Linking riverine partial pressure of carbon dioxide to dissolved organic matter optical properties in a Dry-hot Valley Region

Maofei Ni; Siyue Li; Isaac Santos; Jing Zhang; Jiachen Luo

doi:10.1016/j.scitotenv.2019.135353

Linking riverine partial pressure of carbon dioxide to dissolved organic matter optical properties in a Dry-hot Valley Region

Sci Total Environ. 2020 Feb 20:704:135353. doi: 10.1016/j.scitotenv.2019.135353. Epub 2019 Nov 23.

Authors

Maofei Ni¹, Siyue Li², Isaac Santos³, Jing Zhang⁴, Jiachen Luo¹

Affiliations

¹ Key Laboratory of Reservoir Aquatic Environment, Research Center for Ecohydrology, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China; University of Chinese Academy of Sciences, Beijing 100049, China.
² Key Laboratory of Reservoir Aquatic Environment, Research Center for Ecohydrology, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China. Electronic address: syli2006@163.com.
³ National Marine Science Centre, Southern Cross University, PO Box 4321, Coffs Harbour, New South Wales 2450, Australia.
⁴ Key Laboratory of Reservoir Aquatic Environment, Research Center for Ecohydrology, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China; College of Resources and Environment, Southwest University, Chongqing 400716, China.

PMID: 31812378
DOI: 10.1016/j.scitotenv.2019.135353

Abstract

The mineralization of dissolved organic matter (DOM) can partially explain riverine carbon dioxide (CO₂) emissions to the atmosphere. However, little is known about how the DOM origin and composition drive CO₂ partial pressures (pCO₂). Here, we reveal links between aquatic pCO₂, DOM optical parameters (a₂₅₄, a₃₅₀ and S_275-295 and S_350-400) and nutrients in a subtropical river in China's Dry-hot Valley Region. Biodegradation preferentially decomposed low molecular weight (LMW) DOMs, increasing high molecular weight (HMW) DOMs along the main stem. pCO₂ was positively correlated with aromatic and lignin compounds, but negatively correlated with DOM molecular weight. Aquatic respiration of DOMs largely explained the pCO₂ levels in the drought period, while terrestrial inputs were a pCO₂ source in the initial-wet period. Our results illustrate how both DOM concentrations and speciation can explain pCO₂ distribution and sources in rivers.

Keywords: CO(2) partial pressure (pCO(2)); Dissolved organic matter (DOM); Longitudinal Range-Gorge region; Trophic levels; pCO(2) – DOM couplings.