Exploring Fate of Fipronil in Different Agricultural Soils Using Adsorption–Desorption and Degradation Processes

The adsorption–desorption characteristics of fipronil vary widely among soil types and are intricate and complex. These interactions greatly influence its environmental behaviour, impacting its mobility, bioavailability, persistence, and possible risks. To properly anticipate the behaviour of fipronil in different soil ecosystems, in-depth studies focusing on particular soil features and local environmental variables are required. Adsorption–desorption characteristics of fipronil on three different soils in Eastern Uttar Pradesh were studied. Distribution coefficient (K_d) values ranged from 2.90—0.686 L kg⁻¹, found maximum for soil S3 and minimum for soil S2 and had a close relationship with the soil's organic carbon content. The adsorption capacities of different soils were as follows: vertisol (S3) > inceptisol (S1) > alfisol (S2). Freundlich model is a better fit for the adsorption isotherms, and Freundlich adsorption coefficients (K_f) values increased as the soils' organic carbon content increased. Maximum hysteresis effect (minimum Hysteresis-Index) was observed for soil S3. The calculated Gibbs energy change (ΔG) value for each soil was ~ 13 kJ mol⁻¹, indicating that van der Waals force is predominant in adsorption of fipronil in the soil. The degradation rate was found to be maximum for soil S3 and minimum for soil S2. It is imperative to comprehend and manage these processes with the intent of ensuring the safe use of fipronil in industry, agriculture, and other sectors for the maintenance of environmental health. Designing soil and water remediation-techniques requires understanding these features since adding materials that improve adsorption can help immobilise pollutants like pesticides including fipronil.