title: Silver sulfide nanoparticles (Ag2S-NPs) are taken up by plants and are phytotoxic.
abstract: Silver nanoparticles (NPs) are used in more consumer products than any other nanomaterial and their release into the environment is unavoidable. Of primary concern is the wastewater stream in which most silver NPs are transformed to silver sulfide NPs (Ag2S-NPs) before being applied to agricultural soils within biosolids. While Ag2S-NPs are assumed to be biologically inert, nothing is known of their effects on terrestrial plants. The phytotoxicity of Ag and its accumulation was examined in short-term (24 h) and longer-term (2-week) solution culture experiments with cowpea (Vigna unguiculata L. Walp.) and wheat (Triticum aestivum L.) exposed to Ag2S-NPs (0-20 mg Ag L(-1)), metallic Ag-NPs (0-1.6 mg Ag L(-1)), or ionic Ag (AgNO3; 0-0.086 mg Ag L(-1)). Although not inducing any effects during 24-h exposure, Ag2S-NPs reduced growth by up to 52% over a 2-week period. This toxicity did not result from their dissolution and release of toxic Ag(+) in the rooting medium, with soluble Ag concentrations remaining below 0.001 mg Ag L(-1). Rather, Ag accumulated as Ag2S in the root and shoot tissues when plants were exposed to Ag2S-NPs, consistent with their direct uptake. Importantly, this differed from the form of Ag present in tissues of plants exposed to AgNO3. For the first time, our findings have shown that Ag2S-NPs exert toxic effects through their direct accumulation in terrestrial plant tissues. These findings need to be considered to ensure high yield of food crops, and to avoid increasing Ag in the food chain.
authors: a School of Agriculture and Food Sciences, The University of Queensland , Queensland , Australia .
authors: Peng
authors: P
authors: Wang
authors: a School of Agriculture and Food Sciences, The University of Queensland , Queensland , Australia .
authors: Neal W
authors: NW
authors: Menzies
authors: b Centre for Environmental Risk Assessment and Remediation, University of South Australia , South Australia , Australia .
authors: Enzo
authors: E
authors: Lombi
authors: b Centre for Environmental Risk Assessment and Remediation, University of South Australia , South Australia , Australia .
authors: Ryo
authors: R
authors: Sekine
authors: a School of Agriculture and Food Sciences, The University of Queensland , Queensland , Australia .
authors: F Pax C
authors: FP
authors: Blamey
authors: a School of Agriculture and Food Sciences, The University of Queensland , Queensland , Australia .
authors: Maria C
authors: MC
authors: Hernandez-Soriano
authors: c Centre for AgriBioscience, La Trobe University , Victoria , Australia .
authors: Miaomiao
authors: M
authors: Cheng
authors: d Australian Synchrotron , Clayton , Victoria , Australia .
authors: Peter
authors: P
authors: Kappen
authors: e National Institute of Public Health and the Environment (RIVM) , Bilthoven , The Netherlands , and.|f Institute of Environmental Sciences (CML), Leiden University , Leiden , The Netherlands.
authors: Willie J G M
authors: WJ
authors: Peijnenburg
authors: c Centre for AgriBioscience, La Trobe University , Victoria , Australia .
authors: Caixian
authors: C
authors: Tang
authors: a School of Agriculture and Food Sciences, The University of Queensland , Queensland , Australia .
authors: Peter M
authors: PM
authors: Kopittke
mesh_terms: D004305:Dose-Response Relationship, Drug; D007477:Ions / Q000633:toxicity; D053768:Metal Nanoparticles / Q000633:toxicity*; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism*; D018030:Silver Compounds / Q000493:pharmacokinetics / Q000633:toxicity*; D012835:Silver Nitrate / Q000493:pharmacokinetics / Q000633:toxicity; D013997:Time Factors; D014908:Triticum / Q000187:drug effects* / Q000254:growth & development; D000070658:Vigna / Q000187:drug effects* / Q000254:growth & development
chemical_list: D007477:Ions; D018030:Silver Compounds; D012835:Silver Nitrate; C013251:silver sulfide
keywords: Cowpea; silver nanoparticles; transformation; uptake; wheat