Influences of carbonate weathering and hyporheic exchange on carbon fluxes in Pearl River Basin, China,Water Research

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Influences of carbonate weathering and hyporheic exchange on carbon fluxes in Pearl River Basin, China
Water Research ( IF 11.4 ) Pub Date : 2024-06-29 , DOI: 10.1016/j.watres.2024.122014
Chao Gu ₁ , Yi Liu ₂ , Hongkai Qi ₃ , Mengqian Lu ₄

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Deciphering riverine dissolved carbon dynamics is pivotal for a comprehensive picture of the global carbon cycle. Through rigorous in-situ sampling across the Pearl River Basin (PRB), our investigation reveals the Pearl River networks function as a significant carbon source, with the annual carbon dioxide (CO2) emission of 2.57 ± 1.94 Tg C, which offsets 10 ± 8 % of the forest carbon sequestration or 65 ± 49 % carbon sink via chemical weathering in the PRB. Based on the mass balance of 222Rn, we initially reveal that the contributions of water flux from the hyporheic zone increased with the river orders (Hack Order) across both dry and wet seasons. Conversely, the evasion rates of dissolved CO2 (CO2*) and dissolved inorganic carbon (DIC) from the hyporheic zone into river channels exhibited a decline with the increasing river orders. The hyporheic exchange contributes 4 – 11 % of the lateral and vertical DIC losses, thereby is a key mechanism in the riverine carbon cycle. Furthermore, CO2* derived from the hyporheic zone was ∼4 times of riverine CO2 emissions and this CO2* flux from the hyporheic zone was buffered into carbonates/bicarbonates in river channels, due to the high riverine pH resulted from carbonate weathering in the basin. These results not only highlight the substantial role of carbonates and hyporheic processes in modulating riverine carbon fluxes but also signify their broader implications on understanding riverine carbon dynamics at both regional and global scales.

中文翻译：

珠江流域碳酸盐风化和潜流交换对碳通量的影响

破译河流溶解碳动态对于全面了解全球碳循环至关重要。通过对珠江流域 (PRB) 进行严格的原位采样，我们的调查显示珠江水网是一个重要的碳源，每年二氧化碳 (CO2) 排放量为 2.57 ± 1.94 Tg C，抵消了 10 ± 8 % 的森林碳固存或 65 ± 49% 通过 PRB 中的化学风化碳汇。基于 222Rn 的质量平衡，我们初步揭示了无论是旱季还是雨季，来自潜流带的水通量的贡献都随着河流阶次（Hack Order）的增加而增加。相反，溶解性二氧化碳（CO2*）和溶解性无机碳（DIC）从潜流带进入河道的逃逸率随着河流等级的增加而呈下降趋势。潜流交换贡献了 4-11% 的横向和纵向 DIC 损失，因此是河流碳循环的关键机制。此外，来自潜流带的 CO2* 是河流 CO2 排放量的 4 倍，并且由于盆地碳酸盐风化导致河流 pH 值较高，来自潜流带的 CO2* 通量被缓冲到河道中的碳酸盐/碳酸氢盐中。这些结果不仅强调了碳酸盐和潜流过程在调节河流碳通量方面的重要作用，而且还表明它们对了解区域和全球尺度的河流碳动态具有更广泛的影响。

更新日期：2024-06-29

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