Heavy metal mobility in contaminated sediments under seawater acidification

The behavior of heavy metals in contaminated sediment is of ecological significance considering the change of pH caused by ocean acidification. This study investigated the mobility of Cd, Cu, Ni, Pb, Fe, and Mn under experimental conditions for seawater acidification via enrichment of CO2 gas at different reaction set-ups. The results indicated that the concerned metals behaved differently in the water compared to the sediment. The heavy metals were considerably transferred from sediment to seawater, and the resultant intensity was controlled by the degree of acidification and the chemical state of specific metals. Moreover, labile fractions of heavy metals in sediments were more susceptible to acidification than other fractions. These findings were observed and confirmed using real-time monitoring conducted via the diffusion gradient technique (DGT). Overall, the results of this study provided new insights into exploring the coupling risk of heavy metals with ocean acidification.