Assessment by self-organizing maps of element release from sediments in contact with acidified seawater in laboratory leaching test conditions

Abstract

Carbon capture and storage (CCS) is gaining interest as a significant global option to reduce emissions of CO2. CCS development requires an assessment of the potential risks associated with CO2 leakages from storage sites. Laboratory leaching tests have proved to be a useful tool to study the potential mobilization of metals from contaminated sediment in a decreased-pH environment that mimics such a leakage event. This work employs a self-organizing map (SOM) tool to interpret and analyze the release of dissolved organic carbon (DOC), As, Cd, Cr, Cu, Ni, Pb, and Zn from equilibrium, column, and pH-dependent leaching tests. In these tests, acidified seawater is used for simulating different CO2 leakage scenarios. Classification was carried out detailing the mobilization of contaminants for environments of varying pH, liquid-to-solid ratio, and type of contact of the laboratory leaching tests. Component planes in the SOMs allow visualization of the results and the determination of the worst case of element release. The pH-dependent leaching test with initial addition of either base or acid was found to mobilize the highest concentrations of metals.