Wang Wanfa, Zhong Jun, Li Si-Liang, Ulloa-Cedamanos F, Xu Sen, Chen Sainan, Lai Manting, Xu Sheng
Key Laboratory of Karst Georesources and Environment, Ministry of Education, Guizhou University, Guiyang 550025, China; College of Resources and Environmental Engineering, Guizhou Karst Environmental Ecosystems Observation and Research Station, Ministry of Education, Guiyang 550025, China.
Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin 300072, China.
Sci Total Environ. 2023 Nov 25;901:166262. doi: 10.1016/j.scitotenv.2023.166262. Epub 2023 Aug 18.
It is generally acknowledged that riverine dissolved inorganic carbon (DIC) behaviors play a critical role in global carbon cycling and hence have an impact on climate change. However, little is known about the intricate DIC dynamics under various meteorological conditions in the alpine areas. Here, we investigated DIC biogeochemical processes in the Bailong River catchment, eastern Qinghai-Tibet Plateau (QTP), by combining measurements of major ions, stable and radioactive isotopic compositions of DIC (δC and ΔC), and physiographic parameters in the Bailong River catchment. Statistics and stoichiometry analyses suggest that multiple biogeochemical processes could affect carbon cycling in the Bailong River catchment. The "old" DIC with low ΔC values (-472.4 ± 127.8 ‰, n = 3) and stoichiometry analysis of dissolved ions showed clear evidence that carbonate weathering is primarily responsible for water chemistry in the upstream (elevation >2000 m). However, upstream samples showed that δC increased between 5 ‰ and 11 ‰ from the theoretical mixing line, concomitant with increasing pH and decreasing pCO, suggesting that isotopic fractionation of DIC due to CO outgassing may be the primary cause of the increased δC values. Additionally, the higher ΔC values (-285.4 ± 123.5 ‰, n = 12) in the downstream region below 2000 m suggest that allochthonous modern carbon had a great impact on DIC variations. The presence of younger DIC may have important implications for the interpretation of inorganic carbon age in downstream rivers. Our study demonstrates that physiographic conditions can regulate DIC behaviors, which can improve estimations of carbon yield and comprehension of global carbon cycle.
人们普遍认为，河流溶解无机碳（DIC）行为在全球碳循环中起着关键作用，因此对气候变化有影响。然而，对于高山地区各种气象条件下复杂的DIC动态，人们了解甚少。在此，我们通过结合对白龙江流域主要离子、DIC的稳定和放射性同位素组成（δC和ΔC）的测量以及白龙江流域的地形参数，研究了青藏高原东部白龙江流域的DIC生物地球化学过程。统计和化学计量分析表明，多种生物地球化学过程可能影响白龙江流域的碳循环。低ΔC值（-472.4±127.8‰，n = 3）的“老”DIC以及溶解离子的化学计量分析表明，碳酸盐风化是上游（海拔>2000米）水化学的主要原因。然而，上游样本显示，δC比理论混合线增加了5‰至11‰，同时pH值升高，pCO降低，这表明由于CO脱气导致的DIC同位素分馏可能是δC值增加的主要原因。此外，在海拔2000米以下的下游地区，较高的ΔC值（-285.4±123.5‰，n = 12）表明，异地现代碳对DIC变化有很大影响。较年轻DIC的存在可能对下游河流无机碳年龄的解释具有重要意义。我们的研究表明，地形条件可以调节DIC行为，这可以改进碳产量的估算并增进对全球碳循环的理解。
