Emission factors of selected air pollutants from rice straw burning in Hanoi, Vietnam

Rice straw open burning (RSOB) after harvest is one of the considerable emission sources in agricultural activities and contributed to air pollution in Vietnam. Determination of country/city-specific emission factors for air pollutants from open burning is important for the better estimation of air pollutant emission. In this research, hood experiments and field experiments were conducted simulating the common small pile burning type used by farmers in the North of Vietnam to determine emission factors (EFs) for gaseous pollutants, particulate matter (PM), and particle-bound polycyclic aromatic hydrocarbons (PAHs). The carbon_mass balance and emission ratio method were used to calculate EFs for the field experiments. The PM2.5 emission factor obtained for open field burning (34.0 ± 17.6 g kg−1 RS), the EFs for SO2 (1.4 ± 1.1 g kg−1 RS for field experiments and 1.82 ± 1.77 g kg−1 RS for hood experiments) in this study was higher in comparison with the values reported in Thailand and China. Laboratory experiments showed positive correlation between RS carbon content and EF of CO2. The higher proportion and the contribution of benzo[a]pyrene (BaP) to the total 10 detected PAHs bound to PM2.5 in RS burning smoke was the first observation in this study. Based on the EFs developed in this study, we estimated that RSOB released the amount of 369.6 Gg for CO2, 13.7 Gg for CO, 0.67 Gg for SO2, 0.35 Gg for NO2, 10.8 Gg for PM2.5, and 32 Mg for total 10 particle-bound PAHs to the atmosphere in Hanoi. These results are useful for integrated air-quality management in local as well as national scale.