Particulate organic carbon potentially increases methane emissions from oxic water of eutrophic lakes

Chuanqiao Zhou; Muchun Zhou; Ruoyu Jia; Yu Peng; Fenjun Zhao; Runze Xu; Shuoyuan Liang; Akihiko Terada; Guoxiang Wang; Tsuyoshi Kinouchi; Xiaoguang Xu

doi:10.1016/j.scitotenv.2023.164339

Particulate organic carbon potentially increases methane emissions from oxic water of eutrophic lakes

Sci Total Environ. 2023 Sep 1:889:164339. doi: 10.1016/j.scitotenv.2023.164339. Epub 2023 May 20.

Authors

Affiliations

¹ School of Environment, Nanjing Normal University, Nanjing 210023, China; Department of Transdisciplinary Science and Engineering, Tokyo Institute of Technology, Tokyo 152-8550, Japan.
² School of Environment, Nanjing Normal University, Nanjing 210023, China; Department of Chemical Engineering, Tokyo University of Agriculture and Technology, Tokyo 184-8588, Japan.
³ School of Environment, Nanjing Normal University, Nanjing 210023, China.
⁴ Department of Transdisciplinary Science and Engineering, Tokyo Institute of Technology, Tokyo 152-8550, Japan.
⁵ Department of Chemical Engineering, Tokyo University of Agriculture and Technology, Tokyo 184-8588, Japan.
⁶ School of Environment, Nanjing Normal University, Nanjing 210023, China. Electronic address: xxg05504118@163.com.

PMID: 37216990
DOI: 10.1016/j.scitotenv.2023.164339

Abstract

Lakes are hot spots for methane (CH₄) emissions and particulate organic carbon (POC) production, which describes the methane paradox phenomenon. However, the current understanding of the source of POC and its effect on CH₄ emissions during eutrophication remains unclear. In this study, 18 shallow lakes in different trophic states were selected to investigate the POC source and its contribution to CH₄ production, particularly to reveal the underlying mechanisms of the methane paradox. The carbon isotopic analysis showed that the δ¹³C_poc ranged from -30.28 ‰ to -21.14 ‰, indicating that cyanobacteria-derived carbon is an important source of POC. The overlying water was aerobic but contained high concentrations of dissolved CH₄. Particularly, in hyper-eutrophic lakes, such as Lakes Taihu, Chaohu, and Dianshan, the dissolved CH₄ concentrations were 2.11, 1.01, and 2.44 μmol/L, while the dissolved oxygen concentrations were 3.11, 2.92, and 3.17 mg/L, respectively. The intensified eutrophication increased the POC concentration, concomitantly promoting the dissolved CH₄ concentration and the CH₄ flux. These correlations revealed the role of POC in CH₄ production and emission fluxes, particularly as a possible cause of the methane paradox, which is crucial for accurately evaluating the carbon budget and balance in shallow freshwater lakes.

Keywords: Eutrophication; Isotope; Methane paradox; Particulate organic carbon; Shallow lakes; cyanobacteria.

MeSH terms

Carbon Isotopes / analysis
Carbon*
Dust / analysis
Lakes*
Methane / analysis
Water / analysis

Substances

Carbon
Methane
Water
Carbon Isotopes
Dust