Nanoparticle-assisted Treatment of Pesticide-contaminated Water for Irrigation Reuse and Growth Promotion in Brassica juncea.

Agriculture is the largest consumer of freshwater, and increasing water scarcity has driven the need for alternative irrigation sources such as treated wastewater. However, water reuse is often limited by pesticide contamination from agricultural runoff, as these compounds persist in water due to their chemical stability and slow degradation, posing risks to crop safety and food security. This study investigates silver-doped zinc oxide nanoparticles (Ag-ZnO NPs) for chlorpyrifos (CPF) degradation and safe agricultural water reuse. A known concentration of CPF solution was treated with Ag-ZnO NPs and compared with bare ZnO NPs. The treated solution was reused to irrigate Brassica juncea seedlings under glasshouse conditions to assess the nanoparticles' dual role as photocatalysts and growth enhancers. The 3% Ag-ZnO NPs achieved the highest CPF degradation efficiency (90.36%) within 90 min under UV light. In the glasshouse study, seedlings received irrigation of distilled water (T1), untreated CPF (T2), CPF treated with ZnO NPs (T3), 1% Ag-ZnO NPs (T4), and 3% Ag-ZnO NPs (T5). Seedlings irrigated with T5 showed the best growth performance, with the highest leaf width, leaf length, relative chlorophyll content, water content, and root volume. T4 and T5 recorded the highest total chlorophyll (0.31 µg/mL) and carotenoid contents (0.06 and 0.05 µg/mL). T5 also exhibited the lowest anthocyanin (0.25 mg/L), flavonoid content (227.02 mg QE/g FW), FRAP activity (5.29 g/g FW), and CPF residue in shoots (0.752 ppm). Overall, 3% Ag-ZnO NPs effectively degraded CPF, enabled safe water reuse, and enhanced plant growth, supporting sustainable agriculture and food security.