Plants colonization accelerates galena oxidation, mineralogical transformation, and microbial community reshaping...

The ongoing weathering of metal sulfides has substantially posed threats to the eco-systems. For remediating metal sulfides-contaminated soils, phytostabilization is a promising nature-based technique that immobilizing heavy metals (HMs) that dissolved from metal sulfides in the rhizosphere, preventing their leaching and migrating into soil and groundwater. However, the underlying mechanism regarding the mineral-root interaction involving primary metal sulfides such as galena (PbS) during the remediation processes has yet been well studied. This study aims to investigate the geochemical alterations, mineralogical transformations, and microbial community reshaping of galena-added soils during plants colonization using two representative plants, ryegrass (Lolium perenne L.) and alfalfa (Medicago sativa.). After 11 weeks of plants colonization, the morphology of galena surface was altered, as massive erosion pits (ca. 200 nm) were visualized by SEM (Scanning Electron Microscope). The microspectroscopic analyses indicated that the PbS may have transformed to PbCO₃ and PbSO₄ during the plants colonization. Additionally, the chemical sequential extraction revealed that the plants colonization could promote the soluble Pb to be associated with carbonates and amorphous Fe/Al (oxyhydr)oxides, thus limiting their bioavailability and mobility. Moreover, the key driving factors of microbial community alteration have shifted from pH and bioavailability Pb to cation exchange capacity (CEC) during the plants colonization process. These findings have uncovered the (bio)geochemical behaviors of PbS in soils during the phytostabilization processes, which may develop an integrated mechanism of mineralogical and geochemical stabilization of HMs for non-pollution outcomes.