## 3 Results and Discussion
### Spatial Dependence of Pollutant Concentrations
Rural areas are usually places with a low presence of buildings and consequently, a low presence of heating systems and a low number of vehicles circulating in the area. Considering the Allumiere station, which is in a low populated area identified as a rural \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **Monitoring Station** & **From July to August** & **From April to June** & **From September to November** & **From November to April** \\ \hline \multirow{5}{*}{**Suburbs**} & Guidonia & 0.48 & 0.60 & 0.72 & 0.82 \\  & C. di Guido & 0.61 & 0.66 & 0.50 & 0.56 \\  & Cavaliere & 0.64 & 0.64 & 0.72 & 0.72 \\  & Ciampino & 0.56 & 0.54 & 0.47 & 0.56 \\  & Malagrotta & 0.69 & 0.73 & 0.67 & 0.77 \\  & Allumiere & 0.19 & 0.28 & 0.15 & 0.27 \\ \hline \multirow{5}{*}{**Provinces**} & Latina & 0.64 & 0.66 & 0.72 & 0.78 \\  & Frosinone & 0.73 & 0.71 & 0.76 & 0.80 \\ \cline{1-1}  & Rieti & 0.53 & 0.59 & 0.59 & 0.63 \\ \cline{1-1}  & Viterbo & 0.47 & 0.47 & 0.69 & 0.71 \\ \cline{1-1}  & Civitavecchia & 0.43 & 0.35 & 0.52 & 0.59 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Cross-correlation values between Roma Green Band and suburbs or province stations of [NO\({}_{\text{X}}\)] in 2015. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **Monitoring Station** & **From July to August** & **From April to June** & **From September to November** & **From November to April** \\ \hline \multirow{5}{*}{**Suburbs**} & Guidonia & 0.48 & 0.55 & 0.67 & 0.75 \\  & C. di Guido & 0.57 & 0.60 & 0.45 & 0.55 \\  & Cavaliere & 0.66 & 0.66 & 0.69 & 0.77 \\  & Ciampino & 0.54 & 0.43 & 0.56 & 0.69 \\  & Malagrotta & 0.63 & 0.67 & 0.62 & 0.72 \\  & Allumiere & 0.23 & 0.30 & 0.25 & 0.42 \\ \hline \multirow{5}{*}{**Provinces**} & Latina & 0.65 & 0.64 & 0.73 & 0.76 \\  & Frosinone & 0.70 & 0.64 & 0.73 & 0.77 \\ \cline{1-1}  & Rieti & 0.45 & 0.48 & 0.62 & 0.70 \\ \cline{1-1}  & Viterbo & 0.50 & 0.47 & 0.70 & 0.78 \\ \cline{1-1}  & Civitavecchia & 0.52 & 0.43 & 0.49 & 0.65 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Cross-correlation values between Roma Green Band and suburbs or province stations of [NO\({}_{\text{2}}\)] in 2015. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **Monitoring Station** & **From July to August** & **From April to June** & **From September to November** & **From November to April** \\ \hline \multirow{5}{*}{**Suburbs**} & Guidonia & 0.48 & 0.65 & 0.71 & 0.81 \\  & C. di Guido & 0.63 & 0.63 & 0.40 & 0.39 \\  & Cavaliere & 0.61 & 0.63 & 0.69 & 0.67 \\  & Ciampino & 0.61 & 0.62 & 0.43 & 0.47 \\  & Malagrotta & 0.71 & 0.74 & 0.59 & 0.74 \\  & Allumiere & 0.19 & 0.23 & 0.05 & 0.16 \\ \hline \multirow{5}{*}{**Provinces**} & Latina & 0.58 & 0.62 & 0.66 & 0.76 \\  & Frosinone & 0.73 & 0.75 & 0.75 & 0.80 \\ \cline{1-1}  & Rieti & 0.60 & 0.70 & 0.49 & 0.56 \\ \cline{1-1}  & Viterbo & 0.33 & 0.51 & 0.57 & 0.64 \\ \cline{1-1}  & Civitavecchia & 0.26 & 0.37 & 0.54 & 0.55 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Cross-correlation values between Roma Green Band and suburbs or province stations of [NO] in 2015.  
area of the Rome suburb, it is possible to notice that the average cross-correlation values are 0.22, 0.30, 0.16, 0.39, and 0.73 for respectively [NO\({}_{\lambda}\)], [NO\({}_{2}\)], [NO], [O\({}_{3}\)] and [PM\({}_{10}\)]. Comparing those values with the ones calculated for the Castel di Guido and Cavaliere stations, which are considered as a rural area of Rome suburb as Allumiere, the cross-correlation values for the same pollutant concentrations are about 0.63, 0.62, 0.58, 0.87, and 0.93. This is an interesting result that shows how the proximity to Rome influences the levels of pollution whenever the location is a rural or urban area. The spatial dependence analysis leads to the consideration that the pollutant concentration trend of the core of Rome city (named Roma Green Band) has the same trend to the other urban areas whenever they have low or high traffic characteristics especially regarding the particular matter ([PM\({}_{10}\)] and [PM\({}_{2.5}\)]).