北京夏季大气HONO的监测研究

在2007-08-14～2007-08-24期间，利用差分光学吸收光谱（DOAS）技术，对北京市大气中HONO、NO₂和O₃等污染物进行了连续监测，分析了HONO和NO₂的日变化特征，讨论了夜间直接排放对HONO来源的贡献，进行了24 h和夜间13 h HONO非均相反应形成与黑碳气溶胶（BC）和相对湿度（RH）等要素的相关分析.结果表明，HONO和NO₂均在01:00左右达到峰值，HONO的另一峰值浓度出现在06:00，比NO₂第2个峰值出现时间07:00早1 h；夜间（19:00～次日07:00）直接排放对HONO的贡献最大达到31.3％，出现在20:00，平均贡献为15％；夜间HONO_corr/NO₂比率与BC和RH具有非常明显的相关性，说明HONO的非均相生成速率与NO₂的浓度以及反应介质BC表面的吸附水的浓度即RH成正比，得到夜间HONO平均转化率(HONO/NO₂)为0.8%·h^-1；而且RH的增加对HONO的非均相形成有利，但是当RH>80%对反应也将产生抑制作用，通过对监测期间的个例分析也证实了这一假设.

Observational Study of Atmospheric HONO in Summer of Beijing

The concentration of HONO, NO₂, O₃ and other atmospheric pollutants were observed continuously by using differential optical absorption spectroscopy (DOAS) from 2007-08-14 to 2007-08-24 in Beijing, China. Diurnal variation characteristics of HONO and NO₂ were analyzed. The HONO levels originated from the nocturnal direct emission were discussed. And the correlation between the heterogeneous formation of HONO and its related factors (BC, RH, and so on) was studied. The results showed that HONO had two peaks at about 01:00 and 06:00, respectively, while two peaks of NO₂ concentrations appeared at about 01:00 and 07:00. The highest HONO_em/HONO ratio of 31.3% was observed at about 20:00 between 19:00 to 07:00, and the average ratio was 15%. Good correlation of HONO_corr/NO₂ ratio with BC and RH at night was obtained. The correlation suggested that heterogeneous NO₂ to HONO conversion processes may occur on BC surfaces by reaction with absorption water, and the average nighttime conversion frequency from NO₂ into HONO (HONO/NO₂) was calculated about 0.8%·h^-1. At the same time, the results showed that heterogeneous formation of HONO was increased with RH and inhibited at RH>80%, and the hypothesis was further supported by detailed analysis of selected case.