Constructing multi-functional Technosols for storm-water management: mixing high-carbon organic amendments, a microcosm experiment

As the global water cycle intensifies – with it’s increased variability projected to cause greater storm-events, more extensive flooding and more severe droughts – the obsolescence of current urban infrastructure is made clear, particularly in the face of an ever increasing urban population. To combat these challenges, concepts have been developed across the globe in order to better manage and utilize stormwater run-off; many leaning on the larger concept of green infrastructure, implementing solutions replicative of a more natural water cycle. The simplistic design, low capital costs and flexible application and incorporation into urban spaces has made bio-infiltration swales an excellent choice for urban planners and a center point of recent research. As the base of these systems, the soil substrate lends significantly to a swale’s services of dewatering, pollutant processing, biodiversity promotion and carbon accumulation. By combining urban mineral and organic wastes, we attempt to optimize the synergies between these services. In a microcosm incubation experiment, an extracted deep soil horizon was mixed with green waste compost to form a fertile constructed Technosol. Subsequently, biochars of varying feedstock and pyrolysis processing temperatures were added individually and in combination to determine their impact on water processing properties and nutrient availability. We hypothesized the combinations of biochars will create a structure that maximizes water-substrate interactions while also retaining a larger variety of pollutants due to their differences in chemical composition. The addition of biochar will also minimize run-off of nutrients introduced by the green waste compost, increasing their availability to potential vegetation.