Instream wood as a potential nature-based solution to nutrient pollution

Howard, Ben Christopher ORCID: 0000-0003-4010-8131 (2023). Instream wood as a potential nature-based solution to nutrient pollution. University of Birmingham. Ph.D.

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Abstract

Poor water quality is a ‘wicked problem’ – an uncertain and complex problem with no optimal solution - which poses risks to planetary and public health. Nature-based solutions (NBS) are vital to address water quality challenges on a sufficient spatial and temporal scale to realise long-term water security. The restoration of instream wood has been recognised as a particularly promising NBS to nutrient pollution, one of the most pervasive water quality challenges. Research was conducted to address knowledge gaps about the coupled hydrological and biogeochemical processes that control nutrient removal in the river corridor, and to evaluate the efficacy of instream wood restoration in different environmental settings. A laboratory experiment evaluated protocols of the resazurin-resorufin smart tracer system, which can be used to measure coupled hydrological and biogeochemical processes, showing that concentrations can change by up to 22.5% in 24 hours but in certain conditions samples can be stored for up to 14 days, increasing the geographical and experimental scope in which it can be applied. A microcosm experiment showed that streambed wood can lead to significant increases in microbial metabolic activity, nitrate removal rate and greenhouse has production. This demonstrates the often-neglected contribution of streambed wood to fundamental biogeochemical processes and the impacts on associated ecosystem (dis)services, with consequences for global models of carbon and nitrogen cycles, and for restoration practice. A before-after-control-impact field experiment, using conservative tracer methods coupled with a transport and storage model analysis, investigated the effects of installing instream wood in a lowland sandy stream on transient storage. The results suggest that in a lowland stream wood restoration could decrease transient storage, contrary to what has been observed in upland settings. For the first time, insights from hyporheic zone research are distilled, synthesised, and presented in a framework which is suitable to directly inform river restoration design.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):