Unexpected low CO2 emission from highly disturbed urban inland waters

Gongqin Wang; Shaoda Liu; Siyue Sun; Xinghui Xia

doi:10.1016/j.envres.2023.116689

Unexpected low CO₂ emission from highly disturbed urban inland waters

Environ Res. 2023 Oct 15:235:116689. doi: 10.1016/j.envres.2023.116689. Epub 2023 Jul 18.

Authors

Gongqin Wang¹, Shaoda Liu², Siyue Sun³, Xinghui Xia⁴

Affiliations

¹ Key Laboratory of Water and Sediment Sciences of Ministry of Education, State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing, China; Hebei Key Laboratory of Close-to-Nature Restoration Technology of Wetlands, School of Eco-Environment, Hebei University, Baoding, 071002, Hebei, China.
² Key Laboratory of Water and Sediment Sciences of Ministry of Education, State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing, China. Electronic address: liushaoda@bnu.edu.cn.
³ Key Laboratory of Water and Sediment Sciences of Ministry of Education, State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing, China.
⁴ Key Laboratory of Water and Sediment Sciences of Ministry of Education, State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing, China. Electronic address: xiaxh@bnu.edu.cn.

PMID: 37474095
DOI: 10.1016/j.envres.2023.116689

Abstract

Constituents and functionality of urban inland waters are significantly perturbed by municipal sewage inputs and tailwater discharge from wastewater treatment plants. However, large knowledge gaps persist in understanding greenhouse gas dynamics in urban inland waters due to a lack of in situ measurements. Herein, via a 3-year field campaign (2018-2020), we report river and lake CO₂ emission and related aquatic factors regulating the emission in the municipality of Beijing. Mean pCO₂ (546 ± 481 μatm) in the two urban lakes was lower than global non-tropical freshwater lakes and CO₂ flux in 47% of the lake observations was negative. Though average pCO₂ in urban rivers (3124 ± 3846 μatm) was among the higher range of global rivers (1300-4300 μatm), average CO₂ flux was much lower than the global river average (99.7 ± 147.5 versus 358.4 mmol m^-2 d^-1). The high pCO₂ cannot release to the atmosphere due to the low gas exchange rate in urban rivers (average k₆₀₀ of 1.3 ± 1.3 m d^-1), resulting in low CO₂ flux in urban rivers. Additionally, eutrophication promotes photosynthetic uptake and aquatic organic substrate production, leading to no clear relationships observed between pCO₂ and phytoplankton photosynthesis or dissolved organic carbon. In consistence with the findings, CO₂ emission accounted for only 32% of the total greenhouse gas (GHG) emission equivalence (CO₂, CH₄ and N₂O) in Beijing waters, in contrast to a major role of anthropogenic CO₂ to anthropogenic GHG in the atmosphere in terms of radiative forcing (66%). These results pointed to unique GHG emission profiles and the need for a special account of urban inland waters in terms of aquatic GHG emissions.

Keywords: CO(2) flux; Gas transfer velocities; Global warming potential; Net CO(2) production; Urban inland waters.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Carbon Dioxide / analysis
Greenhouse Gases* / analysis
Lakes
Methane / analysis
Rivers

Substances

Greenhouse Gases
Carbon Dioxide
Methane