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Environmental fate & pathways

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Aromatic amines mainly sorb to the organic matter of the soil. The sorption of amino-groups to clay-minerals or pH-dependent sorption of acids plays a key role. A normalization to the organic matter of the soil does not significantly reduce the variation in polar substances' sorption coefficients. For polar compounds like the amines, the calculation of a koc-value is of no use. The variation of the sorption behaviour of a polar substance between two soils impedes the applicability to other soils. Experiments indicate that covalent binding (as inferrred from lack of recoverability by simple extraction) of ring-substituted anilines to humates involves two different chemical reactions. When an aniline is mixed with humate, a reversible equilibrium is very rapidly established. This equilibrium is thought to represent reaction of the amino group with aldehyde and ketone groups in the humate to form imine linkages. The second reaction is very slow and not readily reversible. This slow reaction is thought to represent addition of the amines to quinoidal structures followed by oxidation of the product to a nitrogen-substituted quinoid ring. In addition, the conclusions are supported by the observation that N-methylaniline (which cannot form imines, but which adds to quinoid rings) reacted slowly with humate.