Biomass Burning Is a Non‐Negligible Source for Ammonium During Winter Haze Episodes in Rural North China: Evidence From High Time Resolution <sup>15</sup>N‐Stable Isotope
Xinxin Feng, Yingjun Chen, Huiyun Du, Yanli Feng, Yujing Mu, Jianmin Chen
Abstract
Abstract The refined source apportionment of ammonium (NH 4 + ), especially for biomass burning emissions, is unclear. Hourly resolution δ 15 N‐NH 4 + values for three winter haze episodes (EP1–EP3) were determined in the North China Plain (NCP) in 2019 to identify and quantify the contribution of biomass burning. A reasonable source‐resolved structure of NH 4 + was obtained after using the corrected source signatures of 15 N and considering biomass burning emissions. The time‐series variation in biomass burning and vehicle sources identified by δ 15 N was more reasonable and matched better with their tracers (e.g., levoglucosan). The non‐negligible contribution of biomass burning in the NCP was found and contributed 13.0% ± 11.4% to NH 4 + in haze episodes, but in special stages was as high as 29% ± 11% in local emission of EP1 and 23% ± 15% in southwest transportation of EP2. The redistribution of NH 4 + sources further emphasize the contribution of biomass burning to haze episodes, as its contribution to PM 2.5 increased up to 5% (without considering SO 4 2− and NO 3 − ). Considering NH 4 + uniqueness in the formation of new particles, the role of biomass burning during haze episodes should be considered. This study indicates that further studies need to be conducted to reduce biomass burning emissions in the NCP.