Efficient atrazine removal in bioaugmentation constructed wetland: Insight from stable isotope fractionation analysis

Abstract

Constructed wetlands (CW) provides a sustainable approach to remove pesticides from agricultural or urban runoff, while the low efficiency of the herbicide atrazine remains a challenge. Focused on improving atrazine removal in CW, a bioaugmentation strategy was implemented using the mixed culture of atrazine-degrading bacteria. The results shown a significant increase in atrazine removal from 26.2 ± 6.9% to 60.9 ± 8.7–90.6 ± 4.1% during the bioaugmentation phases. To investigate in-situ degradation processes of atrazine, compound-specific stable isotope analysis (CSIA) was conducted. The carbon and nitrogen isotope fractionation pattern revealed atrazine was primarily degraded via a hydrolysis pathway mediated by microorganisms. The biodegradation extent of atrazine calculated from δ13C signatures suggested that 90% of atrazine was removed via the hydrolysis pathway, with only a small portion being removed abiotically. This was additionally supported by an increase in microbial diversity and the abundance of specific bacteria (such as Rhizobium sp. and Pseudomonas sp.) capable of degrading atrazine. Altogether, this study demonstrated the effectiveness of atrazine-degrading mixed culture and its feasibility on bioaugmentation atrazine removal in CW. This work highlights the potential of bioaugmentation in sustainable pesticide removal approaches and CSIA can contribute to an understanding of in-situ pesticide transformation processes in wetland systems.