## 3 Results
### Comparison with Other Scenarios Worldwide  
Table 5 shows a comparison among the element levels in the three fractions determined in this study and similar determinations in other locations. First, it should be underlined that in the literature, very few papers have dealt with such evaluations in different fractions: basically, the main fractions considered are PM\({}_{10}\) and PM\({}_{2.5}\), whereas few authors have approached the PM\({}_{1}\) fraction. In the table, different scenarios are reported: PM\({}_{10}\) and PM\({}_{2.5}\) were determined around a waste-to-energy plant in the Central of Italy; PM\({}_{10}\) around a hazard waste landfill (HWL) in Spain; PM\({}_{2.5}\) sampled in different areas around Shanghai; and PM\({}_{10}\), PM\({}_{2.5}\), and PM\({}_{1}\) in downtown Algiers and Rome [1; 2; 26; 54; 55; 56]. Preliminarily, the levels determined in this study were lower than those reported by [PERSON] et al. [26], where PM\({}_{10}\) and PM\({}_{2.5}\) were determined around a waste plant: in fact, the difference was not that great, but As, Hg, and Sb showed lower levels whereas Cd and Ni had similar values. No information on fraction PM\({}_{1}\) has been reported for that site. On the other hand, the comparison between similar fractions (PM\({}_{10}\)) investigated at this site and around the HWL plant in Spain [54] reported almost 10-times lower levels at the Spanish site (e.g., Cr 3.6 vs. 0.4 ng m\({}^{-3}\); Ni 3.8 vs. 0.58 ng m\({}^{-3}\); Hg 0.12 ng m\({}^{-3}\) vs. not detected). Furthermore, the comparisons with the data determined in downtown Rome [1; 2] or in urban, residential, suburban, or industrial locations around Shanghai [55] showed significant differences between the three sites. Finally, in Algiers [56], where the three fractions were determined, the levels were very high (e.g., As at 59.8-178.5 ng m\({}^{-3}\) for PM\({}_{10}\), 48.5-137.9 ng m\({}^{-3}\) for PM\({}_{2.5}\), 38.4-70.9 ng m\({}^{-3}\) for PM\({}_{1}\); Cr 57.3-100.2 ng m\({}^{-3}\), 30.7-60.2 ng m\({}^{-3}\), 7.3-32.3 ng m\({}^{-3}\), respectively). Among the different reasons for these very high levels found in Algiers, the authors reported \"poor combustion of the car fleet, which is increasingly dieselized, aging and poorly maintained and where the use of unleaded gasoline is still very low\", a scenario quite different with respect to that present in European countries. Some comments could be also withdrawn in relationship to the PM\({}_{\rm x}\) amount: in this case, the global situation is quite different. First, no comparison was possible with the data collected around the waste-to-energy plant in Cassino, Italy [26] (data not available in the paper). Regarding the comparison with the data from Rome (site B in Table 5), some elements determined in this study showed a higher presence in relation to their respective PM\({}_{10}\) and PM\({}_{2.5}\) levels: among all elements, Ba, Cd, Co, Fe, La, Ni, Se, and Zn in PM\({}_{10}\) and Ba, Co, Cr, Fe, La, Mo, Ni, Se, and Zn in PM\({}_{2.5}\) should be considered for their environmental and human health roles. Similarly, the same comparison with the data collected at sites D and E (Table 5) described a different situation. Each site showed minimum and maximum data for each element, so the comparison occurred with low and high values. Looking at the PM data, both sites evidenced data lower than those determined in this study, especially in Algiers. At this site, only Ca in the PM\({}_{10}\) and PM\({}_{2.5}\) fractions and Cr in PM\({}_{1}\) was displayed in proportion to the PM measures. \begin{table}
\begin{tabular}{c|c c c c c c c c|c|c c c c} \hline  
The identification of natural and anthropogenic origins of the investigated elements was an important aspect of this research: in comparison with previous studies or speculation of the sources, the authors focused their attention on the study of the Enrichment Factors (EFs).