Bioconcentration factor-based management of soil pesticide residues: Endosulfan uptake by carrot and potato plants

Abstract

Uptake characteristics of endosulfan (ED), including α-, β-isomers and sulfate-metabolites, from the soils by carrot and potato plants were investigated to establish a method that may be used to calculate recommended permissible soil contaminant concentrations (Cs, permissible) at time of planting so that maximum residue level (MRL) standards are not exceeded. The residues of ED were analyzed in soils treated with ED at concentrations of either 2 or 10 mg kg soil−1 and in the plants (carrots and potatoes) grown in such soils for 60–90 d. Presence of plants increased ED dissipation rates in soils in patterns that were best fit to a double-exponential decay model (R2 of 0.84–0.99). The ED uptake extent varied with type of crop, ED isomer, plant growth duration, and plant compartments. However, ED concentrations in all edible parts of crops eventually exceeded their maximum residue limits. Total ED bioconcentration factor (BCF), the ratio of soil ED concentration at planting time to that in edible part of each crop at harvest day, was found to decrease with time due to decreasing soil ED concentration and increasing plant biomass in a pattern that followed a first order kinetic model. Using this model, the Cs, permissible values, specific to the soils used in this study, were calculated to be 0.32 and 0.19 mg kg soil−1 for carrots and potatoes, respectively. The results and methods developed in this study may be utilized as a prediction tool to ensure crop safety from pesticide residues.