Carbaryl Photochemical Degradation on Soil Model Surfaces

Marie Siampiringue,Mohamed Sarakha,Rajae Chahboune,Pascal Wong-Wah-Chung

doi:10.3390/soilsystems3010017

Abstract

The phototransformation of carbaryl was investigated upon solar light exposure on three surfaces, silica, kaolin and sand, as soil models. By excitation with a Suntest set up at the surface of the three solid supports, the degradation of carbaryl followed first-order kinetics with a rate constant of 0.10 h−1. By using the Kubelka Munk model, the quantum yield disappearance at the surface of kaolin was evaluated to 2.4 × 10−3. Such a value is roughly one order of magnitude higher than that obtained in aqueous solutions. The results indicated that the particle size and the specific surface area of the various models have significant effects. The photo-oxidative properties as well as the byproduct elucidation by liquid chromatography combined with diode arrays (LC-DAD) and liquid chromatography coupled mass spectrometry (LC-MS) analyses allowed us to propose the degradation mechanism pathways. The main products were 1-naphtol and 2-hydroxy-1,4-naphthoquinone, which arise from a photo-oxidation process together with products from photo-Fries, photo-ejection and methyl carbamate hydrolysis. The toxicity tests clearly showed a significant decrease of the toxicity in the early stages of the irradiation. This clearly shows that the generated products are less toxic than the parent compound.

Highlights

Carbaryl, 1-naphtyl N-methylcarbamate, known by the trade name Sevin®, is distributed by the Bayer Company
Part, we we investigate investigate the the toxicity toxicity evolution evolution of of carbaryl carbaryl on on aa solid solid support support surface surface under under solar light exposure by Analyses were realized on spiked kaolin layer samples solar solar light light exposure exposure by by TLS-FIA
Throughout this study, we clearly demonstrated that carbaryl photodegradation at the surface this study, clearly demonstrated carbaryl at the of theThroughout three solid supports of we silica, kaolin and sand is that effective

Summary

Introduction

1-naphtyl N-methylcarbamate, known by the trade name Sevin® , is distributed by the Bayer Company. It is used as a substitute for some organochloride pesticides and represents one of the most commonly used insecticides [1]. Carbaryl has been used against many harmful insects on different crops by contact [2,3,4]. It has been employed in golf courses, lawns, and alandscapes for flea, lice or mosquito treatment [5,6].

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