Enhanced weathering rates of kimberlite residues - Insights from field and laboratory studies
At a Glance
Section titled āAt a Glanceā| Metadata | Details |
|---|---|
| Publication Date | 2022-01-01 |
| Journal | Goldschmidt2022 abstracts |
| Authors | Zivi Schaffer, Kwon Rausis, Ian Power, Carlos Paulo |
| Institutions | Trent University |
Abstract
Section titled āAbstractāEnhanced rock weathering (ERW) is a negative emissions technology with the potential to remove gigatonnes of atmospheric CO 2 .Accurate carbon accounting is a key challenge of ERW due to the slow reaction of CO 2 with Mg-and Casilicates, storage of carbon as either a soluble or solid phase, and spatially and temporally viabilities in soil carbon content in large open systems.The goal of our laboratory and field studies is to develop a scalable methodology for measuring CO 2 sequestration rates through ERW of kimberlite mine residues from De Beersā Gahcho KuĆ© diamond mine (Canada).These mine wastes contained 30.2 wt.% lizardite [Mg 3 Si 2 O 5 (OH) 4 ] and 9.4 wt.% forsterite (Mg 2 SiO 4 ), nutrients including K (2.12%), and numerous trace elements, e.g., Ba, Ni, Sr, and Co (1171, 1151, 471, 69 ppm, respectively).Soil-kimberlite mixtures (0-100 wt.% residues; 250 mg total mass) were leached in plastic 250 mL flasks with 100 mL deionized water in a CO 2 incubator (10% CO 2 ; 35 Ā°C).Principal component analysis of leachate chemical data indicates that the release of Mg, Si, K, Na, Ba, Ni, and Sr were distinct to kimberlite.Field experiments (1 m 2 plots) involved mixing 10 and 20 kg of kimberlite residues into native soil, followed by monitoring of CO 2 fluxes, CO 2 pore gas concentrations, soil moisture, and porewater chemistry for 1 yr.CO 2 fluxes were only negative during the first day of the experiment, removing atmospheric CO 2 at a rate of up to -5.6 kg/m 2 /yr.However, CO 2 fluxes quickly became positive and indistinguishable from unamended soil (0-13.5 kg CO 2 /m 2 /yr).These high soil CO 2 fluxes raise the question of whether ERW is a negative emissions technology or CO 2 avoidance technology, though both are beneficial.Porewaters from the 20 kg residues/m 2 plot were distinguishable from the control soil plot, characterized by higher concentrations of major (Mg, Si, K, Na) and trace (Ba, Ni, Sr) elements, as well as greater alkalinity (8.5 Ā± 1.5 and 6.6 Ā± 0.9 mmol/L, respectively).In this ongoing research, monitoring multiple parameters, including distinct trace elements, will aid in developing approaches to assess ERW rates in soil environments.