Aerosol pollutants during agricultural biomass burning: A case study in Ba Vi Region in Hanoi, Vietnam

Impact of traditional biomass burning activities on regional air quality is a major environmental concern. Measurement campaigns were performed during post-harvesting activities in the Ba Vi region in Hanoi in May–June of 2015 and 2016. To quantify the source for regional haze the sampling of rice straw burning emissions was performed on fields. Carbonaceous (OC, EC, BrC) fractions, heavy metals, organic and ionic composition, and microstructure were characterized. A set of functionalities (hydroxyl, aliphatic, carbonyl, carboxylate, and nitro groups) revealed a functional marker of pile combustion. Optical, microstructural, and chemical analyses of environmentally-dangerous pollutants from traffic and cooking sources provided characteristics and functional markers of different pollution sources. Chemical features of rice straw burning were identified on the Ba Vi site during the haze episode of 2015, when PM10 mass approached the high smoke intensity, up to 167 μg m–3. Small-scale meteorology affected PM10, OC and EC, and ion mass in days of highest relative humidity and fogs. In days of highest smoke OC dominated PM10 mass by up to 42%, the OC/EC ratio approached 20, in line with observations of mainly smoldering emissions across the fields. Spectral features of regional haze smoke demonstrated the absorption of rice straw burning whereas the impact of biogenic, traffic, and cooking sources were significantly lower. Individual particle analyses showed carbonaceous particles internally/externally mixed with inorganic fly ash and dust. Smoke micromarkers revealed the microstructure of regional aerosols representative for Southeast Asia in BB periods. Significantly lower PM10 mass concentrations and strong difference in aerosol composition before post-harvesting activities suggested that agricultural burning represents a large contribution to air quality degradation in the rural area of Vietnam.