Silver nanoparticles in aquatic sediments: Occurrence, chemical transformations, toxicity, and analytical methods

Area of Science:

• Environmental Science
• Nanotechnology
• Ecotoxicology

Background:

• Sediments are the primary sink for silver nanoparticles (AgNPs) in aquatic systems.
• The environmental fate and toxicity of AgNPs depend on their chemical speciation, not just concentration.
• Previous research has not fully detailed AgNP transformations within sediments.

Purpose of the Study:

• To review the chemical transformations of AgNPs in sediments.
• To outline AgNP concentrations and resulting species (e.g., Ag2S, Ag-humic complexes, AgCl, Ag+).
• To discuss the impact of these transformations on AgNP toxicity and bioavailability.

Main Methods:

• Literature review focusing on AgNP chemical transformations in sediments.
• Analysis of predicted AgNP concentrations in sediment studies (1-5 µg kg-1).
• Identification of key transformation processes: oxidative dissolution, sulfidation, chlorination, and complexation.

Main Results:

• AgNPs undergo diverse chemical transformations in sediments, forming species like silver sulfide and silver chloride.
• These transformations generally reduce AgNP bioavailability and the release of toxic silver ions (Ag+).
• AgNPs accumulate in benthic organisms and can transfer through aquatic food webs.

Conclusions:

• Chemical speciation dictates AgNP environmental behavior and toxicity in sediments.
• AgNP transformations mitigate risks but pose threats to benthic invertebrates and microbes.
• Further research using advanced techniques and models is needed to understand diverse AgNP transformations in various sediment types.