Effect of silver nanoparticle surface coating on bioaccumulation and reproductive toxicity in earthworms (Eisenia fetida)

Abstract

The purpose of this study was to investigate the effect of surface coating on the toxicity of silver nanoparticles (Ag NPs) soil. Earthworms (Eisenia fetida) were exposed to AgNO₃ and Ag NPs with similar size ranges coated with either polyvinylpyrrolidone (hydrophilic) or oleic acid (amphiphilic) during a standard sub-chronic reproduction toxicity test. No significant effects on growth or mortality were observed within any of the test treatments. Significant decreases in reproduction were seen in earthworms exposed to AgNO3, (94.21 mg kg^-1) as well as earthworms exposed to Ag NPs with either coating (727.6 mg kg^-1 for oleic acid and 773.3 mg kg^-1 for polyvinylpyrrolidone). The concentrations of Ag NPs at which effects were observed are much higher than predicted concentrations of Ag NPs in sewage sludge amended soils; however, the concentrations at which adverse effects of AgNO₃ were observed are similar to the highest concentrations of Ag presently observed in sewage sludge in the United States. Earthworms accumulated Ag in a concentration-dependent manner from all Ag sources, with more Ag accumulating in tissues from AgNO₃ compared to earthorms exposed to equivalent concentrations of Ag NPs. No differences were observed in Ag accumulation or toxicity between earthworms exposed to Ag NPs with polyvinylpyrrolidone or oleic acid coatings.

Keywords::

• Eisenia fetida
• silver nanoparticles
• reproductive toxicity
• bioaccumulation
• X-ray absorption spectroscopy

Acknowledgements

The authors wish to acknowledge the assistance of M. Lacey, E. Harding, J. Backus, J. Song, O. Zhurbich and two anonymous reviewers. Portions of this research were carried out at the Stanford Synchrotron Radiation Laboratory, a national user facility operated by Stanford University on behalf of the U.S. Department of Energy, Office of Basic Energy Sciences. We thank Dr C. Kim and the members of his Environmental Geochemistry Lab of Chapman University for sample preparation and analysis support. Also, thanks to the staff and beamline scientists at SSRL.

Declaration of interest: Major funding for this research was provided by the United States Environmental Protection Agency (U.S. EPA) through Science to Achieve Results Grant # RD 833335 and through support of the National Science Foundation (NSF) and U.S. EPA for the Center for Environmental Implications of Nanotechnology (CEINT). It was also funded in part by the National Science Foundation (BES-0608646 and EF-0830093), and the U.S. EPA R833326. The authors report no conflict of interest. The authors alone are responsible for the content and writing of the paper.