Environmentally persistent free radical generation on contaminated soil and their potential biotoxicity to luminous bacteria

Environmentally persistent free radicals (EPFRs) are detected in the clay, mineral or humic part of the soil, especially in soil contaminated with phenolic compounds. To clarify the detailed information on the formation of EPFRs, we used the contaminated soil with catechol to mimic their formation process in laboratory scale and tested their biotoxicity with luminescent bacteria (Photobacterium phosphoreum, P. phosphoreum). Our results showed that the concentration of EPFRs reached the maximum at pyrolysis temperature of 300 °C, and EPFRs could significantly inhibit the luminescence of P. phosphoreum. Based on the detection of OH radicals in the aquatic system we used, we speculated that the generation of OH may be a crucial contributor to the toxicity of EPFRs. Our results aid to understand the detailed process on the formation of EPFRs in contaminated soil, as well as the basic biotoxicity data of EPFRs, which will be helpful and essential for their potential environmental risk assessments. [Display omitted] •EPFRs preparation was mimicked using the soil contaminated by organics (e.g. catechol).•Formation of EPFRs can be induced by pyrolysis or UV irradiation.•Hydroxyl radicals were detected when EPFRs particles in water.•EPFRs-containing soil did exhibit acute toxicity to luminous bacteria.