Dam construction significantly mitigates methane emissions along river-estuary continuum of the Yangtze River
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Methane (CH4), the second most important greenhouse gas, has approximately triply increased in the atmosphere from the pre-industrial era to now. Despite occupying only 0.58% of Earth’s non-glaciated land surface, rivers play a critical role in carbon delivery and transformation within aquatic networks, rendering them a significant contributor of CH4 to the atmosphere.
With the proliferation of dam construction driven by the growing utilization of hydropower since the mid-20th century, they have a potential to impede carbon transport and undoubtedly impact the biogeochemical cycling of CH4, leading to an uncertainty in riverine CH4 emissions. However, the only existing study comprehensively assessed the influence of dam construction on riverine CH4 emission by using artificial neural networks, whereas the methanogenic pathways were not taken into consideration.
Supervised by Prof. WU Qinglong, Dr. LI Biao, a research assistant of NIGLAS, along with their collaborators, have carried out an extensive examination of CH4 dynamics along the river-estuary continuum of the Yangtze River. Utilizing a process-based model according to the methanogenic pathway, they found hydrogenotrophic methanogenesis is the dominant pathway, furtherly demonstrating a remarkable 82.5% decrease in CH4 emissions since the implementation of the Three Gorges Dam.
Their findings were published in Water Research on 20 May 2023.
By analyzing the stable carbon isotope signature (δ13C-CH4) along the river-estuary continuum of the Yangtze River, it strongly supports the persistence of hydrogenotrophic methanogenesis as the primary pathway within the study area.
In order to provide further validation for this hypothesis, comprehensive tests involving methanogenic community composition and substrate amendment were carried out, ultimately confirming the prevailing role of hydrogenotrophic methanogenesis along the river-estuary continuum of the Yangtze River.
Through field investigations, a robust correlation was identified between dissolved carbon dioxide (CO2) and dissolved CH4. Expanding on the established predominance of hydrogenotrophic methanogenesis, a process-based model was developed. Historical CO2 data were furtherly employed to retrospectively examine the historical fluctuations in CH4, uncovering a substantial reduction of 82.5% in methane emissions after the construction of the Three Gorges Dam.
“Our study provides a new insight from a microbial perspective on CH4 cycling, and it is necessary to take the methanogenic pathway into account when predicting CH4 emission from inland waters in the future.” said Dr. LI.
CH4 emission before and after the dam construction along river-estuary continuum of the Yangtze River （Image by LI Biao）
Link: https://www.sciencedirect.com/science/article/pii/S0043135423005328?ref=pdf_download&fr=RR-2&rr=7ca4e1fc3e2d0489
Contact
TAN Lei
Nanjing Institute of Geography and Limnology
E-mail: ltan@niglas.ac.cn