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ARS Home » Plains Area » Las Cruces, New Mexico » Range Management Research » Research » Publications at this Location » Publication #310856
Title: Capturing spatial variability of concentrations and reaction rates in wetland water and soil through model compartmentalization

Author
item SHARIFI, AMIRREZA - University Of Maryland
item KALIN, LATIF - Auburn University
item HANTUSH, MOHAMED - Us Environmental Protection Agency (EPA)
item O'GEEN, ANTHONY - University Of California
item DAHIGREN, RANDY - University Of California
item Maynard, Jonathan

Submitted to: Journal Hydrologic Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/29/2015
Publication Date: 3/18/2015
Citation: Sharifi, A., Kalin, L., Hantush, M.M., O'Geen, A., Dahigren, R., Maynard, J.J. 2015. Capturing spatial variability of concentrations and reaction rates in wetland water and soil through model compartmentalization. Journal Hydrologic Engineering. 22(1). https://doi.org/10.1061/(asce)he.1943-5584.0001196.
DOI: https://doi.org/10.1061/(asce)he.1943-5584.0001196

Interpretive Summary: The short circuiting of flow and formation of stagnant zones that are only indirectly connected with inflowing water is a common phenomenon observed in constructed wetlands. Geochemistry of passive areas is potentially much different than that of active zones, and thus the main objective of this study was to develop a wetland nutrient cycling model that can capture the spatial variability of concentrations and reaction rates of nitrogen and carbon throughout both active and passive hydrologic zones within wetlands. The wetland nutrient cycling model (WetQual) was applied to data collected from a restored wetland in California that was characterized by the formation of a large stagnant zone at the southern end of the wetland. The WetQual model was able to effectively model the concentration and reaction rates of both nitrogen and carbon within the active and passive zones, revealing that nitrogen cycling decreased along the activity gradient from active to passive zones. Additionally, model results also revealed that anaerobic processes become more significant along the activity gradient toward passive areas. The development of spatially explicit wetland nutrient cycling models, such as WetQual, will help improve our understanding on nutrient cycling processes which will allow for greater optimization of wetland designs for water quality improvement.

Technical Abstract: A common phenomenon observed in constructed wetlands is short circuiting of flow and formation of stagnant zones that are only indirectly connected with the incoming water. Geochemistry of passive areas is potentially much different than that of active zones. In this study, the spatial resolution of a previously developed wetland nutrient cycling model, namely WetQual model, was improved in order to capture the spatial variability of concentrations and reaction rates regarding nitrogen (N) and carbon (C) cycles throughout active and passive zones of wetlands. The upgraded model allows for several compartments in the horizontal domain, with all neighboring compartments connected through advective and dispersive/diffusive mass transport. The model was applied to data collected from a restored wetland in California that was characterized by the formation of a large stagnant zone at the southern end of the wetland due to close vicinity of the inlet and outlet structures. Mass balance analysis revealed that over the course of the study period, about 23.4 ± 3.9% of the incoming total nitrogen (TN) load was removed or retained by the wetland. It was observed that mass of all exchanges (physical and biogeochemical) regarding nitrogen cycling decreased along the activity gradient from active to passive zones. Model results also revealed that anaerobic processes become more significant along the activity gradient toward passive areas.