Silver nanoparticles (AgNPs) are the most used NP in consumer products and mainly end up in water environment. Within the wastewater-treatment, sewage sludge represents a major sink for AgNPs. This sludge is then used worldwide as a fertilizer in agriculture. Existing studies were performed on standard soils and selected organisms, which means there is not enough data to conclude whether silver in the environmental soils is available to higher trophic levels. In this study we used four soils with different physical and chemical characteristics to analyze biokinetics of different silver species (Ag ions, AgNPs, Ag2S) in terrestrial isopod P. scaber. Our results support the findings of other studies, affirming that during the exposure to AgNPs the Ag is bioaccumulated because of the uptake of dissolved Ag ions. In the case of Ag2S negligible amount of bioaccumulation was observed, since this form is considerably less bioavailable compared to AgNPs. This is a positive finding from the nature conservation perspective, as AgNPs are expected to efficiently convert to sparingly soluble Ag2S during the ageing process. Our results show that soil pH and organic matter content are the soil characteristics with the strongest influence on Ag bioavailability of all the tested soil characteristics. However, more experiments using several different soil types are needed to completely understand the impact of soil properties on Ag bioavailability.
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