Abstract The present paper reports the results derived from PM2.5 and PM10 concentrations during October 2016–May 2018 using MICROTOPS-II Sunphotometer and high volume samplers at Varanasi. Observed data were categorized and analyzed in order to understand the nature, source of origin and variability with seasons. Observations showed aerosol mass loading during the post-monsoon 2016 and winter 2017 as compared to the pre-monsoon 2018 values, which typically exceed national standard. The close relationships between PM2.5 and PM10 during post-monsoon (r = 0.571) and winter (r = 0.799) suggested that both type of particulates might have originated from the same source. Further, the PM2.5/PM10 indicated that the fine particles were dominantly present during the post-monsoon and winter season where as coarse particles were found dominant in the pre-monsoon season. The measured high values of aerosol optical depth (AOD) and angstrom exponent (AE) during post-monsoon and winter attributed to the accumulation of aerosols from sources and biomass/crop residue burning in the surrounding region and low dispersal due to shallow boundary layer and lower wind velocity. In contrast during pre-monsoon months the aerosols were accumulated as a mixture of transported from deserts and other far away regions including mineral from earth crust. The effect of meteorological parameters (temperature, wind speed and relative humidity) was also studied. Temperature did not show any relation during the pre monsoon when it was quite high, whereas during the winter months it showed negative trend with concentration. Wind showed negative correlation during the whole observation period. Relative humidity showed weak positive correlation during winter months for PM2.5 and PM10 where as PM2.5 did not show any relation during pre and post monsoon. PM10 showed weak negative relation during pre monsoon months. In order to understand elemental and ionic composition Scanning electron microscope (SEM) coupled with energy dispersive X-ray microanalyzer (EDX) analysis were done which showed dominant presence of C, F, O, Si, N, Na, K, Al, Ca and S. The following trend SO42− > NO3− > Na+> Ca2+> K+> Cl− > F− > Mg2+> Li+ was observed from the Ion chromatograph (IC) analysis. The source for these elements may have been different industrial activities, biomass burning and vehicular emissions. The results are useful for further planning of city developments and climate studies.

中文翻译：

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评估瓦拉纳西上空的大气气溶胶：物理、光学和化学特性以及气象影响

摘要 本文报告了在 2016 年 10 月至 2018 年 5 月期间使用 MICROTOPS-II 太阳光度计和瓦拉纳西大容量采样器从 PM2.5 和 PM10 浓度得出的结果。对观测数据进行分类和分析，以了解其性质、来源和季节变化。观测表明，与 2018 年季风前的值相比，2016 年季风后和 2017 年冬季的气溶胶质量负荷通常超过国家标准。PM2.5 和 PM10 在季风后 (r = 0.571) 和冬季 (r = 0.799) 之间的密切关系表明这两种类型的颗粒物可能来自同一来源。此外，PM2. 5/PM10 表明细颗粒物主要存在于季风后和冬季，而粗颗粒物主要存在于季风前季节。季风后和冬季期间测量的气溶胶光学深度 (AOD) 和埃指数 (AE) 的高值归因于来自周围地区的源和生物量/作物残留物燃烧的气溶胶的积累以及由于浅边界层和较低的风速。相比之下，在季风前几个月，气溶胶是从沙漠和其他遥远地区（包括来自地壳的矿物）运输的混合物积累的。还研究了气象参数（温度、风速和相对湿度）的影响。在季风前相当高的时候，温度没有表现出任何关系，而在冬季，它随着浓度呈负趋势。风在整个观测期间呈负相关。PM2.5 和 PM10 在冬季月份的相对湿度显示出微弱的正相关，而 PM2.5 在季风前后没有任何关系。PM10 在季风前几个月呈弱负相关。为了了解元素和离子组成，我们进行了扫描电子显微镜 (SEM) 和能量色散 X 射线显微分析仪 (EDX) 分析，结果表明 C、F、O、Si、N、Na、K、Al、Ca 占主导地位和 S。从离子色谱 (IC) 分析中观察到以下趋势 SO42− > NO3− > Na+> Ca2+> K+> Cl− > F− > Mg2+ > Li+。这些元素的来源可能是不同的工业活动，生物质燃烧和车辆排放。结果有助于进一步规划城市发展和气候研究。