Metribuzin Mobility and Degradation in Undisturbed Soil Columns

Locke, Martin A.; Harper, Sidney S.; Gaston, Lewis A.

doi:10.1097/00010694-199405000-00002

Cited by 19 publications

(23 citation statements)

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“…The amount of DADK is high in soil A after 15 days of incubation, while it is very low (traces) in soil B, confirming the weak capacity of this soil for reductive reactions. Locke et al (1994) showed that a first stage deamination leads to accumulation of metabolite DA and then to transformation of DA to DADK. Moreover, if the soil is worked and aerated, DADK forms rapidly on account of DA, but the values stay very low.…”

Section: Soil Columnsmentioning

confidence: 99%

Retention and degradation of metribuzin in sandy loam and clay soils of Lebanon

et al. 2003

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Summary The retention and degradation of metribuzin herbicide were studied under two environmental conditions. Field studies were carried out on two soils, a sandy loam soil (soil A) and a clay soil (soil B). Metribuzin was applied with a jet sprayer at 1060 g a.i. ha−1 and 1960 g a.i. ha−1 on soils A and B respectively. Reconstituted soil columns were used to study the herbicide movement and metabolism in the two soils. Analyses of metribuzin and its metabolites were carried out using standardized methods. The results indicated a very weak capacity of adsorption of metribuzin in the two soils, and the weak adsorbed fraction is easily desorbed. Degradation and mobility of metribuzin in the field and laboratory soil columns were very intense and rapid. Soil A favoured reductive deamination whereas soil B favoured oxidative desulphuration and the respective metabolites deaminometribuzin and diketometribuzin yield the same product deaminodiketometribuzin. Both leaching by rainfall and degradation were important in the disappearance of metribuzin from the soils.

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Section: Soil Columnsmentioning

confidence: 99%

Retention and degradation of metribuzin in sandy loam and clay soils of Lebanon

et al. 2003

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“…Pesticides may be degraded by purely abiotic processes as exemplified by the hydrolysis of aldicarb, but a review of several pesticides has shown that in subsoils the degradation is primarily microbial (Fomsgaard, 1995). Regarding metribuzin the microbial degradation and the mobility in natural aquifers and soil columns has been characterized (Locke and Harper, 1991; Agertved et al, 1992; Locke et al, 1994; Buss et al, 2006). Likewise, the microbial degradation of MCPA has been described (Loos et al, 1979; Sorensen et al, 2006).…”

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Impact of Basic Soil Parameters on Pesticide Disappearance Investigated by Multivariate Partial Least Square Regression and Statistics

et al. 2008

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Dissipation time is a key parameter when studying and modeling the environmental fate of pesticides. This study was conducted to characterize the variability of pesticide disappearance in soil and to identify possible controlling parameters related to intrinsic soil properties and microbiology. Multivariate data analysis was used to study spatial variability in three horizons from 24 sandy soil profiles. The time for 50% disappearance (DT(50)) was characterized for two herbicides, metribuzin (MBZ) and MCPA, and methyltriazine amine (MTA; transformation product of metsulfuron-methyl, tribenuron-methyl, thifensulfuron-methyl, and chlorsulfuron). Normal and log-normal distributions were compared for DT(50) and soil properties and descriptive statistics were calculated. Conformity with log-transformed distributions was observed and assuming normality of the DT(50) data would cause 5 to 35% overestimation. Mean DT(50) were: MCPA 9.5, MBZ 168, and MTA 127. Significant effect of soil depth on DT(50) was shown for MCPA and MBZ, with low values in deeper horizons. Simple linear correlation for combinations of MCPA, MTA, pH, and total organic carbon (TOC) was observed. Using partial least squares regression (PLS) 71 to 85% of the total DT(50) variance was explained. A specific predictor variable could not be identified as the controlling components differed within horizons and compounds. For MCPA the overall important predictor variables were microbiology and TOC, whereas for MTA and MBZ it was inorganic variables (Al, Fe, cation exchange capacity, base saturation percent, and pH) and microbiology. The study indicates that PLS generated input data can improve pesticide fate modeling and reduce the uncertainty in dissipation estimation.

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“…The primary products from metribuzin transformation in soil are DA, DK, and DADK. Other unidentified metabolites are detected in experiments using 14 C‐labeled metribuzin (Moorman and Harper, 1989; Locke et al, 1994). Total degradation of metribuzin to inorganic species (mineralization) is usually below 10% of the metribuzin applied (Ladlie et al, 1976; Locke et al, 1994; Mallawatantri et al, 1996) and the highest result measured is 20% within 90 d (Moorman and Harper, 1989).…”

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Degradation and Sorption of Metribuzin and Primary Metabolites in a Sandy Soil

2004

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Leaching to the ground water of metabolites from the herbicide metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5-one] has been measured in a Danish field experiment in concentrations exceeding the European Union threshold limit for pesticides at 0.1 microg/L. In the present work, degradation and sorption of metribuzin and the metabolites desamino-metribuzin (DA), diketo-metribuzin (DK), and desamino-diketo-metribuzin (DADK) were studied in a Danish sandy loam topsoil and subsoil from the field in question, using accelerated solvent extraction and liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Fast dissipation of metribuzin and the metabolites was observed in the topsoil, with 50% disappearance within 30 to 40 d. A two-compartment model described degradation of metribuzin and DA, whereas that of DADK could be described using first-order kinetics. Part of the dissipation was probably due to incorporation into soil organic matter. Degradation in subsoil occurred very slowly, with extrapolated half-lives of more than one year. Sorption in the topsoil followed the order DA > metribuzin > DK > DADK. Subsoil sorption was considerably lower, and was hardly measurable for metribuzin and DK. Abiotic degradation was considerably higher in the topsoil than the subsoil, especially concerning the de-amination step, indicating that organic matter may be related to the degradation process. The present results confirm observations of metribuzin and transformation product leaching made in the field experiment and demonstrate the need for knowledge on primary metabolites when assessing the risk for pesticide leaching.

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Metribuzin Mobility and Degradation in Undisturbed Soil Columns

Cited by 19 publications

References 0 publications

Retention and degradation of metribuzin in sandy loam and clay soils of Lebanon

Retention and degradation of metribuzin in sandy loam and clay soils of Lebanon

Impact of Basic Soil Parameters on Pesticide Disappearance Investigated by Multivariate Partial Least Square Regression and Statistics

Degradation and Sorption of Metribuzin and Primary Metabolites in a Sandy Soil

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