Influence of atmospheric stability on the mass concentration and chemical composition of atmospheric particles: a case study in Rome, Italy.

PM(10) concentration and chemical composition (ions and carbon compounds) at three sampling stations in Rome and in its surroundings was determined daily during a one-month field study, carried out during December 2003. PM concentration at the traffic station was considerably higher than at the urban background and semi-rural stations; elemental carbon was detected as one of the chemical components responsible for this increase. The difference in the concentration of sulphate and ammonium was negligible, as it was expected for secondary pollutants. A negative artefact in the determination of ammonium nitrate by means of heated automatic monitors was highlighted. The dilution properties of the lower atmosphere were traced by means of a natural radioactivity monitor. This parameter has been found to play an essential role in pollution buildup. A considerable increase in PM concentration was observed to coincide with periods of atmospheric stability. The main difference in PM composition between periods of high concentration and periods of "clean" air was found to be in the increase of ammonium nitrate concentration.

Complex formation equilibria of some aromatic beta-amino-alcohols.

Complex formation equilibria of some aromatic beta-amino-alcohols with zinc(II), cadmium(II) and silver(I) have been investigated. The structure of the considered ligands (2-amino-1-phenyl-1-propanol, 2-amino-3-phenyl-1-propanol and 2-amino-1,3-propanediol) are similar to some hormones and alcaloids, like adrenaline, noradrenaline and ephedrine, and differ each other for the number and the relative position of alcoholic and phenyl groups. Equilibria constants at 25 degrees C and micro = 0.5 M (KNO3) have been determined by potentiometric titrations. The comparison of the obtained values with those previously determined for some aliphatic beta-amino-alcohols with the same polar heads has allowed to evidence the influence of aromatic ring on the coordinating properties of ligands, which is different depending on the considered metal ion. In particular, two contrasting effects have been evidenced. The electron withdrawing effect of the aromatic ring causes a decrease of amine basicity, more relevant when phenyl and hydroxylic groups are in 1-3 position, which reflects in a reduction of metal-NH2 coordination bond. This effect is predominant in the case of zinc(II) complexes and causes a reduction of complex stability which results directly proportional to the amine group basicity. On the other hand, in the case of silver(I) and cadmium(II) complexes, phenyl group seems to contribute directly to the coordination of the metal ion causing a stabilization of complexes.