Silver toxicity to the earthworm Eisenia fetida is inconsistent in natural and artificial soils amended with wastewater biosolids

Silver nanoparticles (AgNPs) are present in biosolids from wastewater treatment facilities, a common soil amendment. Exposing earthworms (Eisenia fetida) to AgNP and AgNO3 in soil with 0 and 7.5 g biosolids kg-1 for 28 days showed AgNO3 was more lethal to earthworms in artificial soil (LC20 <= 325 mg Ag kg(-1)) than natural soil (LC20 >= 573 mg Ag kg(-1)). In contrast, AgNPs were more lethal in natural soil (LC20 <= 425 mg Ag kg(-1)) than artificial soil (LC20 >= 653 mg Ag kg(-1)). Earthworm response to silver in artificial soil may not reflect toxicity in biosolids-amended natural soils.