To better understand the causes of visibility degradation in Taiyuan, the concentrations of PM_1.5 and main chemical compositions were analyzed during the period from July 28, 2014 to April 26, 2015. The average concentration of PM_1.5 during the sampling period was 107.6 ± 51.0 μg/m³. The concentrations of secondary inorganic water-soluble ions (SIA, the sum of SO₄²⁻, NO₃⁻ and NH₄⁺), OC and EC were 31.0 μg/m³, 14.6 μg/m³ and 6.0 μg/m³, accounting for 28.8%, 13.5% and 5.6% of PM_1.5, respectively. Light extinction coefficients (b_ext) were estimated by the revised US Interagency Monitoring of Protected Visual Environments (IMPROVE) equation. (NH₄)₂SO₄ (48.7%) was the largest contributor to b_ext in summer, while the contribution of organic matter (OM) to b_ext was the highest in spring (25.0%) and winter (42.0%). Compared with non-haze days in summer and winter, the contributions of (NH₄)₂SO₄ and NH₄NO₃ to b_ext during haze days increased, while the contributions of OM, EC, fine soil and coarse matter (PM_1.5-10) decreased. Air masses from the southern areas had the largest b_ext and contribution of (NH₄)₂SO₄ in summer and winter. The results of source apportionment by positive matrix factorization model found that secondary sulfate, secondary nitrate, coal combustion, vehicle emission, fugitive dust, biomass burning were the main sources to b_ext in Taiyuan. Secondary sulfate (81.7%) and coal combustion (43.1%) were the largest contributors to the b_ext in summer and winter during haze days, respectively. The results of our study could improve the understanding of the major sources that affect visibility degradation in Taiyuan.

为更好地了解太原能见度下降的原因，对2014年7月28日至2015年4月26日期间PM _1.5浓度及主要化学成分进行了分析，采样期间PM _1.5平均浓度为107.6±51.0微克/米³。二级无机水溶性离子（SIA，SO ₄ ^2-、NO ₃ ^-和NH ₄ ⁺的总和）、OC和EC的浓度分别为31.0 μg/m ³、14.6 μg/m ³和6.0 μg/m ³，分别占 PM _{1.5 的}28.8%、13.5% 和 5.6% 。消光系数 (b _ext) 由修订后的美国受保护视觉环境机构间监测 (IMPROVE) 方程估计。(NH ₄ ) ₂ SO ₄ (48.7%)在夏季对b _ext的贡献最大，而有机质(OM)对b _ext的贡献在春季(25.0%)和冬季(42.0%)最高。在夏季和冬季非霾天相比，（NH的贡献₄）₂ SO ₄和NH ₄ NO ₃至b _EXT期间霾天增加，而OM，EC，细土和粗物质（PM的贡献_{1.5 -10}) 减少。南部地区_气团在夏季和冬季的_bext和(NH ₄ ) ₂ SO ₄贡献最大。通过正矩阵分解模型源解析的结果发现，二次硫酸盐，硝酸盐二次，煤燃烧，汽车排放，扬尘，生物质燃烧分别为a〜b的主要来源_分机太原。二次硫酸盐 (81.7%) 和燃煤 (43.1%) 分别是夏季和冬季雾霾天b _ext的最大贡献者。我们的研究结果可以提高对影响太原能见度下降的主要来源的理解。