# Bioaccumulation of Trace Elements along the Body Longitudinal Axis in Honey Bees
## 5 Conclusions  
The study of the bioaccumulation of 30 elements in _Apis mellifera ligustica_ from Al-viano Lake (Central Italy), a rural and protected natural area, highlighted a low level of contamination in the tissues of these bioindicators. The concentrations found for the analysed elements could be considered reference models for low-environmental-impact territories. Even mercury, despite the environmental context, showed usually limited contamination levels, except in a single sample. On the other hand, the natural processes of water-volcanic rock interaction influenced the arsenic levels, which showed higher concentrations than those found in bee tissues from other rural areas. However, As concentrations were lower than those measured in samples from urban and productive areas. Other toxic elements, such as Cd and Pb, showed lower levels compared to the low contamination threshold values known in the literature, which were used for the HCI calculation. The analysis highlighted the extent of the 30 elements analysed in the bee tissues. Be and Ag were the elements with the lowest values, while S, P, and K had the highest values. The analysis of the elements along the longitudinal axis of the body of the bees showed that the gaster, the location of most of the digestive and excretory systems, showed a greater and more significant presence of these elements compared to the remaining part of the bee body (body without the gaster), in particular for V, Al, Be, Pb, Cd, Co, Mn, Ba, and especially Sr. The only exceptions were As, S, and, to a lesser extent, Hg due to the affinity of As and Hg towards the -SH groups of muscle proteins. **Supplementary Materials:** The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app13126918/s1](https://www.mdpi.com/article/10.3390/app13126918/s1)]([https://www.mdpi.com/article/10.3390/app13126918/s1](https://www.mdpi.com/article/10.3390/app13126918/s1)). Table S1. (a) Concentrations of the 30 trace elements in the whole honey bee body (B) (mg kg\({}^{-1}\) dry weight; single values, means, standard deviations, maxima and minima, limit of detection) for Alviano Lake and control area (Perugia) sites. 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. (b) Concentrations of the 30 trace elements in the abdominal segments after the petiole (G) (mg kg\({}^{-1}\) dry weight; single values, means, standard deviations, maxima and minima, limit of detection) for Alviano Lake and control area (Perugia) sites. 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. (c) Concentrations of the 30 trace elements in the remaining part of the bee body (B\(-\)G) (mg kg\({}^{-1}\) dry weight; single values, means, standard deviations, maxima and minima, limit of detection) for the Alviano Lake and control area (Perugia) sites. For each sample is indicated the site sampled: 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. **Author Contributions:** Conceptualisation, E.G., M.P., G.L.P., A.C.E., T.G., C.P., P.G., F.B., R.S. and D.C.; data curation, E.G., M.P., G.L.P., C.P., F.B., R.S. and D.C.; methodology, E.G., M.P., G.L.P., A.C.E., T.G., C.P., P.G., F.B., R.S. and D.C.; investigation, E.G., M.P., G.L.P. and P.G. ; writing--original draft, E.G., M.P., R.S. and D.C.; writing--review and editing, E.G., M.P., R.S. and D.C. All authors have read and agreed to the published version of the manuscript. **Funding:** This research was funded by the Ministero Istruzione dell'Universita e della Ricerca (MIUR) and the University of Perugia through the program \"Dipartimenti di Eccellenza 2018-2022\" (grant AMIS).