Some lichens were recently reported to modify the surface state of asbestos. Here we report some new insight on the physico-chemical modifications induced by natural chelators (lichen metabolites) on two asbestos samples collected in two different locations. A biomimetic approach was followed by reproducing in the laboratory the weathering effect of lichen metabolites. Norstictic,pulvinic and oxalic acid (0.005,0.5 and 50 mm) were put in contact with chrysotile fibres,either in pure form (A) or intergrown with balangeroite, an iron-rich asbestiform phase (B). Mg and Si removal,measured by inductively coupled plasma atomic emission spectrometry (ICPAES) and scanning electron microscopy– energy dispersive X-ray spectroscopy (SEM-EDS),reveals an incongruent dissolution for pure chrysotile (A), with Mg removal always exceeding that of Si,while chrysotile–balangeroite (B) follows a congruent dissolution pattern in all cases except in the presence of 50 mm oxalic acid. A much larger removal of Mg than Si in the solutions of 0.5 and 50 mm oxalic acid with chrysotile (A) suggests a structural collapse, which in the case of chrysotile–balangeroite (B) only occurs with 50 mm oxalic acid; in these cases both samples are converted into amorphous silica (as detected by X-ray diffraction (XRD)). Subsequent to incubation,some new phases (Fe2O3,Ca MgACHTUNGTRENUNG(CO3)2,Ca- ACHTUNGTRENUNG(C2O4)·H2O and MgACHTUNGTRENUNG(C2O4)·2H2O), similar to those observed in the field, were detected by XRD and micro- Raman spectroscopy. The leaching effect of lichen metabolites also modifies the Fenton activity,a process widely correlated with asbestos pathogenicity: pure chrysotile (A) activity is reduced by 50 mm oxalic acid,while all lichen metabolites reduce the activity of chrysotile–balangeroite (B). The selective removal of poorly coordinated, highly reactive iron ions,evide nced by NO adsorption,accounts for the loss in Fenton activity. Such fibres were chemically close to the ones observed in the field. Chrysotile-rich rocks,colonis ed by lichens,could be exposed to a natural bioattenuation and considered as a transient environmental hazard.

A biomimetic approach to the chemical inactivation of chrysotile fibres by lichen metabolites

TURCI, Francesco;FAVERO LONGO, Sergio Enrico;TOMATIS, Maura;MARTRA, Gianmario;CASTELLI, Daniele Carlo Cesare;PIERVITTORI, Rosanna;FUBINI, Bice
2007

Abstract

Some lichens were recently reported to modify the surface state of asbestos. Here we report some new insight on the physico-chemical modifications induced by natural chelators (lichen metabolites) on two asbestos samples collected in two different locations. A biomimetic approach was followed by reproducing in the laboratory the weathering effect of lichen metabolites. Norstictic,pulvinic and oxalic acid (0.005,0.5 and 50 mm) were put in contact with chrysotile fibres,either in pure form (A) or intergrown with balangeroite, an iron-rich asbestiform phase (B). Mg and Si removal,measured by inductively coupled plasma atomic emission spectrometry (ICPAES) and scanning electron microscopy– energy dispersive X-ray spectroscopy (SEM-EDS),reveals an incongruent dissolution for pure chrysotile (A), with Mg removal always exceeding that of Si,while chrysotile–balangeroite (B) follows a congruent dissolution pattern in all cases except in the presence of 50 mm oxalic acid. A much larger removal of Mg than Si in the solutions of 0.5 and 50 mm oxalic acid with chrysotile (A) suggests a structural collapse, which in the case of chrysotile–balangeroite (B) only occurs with 50 mm oxalic acid; in these cases both samples are converted into amorphous silica (as detected by X-ray diffraction (XRD)). Subsequent to incubation,some new phases (Fe2O3,Ca MgACHTUNGTRENUNG(CO3)2,Ca- ACHTUNGTRENUNG(C2O4)·H2O and MgACHTUNGTRENUNG(C2O4)·2H2O), similar to those observed in the field, were detected by XRD and micro- Raman spectroscopy. The leaching effect of lichen metabolites also modifies the Fenton activity,a process widely correlated with asbestos pathogenicity: pure chrysotile (A) activity is reduced by 50 mm oxalic acid,while all lichen metabolites reduce the activity of chrysotile–balangeroite (B). The selective removal of poorly coordinated, highly reactive iron ions,evide nced by NO adsorption,accounts for the loss in Fenton activity. Such fibres were chemically close to the ones observed in the field. Chrysotile-rich rocks,colonis ed by lichens,could be exposed to a natural bioattenuation and considered as a transient environmental hazard.
13(14)
4081
4093
http://dx.doi.org/10.1002/chem.200600991
asbestos; iron; lichen; metabolites; radicals; surface chemistry
F. TURCI; S.E. FAVERO-LONGO; M. TOMATIS; G. MARTRA; D. CASTELLI; R. PIERVITTORI; B. FUBINI
File in questo prodotto:
File Dimensione Formato  
Chemistry - A European Journal 13(2007).pdf

Accesso riservato

Tipo di file: POSTPRINT (VERSIONE FINALE DELL’AUTORE)
Dimensione 423.42 kB
Formato Adobe PDF
423.42 kB Adobe PDF   Visualizza/Apri   Richiedi una copia

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2318/37459
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 39
  • ???jsp.display-item.citation.isi??? 37
social impact