Potential Environmental Impacts and Management Strategies for Metal Release during Ocean Alkalinity Enhancement Using Olivine.

Ocean alkalinity enhancement (OAE) based on enhanced weathering of olivine (EWO) is a promising marine carbon dioxide removal (mCDR) technique. Previous research primarily focuses on the toxicological effects of potentially toxic metals (PTMs) released from olivine. In this Perspective, we explore the overlooked impacts of EWO on environmental media in two scenarios: olivine applied to beaches/shallow continental shelves and offshore dispersion by vessels. We analyze the potential migration pathways of iron and PTMs (e.g., nickel and chromium) after their release, and their interactions with manganese oxides in sediments, potentially causing secondary contamination. Additionally, we propose mitigation strategies to prevent PTM concentrations from exceeding local environmental quality standards, including the use of alkalization equipment to control PTM levels. This Perspective underscores the need for thorough environmental assessments prior to large-scale implementation to ensure the sustainability and efficacy of mCDR efforts.