Chlorpyrifos Attenuation and Accumulation by Lindernia rotundifolia: Evidence from Laboratory and Outdoor Mesocosm Experiments

Chlorpyrifos (CPF) is frequently detected in freshwater ecosystems and continues to raise environmental concerns, particularly in regions where its use remains weakly regulated. While phytoremediation has been proposed as a low-impact strategy for pesticide removal from water, the capacity of many aquatic macrophytes remains poorly documented. Here, we examined the ability of the semi-aquatic macrophyte Lindernia rotundifolia to contribute to CPF attenuation using a combination of controlled laboratory experiments and an outdoor mesocosm assay conducted in the Ecuadorian Amazon. Under laboratory conditions, plants were exposed to CPF concentrations ranging from 1 to 1000 µg L−1 for 14 days, while the mesocosm assay was carried out at an environmentally relevant concentration of 10 µg L−1 over 26 days. CPF dissipation from the aqueous phase, accumulation in plant tissues, bioconcentration factors (BCFs), and dissipation kinetics were quantified. In laboratory assays, aqueous CPF concentrations were significantly lower in planted than in plant-free systems at 1, 100, and 1000 µg L−1, with removal efficiencies of 64.36 ± 17.63%, 94.63 ± 2.39%, and 60.18 ± 12.27%, respectively. CPF accumulated in plant tissues across all exposure levels. BCF values ranged from 191.3 to 10,748.7 L kg−1 and differed significantly among concentrations (p < 0.001), showing a non-linear response to increasing exposure concentrations. In the mesocosm assay, CPF dissipation in planted units followed biphasic kinetics (k1 = 0.798 d−1; k2 = 0.041 d−1), in contrast to the first-order decay observed in unplanted controls (k = 0.16 d−1), indicating plant-associated enhancement of early CPF attenuation. BCF values in mesocosms declined significantly between days 12 and 26 (p < 0.05) but remained above unity at both points. Together, these findings highlight L. rotundifolia as a promising candidate for CPF phytoremediation in tropical freshwater systems.