The bioaccumulation of silver in Eisenia andrei exposed to silver nanoparticles and silver nitrate in soil

Abstract

The bioaccumulation potential of silver from exposure to AgNO3 and Ag nanoparticles (AgNP) was investigated. In the first exposure, the bioaccumulation of Ag in Eisenia andrei was compared between AgNO3 (1.09mgAgkg−1 dry soil) and AgNPA (20nm, PVP-coated at 3.90mgAgkg−1 dry soil) when amended into a natural field soil. In a second experiment, AgNPB (40nm, PVP-coated) was added to biosolids, aged for 3 d, and then mixed into the field soil (77.95mgAgkg−1 dry soil). Results demonstrated very low bioaccumulation potential for all exposure scenarios, producing bioaccumulation factors (BAFk) of 0.89 and 0.74 for with AgNPA (20nm) and Ag+ (as AgNO3), respectively, in soil, and 0.12 AgNPB in biosolids-amended soil. Earthworms exposed to AgNPB in the biosolids-amended soil showed reduced tissue Ag concentrations following the 21-d elimination period compared to the earthworms from the AgNPA exposure in soil. Uptake of Ag into tissue was not related to the measureable Ag+ within test soil extracts, and evaluation of earthworm tissue via transmission electron microscopy (TEM) confirmed the presence of AgNP within exposed test organisms, despite differences in nanoparticle size, exposure concentrations and matrices between the tests. The growing evidence of accumulation of AgNP within test organisms warrant further long-term research efforts to evaluate the significance of the long-term fate and effects of AgNPs in general.