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Incubation Time Effects on Imazaquin Desorption as Determined by Nonequilibrium Thin‐Soil Disc Flow
Author(s) -
Smith M. Cade,
Shaw David R.,
Massey Joseph H.,
Boyette Michele,
Kingery William
Publication year - 2004
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2004.5810
Subject(s) - chemistry , desorption , incubation , leaching (pedology) , environmental chemistry , sorption , chromatography , soil water , soil science , adsorption , biochemistry , geology , organic chemistry
ABSTRACT Because organic sorption in soil may never reach equilibrium, a thin‐disc flow nonequilibrium method may be helpful in understanding herbicide–soil interactions. This research was conducted to (i) determine the influence of incubation time on imazaquin [2‐(4,5‐dihydro‐4‐methyl‐4‐(1‐methylethyl)‐5‐oxo‐1 H ‐imidazol‐2‐yl)‐3‐quinolinecarboxylic acid] desorption from soil, (ii) examine the influence of solution flow velocities on desorption, and (iii) elucidate the most appropriate kinetic model to describe imazaquin leaching. Soil at 7.5% moisture w/w was treated with imazaquin and incubated for 24, 72, and 168 h. Treated soil was sealed in an in‐line filter apparatus and rinsed with 5.0 m M CaCl 2 at 0.33, 0.67, or 1.0 mL min −1 Effluent was collected as 1.0‐mL fractions for a total of 50 mL. Flow was stopped for 24 h. When flow resumed, fractions were collected for an additional 15 mL. After the initial desorption, 79% of the imazaquin incubated for 24 h was leached. Increasing incubation time beyond 24 h reduced imazaquin leaching. After both desorption events, 13% of the initially applied imazaquin remained in the soil incubated for 168 h, compared with 7% with soil incubated for 24 h. Elovich and Freundlich kinetics accounted for 98% of the variance observed in the imazaquin desorption curves. First‐order and diffusion kinetics accounted for 91% of the variance. Incubating soil for 72 h before desorption reduced the rate of imazaquin desorption by approximately 12%, compared with the 24‐h incubation treatment. Imazaquin desorption was not affected by wash solution flow rate. These data suggest that the kinetics of desorption in prolonged desorption events are limited by transport phenomena (i.e., particle and film diffusion).