I am working on the oceanic environment changes (mainly productivity and redox conditions) during the several mass extinction during the Earth History, especially for the three extinction events during the Paleozoic Era, which including Permian-Triassic boundary (PTB), Ordovician-Silurian boundary (OSB), and Frasnian—Famennian boundary(FFB). By using the (major and trace) elements concentrations and metals isotopes (Zn, Cr, Mo, U, and Hg isotope).