# Bioaccumulation of Trace Elements along the Body Longitudinal Axis in Honey Bees
## 4 Discussion  
Our study analysed the concentrations of 30 elements in the tissues of the whole bee body (B), in the gaster, and in the remaining part of the bee body without the gaster. In the body samples, significant differences between the concentrations measured in the Alviano Lake area and in the control area were found for eight elements, of which six elements (Mg, Na, Sr, Cs, Rb, and As) showed higher average values at Alviano Lake, while only two elements (Ca and Cd) had higher concentrations in the control area. The other 22 elements showed a certain degree of similarity between Alviano Lake and the control area, which was chosen as a low-impact zone of metal contamination in the Umbria region of Central Italy [40]. In the literature, studies analysing the concentrations of a high number of elements in the tissues of whole bees are rare. In this regard, the careful investigation of [PERSON] et al. (2021) [47], conducted at an apiary composed of 21 hives (28 elements measured in 17 specimens per hive, for a total of 357 analyses) in the village of Mesic close to Vrsac, Serbia, was taken as a reference. The apiary is located in an agricultural territory connected to a protected area and therefore has environmental characteristics very similar to the agricultural and protected areas of Alviano Lake. In Mesic, the following decreasing sequence for the elements analysed in the bees' tissues (concentration mg kg\({}^{-1}\), dw) was found: K (8604.10) \(>\) P (7199.10) \(>\) S (5434.48) \(>\) Ca (1067.19) \(>\) Mg (993.52) \(>\) Na (933.81) \(>\) Fe (139.90) \(>\) Zn (104.43) \(>\) Mn (83.81) \(>\) Al (52.05) \(>\) Cu (20.67) \(>\) B (6.959) \(>\) Sr (4.49) \(>\) Ba (4.28) \(>\) Rb (3.97) \(>\) Cd (0.43) \(>\) Mo (0.22) \(>\) Cr (0.14) \(>\) Co (0.12) \(>\) Pb (0.11) \(>\) Se (0.08) \(>\) V (0.08) \(>\) As (0.07) \(>\) Li (0.04) \(>\) Sb (0.01) \(>\) Cs (0.01) \(>\) U (0.01) \(>\) Tl (0.004). Some elements have been examined only at Alviano Lake, i.e., Si, Ni, Hg, Ga, Ag, and Be, while Mo, Se, Sb, and U are elements only measured in Mesic. A comparison of the study carried out in Mesic with our results (Table 1a) shows a similar sequence of elements, with higher concentration levels in Alviano Lake only for Rb, Tl, As, and Li. Figure 3: Mean HCI (Honeybee Contamination Index) of the four analysed metals (i.e., Cd, Pb, Cr, and Ni); a positive HCI\({}_{1}\) indicates a high contamination, a negative HCI\({}_{2}\) indicates a low contamination, and finally, when HCI\({}_{1}\) is negative and HCI\({}_{2}\) is positive, an intermediate contamination level is present. For each sample is indicated the site number: 1, 2 (Alviano Lake sites), C3, C4, C5, C6 (control area (Perugia) sites); the different hives analysed at each site: a, b, c; and the month and year of sample collection. Concerning arsenic in bee tissues, in a subsequent survey by [PERSON] et al. (2022) [48], conducted as well in the locality of Mesic, again a low average value (0.041 mg kg\({}^{-1}\)) was found, while at other sites subjected to a more significant environmental impact, such as Belgrade and the thermal power plant region (TPP), higher mean values of 0.21 mg kg\({}^{-1}\) and 0.37 mg kg\({}^{-1}\) were found, respectively. The average level of contamination of As found in the bees of Alviano Lake (0.105 mg kg\({}^{-1}\); Figure 4) is, however, lower than what was found in the study of [PERSON] et al. (2016) [5] conducted throughout the Dutch territory on 150 apiaries (As: average 0.85 \(\pm\) 0.33, range 0.13-1.64 in mg kg\({}^{-1}\)). In addition, these results [5] were comparable to those found in the previous survey conducted in 2006 at the three Dutch sites of Maastricht (urban area with industries), Buggenum (rural area with a power plant), and Hoek van Holland (port and large industrial area), with an average value of As of 0.71 \(\pm\) 0.02 mg kg\({}^{-1}\)[45]. In the study of [PERSON] et al.