Formation of Zn and Pb sulfides in a redox-sensitive modern system due to high atmospheric fallout

Human activities have led to a considerable increase in trace metal cycling recent times. The mobilized elements get subjected variety of processes leading eventually their re-concentration. polluted sites, transformed by Earth's surface processes, become similar accumulations known from geological records. This study examines authigenic sulfide mineralization two peatlands atmospheric deposition nearby Pb-Zn smelter. We use the as small-scale model Zn-Cd-Pb deposit determine role organic matter ore genesis and textural structural organization biogenic precipitates. shows that air-derived enrichment (up 2.3 g Zn kg−1, 1.1 Pb 62 mg Cd kg−1) is retained thin layer (∼30 cm) around 10–15 cm below peat surface. A combination focused ion beam (FIB) technology scanning (SEM) transmission (TEM) electron microscopy reveals micrometric spheroids are most characteristic for ZnS (Zn,Cd)S, although sulfides readily form pseudomorphs after different plant tissues resulting much larger aggregates. aggregates complex polycrystalline sphalerite structure more advanced than typically obtained during low-temperature synthesis or observed other modern occurrences. Platy highly-disordered radially-aggregated submicrometre crystals develop within time constraints several decades cold (∼15 °C) acid (pH 3.4–4.4) peat. less abundant occur small cube-like (<1µm) between flat irregular square patches on root macrofossils. All PbS crystalline defect-free. complexation with dissolved solid probably responsible low number equilibrium shape crystals. Iron absent occurs entirely organically bound ferric iron (Fe3+), revealed Mössbauer spectroscopy. affinity metals enhances precipitation over Fe. Our findings demonstrate human lead formation near-surface stratiform peat, sites can be understand reconstruct ancient deposits' mechanisms formation.