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Inter-transformation between silver nanoparticles and Ag+ induced by humic acid under light or dark conditions.

Authors
  • Liu, Yujia1, 2
  • Li, Chao1
  • Luo, Si2
  • Wang, Xi2
  • Zhang, Qingmei3
  • Wu, Haiyong4
  • 1 Soil and Fertilizer Institute of Hunan Province, Hunan Academy of Agricultural Sciences, 401125, Changsha, China. , (China)
  • 2 College of Resources and Environment, Hunan Agricultural University, 410128, Changsha, China. , (China)
  • 3 Hunan Provincial Environmental Protection Air Compound Pollution Prevention Engineering Technology Center, Hunan Research Academy of Environmental Science, 410004, Changsha, China. [email protected] , (China)
  • 4 Soil and Fertilizer Institute of Hunan Province, Hunan Academy of Agricultural Sciences, 401125, Changsha, China. [email protected] , (China)
Type
Published Article
Journal
Ecotoxicology (London, England)
Publication Date
Sep 01, 2021
Volume
30
Issue
7
Pages
1376–1385
Identifiers
DOI: 10.1007/s10646-020-02284-3
PMID: 33068202
Source
Medline
Keywords
Language
English
License
Unknown

Abstract

The fate and toxicity of silver nanoparticles (AgNPs) and ions in water bodies is largely determined by the natural organic matter (NOM)-mediated redox cycling. However, the process of NOM-mediated redox cycling in the day/night cycles remains elusive. In this study, the inter-transformation between AgNPs and Ag+ ion caused by humic acid (HA) was investigated under controlled light and dark conditions. It was shown that HA induced the reduction of Ag+ into AgNPs in simulated sunlight, and also oxidize AgNPs to release Ag+ in darkness. Kinetics data demonstrated that the rates of AgNPs formation and dissolution increased along with the increment of HA concentrations. Along with the pH increase, the reduction of Ag+ accelerated, but the oxidative dissolution of AgNPs was inhibited. In day-night cycles, the AgNPs and Ag+ concentrations exhibited similar wave-shaped change curves. The peaks of AgNPs and Ag+ ion appeared at 7 p.m. and 7 a.m., respectively. The toxicity of AgNPs/Ag+ to Escherichia coli was determined primarily by the concentration of dissolved Ag+, but also affected by the particle-specific toxicity. The dual role of HA implied that previous reports about the photo-reduction of Ag+ to AgNPs by NOM should be reconsidered, and the oxidizability of HA in darkness strongly affect the transformation and toxicity of AgNPs in water. © 2020. Springer Science+Business Media, LLC, part of Springer Nature.

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