Public Abstract

DE-SC0019422: Trace Metal Dynamics and Limitations on Biogeochemical Cycling in Wetland Soils and Hyporheic Zones

Award Status: Inactive

Institution: Washington University, St Louis, MO
UEI: L6NFUM28LQM5
DUNS: 068552207

Most Recent Award Date: 07/07/2021
Number of Support Periods: 3
PM: Bayer, Paul

Current Budget Period: 09/15/2020 - 09/14/2022
Current Project Period: 09/15/2018 - 09/14/2022
PI: Catalano, Jeffrey

Supplement Budget Period: N/A

Public Abstract

Trace Metal Dynamics and Limitations on Biogeochemical Cycling in Wetland Soils and Hyporheic Zones Jeffrey G. Catalano, Washington University (Principal Investigator) Daniel E. Giammar, Washington University (Co-Investigator) Scott C. Brooks, Oak Ridge National Laboratory (Co-Investigator) Kenneth M. Kemner, Argonne National Laboratory (Co-Investigator Aquatic ecosystems display strong coupling between hydrologic conditions and the cycling of carbon, nitrogen, and other major elements as well as trace metal micronutrients and contaminants. In many such systems, including wetland soils and the hyporheic zone of stream beds, sharp redox gradients can produce spatially-varying zones of biogeochemical activity. In shallow regions of these subsurface environments, oxygen diffusion promotes processes including aerobic methanotrophy and nitrification. Deeper in the soil or sediment profiles, anaerobic processes such as methanogenesis, denitrification, and mercury methylation occur. Iron and sulfur undergo redox cycling at the interface between these regions. The biogeochemistry of subsurface zones of aquatic systems has been widely explored from the perspective of redox conditions, substrate availability, and thermodynamic controls on metabolic processes. However, an additional yet under-examined constraint is the availability of trace metal micronutrients. An array of enzymes that contain metals are essential to many biological pathways associated with microbial carbon and nitrogen cycling and mercury methylation. Laboratory studies using isolate microorganisms have demonstrated that low metal availability inhibits key biological pathways. There are few studies of metal limitations in natural systems, but preliminary data generated under a recent exploratory project supported by the DOE-BER Subsurface Biogeochemical Research program show that methane production from a sulfur-rich freshwater wetland soil increases by a factor of 10 upon addition of nickel. However, a low-sulfur wetland soil with lower native metal content displayed no response to metal addition. Metal limitations on biogeochemical processes in aquatic systems thus clearly occur but may not be universal, and the conditions that promote such limitations and the processes that are predominantly affected are currently unknown. The project seeks to establish whether natural aquatic systems display trace metal-limitations on biogeochemical processes. Specific objectives are to: (1) determine the seasonal and spatial dynamics of trace metal micronutrient availability in riparian and marsh wetland soils and stream hyporheic zones; (2) assess how addition of trace metals to wetland soils and hyporheic zone sediments alters methanogenesis, methanotrophy, anaerobic methane oxidation, denitrification, nitrous oxide reduction, and mercury methylation, all of which involve metal-containing enzymes; (3) identify how fluctuating redox conditions affect trace metal availability in wetland soils and hyporheic zone sediments. We hypothesize that solid-phase speciation is the primary control on metal availability and that biogeochemical processes utilizing a pathway containing single, metal-requiring enzyme are most susceptible to metal limitations. This project will integrate field and laboratory studies of trace metal availability and biogeochemical processes occurring in wetland soils and hyporheic zone sediments. Primary field studies will investigate (1) a riparian wetland, Tims Branch and Steed Pond, at the Savannah River National Laboratory, South Carolina, in collaboration with the Argonne National Laboratory Scientific Focus Area (SFA) team and (2) the hyporheic zone of the East Fork Poplar Creek field site in Tennessee in collaboration with the Oak Ridge National Laboratory SFA team. Additional studies will investigate marsh wetlands at the Argonne National Laboratory site in Illinois as well as a site in Missouri near Washington University. Our field investigations will assess the spatial and temporal variations in metal availability in wetland soils and hyporheic zone sediments. Our complementary laboratory studies will investigate how biogeochemical processes in soils and sediments from our field sites respond to increased metal availability as well as how fluctuating redox conditions affect such availability. These studies will utilize DOE-supported synchrotron lightsources as well as unique instrumentation at EMSL. The proposed research will document the role of metals in controlling the biogeochemistry or carbon, nitrogen, and mercury in subsurface aquatic systems. This work may reveal novel ways in which human modification of natural hydrologic conditions and releases of metals to the environment associated with energy production alter biogeochemical processes by perturbing trace metal availability.

Trace Metal Dynamics and Limitations on Biogeochemical Cycling in Wetland Soils and Hyporheic Zones
Jeffrey G. Catalano, Washington University (Principal Investigator)
Daniel E. Giammar, Washington University (Co-Investigator)
Scott C. Brooks, Oak Ridge National Laboratory (Co-Investigator)
Kenneth M. Kemner, Argonne National Laboratory (Co-Investigator

Aquatic ecosystems display strong coupling between hydrologic conditions and the cycling of carbon, nitrogen, and other major elements as well as trace metal micronutrients and contaminants. In many such systems, including wetland soils and the hyporheic zone of stream beds, sharp redox gradients can produce spatially-varying zones of biogeochemical activity. In shallow regions of these subsurface environments, oxygen diffusion promotes processes including aerobic methanotrophy and nitrification. Deeper in the soil or sediment profiles, anaerobic processes such as methanogenesis, denitrification, and mercury methylation occur. Iron and sulfur undergo redox cycling at the interface between these regions. The biogeochemistry of subsurface zones of aquatic systems has been widely explored from the perspective of redox conditions, substrate availability, and thermodynamic controls on metabolic processes. However, an additional yet under-examined constraint is the availability of trace metal micronutrients. An array of enzymes that contain metals are essential to many biological pathways associated with microbial carbon and nitrogen cycling and mercury methylation. Laboratory studies using isolate microorganisms have demonstrated that low metal availability inhibits key biological pathways. There are few studies of metal limitations in natural systems, but preliminary data generated under a recent exploratory project supported by the DOE-BER Subsurface Biogeochemical Research program show that methane production from a sulfur-rich freshwater wetland soil increases by a factor of 10 upon addition of nickel. However, a low-sulfur wetland soil with lower native metal content displayed no response to metal addition. Metal limitations on biogeochemical processes in aquatic systems thus clearly occur but may not be universal, and the conditions that promote such limitations and the processes that are predominantly affected are currently unknown.

The project seeks to establish whether natural aquatic systems display trace metal-limitations on biogeochemical processes. Specific objectives are to: (1) determine the seasonal and spatial dynamics of trace metal micronutrient availability in riparian and marsh wetland soils and stream hyporheic zones; (2) assess how addition of trace metals to wetland soils and hyporheic zone sediments alters methanogenesis, methanotrophy, anaerobic methane oxidation, denitrification, nitrous oxide reduction, and mercury methylation, all of which involve metal-containing enzymes; (3) identify how fluctuating redox conditions affect trace metal availability in wetland soils and hyporheic zone sediments. We hypothesize that solid-phase speciation is the primary control on metal availability and that biogeochemical processes utilizing a pathway containing single, metal-requiring enzyme are most susceptible to metal limitations. This project will integrate field and laboratory studies of trace metal availability and biogeochemical processes occurring in wetland soils and hyporheic zone sediments. Primary field studies will investigate (1) a riparian wetland, Tims Branch and Steed Pond, at the Savannah River National Laboratory, South Carolina, in collaboration with the Argonne National Laboratory Scientific Focus Area (SFA) team and (2) the hyporheic zone of the East Fork Poplar Creek field site in Tennessee in collaboration with the Oak Ridge National Laboratory SFA team. Additional studies will investigate marsh wetlands at the Argonne National Laboratory site in Illinois as well as a site in Missouri near Washington University. Our field investigations will assess the spatial and temporal variations in metal availability in wetland soils and hyporheic zone sediments. Our complementary laboratory studies will investigate how biogeochemical processes in soils and sediments from our field sites respond to increased metal availability as well as how fluctuating redox conditions affect such availability. These studies will utilize DOE-supported synchrotron lightsources as well as unique instrumentation at EMSL. The proposed research will document the role of metals in controlling the biogeochemistry or carbon, nitrogen, and mercury in subsurface aquatic systems. This work may reveal novel ways in which human modification of natural hydrologic conditions and releases of metals to the environment associated with energy production alter biogeochemical processes by perturbing trace metal availability.