Biological transfer of silver under silver nanoparticle exposure and nitrogen transfer via a collembolan-predatory mite food-chain and ecotoxicity of silver sulfide

Abstract

The development of nanotechnology has accelerated the use of silver nanoparticles (AgNPs) in household chemicals and the accumulation of Ag in sewage treatment systems. The application of sewage sludge products to soils raises concerns over the safety of Ag in the function and biogeochemical cycles of the soil belowground ecosystem. Here, we assess the potential risk of the accumulation and transfer of Ag under AgNPs exposure and its effects on the trophic transfer of nitrogen (N) through a soil animal food chain (Folsomia candida-Hypoaspis aculeifer). The formation of stable silver sulfide (Ag2S) was also studied via a single species test using F. candida. Concentrations of Ag in F. candida increased with increasing AgNPs concentration, as did those in the predator H. aculeifer, but the Ag bioaccumulation factors of both animals were < 1. Folsomia candida body tissue 15N abundance declined markedly compared with that of H. aculeifer. Silver sulfide did have adverse effects on the survival and reproduction of F. candida. The Ag concentrations of F. candida increased with increasing Ag2S concentration in sludge-treated soils. Silver sulfide showed ecotoxicity to the collembolan, therefore ecotoxicity resulting from the transformation and fate of AgNPs in soils needs to be considered before biosolid products are applied to agricultural soils.