In the present work, we studied the concentration of twelve metals (Al, As, Cd, Cr, Cu, Fe, Hg, Ni, Mn, Pb, Se, Zn), in the hairs of the wild mouse Apodemus sylvaticus to verify its suitability as biomonitor of environmental pollution. The samples were air-dried for seven days before the microwave digestion (0,2 mL of HNO3 and 0,5 mL of H2O2). The digested solutions were analyzed by ICP-MS to determine metal concentration. Reagent blanks were prepared following the same procedure applied to the samples. The final concentrations were reported as μg/g dry weight. Twelve metals are concentrated according to the gradient Zn > Al > Fe > Cu > Pb > Cr > Ni > Mn > Cd > Se > As > Hg. Ubiquitous metals such as Zn, Al, Fe, and Cu are more abundant than others of ecotoxicological interest, such as Cd, Se, As, and Hg, with concentrations below 1 µg/g. In both males and females, the metals studied follow the gradient Zn > Al > Fe > Cu > Pb > Cr > Ni > Mn > Cd > Se > As > Hg, but only the concentration of chromium is statistically significant, with a higher concentration in males. The variability of concentrations is high in both sexes, and we observed large differences between minima and maxima, especially for Pb, Hg, and Cr. No significant differences were observed between adults and juveniles; thus, age is a factor that does not affect contamination or bioaccumulation. The lack of differences was expected since the wild mouse is a fossorial species, and no differences between the sexes are known in the time activity underground; the higher concentration of Cr in males could be explained by their greater mobility, which could expose males to a higher risk of contact with sources of contamination that are well established adjacent to the nature reserve. The mercury concentration is low and similar in males and females, suggesting a primary consumer role in the trophic chain of the forest habitat, slightly different from the opportunist role described in the literature. Comparison of mercury concentration in the different trophic levels of agroecosystems studied so far shows maximum bioaccumulation levels close to those in soil, in predators, and much lower in insects and wild mice, supporting the hypothesis of a primary consumer role. A comparison of metal concentrations in soil and hairs shows that A. sylvaticus, despite its fossorial habits, is scarcely influenced by soil chemistry. Fe and Zn are present in low or similar amounts to those of soil, and the concentration of metals in hair does not reflect that of the matrix. Comparison with other wild mouse populations seems to indicate higher concentrations in the hair of our population, which supports the hypothesis that the Bosco Negri population, a protected area, experiences high relative contamination by metals typical of urban and peri-urban industrial areas, such as chromium, lead, cadmium, and nickel. In particular, xenobiotic lead of anthropogenic origin is present in the soil in relatively high concentrations (28.3 µg/g). Its concentration is low in the hairs of primary producers, but it increases in consumers and predators, ranging from 0.22 µg/g in insects to 5.5 µg/g in wild mice. These data suggest that lead dynamics, long banned in fuels but still used in hunting, disrupt the trophic dynamics in the food chains of lowland ecosystems. More generally, therefore, the proximity of the protected area to the built-up area may be enough to protect the landscape and biodiversity but not to remove some of its components from deeper ecological dynamics, such as contamination or bioaccumulation via the food chain.
Lo scopo di questa tesi sperimentale è valutare l’inquinamento da metalli pesanti nell’area protetta ‘’Bosco Negri’’ di Pavia, utilizzando il pelo del topo selvatico Apodemus sylvaticus, come tessuto indicatore. È stato analizzato il contenuto di 12 metalli (Al, As, Cd, Cr, Cu, Fe, Hg, Ni, Mn, Pb, Se, Zn) nel pelo di 27 esemplari; i dati sono stati confrontati fra sessi e categorie di età. Inoltre, i risultati sono stati confrontati con i dati di tesi, svolte su altri organismi appartenenti a diversi livelli trofici (produttori primari, consumatori primari, consumatori secondari e predatori). Infine, abbiamo confrontato i dati raccolti nel mio studio con dati analoghi raccolti per specie vicarianti ecologiche, come M. spretus.
Contaminazione da elementi in traccia nel topo selvatico Apodemus sylvaticus: l’uso del pelo per il biomonitoraggio
FANALI, FRANCESCA CANDIDA
2022/2023
Abstract
In the present work, we studied the concentration of twelve metals (Al, As, Cd, Cr, Cu, Fe, Hg, Ni, Mn, Pb, Se, Zn), in the hairs of the wild mouse Apodemus sylvaticus to verify its suitability as biomonitor of environmental pollution. The samples were air-dried for seven days before the microwave digestion (0,2 mL of HNO3 and 0,5 mL of H2O2). The digested solutions were analyzed by ICP-MS to determine metal concentration. Reagent blanks were prepared following the same procedure applied to the samples. The final concentrations were reported as μg/g dry weight. Twelve metals are concentrated according to the gradient Zn > Al > Fe > Cu > Pb > Cr > Ni > Mn > Cd > Se > As > Hg. Ubiquitous metals such as Zn, Al, Fe, and Cu are more abundant than others of ecotoxicological interest, such as Cd, Se, As, and Hg, with concentrations below 1 µg/g. In both males and females, the metals studied follow the gradient Zn > Al > Fe > Cu > Pb > Cr > Ni > Mn > Cd > Se > As > Hg, but only the concentration of chromium is statistically significant, with a higher concentration in males. The variability of concentrations is high in both sexes, and we observed large differences between minima and maxima, especially for Pb, Hg, and Cr. No significant differences were observed between adults and juveniles; thus, age is a factor that does not affect contamination or bioaccumulation. The lack of differences was expected since the wild mouse is a fossorial species, and no differences between the sexes are known in the time activity underground; the higher concentration of Cr in males could be explained by their greater mobility, which could expose males to a higher risk of contact with sources of contamination that are well established adjacent to the nature reserve. The mercury concentration is low and similar in males and females, suggesting a primary consumer role in the trophic chain of the forest habitat, slightly different from the opportunist role described in the literature. Comparison of mercury concentration in the different trophic levels of agroecosystems studied so far shows maximum bioaccumulation levels close to those in soil, in predators, and much lower in insects and wild mice, supporting the hypothesis of a primary consumer role. A comparison of metal concentrations in soil and hairs shows that A. sylvaticus, despite its fossorial habits, is scarcely influenced by soil chemistry. Fe and Zn are present in low or similar amounts to those of soil, and the concentration of metals in hair does not reflect that of the matrix. Comparison with other wild mouse populations seems to indicate higher concentrations in the hair of our population, which supports the hypothesis that the Bosco Negri population, a protected area, experiences high relative contamination by metals typical of urban and peri-urban industrial areas, such as chromium, lead, cadmium, and nickel. In particular, xenobiotic lead of anthropogenic origin is present in the soil in relatively high concentrations (28.3 µg/g). Its concentration is low in the hairs of primary producers, but it increases in consumers and predators, ranging from 0.22 µg/g in insects to 5.5 µg/g in wild mice. These data suggest that lead dynamics, long banned in fuels but still used in hunting, disrupt the trophic dynamics in the food chains of lowland ecosystems. More generally, therefore, the proximity of the protected area to the built-up area may be enough to protect the landscape and biodiversity but not to remove some of its components from deeper ecological dynamics, such as contamination or bioaccumulation via the food chain.È consentito all'utente scaricare e condividere i documenti disponibili a testo pieno in UNITESI UNIPV nel rispetto della licenza Creative Commons del tipo CC BY NC ND.
Per maggiori informazioni e per verifiche sull'eventuale disponibilità del file scrivere a: unitesi@unipv.it.
https://hdl.handle.net/20.500.14239/17393