Nano mercury selenide as a source of mercury for rice

Hongxin Xie; Lina He; Xue Tian; Wei Zhang; Liwei Cui; Lihai Shang; Jiating Zhao; Bai Li; Yu-Feng Li

doi:10.1016/j.envpol.2022.120918

Nano mercury selenide as a source of mercury for rice

Environ Pollut. 2023 Feb 1:318:120918. doi: 10.1016/j.envpol.2022.120918. Epub 2022 Dec 20.

Authors

Hongxin Xie¹, Lina He², Xue Tian¹, Wei Zhang³, Liwei Cui⁴, Lihai Shang⁵, Jiating Zhao⁶, Bai Li¹, Yu-Feng Li⁷

Affiliations

¹ CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, & CAS-HKU Joint Laboratory of Metallomics on Health and Environment, & Beijing Metallomics Facility, & National Consortium for Excellence in Metallomics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China.
² CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, & CAS-HKU Joint Laboratory of Metallomics on Health and Environment, & Beijing Metallomics Facility, & National Consortium for Excellence in Metallomics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China; College of Environmental Science and Engineering, State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai, 200092, China.
³ State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, Guizhou, China; Shandong Police College, Jinan, 250200, Shandong, China.
⁴ University of Chinese Academy of Sciences, Beijing, 100049, China.
⁵ State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, Guizhou, China.
⁶ CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, & CAS-HKU Joint Laboratory of Metallomics on Health and Environment, & Beijing Metallomics Facility, & National Consortium for Excellence in Metallomics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
⁷ CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, & CAS-HKU Joint Laboratory of Metallomics on Health and Environment, & Beijing Metallomics Facility, & National Consortium for Excellence in Metallomics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China; University of Chinese Academy of Sciences, Beijing, 100049, China. Electronic address: liyf@ihep.ac.cn.

PMID: 36563986
DOI: 10.1016/j.envpol.2022.120918

Abstract

Mercury (Hg) is a persistent and toxic metal while mercury selenide (HgSe) is generally considered as the environmental sink of Hg in its biogeochemical cycle. Recent studies found nano-sized HgSe (nano-HgSe) could be transformed by certain bacteria. This raises safety concerns about the application of selenium (Se) to curb Hg contamination in farmlands. Therefore, hydroponic experiments were performed in which rice plants were cultured with different concentrations of nano-HgSe and micro-sized HgSe (micro-HgSe) to explore their bioavailability and toxicity. It was found that both nano-HgSe and micro-HgSe did not affect the germination of rice seeds but affected the growth of rice seedlings. However, nano-HgSe could be more readily absorbed by roots and transferred to the aboveground parts compared to micro-HgSe. The highest Hg and Se levels were found to be 5255.67 ± 2496.14 μg/g and 1743.75 ± 61.87 μg/g, respectively in roots when exposed to 5000 mg/L nano-HgSe. Besides, small portion (1.2%) of methylmercury (MeHg) to total Hg was found accumulated in rice stem when exposed to 100 mg/L nano-HgSe, suggesting that nano-HgSe could be decomposed. Furthermore, nano-HgSe exposure brought oxidative damage to rice with decreased chlorophyll content and GSH-Px activity. In all, nano-HgSe was found to be more absorbable, transportable and methylated in rice plant compared to micro-HgSe. This suggests that although Se application in Hg contaminated farmland is an effective way to reduce the bioavailability of Hg, the risk of the possible remobilization of HgSe should not be neglected. Besides, the finding that nano-HgSe can act as an environmental source of Hg for plants deepens the understanding of biogeochemical cycle of Hg. More works are required to study the factors affecting the formation of nano-HgSe in the environment and the mechanisms of Hg methylation in rice plants after exposure to nano-HgSe.

Keywords: Bioavailability; Micro-sized mercury selenide; Nano-sized mercury selenide; Rice; Spatial metallomics.

MeSH terms

Environmental Monitoring
Mercury* / analysis
Mercury* / toxicity
Methylmercury Compounds* / chemistry
Methylmercury Compounds* / toxicity
Oryza* / chemistry
Selenium* / analysis
Soil Pollutants* / analysis

Substances

Mercury
Soil Pollutants
Methylmercury Compounds
mercury-selenium complex
Selenium