Morphological and Elemental Classification of Freshly-Emitted Individual Particles From Field and Laboratory Residential Biomass Burning

Residential biomass burning significantly contributes to air pollution in developing countries. However, the microscopic properties of individual particles in their emissions have not been well understood. In this study, individual primary particles from 14 kinds of biomass fuels (including firewood, crop residue, and animal dung) were collected in laboratory and field measurements, and their morphology, composition and mixing state were acquired using transmission electron microscope. These results constitute a source profile database of individual primary particles from residential biomass burning. The database reveals that different types of biomass fuels exhibit different emission characteristics, that is, residential firewood burning mainly emits pure carbonaceous particles (including organic matter (OM) and soot particles), crop residue burning mainly emits K-containing particles (including OM-K, soot(-OM)-K, and K-rich particles), and animal dung burning mainly emits pure carbonaceous particles and K-containing particles. Moreover, our results indicate that the emission characteristics obtained from laboratory and field measurements are different. Field measurements conducted in two selected villages in North China Plain exhibit a higher presence of soot particles compared to laboratory measurements, owing to their higher combustion temperatures. In contrast, field measurements conducted in one selected village in Qinghai-Tibet Plateau contain less soot particles than those from laboratory measurements in plain areas, due to the deficient oxygen supply during combustion process in the high-altitude regions. These results warn us that the emission estimation from residential biomass burning should notice the large emission differences among different biomass types and between field and laboratory measurements. Biomass fuel is an important household energy for cooking and heating in the rural regions in developing countries. However, biomass fuel burned in the residential stoves can emit large amount of air pollutants, which could adversely influence air quality, human health, and global climate. To investigate these adverse effects, understanding the microscopic properties of individual primary particles from residential biomass burning is the crucial step, but there is limited information on these microscopic properties. To fill the gaps, we acquired the morphology, composition, and mixing state of individual particles from firewood, crop residue, and animal dung burning using field and laboratory measurements. We found these three types of biomass fuels exhibit obviously different emission characteristics, and emissions from laboratory and field measurements are also different. Moreover, we found that compared to the laboratory biomass burning, field biomass burning conducted in the selected villages in the low-altitude regions can emit more soot particles, while it in the high-altitude regions can emit more organic matters but less soot particles. These emission differences warn us that more field measurements in different regions should be investigated in the future studies. A source profile database of individual primary particles from residential biomass burning was established Different types of biomass fuels exhibit distinctly different emission characteristics Emission characteristics of field and laboratory residential biomass burning are different