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Distribution and breakdown of paraquat in soil
Journal article   Peer reviewed

Distribution and breakdown of paraquat in soil

Richard G Burns and L J Audus
Weed Research, Vol.10(1), pp.49-58
1970
url
https://doi.org/10.1111/j.1365-3180.1970.tb00922.xView
Published Version

Abstract

Crop and Pasture Production Ecological Applications
The degradation of paraquat dichloride in soil by Lipomyces starkeyi Lod. and Rij, was investigated spectrophotometrically and by 14C-labelled carbon dioxide emission. Breakdown occurred within the first 96 hr of incubation in cultures of soil of high organic content. Adsorption isotherms showed that soils rich in organic matter had a greater total adsorption of paraquat from solutions of concentration in excess of 250 ppm. Soil high in organic matter was fractionated by ultrasonic disintegration into its organic and inorganic components. Paraquat degradation occurred in cultures containing the former but not the latter. Slow transfer of 14C-labelled paraquat adsorbed on the organic components was shown to take place through a dialysis membrane to the much stronger adsorption sites on the inorganic components placed outside the membrane. It appears that decomposition of paraquat in soil by L. starkeyi occurs while the herbicide is weakly adsorbed on the organic soil components. Over a period of time (96 hr in one instance), slow transfer to the inorganic soil components rendered the paraquat unavailable for microbial degradation.

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