Atmospheric methane dynamics and its associations with environmental factors in the mid-Indo-Gangetic region (Bihar),...

Atmospheric methane (CH₄) is a potent greenhouse gas with a significantly higher global warming potential than carbon dioxide over a short-term period. In this study, we investigate the spatiotemporal variability of CH₄ concentrations in the Bihar region, India, and assess the association of these concentrations with environmental factors such as meteorological conditions, vegetation indices, livestock population, and population density. Using high-resolution satellite data from the TROPOMI sensor (S5P), MODIS, and meteorological datasets, we analyze CH₄ variations over a period from 2018 to 2023. A 2.8 % increase in XCH₄ concentrations is observed over this period. Our findings reveal seasonal fluctuations in CH₄ levels, with elevated concentrations during the monsoon and post-monsoon periods, attributed to flooding, agricultural practices, particularly rice cultivation, and wetland methanogenesis. Spatially, CH₄ concentrations are highest in the mid-Gangetic plains, where average XCH₄ concentration exceeds 1920 ppb. It attributes to anthropogenic activities, such as agriculture primarily rice and makhana cultivation, and livestock farming significantly contribute to emissions. Pearson correlation and regression analyses demonstrate a strong positive relationship between CH₄ concentrations, vegetation indices (NDVI, EVI, and GPP), and relative humidity. Conversely, wind speed inversely correlates with CH₄, influencing dispersion. The multiple regression model accounted for 43.4 % of the variance (p < 0.001) in XCH₄ concentrations. The study also identifies CH₄ hotspots and coldspots, with high emissions concentrated in flood-prone and agriculturally intensive areas. The identified hotspots exhibit an anomaly of about 12.5 ppb, indicating persistent local intensification of CH₄ sources. Our research highlights the critical role of land-use patterns, climatic variability, and human activities in shaping CH₄ dynamics in the region. These insights are vital for developing targeted mitigation strategies and informing state-level climate action policies to reduce CH₄ emissions in Bihar.