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Strong carbonate buffering in karst cascade river-reservoir systems constrains CO2 production and emissions.

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Title: Strong carbonate buffering in karst cascade river-reservoir systems constrains CO2 production and emissions.
Authors: Hu, Xuan1,2 (AUTHOR), Wang, Wanfa1,2 (AUTHOR) wfwang@gzu.edu.cn, Ran, Lishan3 (AUTHOR), Xu, Sen4 (AUTHOR), Han, Qiong4,5 (AUTHOR), Ulloa-Cedamanos, Francesco6 (AUTHOR), Zhong, Jun4 (AUTHOR), Chen, Bei-Bei4,7 (AUTHOR), Yu, Shengde8 (AUTHOR), He, Dengming1,2 (AUTHOR), Shi, Wenhong1,2 (AUTHOR), Xu, Siqin1,2 (AUTHOR), Li, Si-Liang4 (AUTHOR)
Source: Geochimica et Cosmochimica Acta. Dec2025, Vol. 411, p222-232. 11p.
Subjects: Carbonates, Carbonate reservoirs, Carbon emissions, Carbonate minerals, Carbon cycle, Isotopic analysis
Geographic Terms: Karst (Slovenia & Italy : Region)
Abstract: River cascade damming profoundly alters inland water carbon cycling, yet the carbonate buffering mechanisms under high partial pressure of carbon dioxide (p CO 2) and low pH conditions in the hypolimnion and released water of karst reservoirs remain unclear. This study elucidated dissolved inorganic carbon (DIC) transport and transformation across cascade reservoirs within the Wujiang River basin, emphasizing the role of carbonate buffering in the fluxes and spatiotemporal patterns of CO 2 , as well as the stable isotopic composition of DIC (δ13C DIC). Water chemistry and dual isotope (δ13C DIC and Δ14C DIC) analysises suggest that in carbonate-rich reservoirs, carbonate dissolution and autochthonous particulate inorganic carbon driven by biological carbon pump create a dual buffering effect, reducing CO 2 production and emissions by 57 %–80 %. Quantitative carbonate buffering modeling demonstrates that the strong carbonate buffering extends p CO 2 and δ13C DIC equilibrium timescales by 2–100 times compared to non-buffered scenarios. Over extended timescales, water-carbonate mineral interactions in the cascade reservoirs of the Wujiang River impart buffering capacity, which not only suppresses CO 2 production and emissions but also exerts an influence on isotopic fractionation. Therefore, the hypolimnion contributes to CO 2 reduction (0.01–135.10 Gg CO 2 year−1), while the released water has much lower CO 2 fluxes than non-karst reservoirs, achieving a CO 2 emission reduction of 5.40–93.28 Gg CO 2 year−1. As reservoirs proliferate globally, integrating carbonate buffering into carbon budget assessments is essential for refining reservoir CO 2 emission estimates, especially in karst regions that account for 10 %–15 % of Earth's continental surface. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
Description
Abstract:River cascade damming profoundly alters inland water carbon cycling, yet the carbonate buffering mechanisms under high partial pressure of carbon dioxide (p CO 2) and low pH conditions in the hypolimnion and released water of karst reservoirs remain unclear. This study elucidated dissolved inorganic carbon (DIC) transport and transformation across cascade reservoirs within the Wujiang River basin, emphasizing the role of carbonate buffering in the fluxes and spatiotemporal patterns of CO 2 , as well as the stable isotopic composition of DIC (δ13C DIC). Water chemistry and dual isotope (δ13C DIC and Δ14C DIC) analysises suggest that in carbonate-rich reservoirs, carbonate dissolution and autochthonous particulate inorganic carbon driven by biological carbon pump create a dual buffering effect, reducing CO 2 production and emissions by 57 %–80 %. Quantitative carbonate buffering modeling demonstrates that the strong carbonate buffering extends p CO 2 and δ13C DIC equilibrium timescales by 2–100 times compared to non-buffered scenarios. Over extended timescales, water-carbonate mineral interactions in the cascade reservoirs of the Wujiang River impart buffering capacity, which not only suppresses CO 2 production and emissions but also exerts an influence on isotopic fractionation. Therefore, the hypolimnion contributes to CO 2 reduction (0.01–135.10 Gg CO 2 year−1), while the released water has much lower CO 2 fluxes than non-karst reservoirs, achieving a CO 2 emission reduction of 5.40–93.28 Gg CO 2 year−1. As reservoirs proliferate globally, integrating carbonate buffering into carbon budget assessments is essential for refining reservoir CO 2 emission estimates, especially in karst regions that account for 10 %–15 % of Earth's continental surface. [ABSTRACT FROM AUTHOR]
ISSN:00167037
DOI:10.1016/j.gca.2025.11.003