Key Laboratory of Surficial Geochemistry, Ministry of Education, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China.
Frontiers Science Center for Critical Earth Material Cycling, Nanjing University, Nanjing 210023, China.
Environ Sci Technol. 2023 Sep 12;57(36):13487-13495. doi: 10.1021/acs.est.3c03378. Epub 2023 Aug 29.
The quantification of carbon cycling across the groundwater-stream-atmosphere continuum (GSAC) is crucial for understanding regional and global carbon cycling. However, this quantification remains challenging due to highly coupled carbon exchange and turnover in the GSAC. Here, we disentangled carbon cycling processes in a representative groundwater-stream-atmosphere transect by obtaining and numerically simulating high-resolution time series of dissolved He, Ar, Kr, O, CO, and CH concentrations. The results revealed that groundwater contributed ∼60% of CO and ∼30% of CH inputs to the stream, supporting stream CO and CH emissions to the atmosphere. Furthermore, diurnal variations in stream metabolism (-0.6 to 0.6 mol O m day) induced pronounced carbonate precipitation during the day and dissolution at night. The significant diurnal variability of biogeochemical processes emphasizes the importance of high-resolution time series investigations of carbon dynamics. This study shows that dissolved gases are promising environmental tracers for discerning and quantifying carbon cycling across the GSAC with high spatiotemporal resolution. Our high-resolution carbon exchange and turnover quantification provides a process-oriented and mechanistic understanding of carbon cycling across the GSAC.
量化地下水-河流-大气连续体（GSAC）中的碳循环对于理解区域和全球碳循环至关重要。然而，由于 GSAC 中碳交换和周转的高度耦合，这种量化仍然具有挑战性。在这里，我们通过获取和数值模拟溶解氦、氩、氪、氧、二氧化碳和甲烷浓度的高分辨率时间序列，在具有代表性的地下水-河流-大气连续体横截面上分解了碳循环过程。结果表明，地下水为河流提供了约 60%的 CO 和约 30%的 CH 输入，支持了河流向大气排放 CO 和 CH。此外，河流代谢的昼夜变化（-0.6 到 0.6 mol O m 天）导致白天碳酸盐大量沉淀，夜间溶解。生物地球化学过程的显著昼夜变化强调了高分辨率时间序列对碳动力学进行研究的重要性。本研究表明，溶解气体是区分和量化 GSAC 中碳循环的有前途的环境示踪剂，具有高时空分辨率。我们的高分辨率碳交换和周转量化提供了对 GSAC 中碳循环的面向过程和机制的理解。
