Department of Geology, Sikkim University, Gangtok, Sikkim 737102, India.
Department of Environmental Science, Tezpur University, Tezpur, Assam 784028, India.
Sci Total Environ. 2023 Apr 20;870:161987. doi: 10.1016/j.scitotenv.2023.161987. Epub 2023 Feb 3.
Polycyclic Aromatic Hydrocarbons (PAHs) compounds are ubiquitous in ambient air due to their persistence, carcinogenicity, and mutagenicity. Gangtok being one of the cleanest cities in India located in Eastern Himalayan region, witnesses high developmental activities with enhanced urbanization affecting the ambient air quality. The present study aims to measure PM and PAHs in the ambient atmosphere of the Sikkim Himalaya to understand the influence of natural and anthropogenic activities on aerosol loading and their chemical characteristics. The PM samples were collected and analysed for the duration from Jan 2020 to Feb 2021.The seasonal mean concentrations of PM and PAHs were observed to be high during autumn and low during summer season. Overall, the annual mean concentration of PM was found higher than the prescribed limit of World Health Organization and National Ambient Air Quality Standards. The concentration of the 16 individual PAHs were found to be highest during autumn season (55.26 ± 37.15 ng/m). Among the different PAHs, the annual mean concentration of fluorene (3.29 ± 4.07 ng/m) and naphthalene (1.15 ± 3.76 ng/m) were found to be the highest and lowest, respectively. The Molecular Diagnostic Ratio (MDR) test reveals higher contribution from heavy traffic activities throughout the winter and autumn seasons. The other possible sources identified over the region are fossil fuel combustion, and biomass burning. The multivariate statistical analysis (Multifactor Principal Component Analysis) also indicates a strong association between PM /PAHs and meteorological variables across the region in different seasons. The precipitation and wind pattern during the study period suggests that major contribution of the PM and PAHs were from local sources, with minimal contribution from long-range transport. The findings are important for comprehending the trends of PAH accumulation over a high-altitude urban area, and for developing sustainable air quality control methods in the Himalayan region.
多环芳烃（PAHs）化合物由于其持久性、致癌性和致突变性，在环境空气中普遍存在。甘托克是印度东部喜马拉雅地区最干净的城市之一，由于城市化进程加快，发展活动频繁，导致环境空气质量受到影响。本研究旨在测量锡金喜马拉雅地区环境大气中的 PM 和 PAHs，以了解自然和人为活动对气溶胶负荷及其化学特性的影响。在 2020 年 1 月至 2021 年 2 月期间收集和分析了 PM 样本。观察到 PM 和 PAHs 的季节性平均浓度在秋季最高，夏季最低。总的来说，PM 的年平均浓度高于世界卫生组织和国家环境空气质量标准规定的限值。16 种单体 PAHs 的浓度在秋季最高（55.26±37.15ng/m3）。在不同的 PAHs 中，全年平均浓度氟芴（3.29±4.07ng/m3）和萘（1.15±3.76ng/m3）最高和最低。分子诊断比（MDR）测试显示，整个冬季和秋季，交通活动的影响较大。该地区其他可能的来源包括化石燃料燃烧和生物质燃烧。多元统计分析（多因子主成分分析）也表明，不同季节整个地区的 PM/PAHs 与气象变量之间存在很强的相关性。研究期间的降水和风向模式表明，PM 和 PAHs 的主要贡献来自当地，长距离传输的贡献最小。这些发现对于理解高海拔城市地区 PAH 积累的趋势以及在喜马拉雅地区开发可持续的空气质量控制方法非常重要。
