Impact of Smoke Intensity on Size-Resolved Aerosol Composition and Microstructure during the Biomass Burning Season in Northwest Vietnam

Abstract

Aerosol particles significantly impact the regional environment, including climate change, specifically in periods of extensive biomass burning. The major agricultural and domestic combustion emission sources were assessed in nearsource and ambient monitoring campaigns in northwestern Vietnam during the dry season. The composition and microstructure of on-field burning and cooking emissions were analyzed with a variety of techniques. A wide range of observed PM 2.5 mass concentrations was categorized according to the smoke level, supported by the evolution of carbon fractions (OC and EC) as well as ionic species and molecular tracers (K + , levoglucosan, and mannosan). The OC/EC and individual organic compound ratios on days with high smoke levels indicate smoldering combustion of softwood and other local biomass species, impacting aerosol composition at the regional level. Acid and non-acid carbonyls, carboxylates, and aliphatic carbon functionalities in the PM 2.5 size fraction evolved with increasing smoke intensity, together with carbonates in coarse (PM 1-2.5 and PM 2.5-10 ) size fractions, indicating a large impact of smoke emissions and soil lifted up by the intense fires. Biomass burning influence increased the abundance of soot and organic particles in the submicron fraction from 12% at low to 59% and 68% at moderate and high smoke levels, respectively. Smoke micromarkers of local biomass burning source emissions determined the microstructure of ambient aerosols representative for northern Southeast Asia.

Aerosol Pollutants during Agricultural Biomass Burning: A Case Study in Ba Vi Region in Hanoi, Vietnam

“…Prominent bands relate to aliphatic C-C-H ) and carbonates CO 3 2-in various salts. The whole functional pattern of rice straw burning aerosol obtained on fields in the Ba Vi region demonstrates similar features to emissions from on-field cassava and corn bush burning in Son La province (Popovicheva et al, 2016) due to dominant impact of similar burning practices used by farmers on agricultural fields. It is noteworthy that intensive hydrophilic O-H functionalities are explicitly characteristic of rice straw burning emissions.…”

“…This group is representative of the smoldering phase, and was found to comprise 60% of smoke particles in a combustion chamber (Popovicheva et al, 2015c) and can serve as micromarker of smoldering BB. In on-field emissions in Son La province the abundance of Group Organic was 58% (Popovicheva et al, 2016). Other particles produced during rice straw burning are rich in soil minerals, which are evolved by hot convection during fires (Kavouras et al, 2012).…”

“…According to classification of smoke during BB periods (Popovicheva et al, 2016), PM 2.5 mass ranged from low levels ≤ 40 µg m -3 to moderate ~80 µg m -3…”

“…Aerosol composition relates to combustion phase (open flaming vs. smoldering) and type of biomass (Engling et al, 2009;Popovicheva et al, 2015a). Distinct regional characteristics in BB smoke have been observed, suggesting that local emissions dominate aerosol chemistry (Engling et al, 2011;Lim et al, 2012), while transport from wildfire sources impacts the composition of aged aerosols (Diapouli et al, 2014;Engling et al, 2014;Popovicheva et al, 2016). Specifically, BB may profoundly affect air quality and public health in urban areas, indicating smoke as an indicator of harmful pollution (Amiridis et al, 2012;Popovicheva et al, 2014a).…”

“…Major agricultural and domestic emissions from remote sources were assessed in near-source and ambient campaigns in the Son La province, northwestern Vietnam (Popovicheva et al, 2016). Measurements of sizesegregated OC, EC, organic/inorganic composition, molecular markers, and microstructure revealed the major features of BB in ambient aerosols.…”