Crystal chemical and structural characterization of fibrous tremolite from Susa Valley, Italy, with comments on potential harmful effects on human health

Abstract

This study is part of a broad research project devoted to the “amphibole fibers environmental problem” as related to the proposed excavation of the Susa Valley railway tunnel. In this locality, tunnel excavations are planned through metamorphic formations containing amphibole asbestos minerals, and this may give rise to worker health and public environmental issues. The Susa Valley tremolite shows a marked fibrous character, a small reduction of fiber size under grinding, and a consistent increase of the surface area. From the toxicological point of view, such tremolite fibers have been shown to be very effective in the generation of reactive oxygen species. They exhibit a very high cellular reactivity as a consequence of their morphology, structure, and crystal chemistry. Results of combined electron microprobe analysis, Mössbauer spectroscopy, and parallel-beam X-ray powder diffraction are reported for fibrous tremolite from a serpentine-schist from the “Unità Oceanica della Bassa Val di Susa” collected near Condove, Susa Valley, Italy. Data indicate that Fe2+ (84% of Fetot) is located at both the (M1 + M3) and M2 sites and that Fe3+ is at M2, in an approximate 3:2:1 ratio, respectively. No evidence of a split M4 site has been observed. The presence of M1+M3Fe2+ is confirmed by FTIR spectroscopy to be distributed 70% at M1 and 30% at M3. Both the composition (Ca1.95K0.01Na0.05)Σ2.01(VIAl0.01Fe3+0.02Fe2+0.11Mg4.84Mn0.02)Σ5.00Si8.00O22(OH1.96F0.03Cl0.01)Σ2.00 and the cell volume 907.37(1) Å3 of the fibers are close to those expected for end-member (Ca/Mg = 2/5) tremolite

Environmental and Health: The Importance of Tremolite Occurence in the Pollino Geopark (Southern Italy)

“…The FeO tot content varies from 2.47 to 5.06 wt % and is not related to the Ca content. This fact seems to indicate the absence of a Ca-Fe 2+ substitution scheme according to the results of [55]. The EMP analyses revealed that the average composition that was obtained on single crystals is clearly distinguished from the typical compositions of the tremolite, in particular our samples show high content of Al 2 O 3 (1.84-15.46 wt %) and FeO (2.47-5.06 wt %) with a small percentage of Cr 2 O 3 (0.13-1.41 wt %), TiO 2 (0.50-2.00), and Na 2 O (0.05-1.91) ( Table 2).…”

“…In addition to the typical absorption band at 3675-3673 cm −1 assigned to the vibration of the O-H dipole that was bonded to three Mg cations and arrangement M(1) Mg M(1) Mg M(3 )Mg, which is a prominent band, is observed at 3660 cm −1 and a very weak band at 3647 cm −1 (Figure 4b), both of which were attributed to M(1)+M(3) Fe 2+ [45,56]. Fe 3+ was allocated exclusively to M(2), owing to the absence of absorption bands at Δ = 50 cm −1 from the tremolite reference band in the FT-IR spectrum [55,57,58] possibly indicating the presence of M(1)+M(3) Fe 3+ . The EMPA on fibre bundles showed the chemical homogeneity of the fibres, with a mean composition of tremolite (Table 2, Figure 5).…”

“…The EMPA on fibre bundles showed the chemical homogeneity of the fibres, with a mean composition of tremolite (Table 2, Figure 5). [46] for the tremolite and ferro-actinolite and [55] for tremolite from the Susa Valley. In addition to the typical absorption band at 3675-3673 cm −1 assigned to the vibration of the O-H dipole that was bonded to three Mg cations and arrangement M(1) Mg M(1) Mg M(3 )Mg, which is a prominent band, is observed at 3660 cm −1 and a very weak band at 3647 cm −1 (Figure 4b), both of which were attributed to M(1)+M(3) Fe 2+ [45,56].…”

Mineralogical Asbestos Assessment in the Southern Apennines (Italy): A Review

“…The presence of Fe 2+ is confirmed by FT-IR [33]. No Fe 3+ is present, owing to the absence of absorption bands at ∆ = 50 cm −1 from the tremolite reference band in the FT-IR spectrum [33,[52][53][54][55][56].…”

Lichen deterioration of asbestos and asbestiform minerals of serpentinite rocks in Western Alps

“…The toxicity of asbestos and asbestiform minerals is currently related to several physico chemical features acting together such as fibrous habit, high biopersistence and redox reactive iron ions at the surface, generating Reactive Oxygen Species (ROS) (Kane, 1996;Fubini and Fenoglio, 2007;Ballirano et al, 2008).…”