Metsulfuron Methyl Sorption−Desorption in Field-Moist Soils

Abstract

Pesticide sorption coefficients (K(d)) are generally obtained using batch slurry methods. As a consequence, the results may not adequately reflect sorption processes in field-moist or unsaturated soil. The objective of this study was to determine sorption of metsulfuron methyl, a weak acid, in field-moist soils. Experiments were performed using low density (i.e., 0.3 g mL(-)(1)) supercritical fluid carbon dioxide (SF-CO(2)) to convert anionic metsulfuron methyl to the molecular species and remove it from the soil water phase only, thus allowing calculation of sorption coefficients (K(d)) at low water contents. K(d) values for sorption of the metsulfuron methyl molecular species on sandy loam, silt loam, and clay loam soil at 11% water content were 120, 180, and 320 mL g(-)(1), respectively. Using neutral species K(d) values, the pK(a) of metsulfuron methyl, and the pH of the soil, we could successfully predict the K(d) values obtained using the batch slurry technique, which typically has a predominance of anionic species in solution during the sorption characterization. This application of supercritical fluid extraction to determine sorption coefficients, combined with sulfonylureas' pK(a) values and the soil pH, will provide an easy method to predict sorption in soil at different pH levels.

Adsorption of metsulfuron-methyl on soils under no-till system in semiarid Pampean Region, Argentina

“…All other chemicals (CaCl 2 , HCl, NaOH) were analytical grade chemicals. MM is a weak acid with pK a = 3.5 (Berglöf et al, 2003). The protonated species, which is dominant at pH b 3.5, is a neutral molecule (Fig.…”

“…One of the main processes controlling the behaviour of herbicides in soils is their sorption on soil components (Walker and JuradoExposito, 1998;Berglöf et al, 2003). Herbicides in soils can be found as dissolved molecules in the aqueous phase and/or as molecules bound to the solid phase (minerals, refractory organic matter, plants residuals, etc.).…”

Adsorption-desorption behavior of thiram: effect of soil type, temperature and pH

“…The desorption process of the pesticide determines rate of release and potential mobility of the pesticide in soil (Rama Krishna and Philip, 2008;Liu et al, 2010). Pesticide sorption or binding in the soil has been characterized by determining partitioning of the pesticide between soil and solution, resulting in pesticide sorption coefficients (Kd) (Wauchope et al, 2002;Berglof et al, 2003). Adsorption-desorption isotherms are usually described by linear models and/or Freundlich models.…”

Monitoring of metsulfuron-methyl and its residues in an artificial pond

“…Although many studies have been conducted to evaluate metsulfuron-methyl in soil (Smith 1986;Ghani and Wardle 2001;Berglf et al 2003;Trabue et al 2006;Wang et al 2007;Pei et al 2008), only a few have been conducted to evaluate metsulfuron-methyl in aquatic systems (WendtRasch et al 2003;Cedergreen et al 2004;Sinclair et al 2006). Since metsulfuron-methyl has a high leaching potential, it could be transferred from the site of application to surface waters during and after application via either overland runoff or incorrect disposal of waste (Belfroida et al 1998;Fogg and Boxall 2004;Sondhia 2009).…”