Embryotoxicity of Diafenthiuron to Zebrafish (Danio rerio) After Advanced Oxidation Treatment

Diafenthiuron is a novel derivative of thiourea and is highly toxic to non-target organisms, necessitating its efficient removal from wastewater before discharge. This study compared diafenthiuron removal efficiencies at a target concentration of 1 µM using three methods: a 4 mg/L ozone (O3) treatment; an ultraviolet (UV) light treatment, applying UV254 radiation with a fluence of 60 mJ/cm2 for 10 min; and a combined O3/UV treatment utilizing ozone and ultraviolet light. An acute toxicity assessment was conducted using a modeled zebrafish embryo (Danio rerio). The diafenthiuron removal efficiencies were 49.59%, 54.51%, and 68.90% for the UV light, O3, and O3/UV treatments, respectively. The treatments showed additional benefits of exerting no negative impacts on the survival rate, heart rate, or body length of the zebrafish larvae posttreatment. The survival and heart rates at 120 hpf, as well as the body length at 96 and 120 hpf, showed significant differences between the advanced oxidation and 1 μM diafenthiuron treatment groups. However, these parameters remained consistent with those of the control group. The three treatments alleviated the spatiotemporal downregulation of the liver-specific marker fabp10a caused by diafenthiuron exposure. The UV light and O3/UV treatments were efficient at degrading diafenthiuron, causing decreased reactive oxygen species levels and increased pomc and prl expression levels. The O3-treated diafenthiuron and 1 μM diafenthiuron treatments increased the reactive oxygen species levels and decreased the pomc and prl expression levels. The combined O3/UV treatment showed the highest removal efficiency and the least toxicity, making it the most effective method for diafenthiuron degradation. This study provides valuable insights into the treatment of diafenthiuron-laden wastewater.