An integrated approach for assessing the migration behavior of chlorpyrifos and carbaryl in the unsaturated soil zone

ABSTRACT

Chlorpyrifos (O, O-diethyl O-3,5,6-trichloropyridin-2-yl phosphorothioate) and carbaryl (1-naphthyl methylcarbamate) are often applied concurrently as insecticides in food production. The aim of this study was to research their migration behavior in a real environment. We researched the leaching of both pesticides by setting up field lysimeters on a farm with the typical soil used in fruit production today. In order to analyze the variables involved in this process, we performed complementary adsorption studies, we performed complementary adsorption studies using batches and undisturbed soil laboratory columns for both compounds. The results for pesticide transport through the lysimeters showed that less than 1% of chlorpyrifos was recovered in the leachates, while almost 17% was recovered for carbaryl. Having completed the experiment in undisturbed laboratory columns, soil analysis showed that chlorpyrifos mainly remained in the first 5 cm, while carbaryl moved down to the lower sections. These results can be explained in view of the sorption coefficient values (K_D) obtained in horizons A and B for chlorpyrifos (393 and 184 L kg⁻¹) and carbaryl (3.1 and 4.2 L kg⁻¹), respectively. By integrating the results obtained in the different approaches, we were able to characterize the percolation modes of these pesticides in the soil matrix, thus contributing to the sustainable use of resources.

KEYWORDS:

• Leaching
• chlorpyrifos
• carbaryl
• soil
• sorption

Acknowledgments

The authors are grateful to the Secretariat of Science and Technology, National University of Comahue, Argentina, for their financial support, to the Joint FAO-IAEA Division for their technical support and to the PhD Ana C. Dufilho for her technical assistance.

Supplementary Materials