## 3 Results and Discussion
In this respect, the BFAs consent to correctly evaluate the element accumulation level. When the concentration of an element in an organism is higher than in the natural matrix, the BAF value is greater than 1, which means that bioaccumulation occurs, while the opposite occurs if BAF < 1. Finally, if BAF = 1, the concentration of an element in the organism corresponds to the concentration in its environment, and the organism is called a bioindicator [44]. Table 3 shows the BFA values for analytes detected on the surface of pollen grains in the 2019 and 2021 experiments. No significant differences were found between the mean BAF values of pollutants detected at each site and between those detected at the three sites (ANOVA test, \(p\) > 0.05), which could highlight the presence in the sites of specific and relevant contamination sources. In 2019, the BAF values were greater than 1, which indicates that bioaccumulation occurred for some soluble ions (crustal and anthropic) and toxic metallic elements at all sites. Specifically, this occurred at the MM site for NH4\({}^{+}\), Na, K, and Ca soluble ions and for Cr, Mn, Fe Ni, Cu, Zn, Ba, and Sr; and at the PG site for NH4\({}^{+}\), Na, K, Mg, and Ca soluble cations and for chlorides, sulfates, Cr, Co, Mn, Fe, Ni, Cu, Zn, Pb, Cd, Ba, and Sr. Finally, at the TR site, we obtained BAF values greater than 1 for NH4\({}^{+}\), K, Mg, MSA, chloride, and oxalate soluble ions and for Ni, Cu, and Zn. The highest bioaccumulation values were observed for Zn (BAF = 2.4) at the MM site and for NH4\({}^{+}\) at the PG (BAF = 9) and TR sites (BAF = 3.9) (Table 3 and Figure S1). \begin{table}
\begin{tabular}{l c c c c c c c c c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Monte Martano**} & \multicolumn{6}{c}{**Perugia**} & \multicolumn{6}{c}{**Temi**} \\ \hline  & **2019** & **2021** & & & & **2019** & **2021** & & & & **2019** & **2021** & & & \\ \hline
**Days** & **15** & **7** & **15** & **Mean** & **SD** & **15** & **7** & **15** & **Mean** & **SD** & **15** & **7** & **15** & **Mean** & **SD** \\
**Na\({}^{*}\)** & 1.6 & 1.0 & 0.9 & 1.2 & 0.3 & 1.3 & 0.1 & 0.8 & 0.7 & 0.5 & 0.7 & 2.6 & 1.3 & 1.5 & 0.8 \\
**NH4\({}^{*}\)** & 1.2 & 5.1 & & 3.2 & 2.0 & 9.0 & & 3.5 & 6.3 & 2.8 & 3.9 & & & & & \\
**K\({}^{*}\)** & 1.8 & 10.1 & 1.0 & 4.3 & 4.1 & 6.5 & 1.0 & 6.4 & 4.6 & 2.6 & 3.2 & 21.2 & 10.1 & 11.5 & 7.4 \\
**Mg2\({}^{*}\)** & 0.6 & 6.2 & 2.1 & 3.0 & 2.3 & 3.4 & 1.2 & 4.4 & 3.0 & 1.3 & 1.7 & 39.9 & 8.9 & 16.8 & 16.6 \\
**Ca2\({}^{*}\)** & 1.3 & 0.6 & 1.1 & 1.0 & 0.3 & 6.8 & 0.1 & 1.0 & 2.6 & 3.0 & 0.7 & 2.1 & 1.0 & 1.3 & 0.6 \\ F\({}^{*}\) & & & & & & & & & & & & & 0.4 & 2.2 & 0.8 & 1.2 & 0.8 \\
**HCOO\({}^{-}\)** & & 0.9 & & & & & 1.0 & 1.1 & 1.1 & 0.1 & 0.6 & 3.5 & 3.4 & 2.5 & 1.4 \\
**MSA** & & & & & & & & & & & & & 2.0 & & 1.8 & 1.9 & 0.1 \\
**CI\({}^{-}\)** & 0.7 & 1.5 & 1.0 & 1.1 & 0.4 & 1.5 & 0.1 & 1.1 & 0.9 & 0.6 & 1.3 & 3.2 & 1.5 & 2.0 & 0.9 \\
**NO\({}_{2}\)** & & & & & & & & & & & & & & & \\
**SO\({}^{2}\)-** & 0.5 & 1.2 & 1.0 & 0.9 & 0.3 & 1.3 & 0.12 & 1.0 & 0.8 & 0.5 & 0.7 & 3.0 & 1.2 & 1.6 & 1.0 \\
**CiO\({}^{2}\)-** & & & & & & & & & & & & & 1.9 & & & \\
**Br\({}^{-}\)** & & 1.5 & 0.4 & 1.0 & 0.6 & & 0.2 & 1.0 & 0.6 & 0.4 & - & 6.0 & 2.6 & 4.3 & 1.7 \\
**NO\({}_{3}\)\({}^{-}\)** & 0.4 & 2.0 & 1.1 & 1.2 & 0.7 & 0.6 & 0.1 & 1.0 & 0.6 & 0.3 & 0.4 & 2.5 & 1.3 & 1.4 In 2021, BAF values after 7 days were greater than 1 for ammonium, chlorides, sulfates, bromide, nitrate, K, Mg, Cr, Mn, Co, Ni, Cu, Zn, Pb, Ba, and Sr at the MM site; for Mg and Mn at the PG site; and for all ions and elements characterized by flux values higher than the detection limit at the TR site. The highest bioaccumulation values were observed for Ni (BAF = 31.1) at the MM site, for Mn at the PG site (BAF = 1.9), and for Mg at the TR site (BAF = 39.9) (Table 3 and Figure S2).