The effect of sulfidation and soil type on the uptake of silver nanoparticles in annelid Enchytraeus crypticus.

Hazard assessment of silver nanoparticles is crucial as their presence in agricultural land is increasing through sewage sludge application. This study compared the uptake and elimination kinetics in the annelid Enchytraeus crypticus of AgNPs with different core sizes and coatings in Lufa 2.2 soil, and of AgS NPs (simulating aged AgNPs) in three different soils. For both experiments, AgNO was used as ionic control. E. crypticus was exposed to soil spiked at 10 μg Ag g dry soil for 14 days and then transferred to clean soil for a 14-day elimination phase. The uptake rate constants were similar for 3-8 nm and 60 nm AgNPs and AgNO, but significantly different between 3 and 8 nm and 50 nm AgNPs. The uptake kinetics of Ag from AgS NPs did not significantly differ compared to pristine AgNPs. Therefore, Ag bioavailability was influenced by AgNP form and characteristics. Uptake and elimination rate constants of both Ag forms (AgNO and AgS NPs) significantly differed between different test soils (Lufa 2.2, Dorset, and Woburn). For AgNO, significantly higher uptake and elimination rate constants were found in the Dorset soil compared to the other soils, while for AgS NPs this soil showed the lowest uptake and elimination rate constants. Therefore, not only the form and characteristics but also soil properties affect the bioavailability and uptake of Ag nanoparticles.