Unravelling the metabolism black-box in a dynamic wetland environment using a hybrid model framework: Storm driven changes in oxygen budgets

Junjie Liu; Benya Wang; Carolyn E Oldham; Matthew R Hipsey

doi:10.1016/j.scitotenv.2020.138020

Unravelling the metabolism black-box in a dynamic wetland environment using a hybrid model framework: Storm driven changes in oxygen budgets

Sci Total Environ. 2020 Jun 25:723:138020. doi: 10.1016/j.scitotenv.2020.138020. Epub 2020 Mar 19.

Authors

Junjie Liu¹, Benya Wang², Carolyn E Oldham³, Matthew R Hipsey⁴

Affiliations

¹ State Key Laboratory of Water Resources & Hydropower Engineering Science, Wuhan University, Wuhan 430072, PR China; School of Engineering, The University of Western Australia, Crawley, WA 6009, Australia. Electronic address: liujunjie026@whu.edu.cn.
² School of Engineering, The University of Western Australia, Crawley, WA 6009, Australia.
³ School of Engineering, The University of Western Australia, Crawley, WA 6009, Australia; Cooperative Research Centre for Water Sensitive Cities, Clayton, VIC 3168, Australia.
⁴ UWA School of Agriculture and Environment, The University of Western Australia, Crawley, WA 6009, Australia; Cooperative Research Centre for Water Sensitive Cities, Clayton, VIC 3168, Australia.

PMID: 32217386
DOI: 10.1016/j.scitotenv.2020.138020

Abstract

Estimating gross primary production and ecosystem respiration from oxygen data is performed widely in aquatic systems, yet these estimates can be challenged by high advective fluxes of oxygen. In this study, we develop a hybrid framework linking data-driven and process-based modelling to examine the effect of storm events on oxygen budgets in a constructed wetland. After calibration against measured flow and water temperature data over a two-month period with three storm events, the model was successfully validated against high frequency dissolved oxygen (DO) data exhibiting large diurnal fluctuations. The results demonstrated that pulses of high-DO water injected into the wetland during storm events were able to dramatically change the wetland oxygen budget. A shift was observed in the dominant oxygen inputs, from benthic net production during non-storm periods, to inflows of oxygen during storm events, which served to dampen the classical diurnal oxygen signature. The model also demonstrated the changing balance of pelagic versus benthic production and hypoxia extent in response to storm events, which has implications for the nutrient attenuation performance of constructed wetlands. The study highlights the benefit of linking analysis of high-frequency oxygen data with process-based modelling tools to unravel the varied responses of components of the oxygen budget to storm events.

Keywords: Constructed wetland; Hydrodynamic model; Hypoxia; Machine learning; Photosynthesis; Urban drainage.