Atrazine dissipation in s-triazine-adapted and non-adapted soil from Colorado and Mississippi: implications of enhanced degradation on atrazine fate and transport parameters

Soil bacteria have developed novel metabolic abilities resulting in enhanced atrazine degradation. Consequently, there is a need to evaluate the eff ects of enhanced degradation on parameters used to model atrazine fate and transport. Th e objectives of this study were (i) to screen Colorado (CO) and Mississippi (MS) atrazine-adapted and non-adapted soil for genes that code for enzymes able to rapidly catabolize atrazine and (ii) to compare atrazine persistence, Q10, β, and metabolite profi les between adapted and non-adapted soils. Th e atzABC and/or trzN genes were detected only in adapted soil. Atrazine’s average half-life in adapted soil was 10-fold lower than that of the non-adapted soil and 18-fold lower than the USEPA estimate of 3 to 4 mo. Q10 was greater in adapted soil. No diff erence in β was observed between soils. Th e accumulation and persistence of mono-Ndealkylated metabolites was lower in adapted soil; conversely, under suboptimal moisture levels in CO adapted soil, hydroxyatrazine concentrations exceeded 30% of the parent compounds’ initial mass. Results indicate that (i) enhanced atrazine degradation and atzABC and/or trzN genes are likely widespread across the Western and Southern corn-growing regions of the USA; (ii) persistence of atrazine and its mono- N-dealkylated metabolites is signifi cantly reduced in adapted soil; (iii) hydroxyatrazine can be a major degradation product in adapted soil; and (iv) fate, transport, and risk assessment models that assume historic atrazine degradation pathways and persistence estimates will likely overpredict the compounds’ transport potential in adapted soil.