• pp.67-68
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• 2007

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2004.05a
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• pp.181-182
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• 2004

• Proceedings of the KSRS Conference
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• 2006.03a
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• pp.121-124
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• 2006

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2000.04a
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• pp.328-329
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• 2000

대단위 공단이나 대도시 등의 환경오염물질의 배출이 심각한 지역이 증가함에 따라 다양한 종류의 대기오염물질이 배출되고 이에 따른 효율적 관리가 필요하게 되었다. 현재 유해가스의 검출방식은 촉매와의 반응을 이용한 화학적 측정방법으로부터 유해가스의 광학적 성질을 이용한 광학적 측정방법으로 그 기술이 발전되고 있다. 본 연구에서는 광투과 방식 중 Differential Optical Absorption Spectroscopy(DOAS)를 사용했으며 이는 실시간 오염물질의 이동 경로나 오염원을 찾을 수 있다. (중략)

• Bulletin of the Korean Chemical Society
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• v.35 no.4
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• pp.1191-1194
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• 2014

Imaging Differential Optical Absorption Spectroscopy (Imaging-DOAS) has been utilized in recent years to provide slant column density (SCD) distributions of several trace gas species in the plume. The present study introduces a new method using Imaging-DOAS data to determine two-dimensional plume structure from the plume emissions of power plant in conditions of negligible aerosol effects on radiative transfer within the plume. We demonstrates for the first time that two-dimensional distributions of sulfur dioxide ($SO_2$) and nitrogen dioxide ($NO_2$) in power plant emissions can be determined simultaneously in terms of SCD distribution. The $SO_2$ SCD values generally decreased with increasing distance from the stack and with distance from the center of the plume. Meanwhile, high $NO_2$ SCD was observed at locations several hundred meters away from the first stack due to the ratio change of NO to $NO_2$ in NOx concentration, attributed to the NO oxidation by $O_3$. The results of this study show the capability of the Imaging-DOAS technique as a tool to estimate plume dimensions in power plant emissions.