Elutriates and Leachates of Soil Microcosms Contaminated With 2,4-D, Fipronil, and Their Mixtures Affect the Life‑history Traits of Ceriodaphnia Silvestrii (Crustacea: Cladocera)

Pesticides in soil can migrate to surface water and groundwater. Their behavior and the influence of rainwater on their fate can be studied using ecosystem models, such as microcosms. This study evaluated the impacts of elutriate and leachate from contaminated soil microcosms on the immobility, feeding rate, survival, and reproduction of the Neotropical cladoceran Ceriodaphnia silvestrii. The systems were filled with natural soil and contaminated with 2,4-D and fipronil, both individually and in a mixture, using recommended doses for sugarcane crops. Pesticides were applied once at the beginning of the experiments, and precipitation was simulated twice a week until 21 days of the experiment. Results from the elutriate tests showed a high immobilization for C. silvestrii exposed to fipronil and its binary mixture with 2,4-D, reaching up to 57.5% and 76.25%, respectively. In contrast, acute effects were not observed when organisms were exposed to leachates. Chronic exposure to leachates increased the feeding rates from contaminated treatments. Survival effects were noted solely for 2,4-D, resulting in a 15% reduction, while reproduction decreased in treatments with 2,4-D, fipronil, and their mixture (56%, 42%, and 48%, respectively). These results demonstrate the significant impacts of soil contamination with pesticides on aquatic ecosystems and highlight the importance of evaluating elutriate and leachate in assessing soil ecotoxicity.