Anionic surfactant (SDBS) enhanced metalaxyl accumulation and phytotoxicity in rice seedlings

Surfactants and pesticides are frequently co-detected in field environments, but the effects of surfactants on the bioavailability of pesticides remain unclear. In this study, a rice soil culture experiment was conducted to investigate the effect of anionic surfactant sodium dodecyl benzenesulfonic acid (SDBS) on the absorption of metalaxyl in rice plants. It was found that SDBS enhanced the solubility of metalaxyl, leading to a dose-dependent increase in its concentration in soil pore water. The enrichment of metalaxyl in rice plants was proportional to the content of metalaxyl in soil pore water. Besides, the dissipation rates of metalaxyl were accelerated in the 0.5 mg/kg and 5 mg/kg SDBS groups while slowed down in 50 mg/kg SDBS group. The phenomenon may be caused by the biphasic effect on soil enzyme activity, where SDBS exposure produced low-concentration promotion and high-concentration inhibition of dehydrogenase, carboxylesterase and urease in soil. In addition, it was found that the 50 mg/kg SDBS treatment also inhibited root elongation and disrupted rice growth. Furthermore, metabolomics analysis revealed that key metabolic pathways in rice were affected, as SDBS treatment severely impacted amino acid biosynthesis and reduced the contents of secondary metabolites in rice roots. These findings improve the understanding of the environmental co-exposure effects of surfactants and pesticides and help evaluate their safety to crops.