Abstract

RAYMUNDO-RAYMUNDO, Elias; PRADO-PANO, Blanca Lucía; NIKOLSKII-GAVRILOV, Iourii  and  MENDOZA-HERNANDEZ, José Hipólito Rodolfo. Sorption, degradation and leaching of imazapyr in volcanic soil in Mexico. Tecnol. cienc. agua [online]. 2011, vol.2, n.3, pp.61-75. ISSN 2007-2422.

Pesticide leaching through a soil profile not only implies the risk of surface and ground water contamination but also the reduction of agricultural productivity. The objective of this work was to evaluate the sorption, leaching, and degradation processes present during the transport of imazapyr through the profile of allophanic soil. Batch adsorption experiments and displacement experiments on undisturbed soil columns (8.5 cm diameter and 15 cm length) were performed. On each column, a pulse of H₂¹⁸O and imazapyr was applied. The solutes were displaced through the column by using 10 pore volumes of a reconstituted soil solution. The herbicide behavior in the soil columns was simulated with the CXTFIT 2.1 code. Analytical solutions for the convection-dispersion equation were adjusted to experimental data by means of equilibrium and non-equilibrium models. Water movement showed both physical homogeneity and heterogeneity in the columns. About 99% of the applied imazapyr was recovered in leachates at the end of the experiments. The dispersivity ranged from 0.7 profile depths studied. The calculated imazapyr half-life was > 39 months. It was concluded that for the soils studied, imazapyr was hardly adsorbed and persistent, which contributes to a high mobility of the pesticide through the soil and implies a high risk of ground water contamination.

Keywords : imazapyr; allophanic soil; leaching; degradation.