Ecotoxicological effects on earthworms of fresh and aged nano-sized zero-valent iron (nZVI) in soil

Although nano-sized zero-valent iron (nZVI) has been used for several years for remediation of contaminated soils and aquifers, only a limited number of studies have investigated secondary environmental effects and ecotoxicity of nZVI to soil organisms. In this study we therefore measured the ecotoxicological effects of nZVI coated with carboxymethyl cellulose on two species of earthworms, Eisenia fetida and Lumbricus rubellus, using standard OECD methods with sandy loam and artificial OECD soil. Earthworms were exposed to nZVI concentrations ranging from 0 to 2000 mg nZVI kg soil−1 added freshly to soil or aged in non-saturated soil for 30 d prior to exposure. Regarding avoidance, weight changes and mortality, both earthworm species were significantly affected by nZVI concentrations ⩾500 mg kg−1 soil. Reproduction was affected also at 100 mg nZVI kg−1. Toxicity effects of nZVI were reduced after aging with larger differences between soils compared to non-aged soils. We conclude that doses ⩾500 mg nZVI kg−1 are likely to give acute adverse effects on soil organisms, and that effects on reproduction may occur at significantly lower concentrations.

► Nano-sized zero-valent iron (nZVI) is a new remediation agent with unknown risks. ► Common field doses of nZVI had acute adverse effects on earthworms. ► Worms did not avoid soil with nZVI at concentrations that impeded reproduction. ► Aging or oxidation of nZVI decrease its toxicity to earthworms.