Detection of residual organochlorine and organophosphorus pesticides in agricultural soil in Rio Verde region of San Luis Potosi, Mexico

Abstract

Organochlorine pesticides were intensively used in Mexico from 1950 until their ban and restriction in 1991. However, the presence of these compounds is commonly reported in many regions of the country. The aim of the present study was to identify and quantify residual organochlorine and organophosphorus pesticides in agricultural soil in Rio Verde region, San Luis Potosi state, which has been identified as possibly polluted by pesticides. Composed samples from 24 zones covering an area of approximately 5,440 ha were analyzed. The most frequently found pesticides were p,p´-DDT followed by ,p,p´-DDE, heptachlor, endosulfan and γ-HCH whose frequency rates were 100, 91, 83 and 54%, respectively. The concentration of p,p´-DDT in the crops grown in these soils was in the following order: chili > maize > tomato > alfalfa. The results obtained in this study show that p,p´-DDT values are lower or similar to those found in other agricultural regions of Mexico. Methyl and ethyl parathion were the most frequent organophosphate pesticide detected in 100% and 62.5% of the samples with average concentrations of 25.20 and 47.48 μg kg^–1, respectively. More research is needed to establish the background levels of pesticides in agricultural soils and their potential ecological and human health effects in this region.

Keywords:

• Pesticides
• persistence
• DDT
• heptachlor
• agricultural soil

Acknowledgments

The authors appreciate the support in planning, logistics and execution of work field of the following persons: Mr. Joel Milán Navarro, Mr. José Antonio Undiano Errejón and Mr. Noé Bautista Zarco from SEMARNAT- SLP; Mr. Hilario Charcas Salazar, PhD from the Autonomous University of San Luis Potosi; Mr. Marco Antonio Compeán and Mr. Rolando Mendoza Úrsulo from the common-land “El Refugio”; and Mr. Gustavo López Analco for his technical support in the analysis of the samples. The authors also acknowledge the support of Claudia Granada, MSc, for her help in the elaboration of the maps.

Funding

This work was funded by INE/A1-012/2010 project.