Olivine dissolution in seawater: implications for CO2\ud sequestration through Enhanced Weathering in coastal\ud environments

摘要

Enhanced Weathering of (ultra)basic silicate rocks such olivine-rich dunite has been proposed as a\udlarge-scale climate engineering approach. When implemented in coastal environments, olivine\udweathering is expected to increase seawater alkalinity, thus resulting in additional CO2 uptake from\udthe atmosphere. However, the mechanisms of marine olivine weathering and its effect on seawater\udcarbonate chemistry remain poorly understood. Here, we present results from batch reaction\udexperiments, in which forsteritic olivine was subjected to rotational agitation in different seawater\udmedia for periods of days to months. Olivine dissolution caused a significant increase in alkalinity\udof the seawater, with a consequent DIC increase due to CO2 invasion, thus confirming viability of\udthe basic concept of enhanced silicate weathering. Yet, our experiments also identified several\udimportant challenges with respect to the detailed quantification of the CO2 sequestration efficiency\udunder field conditions, which include non-stoichiometric dissolution, potential pore water saturation\udin the seabed, and the potential occurrence of secondary reactions. Before enhanced weathering of\udolivine in coastal environments can be considered an option to realize negative CO2 emissions for\udclimate mitigation purposes, these aspects need further experimental assessment.