College of Water Conservancy, Shenyang Agricultural University, Shenyang, 110866, China.
Institute of Wetland Research, Chinese Academy of Forestry, Beijing, 100091, China.
Environ Res. 2024 Dec 15;263(Pt 1):120076. doi: 10.1016/j.envres.2024.120076. Epub 2024 Sep 26.
River and stream sediments act as biogeochemical reactors for greenhouse gases, particularly methane. However, understanding how riverbed sediment properties influence river carbon emissions remains relatively unclear. The Liao River in northern China is a typical watershed with heterogeneous water and sediment sources, characterized by varying sediment properties. In this study, we surveyed CH and CO emissions from its mainstem and tributaries during flood and dry seasons. We found consistent seasonal patterns in CH and CO emissions, with peaks occurring during the flood season. The average CH and CO fluxes were 1.64 ± 1.80 mmol m d and 59.66 ± 44.60 mmol m d, respectively. Notably, the percentage of sediment silt was significantly correlated with CH concentration and flux (R = 0.12-0.30, p < 0.05). Fine particles dominated the availability of sediment organic matter and redox conditions, which were related to riverine CH production and emissions. Structural equation modeling revealed that both grain size and the percentage of TOC (total organic carbon) directly influenced riverine CH and CO emissions. The organic content and redox conditions of the riverbed sediment collectively explained 65% of riverine CH emissions, while grain size composition indirectly controlled CH emissions by altering sediment substrate quality and redox conditions. In contrast, river CO emissions were only weakly dependent on anaerobic metabolism in riverbed sediments. These findings enhance our understanding of the sources and metabolic mechanisms of riverine CH and CO emissions and offer potential improvements for estimating carbon fluxes in regional or global riverine networks by considering riverbed sediment properties.
河流和溪流沉积物是温室气体（尤其是甲烷）的生物地球化学反应器。然而，了解河床沉积物特性如何影响河流碳排放量仍然相对不清楚。中国北方的辽河流域是一个具有异质水和泥沙源的典型流域，具有不同的沉积物特性。在这项研究中，我们调查了其干流和支流在洪水和枯水季节的 CH 和 CO 排放。我们发现 CH 和 CO 排放存在一致的季节性模式，峰值出现在洪水季节。平均 CH 和 CO 通量分别为 1.64±1.80mmol m d 和 59.66±44.60mmol m d。值得注意的是，沉积物粉砂的百分比与 CH 浓度和通量呈显著正相关（R=0.12-0.30，p<0.05）。细颗粒主导着沉积物有机质和氧化还原条件的可用性，这与河流 CH 产生和排放有关。结构方程模型表明，粒径和 TOC（总有机碳）的百分比都直接影响着河流 CH 和 CO 的排放。河床沉积物的有机含量和氧化还原条件共同解释了 65%的河流 CH 排放，而粒径组成通过改变沉积物基质质量和氧化还原条件间接控制 CH 排放。相比之下，河流 CO 排放仅与河床沉积物中的厌氧代谢弱相关。这些发现提高了我们对河流 CH 和 CO 排放的来源和代谢机制的理解，并为通过考虑河床沉积物特性来估计区域或全球河流网络中的碳通量提供了潜在的改进。
