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Citation

Liu D, Shi K, Yan N, Spyrakos E, Tyler AN, Woolway RI & Duan H (2025) New insights on carbon forms in China’s rivers and lakes. Science Bulletin. https://doi.org/10.1016/j.scib.2025.02.040

Abstract
First paragraph: Inland waters, including rivers and lakes, serve as transport channels, transformation sites, and storage units within the global carbon cycle [1]. To illustrate, global rivers export 50%–72% of the terrestrial carbon sink, effectively removing it from the terrestrial ecosystem [2], [3]. The significant uncertainties in the estimation of carbon export from the terrestrial ecosystem are partly due to the limited sampling data from Asian rivers and lakes. In addition, it was previously assumed that Asian rivers have low ratios of dissolved-to-particulate organic carbon concentration (DOC/POC < 1.0) [4] and Asian lakes have fixed ratios of dissolved-to-total organic carbon concentration (DOC/TOC = 0.9) [5]. Utilizing recent sampling data of DOC, dissolved inorganic carbon (DIC), and POC concentrations from 356 rivers and 422 lakes across China, (Note S1 online, Fig. S1 online), here we aim to elucidate the carbon forms presented and evaluate the spatial validity of the two key assumptions in the context of diverse aquatic systems across China, the largest country in Asia. The results demonstrated that 56.9% of rivers exhibited DOC/POC ratios of > 1.0, while DOC/TOC ratios in lakes ranged from 0.1 to 0.99. These findings challenge the aforementioned assumptions and highlight the potential for significant uncertainties in quantifying the role of inland waters in the global carbon cycle. The details are presented below.

Journal
Science Bulletin