Rawat Bakhat, Yin Xiufeng, Sharma Chhatra Mani, Tripathee Lekhendra, Truong Minh Tri, Tiwari Pravash, Kandel Kshitiz, Kang Shichang, Zhang Qianggong
State Key Laboratory of Tibetan Plateau Earth System, Environment and Resources (TPESER), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China; Centre for Atmospheric Chemistry, University of Wollongong (UOW), NSW, 2522, Australia.
State Key Laboratory of Tibetan Plateau Earth System, Environment and Resources (TPESER), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China; Key Laboratory of Cryospheric Science and Frozen Soil Engineering, Northwest Institute of Eco-environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China.
J Hazard Mater. 2025 Feb 5;483:136644. doi: 10.1016/j.jhazmat.2024.136644. Epub 2024 Nov 26.
South Asia is a global hotspot of air pollution gaining attention due to its severe implications, in which atmospheric mercury (Hg) could cause detrimental health effects in metropolitan areas. In this study, first-time year-round (January - December 2019) mean total gaseous mercury (TGM) concentration at Kathmandu, Nepal - a sub-tropical city in South Asia was reported at 9.9 ± 10.0 ng m. Seasonal TGM variation at Kathmandu showed highest concentration in winter (16.8 ± 16.9 ng m) and lowest in summer (2.9 ± 2.1 ng m). Generally higher daytime TGM concentration as opposed to night-time TGM indicated Hg build-up within atmospheric boundary layer due to low wind speed and high humidity. Events with high wind speed (> 30 m s) induced regional pollutant transport from nearby brick kilns and cement factories. Principal component analysis associated a major part of TGM with PM and CO and indicated the remarkable influence of fuel combustion and vehicular emissions. Backward trajectory and potential source contribution factor analysis further indicate the impact of regional Hg emissions and transboundary emissions from India towards Nepal, which expands beyond the Himalayas and the Tibetan Plateau. Prominent low-grade coal burning and kilning activities in winter spiked up TGM concentrations, resulting in the highest health quotient (HQ = 0.24) value, which could significantly impact public health. Our study presented the most comprehensive set of continuous annual atmospheric Hg monitoring data from Nepal in the South Asian region. The results serve as a baseline for regional atmospheric Hg levels and offer a critical reference for assessing and addressing air pollution concerns in Nepal as well as throughout South Asia.
南亚是全球空气污染热点地区，因其严重影响而备受关注，其中大气汞（Hg）会对大城市地区的健康造成有害影响。在本研究中，首次报告了尼泊尔加德满都（南亚的一个亚热带城市）2019年全年（1月至12月）的平均总气态汞（TGM）浓度为9.9±10.0纳克/立方米。加德满都的TGM季节性变化显示，冬季浓度最高（16.8±16.9纳克/立方米），夏季最低（2.9±2.1纳克/立方米）。一般来说，白天的TGM浓度高于夜间，这表明由于风速低和湿度高，汞在大气边界层内积聚。高风速（>30米/秒）的事件引发了来自附近砖窑和水泥厂的区域污染物传输。主成分分析将TGM的主要部分与PM和CO相关联，并表明了燃料燃烧和车辆排放的显著影响。后向轨迹和潜在源贡献因子分析进一步表明了印度的区域汞排放和越境排放对尼泊尔的影响，这种影响超出了喜马拉雅山脉和青藏高原。冬季突出的低品位煤炭燃烧和煅烧活动使TGM浓度飙升，导致最高健康商数（HQ = 0.24）值，这可能对公众健康产生重大影响。我们的研究展示了南亚地区来自尼泊尔最全面的连续年度大气汞监测数据集。这些结果为区域大气汞水平提供了基线，并为评估和解决尼泊尔以及整个南亚的空气污染问题提供了关键参考。
