. The spatial distribution of the elements was affected mainly by the nature of the bedrock and by pedological processes. The upper limit of expected background variation for each trace element in the soil is documented, as is its range as a criterion for evaluating which sites may require decontamination.

No abstract

Abstraet--I.R. absorption and X-ray diffraction data on butylammonium complexes of vermiculites show, when compared with the Wyoming montmorillonite complex, that the tetrahedral location of charge determines the keying of the -NH~ groups into the ditrigonal cavities and that these groups have their Ca axes perpendicular to the layers. The aliphatic chains adopt different conformations depending on the area available per exchange position; they will either: (a) adopt an 'all-trans' conformation with their axes inclined 55 ~ to the silicate planes, when the area available is small; (b) rotate 120 ~ around the Cx-C2 bond to adopt a flat disposition relative to the layers, when the area available is larger than the area covered by the organic ion.