四川乡村点新粒子生成特征及其对云凝结核数浓度的贡献

为揭示成渝地区大气复合污染成因,选择乡村点资阳站的冬季,实测了颗粒物数浓度及其粒径谱分布、云凝结核(CCN),在二氧化硫、光解速率(JO1D)实测值基础上估算了新粒子生成的重要前体物气态硫酸的浓度.2012年12月5日到2013年1月5日观测期间,3~582nm颗粒物数浓度水平较高,平均值为(16072±9713)cm-3.颗粒物数谱分布呈现以积聚模态为主体的特征,占总颗粒物数浓度的46%,此比值高于我国北京、上海、广州等城市和珠江三角洲及长江三角洲的乡村点和背景点.在较高颗粒物凝结汇(CS)水平下[(4.3±3.6)×10-2s-1],甄别出7次新粒子生成(NPF)事件,占观测天数的23%.NPF事件发生时,颗粒物生成速率与增长速率分别为(5.2±1.4)cm-3s-1,(3.6±2.5)nm/h. NPF事件对CCN数浓度有明显贡献,NPF发生后CCN数浓度平均增长19%.

Characterization of new particle formation event in the rural site of Sichuan Basin and its contribution to cloud condensation nuclei

To investigate the formation mechanism of complex air pollution in Chengdu-Chongqing district, field campaign was conducted at a rural size Ziyang during the winter time of 2012 to study the new particle formation (NPF) events and their impact to cloud condensation nuclei (CCN) in the high polluted atmosphere background. Particle number size distribution and the number of CCN were measured. The gaseous sulfuric acid concentration was estimates based on the mixing ratio of SO2 and photolysis rate (JO1D). During the whole champion (Dec 5th, 2012 to Jan 5th, 2013), the particle number concentration was high, with an average of (16072±9713)cm-3. The dominate mode was the accumulation mode, accounting for 46% of the total particle number concentration, indicating dominant secondary formation. This ratio was higher than that of rural sites and background sites of Beijing, Shanghai, Guangzhou, the Pearl River Delta, and the Yangtze River Delta. The coagulation condensation sink (CS), indicating preexisting particle concentration was high [(4.3 ± 3.6) × 10- 2s-1]. However, seven NPF events were measured, accounting for 23% of the observed days. Compared with the results of other studies, the particle formation rate was slightly higher [(5.2 ± 1.4)cm-3s-1], and the particle growth rate [(3.6 ± 2.5)nm/h] was lower. NPF events significantly contributed to the number concentration of CCN. After NPF events, the average growth rate of the number concentration of CCN was 19%.