1、Designation: D 6281 06Standard Test Method forAirborne Asbestos Concentration in Ambient and IndoorAtmospheres as Determined by Transmission ElectronMicroscopy Direct Transfer (TEM)1This standard is issued under the fixed designation D 6281; the number immediately following the designation indicates
2、 the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method2is an analytical procedure us
3、ingtransmission electron microscopy (TEM) for the determinationof the concentration of asbestos structures in ambient atmo-spheres and includes measurement of the dimension of struc-tures and of the asbestos fibers found in the structures fromwhich aspect ratios are calculated.1.1.1 This test method
4、 allows determination of the type(s)of asbestos fibers present.1.1.2 This test method cannot always discriminate betweenindividual fibers of the asbestos and non-asbestos analogues ofthe same amphibole mineral.1.2 This test method is suitable for determination of asbes-tos in both ambient (outdoor)
5、and building atmospheres.1.2.1 This test method is defined for polycarbonatecapillary-pore filters or cellulose ester (either mixed esters ofcellulose or cellulose nitrate) filters through which a knownvolume of air has been drawn and for blank filters.1.3 The upper range of concentrations that can
6、be deter-mined by this test method is 7000 s/mm2. The air concentrationrepresented by this value is a function of the volume of airsampled.1.3.1 There is no lower limit to the dimensions of asbestosfibers that can be detected. In practice, microscopists vary intheir ability to detect very small asbe
7、stos fibers. Therefore, aminimum length of 0.5 m has been defined as the shortestfiber to be incorporated in the reported results.1.4 The direct analytical method cannot be used if thegeneral particulate matter loading of the sample collection filteras analyzed exceeds approximately 10 % coverage of
8、 thecollection filter by particulate matter.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulat
9、ory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D 1193 Specification for Reagent WaterD 1356 Terminology Relating to Sampling and Analysis ofAtmospheresD 1357 Practice for Planning the Sampling of the AmbientAtmosphereD 4483 Practice for Evaluating Precision for Test MethodSt
10、andards in the Rubber and Carbon Black ManufacturingIndustries2.2 ISO Standard:4ISO 10312 Ambient air - Determination of asbestos fibres -Direct-transfer transmission electron microscopy method3. Terminology3.1 For definitions of general terms used in this test method,refer to Terminology D 1356 (se
11、e 2.1).3.2 Definitions of Terms Specific to This Standard:3.2.1 acicularthe shape shown by an extremely slendercrystal with cross-sectional dimensions that are small relativeto its length, that is, needle-like.3.2.2 amphibolea group of more than 60 different silicateminerals with similar crystal str
12、uctures and complex composi-tions that conform to the nominal formula:A01B2C5T8O22OH,F,Cl!2(1)where:A = K, Na, Ca,B =Fe2+, Mn, Mg, Ca, Na,C = Al, Cr, Ti, Fe3+, Mg, Fe2+, Mn, andT = Si, Al, Cr, Fe3+,Ti.1This test method is under the jurisdiction of ASTM Committee D22 on AirQuality and is the direct r
13、esponsibility of Subcommittee D22.07 on Sampling andAnalysis of Asbestos.Current edition approved April 1, 2006. Published May 2006. Originallyapproved in 1998. Last previous edition approved in 2004 as D 6281 - 04.2This test method was adapted from International Standard ISO 10312 “Airquality - Det
14、ermination of asbestos fibres - Direct transfer transmission electronmicroscopy method.”3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summa
15、ry page onthe ASTM website.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.In some varieties of amphibole, these elements can
16、bepartially substituted by Li, Pb, Zn, Be, Ba, or Ni. Amphibolesare characterized by a complex monoclinic or orthorhombicstructure that includes a double chain of T-O tetrahedra with aT:O ratio of approximately 4:11; a variable morphology thatranges from columnar to prismatic to acicular to fibrous;
17、 andgood prismatic cleavage at angles of about 56 and 124. Thecleavage may not be readily exhibited by small crystals that arebound by irregular growth and fracture surfaces (1)5.3.2.3 amphibole asbestosamphibole in an asbestiformhabit.3.2.4 analytical sensitivitythe calculated airborne asbes-tos st
18、ructure concentration in asbestos structures/L, equivalentto the counting of one asbestos structure in the analysis.3.2.5 asbestiforma specific type of fibrous habit in whichthe fibers are separable into thinner fibers and ultimately intofibrils. This habit accounts for greater flexibility and highe
19、rtensile strength than other habits of the same mineral.3.2.6 asbestosa collective term that describes a group ofnaturally occurring, inorganic, highly-fibrous, silicate mineralsthat are easily separated into long, thin, flexible, strong fiberswhen crushed or processed.3.2.6.1 DiscussionIncluded in
20、the definition are the as-bestiform varieties of serpentine (chrysotile); riebeckite (cro-cidolite); grunerite (grunerite asbestos Amosite); anthophyl-lite (anthophyllite asbestos); tremolite (tremolite asbestos); andactinolite (actinolite asbestos). The amphibole mineral compo-sitions are defined a
21、ccording to the nomenclature of theInternational Mineralogical Association.Asbestos Chemical Abstracts Service Registry No.6Chrysotile 12001-29-5Crocidolite 12001-28-4Grunerite Asbestos Amosite 12172-73-5Anthophyllite Asbestos 77536-67-5Tremolite Asbestos 77536-68-6Actinolite Asbestos 77536-66-43.2.
22、7 asbestos structurea term applied to isolated fibers orto any connected or overlapping grouping of asbestos fibers orbundles, with or without other nonasbestos particles.3.2.8 aspect ratiothe ratio of length to width of a particle.3.2.9 blanka structure count made on TEM specimensprepared from an u
23、nused filter to determine the backgroundmeasurement.3.2.10 camera lengththe equivalent projection length be-tween the specimen and its electron diffraction pattern, in theabsence of lens action.3.2.11 chrysotilea group of fibrous minerals of the ser-pentine group that have the nominal compositionMg3
24、Si2O5(OH)4and have the crystal structure of either cli-nochrysotile, orthochrysotile, or parachrysotile. Most naturalchrysotile deviates little from this nominal composition.Chrysotile may be partially dehydrated or magnesium-leached,both in nature and in building materials. In some varieties ofchry
25、sotile, minor substitution of silicon by Al3+ may occur.Chrysotile is the most prevalent type of asbestos.3.2.12 cleavagethe breaking of a mineral along one of itscrystallographic directions.3.2.13 cleavage fragmenta fragment of a crystal that isbounded in whole or in part by cleavage faces. Some cl
26、eavagefragments would be included in the fiber definition used in thismethod.3.2.14 clustera structure in which two or more fibers orfiber bundles are randomly oriented in a connected grouping.3.2.15 d-value or interplanar spacingthe perpendiculardistance between identical adjacent and parallel plan
27、es ofatoms in a crystal.3.2.16 electron diffractiontechniques in electron micros-copy, including selected area electron diffraction (SAED) andmicrodiffraction, by which the crystal structure of a specimenis examined.3.2.17 electron scattering powerthe extent to which asubstance scatters electrons fr
28、om their original courses.3.2.18 energy dispersive X-ray analysismeasurement ofthe energies and intensities of X-rays by use of a solid statedetector and multichannel analyzer system.3.2.19 eucentricthe condition when the area of interest ofan object is placed on a tilting axis at the intersection o
29、f theelectron beam with that axis and is in the plane of focus.3.2.20 field blanka filter cassette that has been taken to thesampling site, opened, and then closed. Such a filter is used todetermine the background structure count for the measurement.3.2.21 fibrila single fiber of chrysotile that can
30、not befurther separated longitudinally into smaller components with-out losing its fibrous properties or appearances.3.2.22 fiberan elongated particle that has parallel orstepped sides. For the purposes of this test method, a fiber isdefined as having an aspect ratio equal to or greater than 5:1and
31、a minimum length of 0.5 m.3.2.23 fiber bundlea structure composed of parallel,smaller-diameter fibers attached along its length.Afiber bundlemay exhibit diverging fibers at one or both ends.3.2.24 fibrous structurea fiber or connected grouping offibers with or without other particles.3.2.25 habitthe
32、 characteristic crystal growth form orcombination of these forms of a mineral, including character-istic irregularities.3.2.26 limit of detectionthe calculated airborne asbestosstructure concentration in structures/L, equivalent to counting2.99 asbestos structures in the analysis. The detection limi
33、t hasbeen set at 2.99 structures counted in any area of any filterbecause of concerns that false positives (counting a structurewhen none exists) may occur in both blanks and sample filters.Based on the assumption of a Poisson distribution of falsepositives, the detection limit of 2.99 would protect
34、 against afalse positive rate as high as 5 % (5 false positive structures per100 blank filters counted). This level is very conservative,since the actual false positive rate is believed to be 2 % orlower. Thus, many of the samples reported as being below thedetection limit (less than three structure
35、s counted) will actuallycontain true positives. Note that concentration values areincluded in the test report, even if they are below the limit ofdetection.5The boldface numbers in parentheses refer to the list of references at the end ofthis standard.6The non-asbestiform variations of the minerals
36、indicated in 5.2.6 have differentChemical Abstracts Service (CAS) numbers.D62810623.2.27 matrixa structure in which one or more fibers orfiber bundles touch, are attached to, or partially concealed by asingle particle or connected group of nonfibrous particles.3.2.28 miller indexa set of three integ
37、er numbers used tospecify the orientation of a crystallographic plane in relation tothe crystal axes.3.2.29 PCM equivalent fibera particle of aspect ratio thatis greater than or equal to 3:1, is longer than 5 m, and that hasa diameter between 0.2 and 3.0 m3.2.30 PCM equivalent structurea fibrous str
38、ucture ofaspect ratio that is greater than or equal to 3:1, is longer than5 m, and has a diameter between 0.2 and 3.0 m.3.2.31 primary structurea fibrous structure that is a sepa-rate entity in the TEM image.3.2.32 replicationa procedure in electron microscopyspecimen preparation in which a thin cop
39、y, or replica, of asurface is made.3.2.33 residual structurematrix or cluster material con-taining asbestos fibers that remains after accounting for theprominent component fibers or bundles, or both.3.2.34 serpentinea group of common rock-forming min-erals having the nominal formula: Mg3Si2O5(OH)4.3
40、.2.35 structurea single fiber, fiber bundle, cluster, ormatrix.3.2.36 twinningthe occurrence of crystals of the samespecies joined together at a particular mutual orientation, andsuch that the relative orientations are related by a definite law.3.2.37 unopened fiber bundlea large-diameter asbestosfi
41、ber bundle that has not been separated into its constituentfibrils or fibers.3.2.38 zone-axisthe crystallographic direction parallel tothe intersection edges of the crystal faces defining the crystalzone.3.3 Symbols:eV = electron voltkV = kilovoltL/min = liters per minuteg = micrograms (106g)m = mic
42、rometer (106m)nm = nanometer (109m)W = wattPa = Pascals3.4 Abbreviations:DMF = dimethyl formamideED = electron diffractionEDXA = energy dispersive X-ray analysisFWHM = full width, half maximumHEPA = high-efficiency particle absoluteMCE = mixed cellulose ester; also refers to pure cellu-lose nitrate
43、filtersPC = polycarbonatePCM = phase contrast optical microscopyED = selected area electron diffractionSEM = scanning electron microscopeSTEM = scanning transmission electron microscopeTEM = transmission electron microscopeUICC = Union Internationale Contre le Cancer4. Summary of Test Method4.1 A sa
44、mple of airborne particulate matter is collected bydrawing a measured volume of air through either a capillary-pore polycarbonate membrane filter of maximum pore size 0.4m or a cellulose ester (either mixed esters of cellulose orcellulose nitrate) membrane filter of maximum pore size 0.45m by means
45、of a battery-powered or mains-powered pump.TEM specimens are prepared from polycarbonate filters byapplying a thin film of carbon to the filter surface by vacuumevaporation. Small areas are cut from the carbon-coated filter,supported on TEM specimen grids, and the filter medium isdissolved away by a
46、 solvent extraction procedure. This proce-dure leaves a thin film of carbon that bridges the openings inthe TEM specimen grid and that supports each particle fromthe original filter in its original position. Cellulose ester filtersare chemically treated to collapse the pore structure of thefilter, a
47、nd the surface of the collapsed filter is then etched in anoxygen plasma to try to expose particles embedded in thecollapsed filter. A thin film of carbon is evaporated onto thefilter surface and small areas are cut from the filter. Thesesections are supported on TEM specimen grids, and the filterme
48、dium is dissolved by a solvent extraction procedure.4.2 The TEM specimen grids from either preparationmethod are examined at both low and high magnifications tocheck that they are suitable for analysis before carrying out aquantitative structure count on randomly-selected grid open-ings. In the TEM
49、analysis, electron diffraction (ED) is used toexamine the crystal structure of a fiber, and its elementalcomposition is determined by energy dispersive X-ray analysis(EDXA). For a number of reasons, it is not possible to identifyeach fiber unequivocally and fibers are classified according tothe techniques that have been used to identify them. For eachfiber, a simple code is used to record the manner in which itwas classified. The fiber classification procedure is based onsuccessive inspection of the morphology, the ED pattern, a
