西安市秋季大气颗粒物散射特征及其影响因素

 为研究污染条件下西安市秋季大气颗粒物的散射特征及其影响因素, 于2012 年11 月监测大气颗粒物散射系数并采集PM_2.5样品。探讨了大气颗粒物的散射日变化特征, 通过实验分析PM_2.5中水溶性离子(Na⁺、NH₄⁺、K⁺、Mg²⁺、Ca²⁺、F^-、Cl^-、NO₃^-和SO₄^2-)和含碳物质(有机碳和元素碳)的污染水平, 并讨论它们的来源及对散射系数的影响。结果表明, 颗粒物的散射系数均值为(579±387)Mm^-1, 夜间高日间低。PM_2.5质量浓度与散射系数呈现出较强的线性关系(相关系数为0.85), 通过回归方程得到PM_2.5散射效率为3.09 m²·g^-1。在PM_2.5化学组分中, 有机物对消光系数的贡献最大, 占52.3%;其次是NH₄NO₃和(NH₄)₂SO₄, 贡献率分别为16.2%和13.7%。

Characteristics of aerosol scattering coefficient in autumn Xi'an,China

To investigate the impact of PM_2.5 chemical species on light scattering in autumn Xi'an, light scattering coefficient and PM_2.5 samples were collected daily in November 2012 at the Institute of Earth Environment, Chinese Academy of Sciences. The PM_2.5 water-soluble ionic species (Na⁺, NH₄⁺, K⁺, Mg²⁺, Ca²⁺, F^-, Cl^-, NO₃^- and SO₄^2-) and carbonaceous (organic carbon and elemental carbon) were analyzed to characterize their impacts on the light scattering coefficient. The average PM_2.5 during the sampling period was (195.4±83.5) μg·m^-3. The average light scattering coefficient was (579±387) Mm^-1, with high value at night and low value in the daytime. The concentration of PM_2.5 showed a strong correlation with light scattering coefficient, with a correlation coefficient of 0.85. The estimated light scattering efficiency of PM_2.5 was 3.09 m²·g^-1. Among the PM_2.5 chemical species, NH₄⁺, K⁺, SO₄^2- and OC had a strong correlation with light scattering coefficient, suggesting that they are the main contribution sources for light extinction coefficient. The revised IMPROVE equation was used to estimate chemical extinction (b_ext), which was lower than measured bsp, wet. Among the PM_2.5 chemical species, organics had the largest contribution to light extinction, accounting for 52.3%, followed by NH₄NO₃ (16.2%) and (NH₄)₂SO₄ (13.7%).