Leaching Kinetics of Atrazine and Inorganic Chemicals in Tilled and Orchard Soils

Abstract

A b s t r a c t. The aim of this study was to verify first-order kinetic reaction rate model performance in predicting of leaching of atrazine and inorganic compounds (K -and PO 4 -3 ) from tilled and orchard silty loam soils. This model provided an excellent fit to the experimental concentration changes of the compounds vs. time data during leaching. Calculated values of the first-order reaction rate constants for the changes of all chemicals were from 3.8 to 19.0 times higher in orchard than in tilled soil. Higher first-order reaction constants for orchard than tilled soil correspond with both higher total porosity and contribution of biological pores in the former. The first order reaction constants for the leaching of chemical compounds enables prediction of the actual compound concentration and the interactions between compound and soil as affected by management system. The study demonstrates the effectiveness of simultaneous chemical and physical analyses as a tool for the understanding of leaching in variously managed soils.K e y w o r d s: leaching, kinetics, atrazine, inorganic chemicals, tilled and orchard soils INTRODUCTION Atrazine, a derivative of the S-triazine group of herbicides, is one of the most widely used pesticides in the world, due to the lowest cost associated with ease of application. This substance is one of the most effective soil-applied herbicides for control of narrow-and broad-leaved weeds in cereal crops, fruit orchards, vegetables, maize, sugar cane, vines, citrus groves, grassland and forestry. High mobility of atrazine in soil (Tindall and Vencil, 1995) and its potential contamination of ground waters (Ritter et al., 1994) represent a serious human health hazard because of the potential carcinogenic effects. Taking into account atrazine toxicity, high mobility, long life-time (10 to 12 months), the rate of leaching in every soil system should be of great interest.Leaching and concentration of chemicals in variously managed soil is largely associated with aggregate and pore structure (Holland et al., 2004;Lipiec et al., 2011). In general, orchard grassed soils, in comparison with tilled soils are characterized by a greater contribution of continuous biological pores made by soil fauna and plant roots that raise infiltration under ponded conditions (S³owiñska-Jurkiewicz et al., 2001). Quantification of pore size distribution over a wide range of pore size revealed that the nature of the pore system is more heterogeneous in untilled orchard than in tilled soil (Hajnos et al., 2006). There is substantial evidence that increased root growth in the grassed soil enhances soil aggregation and produces lines of weakness along which the clod or soil mass break into smaller aggregates that are stabilized by root exudation and associated microbial activity (Six et al., 2004). Change of land use from tilled to grass or no-till system leads further to a higher soil organic carbon content and modified soil acidity (Lipiec et al., 2011). The differences in aggregate and pore structure and soi...

Soil Mobility of Allyl Isothiocyanate and Chloropicrin as Influenced by Surfactants and Soil Texture

“…K is the first-order rate constant in units of L/time, and the reaction rate unit is presented as concentration/time. The units can vary with other order reactions (Szajdak et al, 2014) Table 2 shows the statistical parameters of the first-order kinetics model with a good fit for the measured concentration change over time (Fig. 1).…”

“…This difference could be a result of the higher organic matter and the specific interaction between nonionic-2 and organic matter. Szajdak et al (2014) showed that higher K values are associated with higher organic matter. The effect of nonionic-1 on K values could be attributed to the fumigant staying longer in solution and not adsorbing on soil particles, thereby possibly increasing fumigant residence time in soil.…”

“…Time-dependent behavior of the fumigant due to the addition of the surfactant was determined using a first-order kinetic model. The model described the linear movement of the fumigant based on concentration (Szajdak et al, 2014). The model was described by the following firstorder differential equation:…”

“…The data suggest that nonionic-1 allows the CP to stay in solution longer, resulting in higher concentrations in the leachate when compared with CP applied alone without any surfactants. In Chualar loam soil, CP applied with nonionic-1 had the highest K value (Table 2) and the lowest half-life time, suggesting that with CP, the surfactant could affect the adsorption of the chemical due to soil textural differences (Szajdak et al, 2014). CP applied in Blanco clay loam soil with nonionic-1 resulted in the highest K value ( Table 2).…”

Impact of some amendments on kinetics of leaching dissolved organic carbon and ammonium in calcareous sandy soil under vinasse addition

“…The first-order interaction model is used to study the leaching of chemical compounds and nutrients from the soil, which helps to predict the actual concentration of these compounds and the interactions between these compounds and the soil as a result of the management practices 71 . Physicochemical properties of the soils such as texture, bulk density, organic carbon, and pH have a great impact on the rate constants of a first-order reaction.…”