In this study, the temporal variation of Equivalent Black Carbon (eBC) and its source apportionment is studied using a yearlong (Dec. 2020–Nov. 2021) multiwavelength Aethalometer (AE-33 model) measurements over Varanasi, located in the central Indo-Gangetic Basin (IGB). Results suggest that mean mass concentrations of eBC vary in the range between 0.46 ± 0.13 to 11.22 ± 5.09 μg m with an annual mean value of ∼3.57 ± 2.39 μg m during the study period. A strong temporal variation in eBC and its components i.e., eBC (eBC from fossil fuel), and eBC (eBC from biomass burning) are found which shows a large variation on different temporal scales with an average value during winter (6.21 ± 3.56 μg m), summer (5.09 ± 3.61 μg m), monsoon season (1.52 ± 1.03 μg m), and post-monsoon (3.75 ± 2.68 μg m). The diurnal variation of eBC shows two different maxima between 07:00–08:00 a.m. and 08:00–10:00 p.m. An inverse relationship between eBC concentration and all meteorological parameters (temperature, wind speed, and boundary layer height) is found except relative humidity. The concentration of eBC increases with respect to RH (up to 70 %) suggesting hygroscopic growth while for higher RH (>70 %) value, eBC concentration decreases and indicates the possible wet scavenging processes in the atmosphere. Source apportionment of eBC using the “Aethalometer Model” reveals that eBC is dominant over eBC in total eBC loading during the study period. Cluster analysis of HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory) model computed five days airmass back-trajectory suggests that airmass reached at Varanasi passes through a highly dense fire count region over the northwestern IGB and surrounding which could be the most responsible for the black carbon loading over the study region.

中文翻译：

---

印度恒河盆地瓦拉纳西当量黑碳变化及其来源解析评估

在本研究中，利用位于印度中部的瓦拉纳西地区长达一年（2020 年 12 月至 2021 年 11 月）的多波长空气质量计（AE-33 型号）测量，研究了当量黑碳 (eBC) 的时间变化及其来源解析。恒河盆地（IGB）。结果表明，研究期间 eBC 的平均质量浓度在 0.46 ± 0.13 至 11.22 ± 5.09 μg m 之间变化，年平均值为 ∼3.57 ± 2.39 μg m 。 eBC 及其组成部分，即 eBC（来自化石燃料的 eBC）和 eBC（来自生物质燃烧的 eBC）存在强烈的时间变化，在不同时间尺度上表现出很大的变化，冬季平均值为（6.21 ± 3.56 μg m） ）、夏季（5.09 ± 3.61 μg m）、季风季节（1.52 ± 1.03 μg m）和季风后（3.75 ± 2.68 μg m）。 eBC 的日变化在上午 07:00–08:00 和下午 08:00–10:00 之间显示出两个不同的最大值 发现 eBC 浓度与所有气象参数（温度、风速和边界层高度）之间呈反比关系除了相对湿度。 eBC 浓度相对于 RH 增加（高达 70%），表明吸湿性增长，而对于较高的 RH（>70%）值，eBC 浓度降低，表明大气中可能存在湿清除过程。使用“Aethalometer 模型”对 eBC 进行源解析表明，在研究期间，eBC 在总 eBC 负荷中占主导地位。 HYSPLIT（混合单粒子拉格朗日积分轨迹）模型的聚类分析计算出五天的气团反向轨迹，表明到达瓦拉纳西的气团穿过西北 IGB 及其周围的高度密集的火灾计数区域，该区域可能是造成黑碳的主要原因在研究区域上加载。