Removal and attenuation of imidacloprid and tebuconazole pesticide toxicity by constructed wetlands

Abstract

Pesticide losses through drift and runoff from agroecosystems contribute to water body contamination, posing a toxic risk to non-target organisms. Consequently, developing strategies to reduce pesticide transport to surface waters and mitigate its environmental impact is a key challenge in environmental sciences. This study aimed to evaluate the efficiency of constructed wetlands (CWs) in removing and attenuating the toxicity of two formulated pesticides: imidacloprid and tebuconazole. Additionally, the behavior of CWs was studied after the period of exposure to the pesticides to evaluate their recovery capacity and long-term sustainability. Synthetic agricultural wastewater, either alone or spiked with commercial formulations of imidacloprid (180 mg a.i./L) and tebuconazole (125 mg a.i./L), was continuously incorporated through the CWs for two months (Exposure phase). Subsequently, uncontaminated synthetic agricultural wastewater was introduced for one month to assess system recovery (Post-exposure phase). The efficiency of the CWs was evaluated from the difference in pesticide concentration and toxicity in the influent and effluent. The ecotoxicological evaluation was performed using Daphnia magna as a test organism. Imidacloprid removal efficiency was approximately 20 %, whereas its toxicity attenuation was considerably higher (67 %). Tebuconazole removal efficiency and toxicity attenuation were 74 and 50 %, respectively. During the post-exposure phase, the effluents showed measurable pesticide concentrations but a rapid decrease in toxicity. CWs effectively reduced the toxicity of effluents contaminated by both pesticides, demonstrating their potential to mitigate environmental risks associated with agricultural wastewater.