深圳大气中亚硝酸和甲醛的四季污染特征

Pollution characteristics of nitrous acid and formaldehyde during the four seasons in Shenzhen

亚硝酸(HONO)和甲醛(HCHO)光解是大气中羟基(OH)自由基的重要来源,强烈影响臭氧生成.为了探究大气中HONO和HCHO的污染特征,于2022年1月~2023年9月在中国深圳市开展了对HONO和HCHO的长期观测.结果表明,观测期间深圳市四季HONO平均浓度呈现出冬季(0.71×10^(-9))>秋季(0.64×10^(-9))>春季(0.59×10^(-9))>夏季(0.49×10^(-9)),HCHO平均浓度呈现出夏季(3.79×10^(-9))>秋季(2.74×10^(-9))>冬季(2.44×10^(-9))>春季(2.13×10^(-9)).HONO四季日变化均呈现明显的昼夜变化趋势,存在白天谷值和夜间峰值,还会在早晚高峰时期受到交通排放源的影响,HCHO则呈现较明显的日间单峰型的日变化特征,光化学生成特征突出.对OH自由基贡献的分析表明,HONO光解是深圳市OH自由基产率的主要贡献者(60%),并且对清晨的光化学反应活性有明显的促进作用,特别是在冬季;而HCHO则在夏季和午间发挥了相对更重要的作用.因此,通过有效控制HONO和HCHO可以降低大气氧化性,从而有助于控制O3污染.

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.