Impacts of new particle formation on aerosol cloud condensation nuclei (CCN) activity in Shanghai: case study
Impacts of new particle formation on aerosol cloud condensation nuclei (CCN) activity in Shanghai: case study
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DOI：
10.5194/acp-14-11353-2014
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发表时间：
2014-10
影响因子：
6.3
通讯作者：
C. Leng;Q. Zhang;J. Tao;Hui Zhang;Deqin Zhang;Chen Xu;Xiang Li;Lingdong Kong;T. Cheng
中科院分区：
文献类型：
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作者：
C. Leng;Q. Zhang;J. Tao;Hui Zhang;Deqin Zhang;Chen Xu;Xiang Li;Lingdong Kong;T. Cheng
摘要。利用2012年4月1日至30日在上海市区的连续观测资料，研究了新粒子形成（NPF）事件及其对云凝结核（CCN）的影响。在运动期间，30天中有8天发生NPF，并根据过饱和（SS）增加了1.2-1.8倍的CCN数浓度（NCCN）。选取2012年4月3日的NPF事件为例，调查NPF对CCN活动的影响。在该NPF事件中，二次气溶胶持续产生，PM2.5质量浓度以4.33 μg cm−3 h−1的速率增加，生长速率（GR）和形成速率（FR）平均分别为5 nm h−1和0.36 cm−3 s−1。新形成的颗粒从成核模式（10 ~ 20 nm）迅速生长到CCN尺寸范围。在SS为0.4 ~ 1.0%时，NCCN迅速增加，但在SS为0.2%时，NCCN增加较弱。相应的，在SS为0.2 ~ 1.0%时，气溶胶CCN活性（活化气溶胶颗粒占总气溶胶的比例，NCCN/NCN）由0.24 ~ 0.60显著提高到0.30 ~ 0.91。在κ-Kohler理论的基础上，利用同时测量的气溶胶粒径分布和化学成分来预测NCCN。NCCN预测值与实测值吻合较好（R2=0.96, npredicting /Nmeasured=1.04）。研究表明，NPF对气溶胶颗粒丰度和粒径谱有较大影响；因此，它显著促进了该城市环境中NCCN和气溶胶CCN的活动。在所有SS水平下，NPF的GR是控制新形成颗粒成为CCN的关键因素，而FR仅在高SS（例如1.0%）条件下是有效因素。
Abstract. New particle formation (NPF) events and their impacts on cloud condensation nuclei (CCN) were investigated using continuous measurements collected in urban Shanghai from 1 to 30 April 2012. During the campaign, NPF occurred in 8 out of the 30 days and enhanced CCN number concentration (NCCN) by a factor of 1.2–1.8, depending on supersaturation (SS). The NPF event on 3 April 2012 was chosen as an example to investigate the NPF influence on CCN activity. In this NPF event, secondary aerosols were produced continuously and increased PM2.5 mass concentration at a rate of 4.33 μg cm−3 h−1, and the growth rate (GR) and formation rate (FR) were on average 5 nm h−1 and 0.36 cm−3 s−1, respectively. The newly formed particles grew quickly from nucleation mode (10–20 nm) into CCN size range. NCCN increased rapidly at SS of 0.4–1.0% but weakly at SS of 0.2%. Correspondingly, aerosol CCN activities (fractions of activated aerosol particles in total aerosols, NCCN/NCN) were significantly enhanced from 0.24–0.60 to 0.30–0.91 at SS of 0.2–1.0% due to the NPF. On the basis of the κ-Kohler theory, aerosol size distributions and chemical composition measured simultaneously were used to predict NCCN. There was a good agreement between the predicted and measured NCCN (R2=0.96, Npredicted/Nmeasured=1.04). This study reveals that NPF exerts large impacts on aerosol particle abundance and size spectra; thus, it significantly promotes NCCN and aerosol CCN activity in this urban environment. The GR of NPF is the key factor controlling the newly formed particles to become CCN at all SS levels, whereas the FR is an effective factor only under high SS (e.g., 1.0%) conditions.