Earthworm avoidance of silver nanomaterials over time

Area of Science:

• Environmental toxicology
• Ecotoxicology
• Soil science

Background:

• Avoidance behavior in soil organisms provides insight into their interaction with environmental contaminants.
• Understanding organism avoidance is crucial for predicting species distribution and ecological risk.
• Silver compounds, including nanomaterials, are increasingly used, necessitating ecotoxicological assessment.

Purpose of the Study:

• To investigate the avoidance behavior of the earthworm Eisenia fetida exposed to different silver forms.
• To evaluate the influence of exposure duration and concentration on earthworm avoidance.
• To compare the avoidance response to silver nanomaterials and a silver salt.

Main Methods:

• Earthworm avoidance tests were conducted using Eisenia fetida in standard OECD soil.
• Exposure involved four silver forms: three silver nanomaterials (NMs) and silver nitrate (AgNO3).
• Avoidance was assessed at four time points (24, 48, 72, and 96 hours).

Main Results:

• Avoidance behavior was dependent on both the silver material and its concentration.
• Silver nitrate elicited the highest avoidance response across all exposure durations.
• Avoidance of silver nanomaterials followed the order: NM300K < non-coated AgNM = PVP-coated AgNM.
• Avoidance generally increased with exposure time, particularly for silver nitrate.

Conclusions:

• Eisenia fetida exhibits differential avoidance responses to various silver compounds in soil.
• Silver nitrate is more readily avoided by earthworms compared to silver nanomaterials.
• Exposure duration plays a role in avoidance behavior, with longer exposures potentially increasing avoidance.
• No single soil solution fraction could be identified as a universal predictor of avoidance across different silver forms.