Terrestrial dissolved organic matter inputs accompanied by dissolved oxygen depletion and declining pH exacerbate CO2 emissions from a major Chinese reservoir

Zhang T., Zhou L., Zhou Y., Zhang Y., Guo J., Han Y., ...More

Water Research, vol.251, 2024 (SCI-Expanded) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 251
  • Publication Date: 2024
  • Doi Number: 10.1016/j.watres.2024.121155
  • Journal Name: Water Research
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, PASCAL, Aerospace Database, Analytical Abstracts, Applied Science & Technology Source, Aqualine, Aquatic Science & Fisheries Abstracts (ASFA), BIOSIS, Biotechnology Research Abstracts, CAB Abstracts, Chemical Abstracts Core, Chimica, Communication Abstracts, Compendex, Environment Index, Food Science & Technology Abstracts, Geobase, Metadex, Pollution Abstracts, Veterinary Science Database, Civil Engineering Abstracts
  • Keywords: CO2, Dissolved organic matter (DOM), Dissolved oxygen (DO), FT-ICR MS, Lake Qiandao, pH
  • Middle East Technical University Affiliated: No

Abstract

Terrestrial inputs and subsequent degradation of dissolved organic matter (DOM) in lake ecosystems can result in rapid depletion of dissolved oxygen (DO). Inputs of terrestrial DOM including organic acids can also lead to decreases in pH. However, to date, few studies have investigated the linkages between terrestrial DOM inputs, DO and pH levels in the water column, and carbon dioxide (CO2) emissions from lake ecosystems. Based on monthly field sampling campaigns across 100 sites in Lake Qiandao, a major man-made drinking water reservoir in China, from May 2020 to April 2021, we estimated an annual CO2 efflux (FCO2) of 37.2 ± 29.0 gC m−2 yr−1, corresponding to 0.02 ± 0.02 TgC yr−1 from this lake. FCO2 increased significantly with decreasing DO, chlorophyll-a (Chl-a) and δ2H-H2O, while FCO2 increased with increasing specific UV absorbance (SUVA254) and a terrestrial humic-like component (C2). We found that DO concentration and pH declined with increasing terrestrial DOM inputs, i.e. increased SUVA254 and terrestrial humic-like C2 levels. Vertical profile sampling revealed that the partial pressure of CO2 (pCO2) increased with increasing terrestrial DOM fluorescence (FDOM), while DO, pH, and δ13C-CO2 declined with increasing terrestrial FDOM. These results highlight the importance of terrestrial DOM inputs in altering physico-chemical environments and fueling CO2 emissions from this lake and potentially other aquatic ecosystems.