Different HONO Sources for Three Layers at the Urban Area of Beijing

• DOI: 10.1021/acs.est.0c02146
• Publication Date: 2020-09-14T11:48:55Z
• Authors: Wenqian Zhang; Shengrui Tong; Chenhui Jia; Lili Wang; Baoxian Liu; Guiqian Tang; Dongsheng Ji; Bo Hu; Zirui Liu; Weiran Li; Zhen Wang; Yang Liu; Yuesi Wang; Maofa Ge
• Keywords: Aerosols; Atmosphere; Hydroxyl Radical; 13. Climate action; Beijing; 11. Sustainability; Nitrous Acid; 01 natural sciences; 0105 earth and related environmental sciences

Gaseous nitrous acid (HONO) is a crucial precursor of the hydroxyl (OH) radical, which is a "detergent" in the atmosphere. Nowadays, HONO formation mechanisms at polluted urban areas are controversial, which restricts the understanding of atmospheric oxidative capacity and radical cycling. Herein, multiday vertical observation of HONO and NOx was simultaneously performed at three heights at the urban area of Beijing for the first time. The vertical distribution of HONO was often unexpected, and it had the highest HONO concentration at 120 m, followed by those at 8 and 240 m. 0D box model simulations suggest that ground and aerosol surfaces might play similar roles in NO2 conversion at 8 m during the whole measurement. NO2 conversion on aerosol surfaces was the most important HONO source aloft during haze days. At daytime, a strong missing HONO source unexpectedly existed in the urban aloft, and it was relevant to solar radiation and consumed OH.