鄱阳湖湿地反硝化型 CH₄ 厌氧氧化过程及驱动因素分析

Denitrifying anaerobic oxidation of methane (DAMO) is a crucial biogeochemical process that couples the carbon and nitrogen cycles in wetland ecosystems and plays an important role in reducing wetland methane (CH₄) emissions and mitigating global warming. River-lake confluence zones act as convergence points for carbon and nitrogen within watersheds and are therefore hotspots for CH₄emissions. However, DAMO processes and their regulatory mechanisms in these zones remain poorly understood. In this study, the Poyang Lake wetland was selected as the study area. Surface sediment samples (0-5 cm) were collected from the estuaries of the Gan River, Rao River, Fu River, Xiushui River, Xinjiang River, and non-river inflow areas during February (winter) and June (summer) 2021.¹³C isotope tracing technology were used to quantify potential DAMO rates at different river mouths. The results showed that: (1) DAMO rates exhibited pronounced seasonal and spatial heterogeneity. During summer, the average rates of the nitrite-mediated (NO₂^--DAMO) and nitrate-mediated (NO₃-DAMO) processes were 18.71 and 17.92 nmol/(g·d) (expressed as¹³CO₂), respectively, which were significantly higher than those observed in winter (5.66 and 5.72 nmol/(g·d)). The highest DAMO rates occurred at the Fu River estuary, followed by the Xinjiang River estuary, whereas the lowest rates were overserved at the Rao River estuary. (2) The abundance of the mcrA gene exceeded that of pmoA in Poyang Lake wetland sediments (p<0.05), with summer averages of 3.0×10⁷ and 2.9×10⁷ copies/g, respectively, and winter averages of 2.3×10⁷ and 2.2×10⁷ copies/g. Both pmoA and mcrA gene showed significant positive contributions to DAMO rates (p<0.01). (3) Variations in sediment total organic carbon (TOC), Fe²⁺ and Fe³⁺ concentrations significantly influenced mcrA and pmoA gene abundances in the Poyang Lake wetlands, which become the key environmental factors influencing DAMO activity. (4) DAMO in Poyang Lake wetland sediments was estimated to consume 1.39×10⁴ t CH₄ and 3.3×10⁴ t NO_x^- annually, accounting for approximately 26.88% of the lake’s average annual CH₄ emission flux and 2.76% of the total reactive nitrogen input within the watershed. The research indicates that the DAMO process in the Poyang Lake wetland sediments exhibits significant spatiotemporal variation and is regulated by multiple environmental factors. By simultaneously enhancing CH₄ oxidation and removing excess nitrate, DAMO plays a crucial role in mitigating CH₄ emissions and nitrogen loading within lake wetland ecosystems.