Deep Element Determination in Airborne Atmospheric Aerosol in Italian Big City by Neutron Activation Analysis

摘要

The interest in the particulate matter speciation is increased during these last years: in particular, the inorganic fraction is studied for its sanitary implications. In fact, whereas for some elements the toxic effects are well known, for other elements there is little information about it. For instance, in this contest an important role is played by the Rare Earth Elements, e.g. Ce, Eu and Yb. These elements, some of them ubiquitous worldwide, are largely used in different industrial applications (optical fibers and electronics) whereas there are few issues on their physiology properties. In any case, Ce and the other REEs should be considered moderately toxic: recent studies suggest that REEs may bind specifically to endothelial sites in the brain and be relevant to the physiological brain functions. This difficulty is mainly due to their determination: they are at very low levels, ultra-trace levels, and very few analytical techniques can reach such limit of detection. Further, similar analytical problems occur also for other important elements (i.e., Cd, Hg, Ni, V) when their levels are too low (such as in airborne particulate matter). So, in this study we use a methodology based on nuclear analytical technique, i.e. Instrumental Neutron Activation Analysis (INAA), for studying the element composition (almost 40 elements) in PM10 during intensive summer and winter sampling campaigns in downtown Rome. After irradiation in the nuclear reactor the filters are measured by different gamma measurements in order to have more element information as possible. The granulometric fine and coarse fractions are also analyzed and the results commented, especially the correlation among the elements inter- and intra-fractions. Finally, a retrospective study is performed across 40 years of PM10 determination and the Enrichment Factors of both PM10 and coarse fraction are shown and discussed. Differently from other investigations, this study can be considered the first almost complete picture of the inorganic composition of PM10 sampled in a big city, Rome, of the Mediterranean area, benchmark for other researches.