Degradation of the Herbicide Alloxydim-sodium in Soil

Abstract

Alloxydim-sodium (ADS), sodium salt of 2-(1-allyloxyaminobutylidene)-5, 5-dimethyl-4-(methoxycarbonyl)cyclohexane-l, 3-dione, 14C-labeled at butylidene-1 and ring-1, 5, respectively, was degraded with a half-life of about 5 days in Oiso soil at 25oC in the dark. The following were identified as degradation compounds by thin-layer cochromatography and mass spectrometry; deallyloxylated compound (I), two isomers of oxo-tetrahydrobenzoxazoles (II and III), deallyloxyaminated compound (VI), demethoxycarbonylated compound (VII) and ring-opened dicarboxylic acid (XX). These compounds further decomposed to 14C02 for the extent of 20% of applied radioactivity at 28 days. Moreover, the evolution of 14C02 was much faster in the case of XX incubation. In the sterilized soil, ADS degraded slowly and the oxazoles accumulated up to 43% at 28 days. The half-life of ADS under outdoor winter conditions was about 2 days and major degradation compound was I. The amount of soil-bound materials of ADS reached the maximum around 2 months after treatment, but thereafter decreased gradually.

Degradation of Cyclohexanedione Oxime Herbicides

“…Similar results were obtained for alloxydim when it was sprayed on several crops such as sugar beet or wild oat [38,51]. In unsterilized soil, the half-life of alloxydim was 5 to 6 days under dark incubation [52]. In this research, the evolution of 14 CO 2 was investigated as a measure of microorganism activity in the soil.…”

“…Ono et al [52] also concluded that photolysis of alloxydim occurred when a soil spiked with an aqueous solution of this herbicide was exposed to sunlight.…”

“…Other authors have stated the formation of alloxydim amine in the soil and plants, although it is not clear if a biotic or abiotic mechanism is involved. In this sense, Ono et al [52] identified the amine of alloxydim by thin-layer chromatography and mass spectrometry when the photodegradation of this herbicide was studied in sterilized soil. Alloxydim was also readily degraded in sugar beet [38] and soybean [50] and the main transformation product was identified as the amine compound.…”

Photochemical behavior of alloxydim herbicide in environmental waters. Structural elucidation and toxicity of degradation products

“…Although there are several works that study alloxydim photodegradation in different conditions [10,11,21], its mechanism of photolysis is not well-known. involving these species are one of the most common routes of pesticide transformation.…”

“…Although it is known that this herbicide is easily degradated in different conditions there is little information in the literature on the fate of this compound in the environment [9][10][11].…”