Assessing the efficiency and the side effects of atrazine-degrading biocomposites amended to atrazine-contaminated soil

Even decades after being banned in Europe, atrazine and its main metabolites can still be found in soils. While bioaugmentation using pesticide-degrading bacteria is already employed for remediating polluted soils, there is a need to improve its efficiency. Investigating the use of carrier materials to deliver pesticide-degrading microorganisms in situ emerges as a promising approach. Here, we generated atrazine-degrading biocomposites by cultivating either a bacterial strain or a four-species consortium on zeolite as the carrier material. Using a microcosm approach, we evaluated their efficiency to mineralize 14C-atrazine in soil compared to free-living cells, and assessed their side effects on the native soil bacterial community using 16S rRNA metabarcoding. We showed that, right after inoculation, atrazine mineralization potential of the free-living cells was higher than that of the biocomposites. However, microcosms inoculated with the biocomposites displayed significantly higher atrazine mineralization potential after 15 and 45 days of incubation, indicating a higher efficiency but also a better stability in soil. Inoculation of free-living cells and biocomposites differently influenced the diversity and composition of the native microbial community, their impacts being modulated by the atrazine contamination scenario. Altogether, our results provide a thorough evaluation of the efficiency and the ecological impact of atrazine-degrading biocomposites in soil.