# Bioaccumulation of Trace Elements along the Body Longitudinal Axis in Honey Bees
## 3 Results

Table 1: Analysis of the mean concentrations (mg kg\({}^{-1}\), dry weight) of the 30 trace elements for (a) Alviano Lake sites and (b) Perugia control area sites. The mean concentrations are organised into 8 classes (varying by factors of 10), from concentrations lower than 0.001 mg kg\({}^{-1}\) to concentrations higher than 1000 mg kg\({}^{-1}\). This analysis was carried out separately for the three different sample types, i.e., whole honey bee body (B), abdominal segments after the petiole (G), and the remaining part of the body (B\(-\)G). In the other six intermediate classes, all the remaining trace elements were distributed. The results for the most toxic elements highlighted that at Alviano Lake, Hg and As were always more abundant than in the control area, Cd was higher in the control area, and finally Pb was similar between the two areas. Overall, trace element mean concentrations in Alviano honey bee tissues, compared to the mean values measured in honey bees from the control area, showed significant differences for some elements. These elements are listed below, and between brackets is indicated the ratio between the concentrations measured at Alviano and those at the control area: whole bee body (B): Cd (0.6), Ca (0.9), Mg (1.3), Na (1.4), Sr (1.4), Cs (2.4), Rb (3.1), and As (3.8); gaster (G): Ag (0.4), Cd (0.5); Na (1.6), Cs (2.7), As (3.3), and Rb (4.1); and body without gaster (B\(-\)G): Ca (0.9), Na (1.3), Mg (1.3), Cs (2.4), Rb (3.2), and As (4.1). The ratios of the mean concentrations of the 30 trace elements measured in the gaster to those measured in the body without gaster (G/B\(-\)G) were organized into 4 classes (varying by factors of 10), from lower than 1 to higher than 100 (Table 2a,b). The only elements in the Alviano honey bee tissues with a G/B\(-\)G ratio lower than 1 were As (0.60) and S (0.70). Similar values were also found in the control area samples (S, 0.71, and As, 0.75). Ratio values higher than 100 were found only for Sr (107.66) in the Alviano samples, while for the control area, in addition to Sr (104.26), Ba (116.32) also reached this level. Overall, 19 elements showed ratios between 1 and 10 in the Alviano Lake samples. A similar condition was found in the control area, with 20 elements, with the addition of Be and V compared to the Alviano samples, while Ag was instead grouped in the superior class. The class 10-100 ratio in the Alviano samples included 8 elements, and it was differentiated from the control area samples for V and Be (both in the lower class) and Ba (in the superior class), as well as the addition of Ag (Figure 2). In addition, the G/B\(-\)G ratios of the toxic elements for the biota showed lower values in the Alviano Lake samples, in comparison to those from the control area: As (0.60 vs. 0.75), Hg (1.10 vs. 1.91), Pb (13.47 vs. 19.91), and Cd (26.33 vs. 41.76) (Figure 2). To further evaluate the metal contamination levels in honey bee tissues, we applied the Honeybee Contamination Index (HCI) [40]. In the case study, we observed that it was sufficient to apply only \(\mathrm{HCI}_{2}\), the index that uses the lower threshold values, because all the values of this index were negative. In fact, the lower threshold was not exceeded for any element (low contamination condition). The only exception was Ni, for which only 1 sample out of 24 (Alviano site 1, hive b, June 2020) showed a positive \(\mathrm{HCI}_{2}\) value (0.020), which indicated an intermediate contamination condition, considering that the relative \(\mathrm{HCI}_{1}\) value (higher threshold) was \(-0.46\). The mean \(\mathrm{HCI}\) (\(\mathrm{HCI}_{\mathrm{mean}}\)) of the 4 analysed metals (Alviano Lake: \(\mathrm{HCI}_{\mathrm{mean1}}=-1.264\), \(\mathrm{HCI}_{\mathrm{mean2}}=-0.858\); control area: \(\mathrm{HCI}_{\mathrm{mean1}}=-1.091\), \(\mathrm{HCI}_{\mathrm{mean2}}=-0.685\)) highlighted an overall condition of low contamination.