Kinetics and equilibria of Metribuzin sorption on model soil components

Abstract

Sha'ato, R., Buncel, E., Gamble, D. G. and vanLoon, G. W. 2000. Kinetics and equilibria of Metribuzin sorption on model soil components. Can. J. Soil Sci. 80: 301-307. Sorption to solid phase materials is known to significantly affect the transport, bioavailability and ultimate fate of organic contaminants in soils and sediments. In order to develop a complete description of the fate of these compounds, it is necessary to understand both equilibrium interactions and rates and mechanisms of the sorption processes. The object of the present study was to investigate both these factors with respect to the sorption of metribuzin on model soil components, including the clay minerals kaolinite and montmorillonite, amorphous iron and aluminum hydrous oxides and humic acid. In all cases, uptake followed a similar course; there was a very rapid initial sorption process followed by continued uptake at a much slower rate. Rate constants for the slow sorption were smallest for the clay minerals, intermediate for the hydrous oxides and greatest for humic acid. Labile sorption capacities for metribuzin on the humic acid and clay minerals were also determined; the organic material had the largest capacity, and montmorillonite had a greater capacity than kaolinite.Key words: Metribuzin, sorption, clay minerals, humic material Sha'ato, R., Buncel, E., Gamble, D. G. et vanLoon, G. W. 2000. Cinétique et équilibre de la sorption du métribuzin sur les composantes du sol modélisées. Can. J. Soil Sci. 80: 301-307. Il est connu que la sorption sur des matières solides influe sur la migration, sur la biodisponiblité et sur le devenir ultime des contaminants organiques présents dans le sol et dans les sédiments. Mais pour obtenir une description complète du sort de ces substances, nous devons au préalable élucider à la fois les interactions d'équilibre et les rythmes et les mécanismes des processus de sorption. Ce sont ces deux facteurs que nous examinons ici relativement à la sorption du métribuzin sur des composantes du sol modélisées, notamment les minéraux argileux kaolinite et montmorillonite, le fer amorphe, les hydroxydes d'aluminium et l'acide humique. Sur tous ces matériaux, la sorption comportait une phase initiale de sorption très rapide puis une phase beaucoup plus lente d'absorption. Les constantes de rythme pour cette phase étaient basses pour les minéraux argileux, intermédiaires pour les hydroxydes et produisaient les valeurs les plus hautes pour les substances humiques. Nous mesurions aussi la capacité de sorption sous forme labile du métribuzin sur les substances humiques et sur les minéraux argileux. Ce sont les matières humiques qui démontraient le pouvoir de sorption le plus grand, suivies de la montmorillonite puis de la kaolinite.

Reduced metribuzin pollution with phosphatidylcholine–clay formulations

“…Nevertheless, triazines are readily adsorbed on montmorillonites saturated with Ca 27. On the other hand, the affinity of metribuzin is notably lower on kaolinite than on montmorillonite 28. Thus, metribuzin sorption on P44, LM and TM soils is related to the content and type of clay mineral present in the soil (Table 2).…”

“…The highest adsorption of metribuzin was observed on LM soil. This herbicide shows larger sorption kinetics and higher affinity for amorphous oxides of iron and aluminium than clay minerals, even when the latter are saturated with monovalent cations 28. Therefore, the high content of iron and aluminium oxides in LM soil could be responsible for the high metribuzin sorption.…”

Dual Nucleophilic Substitution Reactions of O,O‐Diethyl 2,4‐dinitrophenyl Phosphate and Thionophosphate Triesters

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Competing pathways in the reaction of the pesticide Fenitrothion [O,O-dimethyl O-(3-methyl-4-nitro­phenyl) phosphorothioate] with some nitrogen nucleophiles in aqueous solution

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