Silver nanoparticles (AgNPs) are favoured antibacterial agents in nano-enabled products
and can be released into water resources where they potentially elicit adverse effects. Herein,
interactions of 10 and 40 nm AgNPs (10-AgNPs and 40-AgNPs) with aquatic higher plant Salvinia
minima at 600 g/L in moderately hard water (MHW), MHW of raised calcium (Ca2+), and MHW
containing natural organic matter (NOM) were examined. The exposure media variants altered
the AgNPs’ surface properties, causing size-dependent agglomeration. The bio-accessibility in the
ascending order was: NOM <MHW< Ca2+, was higher in plants exposed to 10-AgNPs, and across all
exposures, accumulation was higher in roots compared to fronds. The AgNPs reduced plant growth
and the production of chlorophyll pigments a and b; the toxic effects were influenced by exposure
media chemistry, and the smaller 10-AgNPs were commonly the most toxic relative to 40-AgNPs.
The toxicity pattern was linked to the averagely higher dissolution of 10-AgNPs compared to the
larger counterparts. The scanning electron microscopy and X-ray fluorescence analytical techniques
were found limited in examining the interaction of the plants with AgNPs at the low exposure
concentration used in this study, thus challenging their applicability considering the even lower
predicted environmental concentrations AgNPs.SUPPORTING INFORMATION: FIGURE S1: Ag NPs size obtained before testing for 10-Ag NPs with (a) TEM and (b) NTA, and 40-nAg NPs with (c) TEM and (d) NTA. Red bars denote the standard error. Inserts in (c) and (d) illustrate relative Ag NPs size intensities, FIGURE S2: The detected elemental analysis for samples exposed to 10-Ag NPs in MWH, Ca, and NOM (top row) and to 40-Ag NPs in MWH, Ca, and NOM (bottom row), FIGURE S3: PCA plots illustrating the association of Ag accumulation (accu) to the Ag NPs size (size), dissolution (diss), and Ag NPs concentration (conc) p for 10-Ag NPs and 40-Ag NPs under different water chemistries (MHW, NOM, and Ca2+), FIGURE S4: Quantification of chlorophyll pigments Chla, Chlb and their ratios in S. minima after exposure to 10- and 40-AgNPs for 48 h. Bars denote standard error (n = 3). Differing symbols on top of error bars indicate statistical difference within a specific photosynthetic parameter. Turkey Kramer HSD, p < 0.05, TABLE S1: The Hoagland’s Medium basal salt recipe used in this study, TABLE S2: freeze dryer settings used in the experimental setup, TABLE S3: The achieved recovery rates for Ag obtained from analysis with ICP-MS, TABLE S4: Comparison of whole plant Ag accumulation ( g/mg dry weight) between 10-Ag NPs and 40-Ag NPs under different water chemistries. In brackets are standard deviations, where n = 3. Student’s t-test, p < 0.05, TABLE S5: Percentage growth reduction relative to respective controls, TABLE S6: Results of AgNPs sizes and concentrations under variant exposure media. The 48 h average particle size were obtained with DLS, modal particle size obtained using NTA over 48 h, and NTA was employed to determine particle concentration over 48 h. The given values are the mean standard error (n = 3). Differing symbols indicate statistical difference (p < 0.05) within a specific AgNPs’ size.The UNESCO Keizo Obuchi Fellowship; the Department of Science and Technology Project on Nano-technology HSE Program, South Africa and the University of Pretoria.https://www.mdpi.com/journal/moleculesam2022Chemical Engineerin
