1、Designation: D6281 09Standard 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 D6281; the number immediately following the designation indicates t
2、he 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 () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method2is an analytical procedure using
3、transmission 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 al
4、lows 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) and
5、 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 be
6、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 asbesto
7、s 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 th
8、ecollection 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 regulatory
9、 limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D1193 Specification for Reagent WaterD1356 Terminology Relating to Sampling and Analysis ofAtmospheresD1357 Practice for Planning the Sampling of the AmbientAtmosphereD4483 Practice for Evaluating Precision for Test MethodStandards
10、 in the Rubber and Carbon Black ManufacturingIndustriesE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ISO Standard:4ISO 10312 Ambient air - Determination of asbestos fibres -
11、Direct-transfer transmission electron microscopy method3. Terminology3.1 For definitions of general terms used in this test method,refer to Terminology D1356 (see 2.1).3.2 Definitions of Terms Specific to This Standard:3.2.1 acicularthe shape shown by an extremely slendercrystal with cross-sectional
12、 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 structures and complex composi-tions that conform to the nominal formula:A01B2C5T8O22OH,F,Cl!2(1)where:1This test method is under the jurisdic
13、tion of ASTM Committee D22 on AirQuality and is the direct responsibility of Subcommittee D22.07 on Sampling andAnalysis of Asbestos.Current edition approved Dec. 1, 2009. Published December 2009. Originallyapproved in 1998. Last previous edition approved in 2006 as D6281 - 06. DOI:10.1520/D6281-09.
14、2This test method was adapted from International Standard ISO 10312 “Airquality - Determination 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 A
15、nnual Book of ASTMStandards volume information, refer to the standards Document Summary 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 Conshohoc
16、ken, PA 19428-2959, United States.A = K, Na, Ca,B =Fe2+, Mn, Mg, Ca, Na,C = Al, Cr, Ti, Fe3+, Mg, Fe2+, Mn, andT = Si, Al, Cr, Fe3+,Ti.In some varieties of amphibole, these elements can bepartially substituted by Li, Pb, Zn, Be, Ba, or Ni. Amphibolesare characterized by a complex monoclinic or ortho
17、rhombicstructure 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; andgood prismatic cleavage at angles of about 56 and 124. Thecleavage may not be readily exhibited by small cryst
18、als 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 structure concentration in asbestos structures/L, equivalentto the counting of one asbestos structure in the analysi
19、s.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 highertensile strength than other habits of the same mineral.3.2.6 asbestosa collective term that describes a group ofn
20、aturally occurring, inorganic, highly-fibrous, silicate mineralsthat are easily separated into long, thin, flexible, strong fiberswhen crushed or processed.3.2.6.1 DiscussionIncluded in the definition are the as-bestiform varieties of serpentine (chrysotile); riebeckite (cro-cidolite); grunerite (gr
21、unerite asbestos Amosite); anthophyl-lite (anthophyllite asbestos); tremolite (tremolite asbestos); andactinolite (actinolite asbestos). The amphibole mineral compo-sitions are defined according to the nomenclature of theInternational Mineralogical Association.Asbestos Chemical Abstracts Service Reg
22、istry No.6Chrysotile 12001-29-5Crocidolite 12001-28-4Grunerite Asbestos Amosite 12172-73-5Anthophyllite Asbestos 77536-67-5Tremolite Asbestos 77536-68-6Actinolite Asbestos 77536-66-43.2.7 asbestos structurea term applied to isolated fibers orto any connected or overlapping grouping of asbestos fiber
23、s 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 unused filter to determine the backgroundmeasurement.3.2.10 camera lengththe equivalent projection length be-tween
24、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 compositionMg3Si2O5(OH)4and have the crystal structure of either cli-nochrysotile, orthochrysotile, or parachrysotile. Most natu
25、ralchrysotile deviates little from this nominal composition.Chrysotile may be partially dehydrated or magnesium-leached,both in nature and in building materials. In some varieties ofchrysotile, minor substitution of silicon by Al3+ may occur.Chrysotile is the most prevalent type of asbestos.3.2.12 c
26、leavagethe 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 cleavagefragments would be included in the fiber definition used in thismethod.3.2.14 clustera structure in which tw
27、o 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 planes ofatoms in a crystal.3.2.16 electron diffractiontechniques in electron micros-copy, including selected area ele
28、ctron diffraction (SAED) andmicrodiffraction, by which the crystal structure of a specimenis examined.3.2.17 electron scattering powerthe extent to which asubstance scatters electrons from their original courses.3.2.18 energy dispersive X-ray analysismeasurement ofthe energies and intensities of X-r
29、ays 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 of theelectron beam with that axis and is in the plane of focus.3.2.20 field blanka filter cassette that has been t
30、aken 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 cannot befurther separated longitudinally into smaller components with-out losing its fibrous properties or appearanc
31、es.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 a minimum length of 0.5 m.3.2.23 fiber bundlea structure composed of parallel,smaller-diameter fibers attached alo
32、ng 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 characteristic crystal growth form orcombination of these forms of a mineral, including character-istic irregular
33、ities.3.2.26 limit of detectionthe calculated airborne asbestosstructure concentration in structures/L, equivalent to counting2.99 asbestos structures in the analysis. The detection limit hasbeen set at 2.99 structures counted in any area of any filterbecause of concerns that false positives (counti
34、ng 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 against afalse positive rate as high as 5 % (5 false positive structures per100 blank filters counted). This leve
35、l 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 structures counted) will actually5The boldface numbers in parentheses refer to the list of references at the end ofthis sta
36、ndard.6The non-asbestiform variations of the minerals indicated in 5.2.6 have differentChemical Abstracts Service (CAS) numbers.D6281 092contain true positives. Note that concentration values areincluded in the test report, even if they are below the limit ofdetection.3.2.27 matrixa structure in whi
37、ch 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 integer numbers used tospecify the orientation of a crystallographic plane in relation tothe crystal axes.3.2.29 PCM e
38、quivalent 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 structure ofaspect ratio that is greater than or equal to 3:1, is longer than5 m, and has a diameter between 0.2 and
39、 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 copy, or replica, of asurface is made.3.2.33 residual structurematrix or cluster material con-taining asbestos fiber
40、s 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)4.3.2.35 structurea single fiber, fiber bundle, cluster, ormatrix.3.2.36 twinningthe occurrence of crystals of the s
41、amespecies 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 asbestosfiber bundle that has not been separated into its constituentfibrils or fibers.3.2.38 zone-axisthe crystallographic
42、 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 = micrometer (106m)nm = nanometer (109m)W = wattPa = Pascals3.4 Abbreviations:DMF = dimethyl formamideED = electron di
43、ffractionEDXA = energy dispersive X-ray analysisFWHM = full width, half maximumHEPA = high-efficiency particle absoluteMCE = mixed cellulose ester; also refers to pure cellu-lose nitrate filtersPC = polycarbonatePCM = phase contrast optical microscopyED = selected area electron diffractionSEM = scan
44、ning electron microscopeSTEM = scanning transmission electron microscopeTEM = transmission electron microscopeUICC = Union Internationale Contre le Cancer4. Summary of Test Method4.1 A sample of airborne particulate matter is collected bydrawing a measured volume of air through either a capillary-po
45、re 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 of a battery-powered or mains-powered pump.TEM specimens are prepared from polycarbonate filters byapplying a thi
46、n 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 solvent extraction procedure. This proce-dure leaves a thin film of carbon that bridges the openings inthe TEM s
47、pecimen 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, and the surface of the collapsed filter is then etched in anoxygen plasma to try to expose particles embedded in t
48、hecollapsed 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 filtermedium is dissolved by a solvent extraction procedure.4.2 The TEM specimen grids from either preparationmethod are
49、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 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.
