Huang Yi-Min, Liu Zi-Rui, Chen Hong, Wang Yue-Si
Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China.
Huan Jing Ke Xue. 2013 Apr;34(4):1236-44.
To investigate the size distribution characteristics of water soluble inorganic ions in haze days, the particle samples were collected by two Andersen cascade impactors in Beijing during summer and winter time and each sampling period lasted two weeks. Online measurement of PM10 and PM2.5 using TEOM were also conducted at the same time. Sources and formation mechanism of water soluble inorganic ions were analyzed based on their size distributions. The results showed that average concentrations of PM10 and PM 2.5 were (245.5 +/- 8.4) microg x m(-3) and (120.2 +/- 2.0) microg x m(-3) during summer haze days (SHD), and were (384.2 +/- 30.2) microg x m(-3) and (252.7 +/- 47.1) microg x m(-3) during winter haze days (WHD), which suggested fine particles predominated haze pollution episode in both seasons. Total water-soluble inorganic ions concentrations were higher in haze days than those in non-haze days, especially in fine particles. Furthermore, concentrations of secondary inorganic ions (SO4(2-), NO3(-) and NH4(+)) increased quicker than other inorganic ions in fine particles during haze days, indicating secondary inorganic ions played an important role in the formation of haze pollution. Similar size distributions were found for all Sinorganic water soluble ions except for NO3(-), during SHD and WHD. SO4(2-) and NH4(+) dominated in the fine mode (PM1.0) while Mg2+ and Ca2+ accumulated in coarse fraction, Na+, Cl- and K+ showed a bimodal distribution. For NO3(-), however, it showed a bimodal distribution during SHD and a unimodal distribution dominated in the fine fraction was found during WHD. The average mass median aerodynamic diameter (MMAD) of SO4(2-) was 0.64 microm in SHD, which suggested the formation of SO4(2-) was mainly attributed to in-cloud processes. Furthermore, a higher apparent conversion rate of sulfur dioxide (SOR) was found in SHD, indicating more fine particles were produced by photochemical reaction in haze days than that in non-haze days. The MMAD of SO4(2-) increased to 0.89 microm in WHD, local emission of SO2 and the subsequently heterogeneous reaction became the main source of SO4(2-) during winter time. The average MMADs of NO3(-) were 2.85 microm and 0.80 microm in SHD and WHD, respectively. Influenced by the seasonal temperature difference, NO3(-) mainly existed in the form of calcium nitrate in coarse mode during SHD while the fine mode nitrate was associated with ammonium during WHD.
为研究雾霾天水溶性无机离子的粒径分布特征，于夏季和冬季在北京通过两台安德森级联撞击器采集颗粒物样本，每个采样期持续两周。同时还使用TEOM对PM10和PM2.5进行在线测量。基于水溶性无机离子的粒径分布分析其来源和形成机制。结果表明，夏季雾霾天（SHD）期间PM10和PM2.5的平均浓度分别为(245.5±8.4)μg·m⁻³和(120.2±2.0)μg·m⁻³，冬季雾霾天（WHD）期间分别为(384.2±30.2)μg·m⁻³和(252.7±47.1)μg·m⁻³，这表明两个季节的雾霾污染事件中细颗粒物占主导。雾霾天总水溶性无机离子浓度高于非雾霾天，尤其是在细颗粒物中。此外，雾霾天细颗粒物中二次无机离子（SO₄²⁻、NO₃⁻和NH₄⁺）的浓度比其他无机离子增加得更快，表明二次无机离子在雾霾污染形成中起重要作用。除NO₃⁻外，在夏季雾霾天和冬季雾霾天所有水溶性无机离子均呈现相似的粒径分布。SO₄²⁻和NH₄⁺在细模态（PM1.0）中占主导，而Mg²⁺和Ca²⁺在粗颗粒中累积，Na⁺、Cl⁻和K⁺呈现双峰分布。然而，对于NO₃⁻，夏季雾霾天呈现双峰分布，冬季雾霾天则呈现以细颗粒为主导的单峰分布。夏季雾霾天SO₄²⁻的平均质量中值空气动力学直径（MMAD）为0.64μm，这表明SO₄²⁻的形成主要归因于云内过程。此外，夏季雾霾天发现较高的二氧化硫表观转化率（SOR），表明雾霾天光化学反应产生的细颗粒物比非雾霾天更多。冬季雾霾天SO₄²⁻的MMAD增加到0.89μm，冬季SO₂的局地排放及随后的非均相反应成为SO₄²⁻的主要来源。夏季雾霾天和冬季雾霾天NO₃⁻的平均MMAD分别为2.85μm和0.80μm。受季节温差影响，夏季雾霾天NO₃⁻主要以硝酸钙形式存在于粗模态中，而冬季雾霾天细模态硝酸盐与铵相关。
