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Author: search.filters.author.Morris, JohnSubject: search.filters.subject.Southeast Asia

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    Seasonal Field Calibration of Low-Cost PM2.5 Sensors in Different Locations with Different Sources in Thailand
    (2023-03-01)
    Dejchanchaiwong, Racha
    ;
    Tekasakul, Perapong
    ;
    Saejio, Apichat
    ;
    Limna, Thanathip
    ;
    Le, Thi Cuc
    Low-cost sensors (LCS) have been increasingly deployed to monitor PM<inf>2.5</inf> concentrations. More than 1500 LCS have been installed in Thailand to increase public awareness of air quality. However, performance of these sensors has not been systematically investigated. In this study, PM<inf>2.5</inf> LCS were co-located next to a PM<inf>2.5</inf> federal equivalent method (FEM) reference instrument at three Thai locations—in the north, center and northeast. We evaluated the performance of a PM<inf>2.5</inf> LCS (PMS7003, Plantower) to understand the key factors affecting performance, including emission sources, relative humidity, temperature and PM<inf>2.5</inf> concentration. Low PM concentration and high humidity levels had a significant impact on performance. Sensors in a high traffic emission area showed low correlation. The unadjusted PM<inf>2.5</inf> LCS performance varied with locations. Errors were mainly observed at low concentrations. They significantly underestimated concentrations in congested urban environments. After calibration, accuracy was improved with multiple regression models. The performance of sensors only at Chiang Mai (CM) during the dry season and Ubon Ratchathani (URT) during the dry and wet seasons were acceptable with coefficient of variation: 5.8 ± 4.7–6.8 ± 5.0%, slope: 0.829–0.945, intercept: 1.12–5.49 µg/m<sup>3</sup>, R<sup>2</sup>: 0.880–0.934 and RMSE: 4.3–5.1 µg/m<sup>3</sup>. In the congested area in Bangkok (BKK), they underestimated concentrations of small particles.
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    Estimation of Ultrafine Particulate Matter Emissions from Biomass Burning Using Satellite Imaging and Burn Severity
    (2023-01-01)
    Tekasakul, Perapong
    ;
    Nuthammachot, Narissara
    ;
    Malinee, Rachane
    ;
    Morris, John
    ;
    Dejchanchaiwong, Racha
    Fine and ultrafine particles emitted from open biomass burning seriously affect air quality in many countries in Southeast Asia during haze episodes. In this study, PM<inf>0.1</inf> and PM<inf>2.5</inf> emissions were estimated for Thailand using agricultural residue burning. Data from Landsat-8 and Sentinel-2 satellites was obtained from 2016 to 2019. Burn severity was evaluated using NIR and SWIR bands. Results suggested agricultural residue burning as a significant contributor accounting for 82-90% of the total burned area, and the forest fires contributed the remainder. Further, the burned areas from agricultural waste during El Niño years were up to 2 times as high as those during La Niña years. Rice residue burning was the most significant contributor, followed by sugarcane and maize. Major burned areas of rice and sugarcane residue were in the northeast. Annual average PM<inf>2.5</inf> and PM<inf>0.1</inf> emissions from crop residue burning in Thailand were about 43.3 and 4.1 Gg/year, respectively. PM<inf>0.1</inf> emissions during El Niño years were also larger at 4.2-5.2 Gg/year compared to 3.7-3.4 Gg/year during La Niña. PM<inf>0.1</inf> emissions from crop residue burning were about 10% of PM<inf>2.5</inf>. These emissions affect local air quality in Thailand and neighboring countries due to long-range transport and vice versa. Annual mean PM<inf>0.1</inf> concentrations during the open biomass burning period ranged from 6.6 to 18.9 µg/m<sup>3</sup>. PM<inf>0.1</inf>-bound PAH concentrations were found to be 3-8 times higher than the background. The study highlights the estimation of fine and ultrafine particle emissions from open biomass burning useful for other researchers.