Study of the degradation of the herbicide clomazone in distilled and in irrigated rice field waters using HPLC-DAD and GC-MS

Renato Zanella,Martha B Adaime,Fábio F Gonçalves,Manoel L Martins,Enio Marchesan,Sérgio L O Machado,Ednei G Primel

doi:10.1590/s0103-50532008000500026

Abstract

This study evaluated the degradation of the herbicide clomazone in distilled water and from irrigated rice fields, through UV irradiation and under natural conditions. After a solid phase extraction (SPE) as preconcentration step, the remained concentration of clomazone was determined by high performance liquid chromatography with diode array detection (HPLC-DAD) and the identification of the degradation products was achieved by gas chromatography-mass spectrometry (GC-MS). Under UV irradiation, the clomazone was degraded faster in distilled water than in surface water. In irrigated rice water, under sunlight irradiation, clomazone presented a half-life time average of 3.2 days in three consecutive harvests, and after application the concentration in water remained higher than 0.1 μg L-1 for 20 days. Several by-products, like 2-chlorobenzaldehyde and 2-chlorobenzene methanol, were identified by GC-MS, which evidenced that the concentration of intermediates at the begining increase and then they also undergo degradation.

Highlights

Environmental water pollution by pesticides is a problem with widespread ecological consequences.[1]
An increase in the degradation of clomazone and of the products were observed in the systems HPLC-DAD and gas chromatography-mass spectrometry (GC-MS), respectively
From the results of the degradation in different water types after UV irradiation (Table 1), it was observed that in distilled water a larger degradation of the herbicide occurs when compared with surface water using an irradiation time up to 120 min

Summary

Introduction

Environmental water pollution by pesticides is a problem with widespread ecological consequences.[1] Herbicides are potential contaminants of environmental water because they are directly applied to the soil or irrigating water. They can be leached to the surface water and transported into the groundwater.[2,3] According to specialized literature,[2,4] a pesticide can pollute the aquatic environmental if its solubility in water is higher than 30 mg L-1; its Koc, organic. CAS number 81777-89-1, [2-[(2-chlorophenyl) methyl]-4,4-dimethyl-3isoxazolidinone] is widely used against species of annual broad leaf weeds and grass.

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Conclusion