Removal of the pesticides imazalil and tebuconazole in saturated constructed wetland mesocosms

• Published in: Water research (Oxford) 2016-03, Vol.91, p.126-136
• Main Authors: Lv, Tao, Zhang, Yang, Zhang, Liang, Carvalho, Pedro N., Arias, Carlos A., Brix, Hans
• Format: Article
• Language: English
• Subjects: Bacteria; Berula erecta; Biocides; Biodegradation, Environmental; Construction; Degradation; Emerging organic pollutants; Fungicides; Fungicides, Industrial - metabolism; Imidazoles - isolation & purification; Imidazoles - metabolism; Iris pseudacorus; Juncus effusus; Macrophytes; Pesticides; Phragmites australis; Phytoremediation; Plants (organisms); Seasons; Summer; Triazoles - isolation & purification; Triazoles - metabolism; Typha latifolia; Uptakes; Waste Disposal, Fluid; Water Pollutants, Chemical - metabolism; Wetlands
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2016.01.007

The aim of this study was to investigate the removal of the pesticides imazalil and tebuconazole at realistic concentration levels (10 and 100 μg L−1) in saturated constructed wetland (CW) mesocosms planted with five wetland plant species (Typha latifolia, Phragmites australis, Iris pseudacorus, Juncus effusus and Berula erecta) at different hydraulic loading rates during summer and winter. The removal of imazalil and tebuconazole was not influenced by the influent concentration, but the removal efficiency for both compounds was lower in winter than in summer. Planted mesocosms had significantly higher removal efficiencies than the unplanted controls only in summer. The first-order kinetics model fitted the tebuconazole removal in all mesocosms, and the reaction rate constants varied by plant species and season (0.1–0.7 d−1 in winter and 0.6–2.9 d−1 in summer). For imazalil, the first-order kinetics model fitted the removal only in mesocosms planted with Phragmites australis (k = 1.2 ± 0.4 d−1) and in the unplanted control (k = 1.2 ± 0.5 d−1 in both summer and winter). The removal of imazalil and tebuconazole by sorption to the bed substrate and plant uptake were low, suggesting a high rate of metabolization in the saturated CW mesocosms. The removal of imazalil and tebuconazole correlated with the rate of evapotranspiration and the removal of nutrients (N and P) during summer and with the DO/oxygen saturation during winter. This reveals two possible metabolization pathways: degradation inside the plant tissue after uptake and plant-stimulated microbial degradation in the bed substrate. Furthermore, the results indicate that nitrifying bacteria may play an active role in the biodegradation of these pesticides. [Display omitted] •Imazalil and tebuconazole removal varied strongly with the season and plant species.•First order kinetics model and Arrhenius model parameters were assessed.•Pesticides removal by substrate sorption and phytoaccumulation was low.•Plant uptake and biodegradation are the main removal pathway of the pesticides.•Degradation inside the plants and nitrifying bacteria may be behind metabolisation.