Deep metamorphic carbon carried by hot spring controls carbon budget of mountainous rivers: Evidence from hydrochemistry and δ13C-DIC, δ13C-DOC isotopes in the south Tibetan Plateau

IF 5 2区地球科学 Q1 WATER RESOURCES

Journal of Hydrology-Regional Studies Pub Date : 2025-10-02 DOI:10.1016/j.ejrh.2025.102818

Jinlin Zhou , Yingchun Wang , Yuhe Fan , Shuang Liao , Pengfei Chen , Zhongping Li , Chunhui Cao , Takahiro Hosono

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引用次数: 0

Abstract

Study region

Southern Tibet includes Cona-Woka Rift, Yadong-Gulu Rift, and Shenzha-Dingjie Rift.

Study focus

This study investigates the effects of groundwater on riverine carbon dynamics in mountainous river systems. Hydrochemical compositions, hydrogen-oxygen isotopes, and δ¹³C-DIC and δ¹³C-DOC isotopes were analyzed for 20 hot springs and their associated upstream and downstream rivers. A mass balance approach, PHREEQC reactive transport models, and entropy-weighted water quality index (EWQI) calculations were employed to quantify the mixing of groundwater and evaluate its impacts on river water chemistry. The groundwater mixing ratio in rivers ranges from 0.2 % to 65.4 %, with an average of 14.5 %, and metamorphic deep-sourced carbon accounts for 82 % of the inorganic carbon carried by groundwater.

New hydrological insights for the region

Groundwater discharge significantly modifies riverine dissolved inorganic carbon (DIC) fluxes, contributing an estimated 10.8 ± 0.38 Tg C/year to rivers across the Qinghai-Tibet Plateau. The mixing of deep-sourced metamorphic carbon not only alters the riverine carbon budget and enhances CO₂ outgassing potential, but also deteriorates downstream water quality. These findings underscore the critical yet previously underestimated role of deep geological processes in regulating surface cycles within high-altitude orogenic systems, offering new perspectives for carbon flux estimations and aquatic ecosystem management in the Tibetan Plateau region.

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本研究探讨了地下水对山地河流水系河流碳动态的影响。对20个温泉及其相关上下游河流的水化学组成、氢氧同位素、δ 13c - dic和δ¹³C-DOC同位素进行了分析。采用质量平衡方法、PHREEQC反应输运模型和熵加权水质指数（EWQI）计算来量化地下水混合并评估其对河流水化学的影响。河流地下水混合比例为0.2 % ~ 65.4 %，平均为14.5 %，变质深源碳占地下水携带无机碳的82 %。地下水排放显著改变了河流溶解无机碳（DIC）通量，贡献了10.8 ± 0。深层变质碳的混合不仅改变了河流的碳收支，提高了CO 2的脱气潜力，而且使下游水质恶化。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Journal of Hydrology-Regional Studies Earth and Planetary Sciences-Earth and Planetary Sciences (miscellaneous)

CiteScore

6.70

自引率

8.50%

发文量

284

审稿时长

60 days

期刊介绍： Journal of Hydrology: Regional Studies publishes original research papers enhancing the science of hydrology and aiming at region-specific problems, past and future conditions, analysis, review and solutions. The journal particularly welcomes research papers that deliver new insights into region-specific hydrological processes and responses to changing conditions, as well as contributions that incorporate interdisciplinarity and translational science.