Among metal-based nanoparticles (NPs), silver is largely used for various products and is finally found in discharged wastewaters. Silver was typically detected in all investigated municipal wastewaters. Once released in the receiving environment, Ag NPs can undergo major transformation and their initial properties can be modified under natural conditions. This study investigated the fate of Ag NPs and transformation products in different types of natural water. Size determination of nanoparticles in suspension in aqueous solutions was carried out by SP-ICP-MS (single particle mode). As we were interested in their degradation rate and transformation products in water, the histogram result presentation was adapted, which relates the detection frequency and the size, taking into account the concentration variations of the different Ag species found in solution. The selected size fractions for investigation were: dissolved/dissociated, intact Ag NP, fragments & aggregates. The developed analytical approach was used for tracking silver nanoparticles and their degradation products over a period of 80 days, in spiked (0.7 µg Ag/L) river water with and without the addition of humic acid (HA). Particle size distributions changed significantly under different experimental conditions where most material was found in coarse colloidal fractions (&lt; 100kDa). The presence of HA slowed degradation of nanoparticles, which is characterized by the increase of free/small ion complexes and the detection of colloids with a size less than 80 nm. Silver distribution was also investigated in the dispersion plume of a major municipal effluent where total and dissolved silver (&lt; 0.45 µm) were measured and Ag NPs characterized by SP-ICP-MS. Future research on nanotoxicity should consider exposure conditions, and then potential transformation, for risk assessment studies.

Transformation of silver nanoparticles in surface waters

255th National Meeting (2018)

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