Impacts of an unknown daytime HONO source on the mixing ratio and budget of HONO, and hydroxyl, hydroperoxyl, and organic peroxy radicals, in the coastal regions of China
Impacts of an unknown daytime HONO source on the mixing ratio and budget of HONO, and hydroxyl, hydroperoxyl, and organic peroxy radicals, in the coastal regions of China
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DOI：
10.5194/acp-15-9381-2015
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发表时间：
2015-08
影响因子：
6.3
通讯作者：
Yujing Tang;Junling An;Fuhui Wang;Y. Li;Yu Qu;Yu Chen;Jian Lin
中科院分区：
文献类型：
--
作者：
Yujing Tang;Junling An;Fuhui Wang;Y. Li;Yu Qu;Yu Chen;Jian Lin
抽象。许多野外实验发现白天城市和农村地区的亚硝酸（HONO）混合比都很高，但这些高的白天HONO混合比不能很好地用气相产生、HONO排放和夜间气溶胶上二氧化氮（NO2）的水解转化来解释，这表明可能存在未知的白天HONO源（Punknown）。利用地球仪13个野外试验的观测数据，得到了Punknown a 19.60[NO2] · J（NO2）的计算公式。三个额外的HONO源（即，将Punknown、夜间NO2在气溶胶上的水解转化率和HONO排放量）耦合到WRF-Chem模式中，评估了Punknown对中国沿海地区HONO和过氧（羟基、氢过氧基和有机过氧基）自由基（ROx）（= OH + HO 2 + RO 2）浓度和收支的影响。结果表明，额外的HONO源产生了显着改善HONO和OH模拟，特别是在白天。中国沿海地区的白天平均Punknown值较高，京津冀地区最高为2.5 ppb h−1。Punknown使中国沿海主要城市近地面的OH、HO_2和RO_2增加了60- 250%，使1000 m以上的白天大气平均混合比增加了5- 48%。当这三个额外的HONO来源被包括在内时，HONO的光解是北京、上海和广州在10：00 LST之前OH产生速率的第二大来源，在北京最大为3.72 ppb h− 1，相应的Punknown贡献为3.06 ppb h−1，而HO 2 + NO（一氧化氮）的反应在10：00 LST之后占主导地位，在北京最大为9.38 ppb h−1，相应的Punknown贡献为7.23 ppb h−1。三种HONO源对整个ROx循环都有加速作用，尤其是Punknown。白天的平均OH产生速率由于三个额外的HONO来源而增加了0.67; [0.64]，由于P未知，通过HO 2 + NO反应增加到4.32 [3.86] ppb h−1，通过HONO的光解增加了0.49 [0.47]到1.86 [1.86] ppb h−1。在北京、上海和广州，通过OH + NO2反应，OH日间平均损失率增加了0.58 [0.55]至2.03 [1.92] ppb h−1，通过OH + CO（一氧化碳）反应，增加了0.31 [0.28]至1.78 [1.64] ppb h−1。同样，三个额外的HONO来源产生了0.31的增加[0.28]通过OH + CO的反应，从1.78 [1.64] ppb h-1（具有相应的Punknown贡献）到0.10 [0.09]到0.63 [0.59] ppb h-1（通过CH 3 O2的反应）（甲基过氧自由基）+ NO在白天的平均HO 2产生速率，和0.67 [0.61]到4.32 [4.27] ppb h−1，通过HO 2 + NO反应在白天的平均HO 2损失速率在北京，上海和广州。上述结果表明，Punknown显著增强了中国沿海地区的ROx浓度，加速了ROx循环，并可显著增加无机气溶胶和二次有机气溶胶的浓度，进一步加剧灰霾天气。
Abstract. Many field experiments have found high nitrous acid (HONO) mixing ratios in both urban and rural areas during daytime, but these high daytime HONO mixing ratios cannot be explained well by gas-phase production, HONO emissions, and nighttime hydrolysis conversion of nitrogen dioxide (NO2) on aerosols, suggesting that an unknown daytime HONO source (Punknown) could exist. The formula Punknown a 19.60[NO2] · J(NO2) was obtained using observed data from 13 field experiments across the globe. The three additional HONO sources (i.e., the Punknown, nighttime hydrolysis conversion of NO2 on aerosols, and HONO emissions) were coupled into the WRF-Chem model (Weather Research and Forecasting model coupled with Chemistry) to assess the Punknown impacts on the concentrations and budgets of HONO and peroxy (hydroxyl, hydroperoxyl, and organic peroxy) radicals (ROx) (= OH + HO2 + RO2) in the coastal regions of China. Results indicated that the additional HONO sources produced a significant improvement in HONO and OH simulations, particularly in the daytime. High daytime average Punknown values were found in the coastal regions of China, with a maximum of 2.5 ppb h−1 in the Beijing–Tianjin–Hebei region. The Punknown produced a 60–250 % increase of OH, HO2, and RO2 near the ground in the major cities of the coastal regions of China, and a 5–48 % increase of OH, HO2, and RO2 in the daytime meridional-mean mixing ratios within 1000 m above the ground. When the three additional HONO sources were included, the photolysis of HONO was the second most important source in the OH production rate in Beijing, Shanghai, and Guangzhou before 10:00 LST with a maximum of 3.72 ppb h−1 and a corresponding Punknown contribution of 3.06 ppb h−1 in Beijing, whereas the reaction of HO2 + NO (nitric oxide) was dominant after 10:00 LST with a maximum of 9.38 ppb h−1 and a corresponding Punknown contribution of 7.23 ppb h−1 in Beijing. The whole ROx cycle was accelerated by the three additional HONO sources, especially the Punknown. The daytime average OH production rate was enhanced by 0.67 due to the three additional HONO sources; [0.64], due to the Punknown, to 4.32 [3.86] ppb h−1, via the reaction of HO2 + NO, and by 0.49 [0.47] to 1.86 [1.86] ppb h−1, via the photolysis of HONO. The OH daytime average loss rate was enhanced by 0.58 [0.55] to 2.03 [1.92] ppb h−1, via the reaction of OH + NO2, and by 0.31 [0.28] to 1.78 [1.64] ppb h−1, via the reaction of OH + CO (carbon monoxide) in Beijing, Shanghai, and Guangzhou. Similarly, the three additional HONO sources produced an increase of 0.31 [0.28] (with a corresponding Punknown contribution) to 1.78 [1.64] ppb h−1, via the reaction of OH + CO, and 0.10 [0.09] to 0.63 [0.59] ppb h−1, via the reaction of CH3O2 (methylperoxy radical) + NO in the daytime average HO2 production rate, and 0.67 [0.61] to 4.32 [4.27] ppb h−1, via the reaction of HO2 + NO in the daytime average HO2 loss rate in Beijing, Shanghai, and Guangzhou. The above results suggest that the Punknown considerably enhanced the ROx concentrations and accelerated ROx cycles in the coastal regions of China, and could produce significant increases in concentrations of inorganic aerosols and secondary organic aerosols and further aggravate haze events in these regions.