High-frequency, paired measurements of the partial pressure of CO₂ (pCO₂) and dissolved O₂ were combined with dissolved organic matter (DOM) characterization to investigate diurnal (7:00–19:00) and seasonal variations in CO₂ dynamics in the lower Ganges River. Diurnal variations in pCO₂ shifted seasonally, concurring with changes in DOM optical properties, biodegradable DOM, and O₂ departures from atmospheric equilibrium (ΔO₂). Increased pCO₂ and CO₂ flux (FCO₂) in August–September corresponded to monsoonal floods carrying more terrestrial materials. Lower dry-season pCO₂ and FCO₂ concurred with higher ΔO₂, and exhibited strong relationships with DO and pH, indicating a dominant influence of phytoplankton production. Despite large variations in pCO₂, the year-long positive FCO₂ implied that the lower Ganges acted as a CO₂ source, reaching 122 mmol m⁻² d⁻¹. Increasing hydrologic variability and pollution in the Ganges Basin can amplify pCO₂ variations linked to seasonal shifts in terrestrial inputs and phytoplankton production.

中文翻译：

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恒河下游 pCO2 和 O2 日变化的季节性变化

_{将 CO 2} ( p CO ₂ ) 和溶解 O ₂分压的高频配对测量与溶解有机物 (DOM) 表征相结合，以研究 CO ₂的昼夜（7:00–19:00）和季节变化恒河下游的动态。p CO ₂的日变化随季节变化，与 DOM 光学特性、可生物降解 DOM 和 O ₂偏离大气平衡 (ΔO ₂ ) 的变化同时发生。增加p CO ₂和 CO ₂通量 ( F CO ₂) 8 月至 9 月对应于携带更多陆地材料的季风洪水。较低的旱季p CO ₂和F CO ₂与较高的 ΔO ₂一致，并且与 DO 和 pH 值有很强的关系，表明浮游植物生产的主要影响。尽管p CO ₂变化很大，但长达一年的正F CO ₂表明恒河下游充当了 CO ₂源，达到 122 mmol m ^-2  d ^-1。恒河盆地不断增加的水文变化和污染可以放大p CO ₂与陆地投入和浮游植物生产的季节性变化有关的变化。