A method to evaluate enhanced rock weathering using intact soil monoliths under field conditions

Enhanced rock weathering (ERW) has attracted considerable attention as a carbon dioxide removal (CDR) strategy. However, a reliable method for accurately measuring, monitoring, and verifying carbon dioxide (CO2) removal, particularly under field conditions, remains elusive. Here we describe a method for installing soil monoliths in an in situ buried apparatus that allows collection of water draining through a soil, undisturbed by external environmental factors that may affect similar apparatus located above ground. The method provides a robust, cost-effective means of collecting, developing, and establishing soil monoliths, allowing through drainage soil water sample collection and analysis, and so facilitating estimation of ERW CO2 removal. A 200 mm diameter polyvinyl chloride (PVC) pipe is inserted into the soil to extract intact monoliths from a site of interest, withdrawn and then fitted with a basal double socket coupling and end cap for leachate collection. It is buried to reproduce soil environmental conditions, and water is collected via a sampling tube to surface. Validity was confirmed through an experimental trial with 36 monoliths over 6 months. This method enables accurate chemical analysis of solute draining through the soil monolith, which can be used to validate models of ERW efficacy. • PVC pipes are inserted into the target soil and subsequently extracted to retrieve intact soil monoliths • PVC sockets, equipped with a mesh and a geotextile membrane in the middle to retain the collected intact soil monolith and prevent soil particle transport, are then attached to the PVC pipe • PVC caps, featuring a small drainage tube attached to its outer side, are used to collect the leachate at the bottom part of the system