High spatial and seasonal heterogeneity of pCO2 and CO2 emissions in a karst groundwater-stream continuum, southern China

Pu, Junbing; Li, Jianhong; Zhang, Tao; Xiong, Xiaofeng; Yuan, Daoxian

doi:10.1007/s11356-019-05820-9

Cited by 11 publications

(3 citation statements)

References 75 publications

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“…The median percentage of CO 2 loss in the first 100 m from groundwater sources in 15 streams worldwide covering tropical, temperate, and boreal catchments was 76% (Duvert et al, 2018). Our pCO 2 measurement unequivocally indicated the evasion of CO 2 along the reach was very substantial and occurred immediately upon entry of the groundwater into the surface stream (Pu et al, 2019). This observation was particularly salient because it reflected the presence of very active gas exchange triggered by strong turbulence in this high gradient headwater stream fed by groundwater and illustrated that groundwater with exceptionally high CO 2 content had a diminishing effect on stream pCO 2 values with increasing distance downstream (Duvert et al, 2018).…”

Section: Carbon Dioxide Exchange Dynamicsmentioning

confidence: 59%

Rapid Loss of Dissolved CO2 From a Subtropical Steep Headwater Stream

et al. 2021

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High-gradient headwater streams are major participants in the carbon (C) cycle because of their capabilities of emitting a significant amount of carbon dioxide (CO2). Notwithstanding, their CO2 emissions have been largely overlooked in previous studies owing to their small water surface area and are sometimes strenuous to be measured because of their narrow channel widths and strong turbulence. This study examined the spatial and seasonal variabilities of CO2 dynamics of a subtropical steep headwater stream fed by groundwater. Our study found that the pH and dissolved oxygen exhibited a general increasing trend away from the source of the headwater whereas the partial pressure of carbon dioxide (pCO2) showed a downward trend. The stream water pCO2 in the upper reach was found to be higher than the ambient level by 19–114 times, with an average drop of >70% at just 9.2 m from the groundwater source, demonstrating the potentially large emission of CO2 into the atmosphere within this short distance. Additionally, the sampling works conducted further downstream revealed that the CO2 derived from groundwater could almost completely dissipate within approximately half a kilometer downstream of the source. The concentrations of dissolved organic carbon and pCO2 were also lower during the period with lower air temperatures in the headwater stream, indicating temperature-dependent metabolism and decomposition of organic matter in soil might modulate the C dynamics in the headwater stream, although the rapid gas exchange along the stream remained the determinative factor. Our findings reassert that headwater streams are an essential source of CO2 and disregarding them from the studies of greenhouse gas emissions of inland waters would underestimate their potency to influence the global C cycle.

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Section: Carbon Dioxide Exchange Dynamicsmentioning

confidence: 59%

Rapid Loss of Dissolved CO2 From a Subtropical Steep Headwater Stream

et al. 2021

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“…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).…”

Section: Hydrological and Climatic Controlsmentioning

confidence: 99%

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

Yang,

Chen,

et al. 2024

JGR Biogeosciences

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Inland waters are significant emitters of greenhouse gases for the atmosphere and play an important role in the global carbon cycle. With a vast land area in East Asia spanning a broad range of climatic conditions, China has a large number of natural and human‐made water bodies. These inland water systems are of global importance because of their high carbon emission fluxes. Over the past decades, China has experienced unprecedented environmental changes driven by rapid economic development, which have profoundly modified its inland water carbon biogeochemistry and associated emissions. This review focuses on carbon dioxide (CO2) and methane (CH4) emission dynamics from China's inland waters in response to global change. Major drivers of CO2 and CH4 emissions, including aquatic metabolism, hydrological and climatic factors, and prevailing human impacts, are examined. To advance our understanding of carbon emissions from China's inland waters, we further identify several critical knowledge gaps, such as inadequate research in headwater streams and the climate‐sensitive Tibetan Plateau aquatic ecosystems. Furthermore, insufficient understanding of carbon emissions from inland waters undergoing extensive human interventions (e.g., damming, flow regulation, pollution, and farming practices in aquaculture ponds) is highlighted. We suggest that future efforts should be made to better capture the spatiotemporal heterogeneity in dissolved CO2 and CH4 concentrations and fluxes across China as well as their long‐term trends. To overcome uncertainties in carbon sources and current flux estimates, future research to mechanistically understand carbon transport and transformation in Chinese inland waters and their underlying processes is particularly needed.

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“…In a similar study, Chen et al 18 calculated organic carbon sink by the biological pump effect in an epikarst spring of Laqiao, Guizhou and found that it was 336 tC/(a•km 2 ), which was about 51 times higher than the organic carbon stored in the marine control waterbody. Pu et al 19 estimated that the total amount of CO 2 released to the atmosphere from groundwater-stream was 21.75 t CO 2 /year, which is only 1.71-5.62% of the dissolved inorganic carbon loss flux.…”

Section: Introductionmentioning

confidence: 99%

Diel Variation of Hydrochemistry and Carbon Flux in the Banzhai River, SW China

Shi

Liu

et al. 2021

Preprint

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This study was undertaken in the Banzhai, a small groundwater-fed stream flowing over carbonate karst terrain in the southwest of Guizhou, China. To assess the biogeochemical processes behind carbon fluxes and sinks and calculate the end-member contribution to the geological carbon sink, samples were collected at a 2-h sampling interval during a two-day period, and the diel-variation of δ13CDIC, δ13CPOC, and C/N were analyzed. During the sampling period, temperature, pH, electrical conductivity (EC), dissolved oxygen (Do), and chlorophyll were measured at a 15-min interval using in situ sensors. The results showed that (1) the hydro-chemical variations reflected the photosynthesis of subaquatic plants and degassing. These processes likely turned a part of HCO3- to organic carbon, which subsequently precipitated. (2) The 13C isotope ratios indicated a varying intensity of photosynthesis and degassing during the HCO3- migration process. Moreover, subaquatic plants changed their metabolic pathway from C3 to C4 carbon fixation due to the lack of CO2 in the water and utilized HCO3- in the water as their carbon source. (3) The net carbon sink flux was 1784.54 kg CO2, where carbonate weathering, the biological carbon pump, and weathering of silicate rocks accounted for 85.80 %, 13.64 %, and 0.56 %, respectively. (4) In the Banzhai ground river, the DIC during the migration process was mainly lost through degassing, allogenic acid, and consumption by photosynthesis of subaquatic plants.

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High spatial and seasonal heterogeneity of pCO2 and CO2 emissions in a karst groundwater-stream continuum, southern China

Cited by 11 publications

References 75 publications

Rapid Loss of Dissolved CO2 From a Subtropical Steep Headwater Stream

Rapid Loss of Dissolved CO2 From a Subtropical Steep Headwater Stream

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

Diel Variation of Hydrochemistry and Carbon Flux in the Banzhai River, SW China

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