Chemical and ecotoxicological assessment of the uptake of pesticides 2,4-D and fipronil by free-floating aquatic macrophytes

Aquatic ecosystems face widespread contamination from agricultural activities, particularly from pesticides that threaten non-target organisms. Free-floating aquatic macrophytes can be used in the phytoremediation of pesticides, helping to reduce their residual ecotoxicity. This study aimed to assess the uptake of 2,4-D and fipronil by free-floating aquatic macrophytes Salvinia auriculata, Eichhornia crassipes, and Pistia stratiotes. These plants were exposed to pesticides individually (224 µg L⁻¹ of 2,4-D and 32 µg L⁻¹ of fipronil) and in a mixture (1:1) for 7 days at 25 °C. Chemical analyses determined the bioaccumulation and translocation of pesticides. The ecotoxicological assessment included both acute and chronic exposure of Ceriodaphnia silvestrii, acute exposure of Ceriodaphnia dubia, Daphnia similis, and Chironomus sancticaroli, as well as the germination of Eruca sativa. All studied plants accumulated both pesticides but did not significantly decrease their concentrations compared to treatments without plants. Aquatic plants accumulated more fipronil in their roots, while 2,4-D mostly translocated to shoots, and S. auriculata demonstrated greater fipronil uptake potential than the other species. However, plants did not significantly reduce ecotoxicity, with fipronil causing immobility in cladocerans and lethality in C. sancticaroli. Immobility of C. silvestrii persisted in samples with fipronil even at dilutions from 6 to 25%. Residues of 2,4-D did not significantly reduce the reproduction of C. silvestrii compared to the control, while they inhibited the growth of E. sativa. Evaluating the pesticide uptake by macrophytes can contribute to water quality management, and assessing residual ecotoxicity can complement chemical analyses for remediation strategies.