Air pollution, particularly biomass burning (BB)–derived particulate matter (PM), remains a major challenge in Southeast Asia, affecting atmospheric processes, climate, human health, and socio-economic systems. This study presents the chemical characterization and source contributions of PM
0.49
at a rural site along the Thailand–Myanmar border in 2023. PM
0.49
concentrations showed pronounced temporal variability, with smoke-haze (SH) concentrations (67.9 ± 46.0 µg/m
3
) nearly six times higher than those during non-haze periods (non-SH; 10.9 ± 4.4 µg/m
3
). Organic carbon (OC) dominated during SH, accounting for 46% of PM
0.49
mass, followed by secondary inorganic aerosols (SO
4
2−
, NO
3
−
, NH
4
+
; 13%) and BB tracers such as K
+
(1.4%) and levoglucosan (2.7%), indicating strong BB influence. K⁺ exhibited strong correlations with levoglucosan (
r
= 0.95) and major anions (
r
= 0.52–0.94), highlighting its dual role as both a neutralizing cation and a BB tracer in both fresh and aged BB aerosols. Elevated OC to elemental carbon ratios (OC/EC; 13.4 ± 4.6) and char-EC/soot-EC ratios (9.68 ± 4.82) indicate smoldering BB as the principal source. Positive matrix factorization attributed 57% of PM
0.49
to BB during SH (up to 69% during peak phase), whereas soil dust dominated during non-SH conditions (70%). Backward trajectories and fire hotspot analyses suggest substantial cross-border transport from Myanmar. Furthermore, the seasonal shift in the effective carbon ratio (ECR), from 0.63 (SH) to 1.13 (non-SH), indicates a transition from light-absorbing to light-scattering aerosol dominance, underscoring the role of PM
0.49
in aerosol transformation under BB influence. These findings suggest air quality and potential climate implications, supporting coordinated mitigation.
In the summer of 2023, comprehensive observations and analyses of water-soluble components in atmospheric aerosols (PM2.5 and TSP) were conducted over the Bohai Sea and Yellow Sea. The study area was jointly influenced by terrestrial anthropogenic emissions and marine biological activities. The total water-soluble ion (WSI) concentrations averaged 4.09 ± 1.79 μg/m
3
in PM2.5 and 4.26 ± 2.14 μg/m
3
in TSP, which were significantly lower than those in inland cities but markedly higher than those in remote oceanic regions. Among these, secondary inorganic ions (SNA: SO
4
−2
, and NH
4
+
) were the dominant WSI components, accounting for 53.4% of the total WSIs in PM
2.5
. Correlation analysis revealed that WSIs showed significant correlations with sea-salt tracer ions (Na
+
) and anthropogenic tracers (K
+
and NO
3
−
), reflecting the combined effects of terrestrial inputs and marine biogenic emissions.
This study characterizes the chemical and optical properties of carbonaceous aerosols in urban Chiang Mai, Thailand, during an intensive monitoring period in March 2024. The campaign coincided with a strong El Niño event, resulting in extreme high temperatures and severe drought conditions. The mean PM2.5 concentration was 64.3 µg/m³, exceeding the WHO 24-hour guideline (15 µg/m³) by approximately 4.3 times. High OC/EC ratios (mean 6.0) and a strong correlation with CO (R = 0.71, 924.5 ppb) indicated a strong influence of biomass burning on particulate air quality, while urban baseline emissions also contributed. Furthermore, severe nighttime atmospheric stagnation trapped pollutants, exacerbating high-concentration episodes. Source apportionment via an Aethalometer model revealed that biomass burning-derived black carbon (BCbb) drove the overall variability during these episodes. Notably, brown carbon (BrC) significantly enhanced shortwave light absorption at 370 nm, accounting for a campaign mean contribution of 35.1% and reaching an hourly maximum of 50.5% during the high-concentration episode. The strong correlation (R = 0.99) between BrC absorption and BCbb mass concentration, despite shared optical input data, further reflects the dominant influence of biomass burning on shortwave light absorption. These results highlight how anomalous meteorological conditions—co-occurring with the regional 2024 El Niño background—coincided with intensified biomass burning and enhanced light absorption, providing insights into aerosol optics under extreme dry season weather. The findings emphasize the imperative need for integrated strategies to mitigate the escalating synergy between climate change and regional air quality. Size-resolved black carbon characteristics, chemical composition, and brown carbon light absorption in the Chiang Mai basin during the 2024 El Niño event. Size-resolved black carbon characteristics, chemical composition, and brown carbon light absorption in the Chiang Mai basin during the 2024 El Niño event.
In-Ho Song, Jong Sung Park, Soyoung Jung et al.· Asian Journal of Atmospheric...· 0 citations
Ambient particulate matter ≤2.5 μm (PM2.5) is a major public health concern in rapidly urbanizing cities such as Lagos, Nigeria, where emissions from diverse anthropogenic sources contribute to poor air quality. However, source-specific information for Lagos remains limited. PM2.5 sources were apportioned using EPA-PMF applied to a 12-month data set (August 2020–July 2021) of 24-h samples collected every third day at six sites. The top 30% of filters by mass concentration were chemically speciated. Mean PM2.5 concentration was 68 μg/m3. Eleven factors were resolved: Dust (27.86%) the dominant source; Diesel Exhaust (16.98%), Pb-Battery Recycling (12.74%), Sulfate (8.70%), Open Waste Burning (8.30%), 2-Stroke Exhaust (7.25%), and Galvanizing (6.13%). Small contributors were E-Waste Processing (3.58%), Cooking Aerosol (3.34%), Gasoline Exhaust (2.63%), and Secondary Nitrate (2.48%). Integrated statistical modeling and meteorological analyses showed that PM2.5 variation was governed by source-specific meteorological controls. Four factors─Dust, Open Waste Burning, Sulfate, and Secondary Nitrate─were directly influenced by meteorology through transport, scavenging, dispersion, and gas–particle chemistry, respectively. Diesel Exhaust was the largest local source and independent of meteorology. These findings highlight that effective PM2.5 mitigation in Lagos requires source-specific control strategies. Priority actions include reducing fossil-fuel generator use, enforcing industrial emissions controls, and upgrading vehicles.
Adebola A. Odu-Onikosi, P. Hopke, I. Stanimirova et al.· ACS ES&T Air· 1 citation
