Size‐resolved measurements of mixing state and cloud‐nucleating ability of aerosols in Nanjing, China
Size‐resolved measurements of mixing state and cloud‐nucleating ability of aerosols in Nanjing, China
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DOI：
10.1002/2017jd026583
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发表时间：
2017-09
期刊：
影响因子：
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通讯作者：
Yan Ma;Shizheng Li;Jun Zheng;A. Khalizov;Xing Wang;Zhen Wang;Yao-yao Zhou
中科院分区：
文献类型：
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作者：
Yan Ma;Shizheng Li;Jun Zheng;A. Khalizov;Xing Wang;Zhen Wang;Yao-yao Zhou
2013年8月，在长江三角洲的特大城市南京部署了一套综合气溶胶分析系统，以测量尺寸分辨的气溶胶混合状态、有效密度、云凝结核(CCN)活动和化学成分。研究发现，气溶胶主要是内部混合的。50、80和120 nm微粒的平均有效密度分别为1.38±0.09、1.48±0.08和1.53±0.07g cm−-3。虽然黑碳(BC)平均只占总颗粒物质量的0.3%、1.6%和3.3%，但在50、80和120 nm处分别占总颗粒物浓度的7%、38%和47%，这表明BC对大气气溶胶总量的贡献可能很大。仅偶尔观察到有效浓度为0.6 7~0.97g cm−3的外部混合细菌。采集的气溶胶具有较高的CCN活性和吸湿性(κ=0.35±0.13)。观察到新形成的粒子和新释放的BC粒子都通过光化学过程迅速老化，粒子CCN活性显著增强，有效密度增加。受四个不同气团影响的气溶胶表现出相似的CCN激活，这表明CCN的激活将主要取决于颗粒大小而不是颗粒来源(因此原始组成)。我们的结果表明，在本研究遇到的高活性光化学条件下，来自局地和区域输送的颗粒物可以通过光化学老化迅速转化为有效的CCN，从而对大气CCN收支做出重要贡献，并对气溶胶间接气候强迫产生深远的影响。
An integrated aerosol analytical system was deployed in Nanjing, a megacity in the Yangtze River Delta, to measure size‐resolved aerosol mixing states, effective densities, cloud condensation nucleus (CCN) activities, and chemical composition in August 2013. It was found that aerosols were predominantly internally mixed. The average effective densities were 1.38 ± 0.09, 1.48 ± 0.08, and 1.53 ± 0.07 g cm−3 for 50, 80, and 120 nm particles, respectively. Although black carbon (BC) represented only 0.3%, 1.6%, and 3.3% of the particle mass, on average, it was present in 7%, 38%, and 47% of the total particle number concentration at 50, 80, and 120 nm, respectively, indicating that BC particles may contribute significantly to the total atmospheric aerosol population. Externally mixed BC was only occasionally observed with an effective density of 0.67–0.97 g cm−3. Aerosols sampled generally exhibited a relatively high CCN activity and hygroscopicity (κ = 0.35 ± 0.13). Both newly formed particles and freshly emitted BC particles were observed to age rapidly from photochemical processes, with a significant enhancement in the particle CCN activity and an increase in the effective density. Aerosols influenced by four different air masses presented similar CCN activation, indicating that CCN activation would be primarily dependent on the particle size rather than the particle origin (and hence original composition). Our results suggest that under highly active photochemical conditions as encountered in this study, particles from both local sources and regional transport can be rapidly converted into efficient CCN by photochemical aging, thereby making important contributions to the atmospheric CCN budget and exerting profound implications on aerosol indirect climate forcing.