Stable carbon and nitrogen isotopic compositions of fine aerosols (PM2.5) during an intensive biomass burning over Southeast Asia: Influence of SOA and aging. (October 2018)

• Record Type: Journal Article
• Authors: Boreddy, Suresh K.R.; Parvin, Fahmida; Kawamura, Kimitaka; Zhu, Chunmao; Lee, Chung-Te
• Is Part Of: Atmospheric environment. Volume 191(2018)
• Page Start: 478
• Page End: 489
• Publication Date: 2018-10
• Subjects: Biomass-burning -- PM2.5 -- C3 plants -- Southeast Asia -- δ13CTC -- δ15NTN; Air -- Pollution -- Periodicals; Air -- Pollution -- Meteorological aspects -- Periodicals; 551.51
• DOI: 10.1016/j.atmosenv.2018.08.034
• Languages: English
• ISSNs: 1352-2310

Abstract

Abstract: The present study reports on total carbon (TC) and nitrogen (TN) and their isotope ratios in PM2.5 (particulate matter ≤ 2.5 μm in aerodynamic diameter) collected at Dai Ang Khang (DAK; 19.93°N, 99.05°E; 1518 m above sea level), Thailand, during March 1 to April 13, 2015, when biomass-burning (BB) was intense in Southeast Asia (SEA), particularly in Myanmar. Concentrations of TC and TN varied from 1.4 to 80 μgC m −3 (mean: 33.8 ± 21.7 μgC m −3 ) and 0.7 to 8.6 μgN m −3 (3.0 ± 1.6 μgN m −3 ), respectively. Temporal variations of TC and TN largely increased from the start of the campaign to March 21 and decreased during March 22–28 and then slightly increased during the period of March 28-April 13. This temporal pattern was consistent with variations of levoglucosan (LG, specific tracer of biomass burning) and MODIS (moderate resolution imaging spectroradiometer)-derived fire spots in SEA, suggesting that BB emissions are major sources of PM2.5 aerosols at DAK. This inference was further supported by higher TC/TN ratios (range: 6–19, mean: 12.7 ± 3.3) and significantly strong positive correlations among TC, TN, and LG during the campaign period. On the other hand, stable isotope ratios of total carbon (δ 13 CTC ) and nitrogen (δ 15 NTN ) in PM2.5 ranged during the sampling period from −23.8 to −29.8‰ (−26.0 ± 1.2‰) and from +15.8 to +25.1‰ (19.4 ± 2.1‰), respectively. The estimated contribution from the burning of C3 plants to TC ranged between 60 and 96% (average, 74 ± 7%) in SEA, indicating the predominance of BB from forest fires. Interestingly, lower δ 13 CTC values were associated with higher contribution of C3 plants, suggesting that primary aerosols derived from the burning of C3 plants caused a depletion of 13 CTC, whereas photochemical aging of organic aerosols may have enhanced δ 13 CTC, particularly in the second half of the campaign. In addition, changes in meteorological conditions and MODIS fire events may also have caused the changes in δ 13 CTC during the campaign period. The δ 13 CTC values reported in this study represent the typical BB aerosols. Our findings improve the fundamental understanding of the sources and transformation processes of atmospheric aerosols in SEA and its outflow regions. Highlights: Biomass burning emissions are major sources of PM2.5 at DAK, Thailand. The background value of δ 13 CTC at DAK was −26.04 ± 0.03‰. The estimated contribution of C3 plants burning to TC ranged 60–96%. The depletion of 13 CTC associated with aerosols from the burning of C3 plants.