EN
The toxicity of silver nanoparticles (AgNPs) to green alga Pseudokirchneriella subcapitata was evaluated in standard nutrient medium
(ISO 8692), lake water samples from an oligotrophic and an eutrophic
lake, and in lake waters supplemented with the standard nutrient medium.
Prior to toxicity testing the agglomeration of polyvinylpyrrolidone (PVP) and
starch-coated AgNPs was studied in each test medium. Agglomeration
was studied by determining the hydrodynamic diameter (HDD). The HDDs
for the PVP- and starch-capped AgNP dispersions in deionized water were
40 and 175 nm respectively, indicating the presence of agglomerates. The
HDDs of AgNPs remained stable throughout the exposure time in all media
used for the toxicity tests. The algae growth inhibition test was performed
as a microplate modification of the ISO method using fluorescence
detection. The effect of concentration at a 50% inhibition value for PVPcoated
AgNPs in standard medium was 115 ± 3 μg/L, and for starchcoated
AgNPs 51 ± 32 μg/L. The eutrophic freshwater conditions
suppressed the toxicity of the PVP- coated AgNPs, but not the starchcoated
NPs. This finding emphasizes the importance of using different
AgNPs and natural waters in assessing the environmental risks of silver
nanoparticles.