Developing a sustainable post-fire soil restoration technique using pulp mill fly ash and AggreBind polymer

Wildfires are significant disturbances to forest ecosystems, and the most critical wildfire impacts including a reduction in vegetation cover and changes in the soil properties and microbiota increase vulnerability to erosion and flooding events. A better understanding of the fire effects on soil stability and emergency post-fire treatments can help safeguard the natural resources and prevent further economic and ecological havoc. Besides the standard mulch and seeding treatments, the chemical soil stabilization with silica and alumina rich materials can be suitable for rehabilitating wildfire-affected landscapes. However, chemical stabilizers have been utilized in Canada to a limited extent in the past due to the negative environmental impacts associated with high alkalinity and heavy metal toxicity. This study aimed to investigate the impacts of Mount Eneas wildfire on the hydromechanical properties of Peachland forest soil in the Okanagan Region of British Columbia and develop a sustainable restoration technique using non-hazardous pulp mill fly ash (PFA) and a polystyrene cross-linking polymer called AggreBind polymer as stabilizing agents. The degree of wildfire impacts was assessed by the comparative evaluation of unburnt and burnt soil properties. The results indicated a coarser soil texture and an increase in surface area, and porosity due to partial decomposition of soil organic matter. Further, the structural degradation of mineral components by burning resulted in low aggregate stability, a larger slaking effect, and low saturation water holding capacity. Further, the engineering and environmental performance of PFA and AggreBind treatment was evaluated by comparing the hydro-mechanical, microstructural, and leachate properties of treated and cured samples vis-à-vis untreated counterpart. The treatment significantly improved soil aggregate stability, soil water retention capacity, field capacity, and hydraulic conductivity due to the formation and deposition of new water-stable cementitious compounds in the macropores and calcium coating on the surface of soil aggregates upon curing. The leachate analysis results demonstrated the environmental advantages of this treatment attributed by the encapsulation of toxic heavy metals within the stabilized soil matrix. Hence, this study indicates that the use of PFA and AggreBind polymer in post-fire soil stabilization can become an accepted engineering option, promoted by state and industrial sectors.Applied Science, Faculty ofEngineering, School of (Okanagan)Graduat