Sorption Kinetics of Atrazine and Diuron in Soils from Southern Brazil

Abstract

Sorption kinetics of atrazine and diuron was evaluated in soil samples from a typical landscape in Paraná. Samples were collected (0-20 cm) in a no-tillage area from Mamborê, PR, which has been cultivated under a crop rotation for the last six years. Six sampling points of the slope were selected to represent a wide range of soil chemical and physical properties found in this area. Radiolabeled tracers (14C-atrazine and 14C-diuron) were used and the radioactivity was detected by liquid scintillation counting (LSC). Sorption was accomplished for increasing equilibration periods (0.5, 1.5, 3, 6, 12, 24, and 48 h). Kinetics data fitted adequately well to Elovich equation, providing evidences that soil reaction occurs in two distinct stages: a fast, initial one followed by a slower one. During the fast phase, 34-42 and 71-79% of total atrazine and diuron applied were sorbed to soil samples. No important differences were found among combinations of soil and herbicide sorption during the slow phase. The unrealistic conditions under batch experiments should be overestimating sorption in the fast phase and underestimating diffusion in the slow phase. Sorption of both herbicides was positively correlated to organic carbon and clay contents of soils, but atrazine was much less sorbed than diuron, showing its higher potential to contaminate groundwater, specially in sandy, low organic carbon soils.

Rainfall effect on dissipation and movement of diuron and simazine in a vineyard soil

“…Even though, for simazine OC content was not the only factor responsible for soil sorption-desorption process, contrary to what has been previously reported (Sullivan & Felbeck, 1968;Senesi & Testini, 1980;Gevao et al, 2000). In this specific soil, other mechanisms such as reaction with clay surfaces could have occurred (Sukop & Cogger, 1992;Inoue et al, 2004), and probably there would be a negative effect of organic substances Rainfall effect on dissipation and movement of diuron and ... on simazine sorption, which could act as a barrier, avoiding the ability of clay, mainly caolinite in this case, to adsorb simazine (Zsolnay et al, 2002).…”

Sorção e dessorção do diuron em quatro latossolos brasileiros

“…Esses resultados corroboram os de Liu et al (2010), que atribuíram essa cinética de sorção do diuron ao fato de que no início há grande número de sítios de sorção disponíveis no solo e, na fase seguinte, os sítios superficiais vagos são difíceis de serem ocupados devido às forças de repulsão entre as moléculas do soluto na fase sólida e as moléculas em solução. Inoue et al (2004) A isoterma de Freundlich ajustou-se adequadamente para descrever a sorção do diuron, como indicado pelos coeficientes de determinação das equações (R 2 ), que foram de 0,99, nas curvas ajustadas de todos os solos (Tabela 3 e Figura 2). As isotermas ajustadas foram do tipo L, a qual apresenta inclinação não linear e côncava em relação à abscissa.…”

Adsorption of atrazine from aqueous electrolyte solutions on humic acid and silica

“…1a and b. The Elovich equation has been successfully used for the description of adsorption kinetics on energetically heterogeneous solid surfaces [50][51][52][53]. As shown in Fig.…”