Removal of mercury from sediment by ultrasound combined with biomass (transgenic Chlamydomonas reinhardtii)

As one of the most pervasive environmental problems, Hg pollution in sediment is particularly difficult to remediate because it cannot be decomposed. The application of ultrasound combined with biomass (transgenic Chlamydomonas reinhardtii (C. reinhardtii), a green alga) for the removal of Hg from model and contaminated sediments (Al2O3, α-HgS, and PACS-2 marine sediment) was investigated in this study. Ultrasound was found to enhance Hg release from Al2O3, α-HgS, and PACS-2 marine sediment into the aqueous phase compared to mechanical shaking. A transgenic C. reinhardtii (2AMT-2) expressing a plasmamembrane-anchored metallothionein polymer effectively recovered Hg(II) released into the aqueous phase by sonication over a broad pH range from 2.0 to 9.0. The results showed that this combined technique of ultrasound and alga biomass (2AMT-2) engineered for enhanced metal recovery was effective to remove Hg from solids and sediments, especially from Al2O3 and α-HgS with no natural organic matter. The results of this study are discussed with respect to the development of in situ remediation techniques for Hg-contaminated sediments.

► Ultrasound enhanced Hg release from Al2O3, α-HgS, and PACS-2 marine sediment into the aqueous phase. ► The algae recovered Hg(II) released into the aqueous phase by sonication over a broad pH range. ► The combination of ultrasound and algae are able to remove and sequester under certain conditions.