Asbestos fibres release from serpentinites during quarry operations: case studies from eastern ligurian ophiolites

Transcription

1 Marescotti P., Gaggero L., Isola E., Malatesta C., Solimano M. DIPTERIS Università di Genova Asbestos fibres release from serpentinites during quarry operations: case studies from eastern ligurian ophiolites Asbesto Risk and Management Roma, 4-6 Dicembre 2006

2 Scale 1:5000 C Year I.R. (limit = 0.1) Method Classification Mechanical scratching Not dangerous Mechanical scratching Not dangerous Mechanical scratching Not dangerous Mechanical scratching Not dangerous Grinding machine Not dangerous Grinding machine Not dangerous Grinding machine Not dangerous Grinding machine Not dangerous Grinding machine Not dangerous Grinding machine Not dangerous Grinding machine Not dangerous 2006 <0.001 Grinding machine Not dangerous 2006 <0.001 Grinding machine Not dangerous 2006 <0.001 Grinding machine Not dangerous B A

3 Scale 1:5000 C B A

4 C B A

5 Field geological and minero-petrographical analyses (following the UNI EN ISO Rocks identification and classification, modified and adapted for the specific case of asbestos-bearing rocks) Complete census of fibres and fibre sheaves occurrences at the outcrop scale Mapping of the quarry fronts and definition of the sampling strategy Mineralogical and petrographical qualitative and quantitative analyses Stereo Microscope (representativity of the sample, selection of sample for further investigations, detection of fibres, estimation of percentage composition) Polarized light microscopy (textural analyses, minerals identification, evaluation of percentage composition by visual estimation and/or point counting) XRPD (minerals identification and quantitative analyses)

6 massive Field geological and minero-petrographical analyses (Quarry A) serpentinites fractured serpentinites fractured serpentinites Scale 1:5000 cataclastic serpentinites

7 mineralogy of massive serpentinites major constituents (in order of decreasing abundance) Lizardite (60-70%) Chrysotile(25-35%) Magnetite( 5%) minor constituents (in order of decreasing abundance) Chlorite Calcite Dolomite Talc

8 massive serpentinites 5 mm mesh textures

9 massive serpentinites 5 mm bastite

10 massive serpentinites 0.5 mm 5 mm ribbon textures

11 mineralogy of fractured and cataclastic serpentinites major constituents (in order of decreasing abundance) Lizardite (50-60%) Chrysotile(35-45%) Magnetite( 5%) minor constituents (in order of decreasing abundance) Chlorite Calcite and Dolomite Tremolite Talc

12 a) serrate chrysotile veins with rigid fibres perpendicular to the vein walls 0.1 mm 5 mm 10-15% of the analyzed veins filling minerals: chrysotile fibre type: easily detachable rigid fibres fibres lenght: mm fibres diameter: mm

13 a) composite chrysotile veins with chaotic growth of soft fibres 0.1 mm 0.5 mm % of the analyzed veins filling minerals: chrysotile ± chlorite ± calcite ± dolomite ± talc fibre type: easily detachable bundles and sheaves of soft fibres fibres lenght: mm fibres diameter: mm

14 a) slip chrysotile veins with parallel aggregates of rigid fibres 1 cm 1 mm 0.1 mm % of the analyzed veins filling minerals: chrysotile ± chlorite fibre type: easily detachable rigid fibres fibres lenght: 5-50 mm fibres diameter: mm

15 Serpentinites Volume in outcrop Mineralogy (major costituents) Asbestos type Fibres lenght (mm) Massive 20-25% lizardite, chrysotile, magnetite chrysotile mass.tex veins Fractured 70-75% lizardite, chrysotile, magnetite, chlorite, talc, calcite Cataclastic 1-5% lizardite, chrysotile, tremolite, magnetite, chlorite, talc, calcite chrysotile chrysotile, tremolite mass.tex veins mass.tex veins Asbestos concentration (XRPD, SEM, PLOM) (mg/kg) (mg/kg) (mg/kg)

16 Free fibres evidences in the quarry fronts

17 Free fibres evidences in the quarry fronts

18 Free fibres evidences in soils and uncosolidated sediments

19 Mineralogy and petrography of quarry soils and uncosolidated sediments Agravel Asand Asoil Bsoil Csoil wt %

20 (355 µm <ø< 1mm): stereo microscope 0.5 mm soil quarry A soil quarry B 1 mm 1 mm detrites quarry A floor 0.5 mm detrites quarry A floor

21 (355 µm <ø< 1mm): polarized light microscopy 0.3 mm 1 mm 0.5 mm 0.5 mm

22 (355 µm <ø< 1mm): polarized light microscopy 0.3 mm Massive Friable Other 60 1 mm 50 wt% mm AF1 AF2 AF3 AS1 AS2 BS1 BS2 BS3 CS1 CS2 0.5 mm

23 <53 µm : water suspension (plane polarized light microscopy) PPL 0.01 mm PPL 0.05 mm 0.01 mm

24 <53 µm : water suspension (plane polarized light microscopy) mean value of 50 fields (field area = 2mm 2 ) Af As Bs Cs 20 PPL n of fibres mm PPL mm 0.01 mm

25 <53 µm : water suspension (plane polarized light microscopy) 10 PPL n of fibres sample/n fibres standard soil mm PPL Af As Bs Cs 0.05 mm 0.01 mm

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27 Estimation of the mean asbestos content of the quarry Determination of the release index Analytical control on the atmospheric aerosol particles Structural and textural characterization of the outcropping rocks Distinction between rocks containing non-releasable (i.e massive) and easily releasable (i.e. friable) asbestos fibres. Mapping of a) occurrences of asbestos free fibres and fibrous bundles; b) occurrences of friable asbestos bearing masses and veins Evaluation of the natural level of asbestos contamination, not only in air, but also in soils and sediments