Biochar reduces the toxicity of silver to barley ( Hordeum vulgare ) and springtails ( Folsomia candida ) in a natural soil

The use of biochar in soil remediation is a promising method to deal with metal contamination. In the present study, the influence of biochar amendment on the toxicity of silver (as AgNO 3 ) to terrestrial organisms was assessed. For this, toxicity tests were conducted with terrestrial plant barley ( Hordeum vulgare ) and invertebrate springtails ( Folsomia candida ) in the standard natural Lufa soil amended or not with a wood-derived biochar at 5% (w/w). Biochar addition increased root length and mass in barley, compared to unamended soil. However, the effects of Ag on barley growth were masked by a great variation among replicates in biochar-amended soil. Photosynthetic pigment contents (total chlorophyll and carotenoids) were lower in plants exposed to Ag in Lufa soil, but not in biochar-amended soil. Moreover, Ag drastically decreased dehydrogenase activity in Lufa soil. For springtails, the addition of biochar clearly decreased the toxicity of Ag. The LC50 was 320 mg Ag/kg in Lufa soil, while no mortality was observed up to 500 mg Ag/kg in biochar-amended soil. The EC50 for effects on reproduction was significantly higher in biochar-amended soil compared to unamended Lufa soil (315 and 215 mg Ag/kg, respectively). The wood-derived biochar used in this study has shown a potential for remediation of contaminated soils, as a decrease in Ag toxicity was observed in most endpoints analysed in barley and springtails.