Date of Award
Spring 2020
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Civil Engineering
First Advisor
Parolari, Anthony J.
Second Advisor
Mayer, Brooke K.
Third Advisor
McDonald, Walter M.
Abstract
The premise of this research was to monitor biogeochemical responses to soil moisture and soil temperature within green stormwater infrastructure soils. Adopting best management practices like green infrastructure in urban areas has the potential to remove incoming nutrients from stormwater runoff through biogeochemical processes, like plant and microbial metabolism. Biogeochemical activity has been suggested to be highly variable, so this research proposed to monitor that variability by tracking the stoichiometry of soil respiration. Additionally, an advection-diffusion-reaction model was used to disaggregate physical and biogeochemical controls on the observed soil respiration. The field data was collected to investigate the biogeochemical processes, their response to soil conditions, and their spatial and temporal variability. Field results showed soil respiration increased with soil moisture at all sites except a wetland lowland plot. The model simulations from the advection-diffusion-reaction model suggested that the soil gas response to soil moisture was driven by biogeochemical process rates rather than the physical processes of gas transport. Soil temperature was related to soil respiration, but the relationship depended on the season and green infrastructure site. The monitored gas concentrations in the green infrastructure soils suggested the carbon dioxide was lower than what is needed for soil respiration to be the main driver of the gas ratios. Instead, abiotic processes like carbon dioxide dissolution or biotic processes like methanogenesis metabolism may be decreasing the carbon dioxide concentrations. Additionally, the field soils may be well aerated causing the oxygen concentrations to be higher than anticipated soil concentrations if soil respiration was the main biogeochemical process driving the gas concentrations. There is little known about the biogeochemistry of green infrastructure soils, and more studies are needed for improved understanding of these engineered systems, including better identifying the biogeochemical processes, modeling the systems, and long-term monitoring.