title: Bioaccumulation of silver nanoparticles in rainbow trout (Oncorhynchus mykiss): influence of concentration and salinity.
abstract: With the increasing use of silver nanoparticles (Ag-NPs), their entrance into aquatic ecosystems is inevitable. Thus, the present study simulated the potential fate, toxicity, and bioaccumulation of Ag-NPs released into aquatic systems with different salinities. The Ag-NPs were characterized using inductively coupled plasma-atomic emission spectroscopy (ICP-AES), dynamic light scattering (DLS), transmission electron microscopy (TEM), energy-dispersive X-ray analysis (EDX), and UV-vis spectroscopy. Juvenile rainbow trout were exposed to Ag-NPs in three different salinity concentrations, including low (0.4 ppt), moderate (6 ± 0.3 ppt), and high (12 ± 0.2 ppt) salinity, for 14 days in static renewal systems. The nominal Ag-NP concentrations in the low salinity were 0.032, 0.1, 0.32, and 1 ppm, while the Ag-NP concentrations in the moderate and high salinity were 3.2, 10, 32, and 100 ppm. UV-vis spectroscopy was used during 48 h (re-dosing time) to evaluate the stability and possible changes in size of the Ag-NPs in the water. The results revealed that the λmax of the Ag-NPs remained stable (415-420 nm) at all concentrations in the low salinity with a reduction of absorbance between 380 and 550 nm. In contrast, the λmax quickly shifted to a longer wavelength and reduced absorbance in the moderate and higher salinity. The bioaccumulation of Ag in the studied tissues was concentration-dependent in all the salinities based on the following order: liver>kidneys≈gills>white muscles. All the tissue silver levels were significantly higher in the high salinity than in the moderate salinity. In addition, all the fish exposed to Ag-NPs in the low, moderate, and high salinity showed a concentration-dependent increase in their hepatosomatic index (HSI). In conclusion, most Ag-NPs that enter into freshwater ecosystems (low ionic strength) remain suspended, representing a potentially negative threat to the biota in an ionic or nanoscale form. However, in a higher salinity, nanoparticles agglomerate and precipitate on the surface of the sediment.
authors.affiliation: Department of Aquaculture, Marine Science Faculty, Tarbiat Modares University, Mazandaran, Noor, Iran. h.salary1365@gmail.com
authors.forename: Hamid
authors.initials: H
authors.lastname: Salari Joo
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Kalbassi
authors.forename: Il Je
authors.initials: IJ
authors.lastname: Yu
authors.forename: Ji Hyun
authors.initials: JH
authors.lastname: Lee
authors.forename: Seyed Ali
authors.initials: SA
authors.lastname: Johari
mesh_terms: D000818:Animals; D005880:Gills / Q000378:metabolism; D053758:Nanoparticles / Q000378:metabolism*; D017686:Oncorhynchus mykiss / Q000378:metabolism*; D054712:Salinity; D012834:Silver / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D014874:Water Pollutants, Chemical; D012834:Silver
keywords: Bioaccumulation; Rainbow trout; Salinity; Silver nanoparticles; UV–vis spectroscopy