The chemical composition of PM and RH (relative humidity) significantly affected the atmospheric visibility. RH can lead to an increase in aerosol size and mass, enhancing the extinction coefficients (B), resulting in a rapid deterioration of visibility. This study conducted simultaneous observations of PM chemical compositions, meteorological factors, and B at commercial and industrial urban areas. A comparison was made between two locations in different seasons regarding the major water-soluble ions of PM and visibility. The study aimed to understand the reasons for differences in PM concentrations corresponding to a visibility threshold of 10 km (PTV) for the two locations. Furthermore, it delved into the contribution of aerosol hygroscopicity to B under different pollution events. The results showed that winter had the poorest visibility in both locations. During this period, SO and NO constituted critical proportions of water-soluble ions in PM mass compositions for both commercial and industrial areas. The PM concentrations corresponding to PTV were 29.5 and 18.3 μg m for the commercial and industrial areas, respectively. In periods of poor visibility, NHNO was a significant component influencing B, accounting for up to 48.9% of the total B in industrial areas. Further analysis revealed that during pollution-retention periods, when RH > 75% compared to RH < 65%, the contribution of hygroscopicity to the B of (NH)SO(hygro) increased by 1.7 times, and for NHNO(hygro), it increased by 5.1 times. Under conditions of high pollution and RH, NHNO(hygro) became the dominant factor in atmospheric B, leading to reduced visibility.

中文翻译：

---

城市PM_(2.)5干燥潮解化学成分消光系数及其对能见度恶化的影响

PM和RH（相对湿度）的化学成分显着影响大气能见度。相对湿度会导致气溶胶尺寸和质量增加，从而提高消光系数 (B)，导致能见度迅速恶化。本研究对商业和工业城市地区的PM化学成分、气象因子和B进行了同步观测。对不同季节两个地点的PM主要水溶性离子和能见度进行了比较。该研究旨在了解两个地点能见度阈值 10 公里 (PTV) 对应的 PM 浓度差异的原因。此外，还深入研究了不同污染事件下气溶胶吸湿性对B的贡献。结果显示，冬季这两个地点的能见度最差。在此期间，SO 和 NO 构成了商业和工业领域 PM 质量成分中水溶性离子的关键比例。商业区和工业区对应 PTV 的 PM 浓度分别为 29.5 和 18.3 μg m。在能见度较差的时期，NHNO是影响B的重要成分，占工业区B总量的48.9%。进一步分析发现，在污染滞留期间，当相对湿度> 75%时，与相对湿度< 65%相比，(NH)SO(hygro)的吸湿性对B的贡献增加了1.7倍，对于NHNO(hygro)来说，吸湿性对B的贡献增加了1.7倍。增长了5.1倍。在高污染和相对湿度条件下，NHNO(hygro)成为大气B中的主导因素，导致能见度降低。