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https://doi.org/10.5194/bg-2018-292
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2018-292
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 20 Aug 2018

Submitted as: research article | 20 Aug 2018

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This preprint has been withdrawn by the authors.

High Riverine CO2 Outgassing affected by Land Cover Types in the Yellow River Source Region

Mingyang Tian1, Xiankun Yang2, Lishan Ran3, Yuanrong Su1, Lingyu Li1, Ruihong Yu1, Haizhu Hu1, and Xi Xi Lu1,4 Mingyang Tian et al.
  • 1Inner Mongolia key laboratory of river and lake ecology, School of ecology and environment, Inner Mongolia University, Hohhot, 010021, China
  • 2School of Geographical Sciences of Guangzhou University, Guangzhou, 510006, China
  • 3Department of Geography, The University of Hong Kong, Hong Kong, China
  • 4Department of Geography, National University of Singapore, 117570, Singapore

Abstract. Rivers connect the land and the oceans, acting as both active pipes and containers transporting carbon and other substances from terrestrial ecosystems to aquatic ecosystems. Meanwhile, rivers can release huge amounts of CO2 to the atmosphere. However, estimates of global riverine CO2 emissions remain greatly uncertain owing to the absence of a comprehensive spatially and temporally CO2 emissions measurement, especially in river source regions. In this study, riverine partial pressure of CO2 (pCO2) and CO2 efflux (FCO2) in the Yellow River source region under different landcover types, including glaciers, permafrost, wetlands, and grasslands, were investigated in April, June, August, and October 2016. The relevant chemical parameters and environmental parameters, including pH, dissolved oxygen (DO), and dissolved organic carbon (DOC), were analyzed to explore the main control factors of riverine pCO2 and FCO2. The results showed that the rivers in the Yellow River source region were a net CO2 source, with the pCO2 ranging from 181 to 2441 μatm and the FCO2 from −221 to 6892 g C m−2 yr−1. Both the pCO2 and FCO2 showed strong spatial and temporal variations. The average FCO2 in August was higher than that in other months, with the lowest in October. In alpine climates, low temperature conditions played a crucial role in limiting biological activity and reducing CO2 emissions. The lowest FCO2 values (−221 g C m−2 yr−1) were observed in the glacier and permafrost regions. By integrating seasonal changes of water surface area, the total CO2 efflux was estimated at 0.37 ± 0.49 Tg C yr−1, which is significantly higher than previous studies. Although it is still a small proportion of CO2 emissions compared with the whole Yellow River Basin, but there is a huge carbon emissions potential. Since the permafrost in the source region of the Yellow River is rich in large amounts of ice and organic carbon, the continuously increasing temperature due to global warming will accelerate not only the mobilization of organic carbon in permafrost, but also the degradation of organic carbon by soil microorganisms. As a consequence, huge amounts of CO2 release from soils and rivers is anticipated.

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Mingyang Tian et al.
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Mingyang Tian et al.
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Short summary
We investigated the spatial and temporal variability of riverine CO2 outgassing characteristics of the Yellow River source region. Riverine CO2 emission were in situ monitored under different land cover types (i.e., glacier, permafrost, wetland, and grassland) in the research area.This study will lead to a better understanding of riverine carbon export, especially for alpine rivers, which will help refine the global estimation of global GHG gas emission.
We investigated the spatial and temporal variability of riverine CO2 outgassing characteristics...
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