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diameter polyvinyl chloride (PVC) pipe is inserted into the soil to extract intact monoliths from a site of interest, withdrawn and then fitted with a basal double socket coupling and end cap for leachate collection.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.