Simulation of branched serial first‐order decay of atrazine and metabolites in adapted and nonadapted soils

Abstract

In the present study a branched serial first-order decay (BSFOD) model is presented and used to derive transformation rates describing the decay of a common herbicide, atrazine, and its metabolites observed in unsaturated soils adapted to previous atrazine applications and in soils with no history of atrazine applications. Calibration of BSFOD models for soils throughout the country can reduce the uncertainty, relative to that of traditional models, in predicting the fate and transport of pesticides and their metabolites and thus support improved agricultural management schemes for reducing threats to the environment. Results from application of the BSFOD model to better understand the degradation of atrazine supports two previously reported conclusions: atrazine (6-chloro-N-ethyl-N'-(1-methylethyl)-1,3,5-triazine-2,4-diamine) and its primary metabolites are less persistent in adapted soils than in nonadapted soils; and hydroxyatrazine was the dominant primary metabolite in most of the soils tested. In addition, a method to simulate BSFOD in a one-dimensional solute-transport unsaturated zone model is also presented.

Enhanced atrazine degradation is widespread across the United States

“…These studies have often focused on its effectiveness as a herbicide, as well as addressing putative environmental and toxicological risks associated with ATZ use . These risks include contamination of water on every continent except Antarctica, endocrine disruption in animals from frogs to fish and human exposure …”

Degradación De La Mezcla Comercial De Los Herbicidas Atrazina Y Ametrina, Utilizando Cultivos Con Células en Suspensión E Inmovilizadas

“…a) Cuantificación por cromatografía de líquidos de alta resolución (HPLC); b) Cuantificación por demanda química de oxígeno (DQO); c) Velocidad de generación (Rvg) teórica (u) y experimental (n) de ácido cianúrico en función de la carga volumétrica del ácido cianúrico (Bacv) generado durante el cultivo continuo en la biobarrera. (Gordon y Crumpton 1998, Webb et al 2011. Para el caso de la ametrina se tienen datos de una vida media de 62 d en suelo y de 10.2 h utilizando un fotoreactor (TOXNET 2017).…”

“…La eficiencia de remoción de la DQO fluctuó entre 85.41 ± 5.58 % (Cuadro I). Con los datos obtenidos en el cultivo por lote semicontinuo se determinó la vida media de la ametrina y de la atrazina, considerando el modelo de desintegración de primer orden (Webb et al 2011). Para los primeros ocho ciclos se obtuvo una vida media de 2.43 ± 0.01 h para la atrazina y de 2.23 ± 0.03 h para la ametrina, para los ciclos nueve al quince la vida media fue de 1.38 ± 0.01 h para la atrazina y de 1.31 ± 0.01 h para la ametrina, en los últimos ocho ciclos la vida media fue de tan sólo 1.08 ± 0.01 h para la atrazina y de 1 ± 0.02 h para la ametrina (Cuadro I).…”

Modelling the Fate of Pesticide Transformation Products From Plot to Catchment Scale—State of Knowledge and Future Challenges

“…m PC and m TP are the masses of the PC and TP, respectively, and k PC and k TP the decay rates (t −1 ) of the PC and TP. A slightly different approach is the usage of a separate parent decay rates (k PC−TP ) towards each TP (Webb et al, 2011). In case of two TPs (TP1 and TP2), the corresponding transformation equations are:…”

“…To overcome the limitations of the LEACHM model regarding the serial transformation scheme, Webb et al (2011) implemented a branched transformation scheme into the code of the model. They applied the modified model for the simulation of the herbicide atrazine and three of its first-order TPs: deethylatrazine, deisopropylatrazine and hydroxyatrazine.…”