Basin‐Scale CO₂ Emissions From the East River in South China: Importance of Small Rivers, Human Impacts and Monsoons

Abstract

River networks are key members in the regional and global carbon (C) cycle (Battin et al., 2009;Cole et al., 2007;Drake et al., 2018). Large quantities of C stabilized by the terrestrial ecosystems are transported from the land to rivers through runoff and groundwater, (Regnier et al., 2022), and this land-river C transport could offset terrestrial C gain and diminish the C sequestration capacity of terrestrial ecosystems (Chi et al., 2020;Duvert et al., 2020;Lauerwald et al., 2020). Emission in the form of carbon dioxide (CO 2 ) from water to the atmosphere is a primary pathway of those land-derived riverine C. Annual CO 2 emissions from rivers could reach up to 2 Pg C (S. Liu et al., 2022), outpacing the C transported by rivers from the land to the ocean or those buried within the river networks (Regnier et al., 2022). However, there is still great uncertainty in estimations of riverine CO 2

Carbon Emissions From Chinese Inland Waters: Current Progress and Future Challenges

“…A similar instantaneous response was also observed by Liu et al. (2023) when examining the effects of floods on CO 2 fluxes in an intermittent stream in Inner Mongolia, China. The CO 2 fluxes immediately after rewetting increased by 27‐fold relative to that before the onset of the floods (Liu et al., 2023).…”

“…In incubation experiments with sediments from more than 200 dry IRES worldwide, von Schiller et al ( 2019) found a 32-to 66-fold increase in the respiration rate after sediment rewetting, with an average CO 2 emission rate of 833 mmol m 2 d 1 . A similar instantaneous response was also observed by Liu et al (2023) when examining the effects of floods on CO 2 fluxes in an intermittent stream in Inner Mongolia, China. The CO 2 fluxes immediately after rewetting increased by 27-fold relative to that before the onset of the floods (Liu et al, 2023).…”

“…Given the size of China and its abundance in various forms of water bodies, carbon emissions from Chinese inland waters are predicted to be substantial and play a potentially important role in the global C budget. There has been notable progress in investigating dissolved CO 2 and CH 4 concentrations and emissions along large Chinese rivers (Table 2), such as the Yangtze (Liu et al., 2016), Yellow (Ran, Lu, Yang, et al., 2015), and Pearl (Liu et al., 2023). In addition, large lakes and reservoirs have received increasing attention due to their importance in freshwater supply and/or hydropower generation.…”

“…(2023) when examining the effects of floods on CO 2 fluxes in an intermittent stream in Inner Mongolia, China. The CO 2 fluxes immediately after rewetting increased by 27‐fold relative to that before the onset of the floods (Liu et al., 2023). However, only a handful of studies have explored CO 2 emissions from IRES systems in China, and no studies on CH 4 dynamics in China's IRES systems have yet been reported.…”

“…In lentic water like reservoirs and lakes, however, rising summer temperature could boost algal primary production, leading to reduced pCO 2 that even turns the lentic waters into CO 2 sinks (Xiao et al, 2021). While increased runoff would dilute pCO 2 for rivers with limited supply of soil CO 2 , as widely observed in river basins like the Yangtze, Yellow, and Pearl (Liu et al, 2023;Liu et al, 2016;Ran, Lu, Richey, et al, 2015), the high soil-groundwater-stream connectivity in karst rivers that facilitates rapid transfer of CO 2 can generally sustain even higher pCO 2 during the rainy season (Pu et al, 2019). Contrary to CO 2 , CH 4 production is more sensitive to temperature changes (Stanley et al, 2016).…”