Phytoextraction capacity of Eichhornia crassipes for the contaminant atrazine

Atrazine is one of the most widely used herbicides in Brazil and has a high potential to contaminate surface and groundwater, persisting in aquatic environments for more than six months. Its exposure may induce the formation of reactive oxygen species (ROS), triggering the activation of antioxidant enzymes such as superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT). This study evaluated the response of these enzymes in the leaves and roots of Eichhornia crassipes (Mart.) Solms exposed to atrazine.

Plants were subjected to control and atrazine treatments (2.0 µg/L), corresponding to the maximum concentration permitted for drinking water according to Brazilian Ordinance GM/MS No. 888/2021. Leaves and roots were collected hourly for six hours and again after 24 hours, while the culture medium was sampled after 6 and 24 hours. APX, CAT, and SOD activities were determined by spectrophotometry and compared between treatments.

Atrazine concentration decreased markedly in the culture medium, reaching 0.0009 µg/L after 6 hours and remaining stable after 24 hours (0.00089 µg/L). No significant accumulation of atrazine was detected in Eichhornia crassipes tissues. The activities of APX, CAT, and SOD showed only slight variations between the control and treated plants, with no statistically significant differences. In the leaves, for instance, SOD activity started at 92 U/mL (H0) for both treatments and ended at 24 hours with very similar values between the control (102 U/mL) and the herbicide (84 U/mL). In the roots, CAT also remained stable, moving from 0.00030 µmol/g/L (H0) to 0.00027 µmol/g/L (control) and 0.00031 µmol/g/L (atrazine) at the end of the experiment. This numerical proximity across all three enzymes may indicate that the herbicide did not disrupt the plant's metabolism.

The reduction in atrazine concentration in the culture medium, combined with the absence of tissue accumulation, suggests that its removal did not occur through plant uptake but may be associated with microbial degradation by bacteria belonging to the genera Pseudomonas, Arthrobacter, and Agrobacterium. The absence of significant changes in APX, CAT, and SOD activities indicates that the concentration tested was insufficient to induce detectable