Spatiotemporal Distribution Characteristics and Main Influencing Factors of Atmospheric CH4 in Northern Zhejiang
Methane (CH4) is a potent greenhouse gas with a global warming potential approximately 28 times that of CO2 over a 100-year horizon. Direct observation of atmospheric CH4 concentrations is essential for quantifying contributions from anthropogenic and natural sources. This study analyzes online CH4 monitoring data from Huzhou City and Deqing County in northern Zhejiang Province, China, to characterize spatiotemporal variations and identify controlling factors. Diurnal patterns show higher nighttime concentrations due to reduced vertical mixing and enhanced stability, with winter maxima and autumn minima. The seasonal background concentration at Huzhou station follows winter > spring > autumn > summer. Deqing, influenced by artificial aquaculture ponds and wetlands, exhibits smaller diurnal amplitude and generally higher CH4 levels than Huzhou, particularly during the plum rain season. Potential Source Contribution Function (PSCF) analysis indicates that high-concentration sources are predominantly located in eastern Zhejiang, with seasonal shifts: spring sources in the Yangtze River Delta and southeast coast, summer sources in southeastern Zhejiang, minimal autumn regional transport, and winter sources in eastern Jiangxi. These findings underscore the roles of local wetland emissions and regional transport in modulating CH4 levels, providing a scientific basis for targeted emission reduction strategies.