Preprints
https://doi.org/10.5194/bg-2021-234
https://doi.org/10.5194/bg-2021-234
29 Sep 2021
 | 29 Sep 2021
Status: this preprint has been withdrawn by the authors.

Methane accumulation affected by particulate organic carbon in upper Yangtze deep valley dammed cascade reservoirs, China

Yuanyuan Zhang, Youheng Su, Zhe Li, Shuhui Guo, Lunhui Lu, Bin Zhang, and Yu Qin

Abstract. Methane (CH4) emissions from freshwaters to the atmosphere have a profound impact on global atmospheric greenhouse gas (GHG) concentrations. Anthropogenic footprints such as dam construction and reservoir operation significantly changed the fate and transport of CH4 in freshwaters. The type of particulate organic carbon (POC) in reservoirs is a critical factor controlling CH4 production and emissions. However, little is known of how reservoir operation mediates the distribution of POC and regulates CH4 accumulation in cascade hydroelectric reservoirs. Here, spatial and temporal variations in POC and CH4 were explored in the Xiluodu (XLD) and Xiangjiaba (XJB) reservoirs which are deep valley dammed cascade reservoirs located in the main channel of the upper Yangtze River. Based on the δ13C-POC and N / C mole ratios of particulate organic matter, the results of multi-endmember stable isotope mixing models by a Bayesian model show that terrestrial POC and autochthonous POC accounted for approximately 56 ± 19 % and 42 ± 19 % (SD, n = 181) of POC, respectively. CH4 concentrations and δ13C-CH4 in the cascade reservoirs were potentially influenced by CH4 oxidation. Together with other physicochemical parameters and structural equation model, these results suggested that the input of terrestrial POC was dominantly influenced by water level variations and flow regulation due to reservoir operation. The cumulative effect of POC caused by cascade reservoirs was not apparent at a bimonthly scale. Terrestrial POC was more likely to dominate CH4 accumulation in cascade reservoirs under reservoir operation.

This preprint has been withdrawn.

Yuanyuan Zhang, Youheng Su, Zhe Li, Shuhui Guo, Lunhui Lu, Bin Zhang, and Yu Qin

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2021-234', Anonymous Referee #1, 05 Nov 2021
    • AC1: 'Reply on RC1', Zhe Li, 07 Nov 2021
  • RC2: 'Comment on bg-2021-234', Anonymous Referee #2, 26 Nov 2021
    • AC2: 'Reply on RC2', Zhe Li, 03 Dec 2021
      • RC3: 'Reply on AC2', Anonymous Referee #2, 06 Dec 2021
        • AC3: 'Reply on RC3', Zhe Li, 07 Dec 2021

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2021-234', Anonymous Referee #1, 05 Nov 2021
    • AC1: 'Reply on RC1', Zhe Li, 07 Nov 2021
  • RC2: 'Comment on bg-2021-234', Anonymous Referee #2, 26 Nov 2021
    • AC2: 'Reply on RC2', Zhe Li, 03 Dec 2021
      • RC3: 'Reply on AC2', Anonymous Referee #2, 06 Dec 2021
        • AC3: 'Reply on RC3', Zhe Li, 07 Dec 2021
Yuanyuan Zhang, Youheng Su, Zhe Li, Shuhui Guo, Lunhui Lu, Bin Zhang, and Yu Qin
Yuanyuan Zhang, Youheng Su, Zhe Li, Shuhui Guo, Lunhui Lu, Bin Zhang, and Yu Qin

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This preprint has been withdrawn.

Short summary
POC in the XLD and XJB reservoirs mainly originates from terrestrial POC (56 %). CH4 oxidation potentially influences the variations in CH4 concentrations and δ13C-CH4 in cascade reservoirs. Water level variations and flow regulation caused by reservoir operation are primary factors for the input of terrestrial POC. The cumulative effect of POC at a bimonthly scale was not significant in the XLD and XJB reservoirs. Terrestrial POC displays more persistent impacts on CH4 accumulation.
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