Earth Science Frontiers ›› 2022, Vol. 29 ›› Issue (3): 155-166.DOI: 10.13745/j.esf.sf.2022.1.35

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Dual carbon isotope (δ13C-Δ14C) characteristics and carbon footprint in the spring-pond systems at the Puding Karst Water-Carbon Cycle Test Site

LI Dong1,2,3(), ZHAO Min1,2,*(), LIU Zaihua1,2,*(), CHEN Bo4   

  1. 1. State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
    2. Puding Karst Ecosystem Research Station, Chinese Ecosystem Research Network, Chinese Academy of Sciences, Puding 562100, China
    3. University of Chinese Academy of Sciences, Beijing 100049, China
    4. Guizhou University of Finance and Economics, Guiyang 550025, China
  • Received:2021-12-05 Revised:2022-01-12 Online:2022-05-25 Published:2022-04-28
  • Contact: ZHAO Min,LIU Zaihua


The dissolved inorganic carbon (DIC) and organic carbon (OC) transported to the ocean by rivers are affected by natural and anthropogenic factors. Understanding the influence of these factors on the age, source, and transformation of DIC and OC can help constrain global carbon budget and improve the assessments of natural and human impacts on the riverine carbon cycle. The present study uses dual carbon isotopes (δ13C-Δ14C) of DIC, particulate organic carbon (POC), and aquatic plants with traditional hydrogeochemical characteristics in the spring (groundwater) and spring-fed pond (surface water) systems at the Puding Karst Water-Carbon Cycle Test Site to identify the relavent carbon sources and carbon transformation processes. The results showed that (1) the Δ14C of DIC and POC in the spring-pond systems displayed the same trend, that is, the Δ14C value is lower in the spring water than in the pond water, indicating likely a younger CO2 invasion of the pond system. (2) The changes in water chemistry and carbon isotope of pond water were controlled by different land use and aquatic plants. (3) The OC concentrations were significantly higher in pond water than in spring water, and the Δ14C values of POC were close to those of submerged plants and DIC (apparent ages of 3200-900 years). Such finding indicates that the POC in the pond water was mainly derived from aquatic photosynthesis, which involved old carbon (DIC)—produced by the weathering of carbonate rocks—as carbon source to generate new autochthonous OC (AOC) with negative Δ14C values and “old” apparent age. (4) The contribution percentage of AOC to POC in surface water was more than 75%. Meanwhile, the AOC flux in the spring-pond systems was between 250-656 t C km-2 a-1, and the surface water system of grassland contributed the most AOC and had the highest AOC flux relative to other land use. Such finding indicates the important role of primary production in the organic carbon cycle in shallow water controlled by submerged plants. Overall, the regulation of aquatic plant communities through land use adjustment in karst areas can have major impact on the increasing of carbon sink capacity in these areas.

Key words: dissolved inorganic carbon, particulate organic carbon, autochthonous organic carbon, dual carbon isotopes, carbon footprint, the Puding Karst Water-Carbon Cycle Test Site

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