Estuaries are important sources of methane (CH₄) to the atmosphere. However, the lack of adequate field studies for understanding the sources/sinks of CH₄ in estuaries hampers global atmospheric budgeting. Therefore, more studies are needed to bridge this gap and improve our understanding of CH₄ dynamics. This study investigated the impacts of tides on CH₄ emissions along a salinity gradient of the subtropical Jiulong River estuary (JRE) during spring, neap tides and over 24 h tidal cycles in 2017 and 2018. Spatially, the CH₄ concentrations increased from the lower reaches to the upper reaches, with values varying widely from 58 to 1726 (393 ± 336) nmol/L, which correspond to saturations of 2513–59,371 (15,549 ± 11,341)%. The CH₄ concentration was inversely and significantly correlated with salinity, indicating the dilution and sulfate inhibition effects of the adjacent saline water. Temporally, the highest CH₄ concentrations and fluxes were detected in the spring tide period, which can enhance the resuspension of particles and CH₄ from sediments, and were accompanied by high turbidity values. Elevated CH₄ concentrations were found during low tide, and horizontal advection of low salinity water could be the driver of the increased CH₄ concentrations during low tide. Due to the lack of agreement among current diffusive models, three different parameterizations were used to assess the water-air fluxes of CH₄ in this study. The flux range was estimated to be 193–18,585 (2793 ± 3812) μmol/m²/d, which is well above that reported for most estuaries worldwide.

河口是大气中甲烷（CH ₄）的重要来源。但是，缺乏足够的实地研究来了解河口CH ₄的来源/汇，这妨碍了全球大气预算。因此，需要更多的研究来弥合这一差距并增进我们对CH ₄动力学的理解。本研究调查潮汐的影响上CH _4个在2017年和2018年春季，小潮期间和24小时以上潮汐周期沿亚热带九龙江口（JRE）的盐度梯度排放空间，所述CH ₄浓度从下游增加到上游，其值在58至1726（393±336）nmol / L之间变化很大，对应于2513–59,371（15,549±11,341）％的饱和度。CH ₄浓度与盐度成反比且显着相关，表明相邻盐水的稀释和硫酸盐抑制作用。暂时，在春季潮汐时期检测到最高的CH ₄浓度和通量，这可以增强颗粒和CH ₄从沉积物中的重悬浮，并伴有较高的浊度值。在退潮期间发现CH ₄浓度升高，低盐度水的水平对流可能是CH ₄增加的驱动力在退潮时集中注意力。由于当前的扩散模型之间缺乏一致性，因此在本研究中使用了三种不同的参数化方法来评估CH ₄的水-空气通量。通量范围估计为193–18,585（2793±3812）μmol/ m ² / d，远高于全球大多数河口的报告范围。