Interactions of selenium and mercury in soil–plant systems: Characterizations, occurrences, and mechanisms

Abstract

Selenium (Se) serves as a natural detoxifier for the typical toxic heavy metal mercury (Hg), and the interactions between Se and Hg have attracted considerable scholarly attention in the field of Se and Hg. However, there is currently a lack of systematic summaries and discussions about Se–Hg interactions in soil–plant systems. This study summarizes the microscopic processes and macroscopic manifestations of Se–Hg interactions by exploring their characteristics, occurrence and mechanisms, revealing a dual-pump driving mechanism that emphasizes the “soil-root” and “atmosphere-leaf” interface of Se–Hg interactions in soil–plant systems. At the soil–root interface, HS⁻ (H₂S), Fe²⁺ and microorganisms are the key factors that cause the transformation of Se and Hg through oxidation, reduction, methylation and demethylation processes controlled by microbial or abiotic factors. Concurrently, Se reinforces the iron plaque barrier to decrease Hg absorption or to form HgSe complexes to limit Hg transportation into roots. Furthermore, the leaves, as the main plant tissue for Hg/Se uptake and bioaccumulation, are the key sites for the morphological transformation of Hg and Se, where Se–Hg interactions are likely to occur, and thus may constitute the other driving mechanism in the atmosphere–leaf interface. Finally, Se–Hg interactions are outlined after concluding the potential mechanisms, challenges and future research directions.

Graphical Abstract

Keywords:

• Dual-pump mechanism, HgSe complexes, mercury
• microbial process, selenium

Handling Editors:

• Hongbo Li/Hyunjung (Nick) Kim

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The authors would like to acknowledge the support from National Natural Science Foundation of China (42107486, 42377456), Qiankehe Platform Talents (GCC [2023] 046), Guizhou Provincial 2021 Science and Technology Subsidies (No. GZ2021SIG), Youth Cross Team Project of CAS (JCTD-2021-17), Youth Innovation Promotion Association CAS (2023415), and the State Key Laboratory of Environmental Geochemistry (SKLEG 2023204).