Ebullition Controls on CH4Emissions in an Urban, Eutrophic River: A Potential Time-Scale Bias in Determining the Aquatic CH4Flux

Shu Chen, Dongqi Wang, Yan Ding, Zhongjie Yu, Lijie Liu, Yu Li, Dong Yang, Yingyuan Gao, Haowen Tian, Rui Cai, Zhenlou Chen

Research output: Contribution to journalArticlepeer-review

Abstract

Rivers and streams contribute significant quantities of methane (CH4) to the atmosphere. However, there is a lack of CH4 flux and ebullitive (bubble) emission data from urban rivers, which might lead to large underestimations of global aquatic CH4 emissions. Here, we conducted high-frequency surveys using the boundary layer model (BLM) supplemented with floating chambers (FCs) and bubble traps to investigate the seasonal and diurnal variability in CH4 emissions in a eutrophic urban river and to evaluate whether the contribution of bubbles is important. We found that ebullition contributed nearly 99% of CH4 emissions and varied on hourly to seasonal time scales, ranging from 0.83 to 230 mmol m-2 d-1, although diffusive emissions and CH4 concentrations in bubbles did not exhibit temporal variability. Ebullitive CH4 emissions presented high temperature sensitivity (r = 0.6 and p < 0.01) in this urban river, and eutrophication might have triggered this high temperature sensitivity. The ebullitive CH4 flux is more likely to be underestimated at low temperatures because capturing the bubble flux is more difficult, given the low frequency of ebullition events. This study suggests that future ebullition measurements on longer time scales are needed to accurately quantify the CH4 budgets of eutrophic urban rivers.

Original languageEnglish (US)
Pages (from-to)7287-7298
Number of pages12
JournalEnvironmental Science and Technology
Volume55
Issue number11
DOIs
StatePublished - Jun 1 2021

Keywords

  • CHemissions
  • bubbles
  • temporal variability
  • urban river
  • warming effect

ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry

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