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Deciphering the role of anaerobic microsites for hot spot/hot moment behavior of metal-organic interactions and methane emissions within riverine floodplains

Active Dates 9/1/2023-8/31/2026
Program Area Environmental Systems Science
Project Description
Deciphering the role of anaerobic microsites for hot spot/hot moment behavior of metal-organic interactions and methane emissions within riverine floodplains

PI:  Amrita Bhattacharyya, University of San Francisco

Anaerobic microsites, a defining feature of soil redox heterogeneity, are zones of oxygen depletion in otherwise oxic environments. Subsequently, anaerobic microsites can serve as hot spots for biogeochemical (BGC) processes, generating and exporting reduced products to oxic environments. Anoxic microsites have been predicted to contribute 21% to the global production of methane (CH4), an important greenhouse gas affecting climate change. They are often generated at terrestrial–aquatic interfaces (TAIs), such as riverine floodplains which are dynamic transition zones between land and water, where seasonal changes in river and groundwater flow conditions lead to redox fluctuations. As a result, TAIs play a significant role for elemental cycling and greenhouse gas (GHG) emissions, while only occupying small areas of the Earth’s surface (0.07%–0.22%).

Despite the presumed importance of anaerobic microsites in TAIs, significant knowledge gaps still exist regarding their abundance over time and space under varying environmental conditions, as well as their specific contributions to BGC processes, especially with regard to CH4 production. Using the novel LOAMS (Laboratory for Observing Anaerobic Microsites in Soils) approach, we will specifically detect and examine the role of anaerobic microsites in methanogenesis and metal redox processes across spatial and temporal scales at current DOE-ESS natural floodplain research sites. The main objectives of this work are to: (i) quantify the abundance and the impact of anaerobic microsites on methanogenesis and elemental speciation; (ii) compare microscale anaerobic microsite characteristics to macroscale field observations of methanogenesis and metal redox chemistry; and (iii) quantify reaction kinetics of relevant BGC processes within anaerobic microsites based on data from controlled laboratory experiments paired with modeling. Furthermore, our experimental data and parametric modeling results will support the future development of refined conceptual and quantitative models, and improve predictions of metal cycling and production of GHG emissions in TAI environments.
Award Recipient(s)
  • University of San Francisco (PI: Bhattacharyya, Amrita)