01713naa a2200217 a 450000100080000000500110000800800410001910000170006024500520007726000090012952011530013865000130129165300180130465300310132265300170135365300190137065300110138965300220140070000170142277300560143918314652012-12-19       1970    bl ---       0--  u    #d1 aBURNS, R. G.  aDistribution and breakdown of paraquat in soil.  c1970  aThe 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.  aParaquat  aConstituintes  aDiferentes camadas do solo  aDiminuição  aDistribuição  aEfeito  aSolo (adsorção)1 aAUDUS, L. J.  tWeed Research, Oxfordgv. 10, n. 1, p. 49-58, 1970.