Abstract
The chlorotriazine herbicides have been applied worldwide for controlling of broadleaf weeds. These herbicides are known carcinogen and thus, their occurrence in surface and ground water is a cause of concern. In the present study, adsorption–desorption behavior of chlorotriazine herbicides namely simazine and atrazine was investigated. For the study, two different types of agricultural soil A (loam, 13.7% organic matter content) and soil B (clay-loam, 4.8% organic matter content) was collected from Punjab, India. The adsorption–desorption study was carried out by batch equilibration procedure. The data fitted well into the Freundlich equation. The adsorption Kf values indicated that the simazine has more soil adsorption ability than atrazine. The extent of herbicides adsorbed to the soil was more under low pH conditions and decreased with the increase in pH value. Increase in temperature decreased herbicides adsorption ability for both the soil types. The Gibb’s free energy (ΔG) values were found less negative with the increase in temperature. Atrazine exhibited better desorption behavior than simazine. Soil A with high organic matter content exhibited sorption–desorption hysteresis. The results indicate that the soil organic matter content and aqueous solubility play an important role in the adsorption–desorption behavior of chlorotriazine herbicides. The present understanding of chlorotriazine herbicides sorption–desorption process will help to determine the herbicides fate and availability in soil, biodegradation, runoff and leaching.
Highlights
The chlorotriazine herbicides namely atrazine and simazine have been widely used since 1950s for controlling of broadleaf weeds and annual grasses in agricultural and non-crop fields [1]
The chlorotriazine herbicides used in the present study were not detected in the soil samples, suggesting absence of atrazine and simazine pre-contamination
The initial step was a very rapid adsorption followed by a slow adsorption. This observation is due to the fact that in initial stage a large number of vacant surface sites were available for adsorption, but once the vacant surfaces were occupied, the repulsive forces between the solute molecules of the solid and bulk phases came into play, delaying the adsorption process
Summary
The chlorotriazine herbicides namely atrazine and simazine have been widely used since 1950s for controlling of broadleaf weeds and annual grasses in agricultural and non-crop fields [1]. United States Environmental Protection Agency (EPA) has reported atrazine and simazine as potential carcinogenic herbicides. Owing to their carcinogenic potentials, the presence of these herbicides in water is a cause of concern for public and regulatory agencies [5,6]. Atrazine and simazine has been reported to cause tumors and cancers, including breast, ovarian, and uterine, leukemia and lymphoma [1,7,8,9]. Atrazine is an endocrine disrupting chemical, interrupting regular hormone function, causing birth defects, reproductive tumors and weight loss in amphibians as well as humans [7,8,9]
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