Pollution characteristics of nitrous acid and formaldehyde during the four seasons in Shenzhen
JIANG Zhen1, TANG Meng-xue1, SHAO Yu-ming1, CAO Li-ming1, HE Li1, LIAO Song-di2, ZHU Man-ni2, HUANG Xiao-feng1, HE Ling-yan1
1. Laboratory of Atmospheric Observation Supersite, School of Environment and Energy, Peking University Shenzhen Graduate School, Shenzhen 518055, China; 2. Institute for Environmental and Climate Research, Jinan University, Guangzhou 511443, China
Abstract：The photolysis of nitrous acid (HONO) and formaldehyde (HCHO) is a critical source of hydroxyl (OH) radicals in the atmosphere, significantly impacting ozone generation. In order to explore the pollution characteristics of HONO and HCHO, long-term observations were conducted in Shenzhen, China, from January 2022 to September 2023. The results showed that the average concentration of HONO in Shenzhen during the observation period was highest in winter (0.71×10-9), followed by autumn (0.64×10-9), spring (0.59×10-9) and summer (0.49×10-9) and the average concentration of HCHO was highest in summer (3.79×10-9), followed by autumn (2.74×10-9), winter (2.44×10-9) and spring (2.13×10-9). The diurnal variation of HONO showed a similar trend throughout the four seasons, with daytime valleys and nighttime peaks. It was also affected by traffic emissions during the morning and evening rush hours. HCHO showed a more obvious diurnal unimodal characteristics and prominent photochemical generation characteristics. OH radical budget analysis showed that HONO photolysis was the main contributor (60%) to OH radical production in Shenzhen, and it had a significant promoting effect on the early morning photochemical reaction, particularly in winter, while HCHO played a more important role in summer and at noon. Therefore, by effectively controlling HONO and HCHO, atmospheric oxidation capacity can be reduced, which helps to control O3 pollution.
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