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The performance of two types of radiello diffusive samplers, filled with a thermally desorbable adsorbent (graphitised carbon Carbograph 4) and with a solvent desorbable adsorbent (activated charcoal), respectively, have been evaluated for the monitoring of BTEX in ambient air, by comparison with active (pumped) samplers. A two year survey was carried out in Padua, a medium-sized town, in a traffic site, close to a busy crossroad. The concentrations of BTEX were measured for 15 campaigns, during which four series of radial diffusive samplers were exposed for 2 day, 7 day, 10 day and 14 day time periods, respectively. Every series of chemical desorption samplers included three replicates; thermal desorption samplers included six replicates, three of them filled with freshly conditioned cartridges and three filled with regenerated cartridges. No significant difference in the levels measured either by new or by regenerated cartridges has been found. During three campaigns (summer 2004, winter and spring 2005) two active (pumped) samplers were added for each sampling period. The diffusive uptake rates have been calculated and modelled under various conditions of concentration, temperature and exposure time. The effects of the environmental factors on the performances of both solvent and thermally desorbable samplers have been evaluated. The repeatability of the whole measurement process (sampling and analysis) was calculated for every sampling duration. The comparison of concentration levels measured by diffusive and active sampling methods shows correlation coefficients R >or= 0.98 (p<0.01) for all the compounds. The uncertainty of the diffusive sampling method under field conditions, using active sampling as the reference method, has been assessed according to the ISO 13752 requirements. On field relative expanded uncertainty for benzene has been found below 20%.

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Angle-scanned photoelectron diffraction measurements have been performed prior to and after CO exposure onto a Ni monolayer deposited on Pt(111). Ni is known to grow epitaxially on Pt(111), but there is evidence for an adsorbate-induced restructuring such that the initial atomically flat Ni layer gives place to at least two-layer-high Ni islands. As far as the driving force for the restructuring is concerned, some hypotheses can be put forward considering the Ni–Ni nearest neighbor distances in the Ni monolayer and in the restructured layer, along with some thermodynamical arguments.

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