SIMULTANEOUS MEASUREMENT OF HYDROGEN AND METHANE: INVESTIGATING THE INHIBITION OF METHANOGENESIS IN WETLAND SEDIMENTS

Abstract

Wetlands sediments have unique sets of microbial and macrophyte communities that perform various biogeochemical processes that are controlled by physical characteristics. The complex interactions between physical processes, dissolved chemicals, and microbial communities remain a challenge to study in situ. Specifically, dissolved hydrogen (H2) is poorly understood due to the challenges associated with taking measurements from wetland sediments. In this dissertation I describe a set of field, laboratory, and process-based modeling results that aim to build a better understanding of the interactions between physical and microbial processes that control methane (CH4) and H2 production and emissions from wetland sediments.

Subsurface dialysis sampling devices, “peepers”, were deployed at three estuarine wetlands in the New Jersey Meadowlands. These devices made it possible to sample equilibrated pore water from these sites over multiple years and from distinct depths without disrupting soils or vegetation. These devices simultaneously measured CH4 and H2 profiles as well as a series of other dissolved compounds and parameters. Using the data from multiple field sites and vegetation types, we are able to explore relationships between these different variables and explore dependencies and controls. This multi-year study indicated that there is a negative correlation between dissolved H2 and CH4 reservoirs. The relationship between H2 and CH4 was explored with a series of incubation experiments. The results from these experiments were incorporated into a microbial model that explains the inhibition of CH4 production by H2 in the lab experiment and explores how other wetland processes may affect this interaction. Hurricane Sandy made landfall in New Jersey and passed through our field site during our field campaign. This gave us a unique opportunity to study the effects of Hurricanes on dissolved gases and chemicals in wetlands. To conclude this dissertation, I bridge the gap between methane emissions in built and natural environments by examining the decision making process for building combined heat and power plants at wastewater treatment facilities.