# Bioaccumulation of Trace Elements along the Body Longitudinal Axis in Honey Bees
## 4 Discussion
(2021) [49] in Quebec City (Canada) at six sites (four in urban areas and two in rural areas), arsenic showed a significantly higher value in bee tissues located in urban sites than in rural sites. In fact, from July to September (2019) the average values of As did not exceed 0.08 mg kg\({}^{-1}\) in rural areas, and they were about 0.15-0.28 mg kg\({}^{-1}\) in urban areas. These surveys showed that, compared to the rural area of Alviano Lake, there are usually higher values of As in the tissues of bees in areas with high environmental impact, such as urban areas, while lower values are found in areas with low environmental impact, such as rural sites. The higher levels of arsenic observed in the rural territory of Alviano Lake are due to natural processes of water-volcanic rock interaction present in the territory of Orvieto, of which the area of Alviano Lake is an integral part [50]. The application of the HCI for the four heavy metals (i.e., Cd, Cr, Ni, and Pb) for which in the literature threshold levels are known showed negative mean values at Alviano Lake for HCI\({}_{\text{mean}}\) (\(-\)1.264) and HCI\({}_{\text{mean2}}\) (\(-\)0.858), which are significantly lower than the HCI\({}_{\text{mean}}\) values for the sites of the Umbria (Italy) region reported in [PERSON] et al., 2020 [40] and compared to the metadata of various sites from Central Italy [9; 11; 22; 51; 52]  
Figure 4: Concentration of As in the whole body tissues of honey bees of the Alviano Lake and control area (Perugia) sites (mg kg\({}^{-1}\) dry weight). 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. and various European regions [5; 12; 13; 45; 53; 54; 55]. Therefore, \(\rm{HCI_{mean}}\) showed a peculiar low level of contamination of bee tissues of the rural sites of Alviano Lake for the four metals considered. With regard to mercury (average value at Alviano Lake area equal to 0.006 mg kg\({}^{-1}\)), in 2014 [PERSON] et al. (2018) [56], in the locality of Mesic, an agricultural locality of Serbia with characteristics similar to the territory of Alviano Lake, found that the level of mercury in bees amounted to 0.026 mg kg\({}^{-1}\), a value that corresponds to 4.5 times that found in Alviano bees. In the study by [PERSON] et al., 2016 [57], carried out in eastern Slovakia in the sites of Kosice (area of the University of Veterinary Medicine and Pharmacy) and Rozhanovce (small, rural village), the levels of Hg detected in the tissues of bees were respectively about 7 times (0.04 mg kg\({}^{-1}\)) and 1.5 times (0.008 mg kg\({}^{-1}\)) the values found at the sites of Alviano Lake. These results show that mercury contamination in the bees of the Alviano Lake area stands at a limited level, even if it is about three times higher than the values found in the control area. This result is probably influenced by the environmental conditions of its catchment area, subjected until 1980 to the intense mining activity of Hg in the nearby Monte Amiata mining district. However, analysing the individual samples of the Alviano Lake area, a peak of Hg in the sample of July 2019 (Site 1a) was revealed. In this sample, Hg values for the body amounted to 0.049 mg kg\({}^{-1}\), thus showing a level comparable to the contamination of productive areas (Figure 5). Examining the levels of trace elements along the body axis of honey bees of Alviano allowed us to highlight differences in bioaccumulation between the two body parts examined. From Table 1a it is noted that the comparison of the element sequences among tissues of the body, gaster, and body without gaster showed a greater variation between body and body without the gaster than between body and gaster, confirming that the higher levels of the elements detected in the gaster affected considerably their relative content in the body.