Enviromental Engineering Division, Department of Civil Engineering, Indian Institute of Technology Madras, Chennai, India.
Centre for Atmospheric and Climate Sciences, Indian Institute of Technology Madras, Chennai, India.
Environ Sci Process Impacts. 2024 Nov 13;26(11):1999-2009. doi: 10.1039/d4em00324a.
Mercury (Hg), a ubiquitous atmospheric trace metal posing serious health risks, originates from natural and anthropogenic sources. India, the world's second-largest Hg emitter and a signatory to the Minamata Convention, is committed to reducing these emissions. However, critical gaps exist in our understanding of the spatial and temporal distribution of Hg across the vast Indian subcontinent due to limited observational data. This study addresses this gap by employing the GEOS-Chem model with various emission inventories (UNEP2010, WHET, EDGAR, STREETS, and UNEP2015) to simulate Hg variability across the Asian domain, with a specific focus on India from 2013 to 2017. Model performance was evaluated using ground-based GMOS observations and available literature data. Emission inventory performance varied across different observational stations. Hence, we employed ensemble results from all inventories. The maximum relative bias for Total Gaseous Mercury (TGM) and Gaseous Elemental Mercury (GEM; Hg) concentrations is about ±20%, indicating simulations with sufficient accuracy. Total Hg wet deposition fluxes are highest over the Western Ghats and the Himalayan foothills due to higher rainfall. During the monsoon, the Hg wet deposition flux is about 65.4% of the annual wet deposition flux. Moreover, westerly winds cause higher wet deposition in summer over Northern and Eastern India. Total Hg dry deposition flux accounts for 72-74% of total deposition over India. Hg dry deposition fluxes are higher over Eastern India, which correlates strongly with the leaf area index. Excluding Indian anthropogenic emissions from the model simulations resulted in a substantial decrease (21.9% and 33.5%) in wet and total Hg deposition fluxes, highlighting the dominant role of human activities in Hg pollution in India.
汞（Hg）是一种普遍存在的大气痕量金属，对健康构成严重威胁，其来源包括自然源和人为源。印度是世界上第二大汞排放国，也是《水俣公约》的签署国，印度致力于减少汞排放。然而，由于观测数据有限，我们对整个印度次大陆汞的时空分布仍缺乏了解。本研究通过使用各种排放清单（环境署 2010 年清单、WHET、EDGAR、STREETS 和环境署 2015 年清单）的 GEOS-Chem 模型来解决这一差距，模拟 2013 年至 2017 年期间亚洲地区汞的变化情况，重点关注印度。使用地面 GMOS 观测数据和现有文献数据对模型性能进行了评估。排放清单的性能在不同的观测站有所不同。因此，我们采用了所有清单的综合结果。总气态汞（TGM）和元素态汞（GEM；Hg）浓度的最大相对偏差约为±20%，表明模拟具有足够的准确性。由于降雨量较高，西高止山脉和喜马拉雅山麓的总汞湿沉降通量最高。在季风期间，汞的湿沉降通量约占年湿沉降通量的 65.4%。此外，西风在夏季导致印度北部和东部的湿沉降通量更高。总汞干沉降通量占印度总沉降量的 72-74%。印度东部的汞干沉降通量较高，这与叶面积指数有很强的相关性。从模型模拟中排除印度人为排放后，湿沉降和总汞沉降通量显著减少（21.9%和 33.5%），这突出表明人类活动在印度汞污染中起主导作用。
