State Key Laboratory of Marine Geology, Tongji University, 1239 Siping Road, Shanghai, 200092, China; School of Earth System Science, Tianjin University, 92 Weijin Road, Tianjin, 300072, China.
School of Earth System Science, Tianjin University, 92 Weijin Road, Tianjin, 300072, China; Tianjin Key Laboratory of Earth Critical Zone Science and Sustainable Development in Bohai Rim, Tianjin University, 92 Weijin Road, Tianjin, 300072, China.
Environ Res. 2024 Dec 15;263(Pt 2):120117. doi: 10.1016/j.envres.2024.120117. Epub 2024 Oct 5.
Glaciers play key roles in capturing, storing, and transforming global carbon and nitrogen, thereby contributing markedly to their cycles. However, an integrated mechanistic approach is still lacking regarding glacier's primary producers (PP), in terms of stable dissolved inorganic carbon isotope (δC-DIC) and its relationship with dissolved carbon and nitrogen transformation d ynamic changes/cycling. Here, we sampled waters from glaciers, streams, tributaries, and the Indus River (IR) mainstream in the Upper IR Basin, Western Himalaya. Dissolved organic matter (DOM) appears to increase, on average, by ∼2.5-23.4% with fluctuations when passing from glaciers to streams-tributaries-IR mainstream (the upper and lower parts, respectively) continuum, implying that DOM originates from glaciers PP and is subsequently degraded. The corresponding fluctuations are observed for fluorescent DOM (FDOM), dissolved organic nitrogen (8.0-106.8%), NO-N (-13.5/+16.6%), NH-N (-8.8/+13.0%), and NO-N (70.7-217.5%). These variations are associated with overall DOM/FDOM transformations, with the production of ending byproducts (e.g. CO/DIC). The δC-DIC values fluctuated from glaciers (-5.3 ± 2.5‰) to streams (-4.4 ± 2.1‰), tributaries (-4.3 ± 1.6‰), and IR mainstream (-4.2 ± 1.3‰). The δC-DIC data are consistent with C transformations that involve lighter CO emission into the atmosphere, whereas highly depleted DIC/CO is the signature of DOM degradation after its fresh production from glaciers PP which originated by photosynthetic activities (e.g. uptake/sink of atmospheric CO: -8.4‰). Finally, glacier-fed meltwaters would simultaneously contribute to the biogeochemical characteristics of downward margins and specific ecosystems (lake/pond/groundwater/hot springs) via transformation dynamics/cycling of dissolved C and N with high photo/microbial lability. Our results highlight the substantial contribution of western Himalayan glaciers-derived DOM to the global C and N cycles.
冰川在捕获、储存和转化全球碳氮方面发挥着关键作用，从而对其循环做出了显著贡献。然而，对于冰川的初级生产者（PP），我们仍然缺乏一种综合的机制方法，特别是在稳定溶解无机碳同位素（δC-DIC）及其与溶解碳和氮转化动态变化/循环的关系方面。在这里，我们从喜马拉雅山西部印度河上游流域的冰川、溪流、支流和印度河干流（分别为上游和下游）连续体中采集了水样。当从冰川流到溪流-支流-印度河干流（分别为上游和下游）连续体时，溶解有机碳（DOM）的含量似乎平均增加了 2.5-23.4%，同时伴随着波动，这表明 DOM 来源于冰川 PP，随后被降解。荧光溶解有机碳（FDOM）、溶解有机氮（8.0-106.8%）、NO-N（-13.5/+16.6%）、NH-N（-8.8/+13.0%）和 NO-N（70.7-217.5%）也观察到了相应的波动。这些变化与整体 DOM/FDOM 转化有关，最终产生了副产物（例如 CO/DIC）。δC-DIC 值从冰川（-5.3 ± 2.5‰）到溪流（-4.4 ± 2.1‰）、支流（-4.3 ± 1.6‰）和印度河干流（-4.2 ± 1.3‰）波动。δC-DIC 数据与涉及更轻 CO 排放到大气中的 C 转化一致，而高度贫化的 DIC/CO 是 DOM 降解的特征，这是源自冰川 PP 的新鲜产物，由光合作用活动产生（例如，大气 CO 的吸收/汇：-8.4‰）。最后，冰川融水通过溶解 C 和 N 的转化动态/循环，同时会对下游边缘和特定生态系统（湖泊/池塘/地下水/温泉）的生物地球化学特征做出贡献，这些生态系统具有较高的光/微生物可变性。我们的结果强调了喜马拉雅山西部冰川产生的 DOM 对全球碳氮循环的巨大贡献。
