Vertical Hydrologic Exchange Flows Control Methane Emissions from Riverbed Sediments

Kewei Chen; Xingyuan Chen; James C. Stegen

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Vertical Hydrologic Exchange Flows Control Methane Emissions from Riverbed Sediments

机译：Vertical Hydrologic Exchange Flows Control Methane Emissions from Riverbed Sediments

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CH4 emissions from inland waters are highly uncertain in the current global CH4 budget, especially for streams, rivers, and other lotic systems. Previous studies have attributed the strong spatiotemporal heterogeneity of riverine CH4 to environmental factors such as sediment type, water level, temperature, or particulate organic carbon abundance through correlation analysis. However, a mechanistic understanding of the basis for such heterogeneity is lacking. Here, we combine sediment CH4 data from the Hanford reach of the Columbia River with a biogeochemical-transport model to show that vertical hydrologic exchange flows (VHEFs), driven by the difference between river stage and groundwater level, determine CH4 flux at the sediment-water interface. CH4 fluxes show a nonlinear relationship with the magnitude of VHEFs, where high VHEFs introduce O2 into riverbed sediments, which inhibit CH4 production and induce CH4 oxidation, and low VHEFs cause transient reduction in CH4 flux (relative to production) due to reduced advective CH4 transport. In addition, VHEFs lead to the hysteresis of temperature rise and CH4 emissions because high river discharge caused by snowmelt in spring leads to strong downwelling flow that offsets increasing CH4 production with temperature rise. Our findings reveal how the interplay between in-stream hydrologic flux besides fluvial-wetland connectivity and microbial metabolic pathways that compete with methanogenic pathways can produce complex patterns in CH4 production and emission in riverbed alluvial sediments.

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来源
《Environmental Science & Technology: ES&T》 |2023年第9期|4014-4026|共13页
作者
Kewei Chen; Xingyuan Chen; James C. Stegen;
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作者单位

Pacific Northwest National Laboratory, Richland, Washington 99354, United States;

School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China;

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收录信息美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
原文格式 PDF
正文语种英语
中图分类环境科学、安全科学;
关键词
riverine CH4 emission; sediment biogeochemical cycling; vertical hydrologic exchange flows; microbial-explicit model; temperature hysteresis;

Vertical Hydrologic Exchange Flows Control Methane Emissions from Riverbed Sediments

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