Sorption and Desorption of Imazethapyr and 5-Hydroxyimazethapyr in Minnesota Soils

Abstract

Laboratory batch equilibrium studies were conducted to evaluate the sorption-desorption behavior of imazethapyr and its major plant metabolite, 5-hydroxyimazethapyr, in three Minnesota soils. Sorption of both compounds on all soils was low, and pH did not significantly influence sorption in the range of 4,8 to 7.1. Less 5-hydroxyimazethapyr was sorbed than imazethapyr on the same soil. Once sorbed, both compounds were only partially desorbable from all soils. Significant hysteresis and formation of nonextractable residues indicate that the small amount of chemical sorbed is bound to selective surfaces with strong bonds. Webster clay loam had greater irreversibility than Waukegen silt loam and Estherville sandy loam soil. The hysteresis observed in desorption may be responsible for the difference between mobility estimations made from laboratory sorption studies and the limited mobility observed in field experiments.

Influence of soil pH‐sorption interactions on the carry‐over of fresh and aged soil residues of imazamox

“…Desorption isotherms fitted the Freundlich equation ( r 2 > 0.90), and hysteresis (1/n fd < 1/n f ) was observed during desorption from all pH soils (Table 4). Hysteresis was previously observed in various soils for a similar chemical, imazethapyr (Gan et al ., 1994; Bresnahan et al ., 2000). Greater desorption hysteresis was observed at higher soil pH levels than at low soil pH.…”

A Bioassay Technique Detects Imazethapyr Leaching and Liming-Dependent Activity1

“…In contrast, Mangels (1991) contends that the K d value (thus, indirectly, bioavailability) of imazethapyr does not decrease with an increase in pH above 6. Gan et al (1994) also stated that pH levels between 5 and 8 did not influence the sorption, thus bioavailability, of imazethapyr.…”

Relationship between Freundlich isotherm Coefficients, logKFand 1 /nfor atrazine desorption from soils in Japan

“…In many studies (Ma et al 1993;Barriuso et al 1994;Gan et al 1994;Seybold and Mersie 1996), desorption isothenns were represented by drawing pattern (a) lines. Desorption isotherms branching from the adsorption isotherm were considered to confirm the presence of hysteresis.…”

“…In most of the reports, the hysteresis of adsorption-desorption phenomena was considered, as evidence of hysteresis is critical in view of consideling the mobility of a hcrbicide in soils. Although the hysteresis of herbicide adsorption had been confirnled (Bowman and Sans 1985;Ma et al 1993;Gan et al 1994), it had tended to be over-estimated by considering irreversihle equilibrium, due to the desorption methods employed. Two methods have been used for the analysis of herbicide desorption in soils.…”