The Impact of Soil Texture on Basalt-Enhanced Rock Weathering: Insights from a Field Mesocosm Study in a Temperate Climate.

Enhanced rock weathering is a promising carbon removal technique that uses the natural process of silicate minerals weathering to capture atmospheric CO₂. This research investigates the relationships between soil texture and the dynamics of basalt-enhanced rock weathering products in a controlled mesocosm experiment. Mesocosms were constructed with three soils of distinct textures: sandy silty loam, sandy loam, and clay, each treated with 0-4 mm crushed basalt rock at an application rate of 100 tons per hectare, alongside control treatments. The duration of the experiment is one year, with pore water collected biweekly using rhizon samplers at depths of 10 cm and 20 cm, as well as leachate samples taken from 30 cm at the bottom of the cores. The crop grown on the soil mesocosms was perennial rye grass at a seeding rate similar to agronomic best practice densities. Results from the experiment include a comprehensive analysis of pore water, solid soil samples (after termination of the experiment), as well as crop uptake. The results indicate that basalt weathering is happening in amended samples compared to control mesocosms across all soil types, however with different responses in pore water concentrations between each soil type. Towards the end of the experiment clear differences between treatment and control are observed in the pore water concentrations of cations in the sandy and loamy soil types, whereas the concentration of cations appears to be similar in the clayey soil type. The variation in response is likely driven by the water retention capacity and cation exchange capacity of each soil type. Understanding the patterns for each soil type is important for accurately measuring MRV and evaluating carbon capture potential in different environments. This research provides an important empirical understanding that can aid in advancing weathering predictions through geochemical models.