1、Designation: D 2914 01 (Reapproved 2007)Standard Test Methods forSulfur Dioxide Content of the Atmosphere (West-GaekeMethod)1This standard is issued under the fixed designation D 2914; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision
2、, 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.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 These test methods cov
3、er the bubbler collection andcolorimetric determination of sulfur dioxide (SO2)intheambient or workplace atmosphere.1.2 These test methods are applicable for determining SO2over the range from approximately 25 g/m3(0.01 ppm(v) to1000 g/m3(0.4 ppm(v), corresponding to a solution concen-tration of 0.0
4、3 gSO2/mL to 1.3 gSO2/mL. Beers law isfollowed through the working analytical range from 0.02 gSO2/mL to 1.4 gSO2/mL.1.3 The lower limit of detection is 0.075 gSO2/mL (1)2,representing an air concentration of 25 gSO2/m3(0.01ppm(v) in a 30min sample, or 13 gSO2/m3(0.005 ppm(v)in a 24h sample.1.4 Thes
5、e test methods incorporate sampling for periodsbetween 30 min and 24 h.1.5 These test methods describe the determination of thecollected (impinged) samples.AMethodAand a Method B aredescribed.1.6 Method A is preferred over Method B, as it gives thehigher sensitivity, but it has a higher blank. Manua
6、l Method Bis pH-dependent, but is more suitable with spectrometershaving a spectral band width greater than 20 nm.NOTE 1These test methods are applicable at concentrations below 25g/m3by sampling larger volumes of air if the absorption efficiency of theparticular system is first determined, as descr
7、ibed in Annex A4.NOTE 2Concentrations higher than 1000 g/m3can be determined byusing smaller gas volumes, larger collection volumes, or by suitabledilution of the collected sample with absorbing solution prior to analysis.1.7 This standard does not purport to address all of thesafety concerns, if an
8、y, 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 limitations prior to use. For specificprecautionary statements, see 8.3.1, Section 9, and A3.1.1.2. Referenced Documen
9、ts2.1 ASTM Standards:3D 1071 Test Methods for Volumetric Measurement of Gas-eous Fuel SamplesD 1193 Specification for Reagent WaterD 1356 Terminology Relating to Sampling and Analysis ofAtmospheresD 1357 Practice for Planning the Sampling of the AmbientAtmosphereD 1605 Practices for SamplingAtmosphe
10、res forAnalysis ofGases and Vapors4D 1914 Practice for Conversion Units and Factors Relatingto Sampling and Analysis of AtmospheresD 3195 Practice for Rotameter CalibrationD 3609 Practice for Calibration Techniques Using Perme-ation TubesD 3631 Test Methods for Measuring Surface AtmosphericPressureE
11、1 Specification for ASTM Liquid-in-Glass ThermometersE 275 Practice for Describing and Measuring Performanceof Ultraviolet, Visible, and Near-Infrared Spectrophotom-eters2.2 Other Standards:40 CFR Part 58 Probe and Monitoring Path Siting Criteriafrom Ambient Air Quality Monitoring, Appendix E53. Ter
12、minology3.1 For definitions of terms used in this method, refer toTerminology D 1356.1These test methods are under the jurisdiction of ASTM Committee D22 on AirQuality and are the direct responsibility of Subcommittee D22.03 on AmbientAtmospheres and Source Emissions.Current edition approved April 1
13、, 2007. Published June 2007. Originallyapproved in 1970. Last previous edition approved in 2001 as D 2914 - 01.2The boldface numbers in parentheses refer to a list of references at the end ofthis standard.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer S
14、ervice at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Withdrawn.5Available from U.S Government Printing Office, Superintendent of Documents,732 North Capitol Street, NW, Mail Stop: SDE, Washington, DC 20401.1C
15、opyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4. Summary of Test Methods4.1 Sulfur dioxide (SO2) is absorbed by aspirating a mea-sured air sample through a tetrachloromercurate (TCM) solu-tion, resulting in the formation of a dichlor
16、osulfonatomercuratecomplex (2,3). Ethylenediaminetetraacetic acid disodium salt(EDTA) is added to this solution to complex heavy metals thatinterfere with this method (4). Dichlorosulfonatomercurate,once formed, is stable to strong oxidants (for example, ozoneand oxides of nitrogen) (2). After the a
17、bsorption is completed,any ozone in the solution is allowed to decay (5). The liquid istreated first with a solution of sulfamic acid to destroy thenitrite anion formed from the absorption of oxides of nitrogenpresent in the atmosphere (6). It is treated next with solutionsof formaldehyde and specia
18、lly purified acid-bleached pararo-saniline containing phosphoric acid (H3PO4) to control pH.Pararosaniline, formaldehyde, and the bisulfite anion react toform the intensely colored pararosaniline methyl sulfonic acidwhich behaves as a two-color pH indicator (2). The pH of thefinal solution is adjust
19、ed to the desired value by the addition ofprescribed amounts of 3 N H3PO4to the pararosaniline reagent(5).5. Significance and Use5.1 Sulfur dioxide is a major air pollutant, commonlyformed by the combustion of sulfur-bearing fuels. The Envi-ronmental Protection Agency (EPA) has set primary andsecond
20、ary air quality standards (7) that are designed to protectthe public health and welfare.5.2 The Occupational Safety and Health Administration(OSHA) has promulgated exposure limits for sulfur dioxide inworkplace atmospheres (8).5.3 These methods have been found satisfactory for mea-suring sulfur diox
21、ide in ambient and workplace atmospheresover the ranges pertinent in 5.1 and 5.2.5.4 Method A has been designed to correspond to theEPA-Designated Reference Method (7) for the determinationof sulfur dioxide.6. Interferences6.1 The interferences of oxides of nitrogen are eliminatedby sulfamic acid (5
22、,6), of ozone by time delay (5), and of heavymetals by EDTA and phosphoric acid (4,5). At least 60 gofFe(III), 10 g of Mn(II), and 10 g of Cr(III), 10 g of Cu(II)and 22 g of V(V) in 10 mL of absorbing reagent can betolerated in the procedure. No significant interference wasfound with 2.3 gofNH3(9).7
23、. Apparatus7.1 For Sampling:7.1.1 Absorber, ShortTerm SamplingAn all-glass midgetimpinger having a solution capacity of 30 mL and a stemclearance of 4 6 1 mm from the bottom of the vessel is usedfor sampling periods of 30 min and 1 h (or any periodconsiderably less than 24 h).7.1.2 Absorber, 24-h Sa
24、mplingA glass or polypropylenetube 32 mm in diameter and 164 mm long with a polypropy-lene two-port cap (rubber stoppers are unacceptable becausethe absorbing reagent can react with the stopper to yielderroneously high SO2concentrations, and cause high andvariable blank values). Insert a glass impin
25、ger stem, 6 mminside diameter and 158 mm long, into one port of the absorbercap. Taper the tip of the stem to a small diameter orifice (0.4 60.1 mm) such that a No. 79 jewelers drill bit will pass throughthe opening but a No. 78 drill bit will not. Clearance from thebottom of the absorber to the tip
26、 of the stem shall be 6 6 2 mm.Perform the orifice test before use to verify the orifice size.Permanently mark the 50 mLvolume level on the absorber. SeeFig. 1.7.1.3 Air Sample ProbeA sample probe meeting therequirements of Section 7 of 40 CFR Part 58, Appendix E,(TFE-fluorocarbon, polypropylene, or
27、 glass with a residencetime less than 20 sec), used to transport ambient air to thesampling train location. Design or orient the end of the probeto preclude the sampling of precipitation, large particles, etc.7.1.4 Moisture TrapGlass or polypropylene trap as shownin Fig. 1, placed between the absorb
28、er tube and flow controldevice to prevent entrained liquid from reaching the flowcontrol device. Pack the tube with coconut charcoal and glasswool or with indicating silica gel. Charcoal is preferred whencollecting long-term samples (1 h or more) if flow changes areroutinely encountered.7.1.5 Cap Se
29、alsSeal the absorber and moisture trap capssecurely to prevent leaks during use, by using heat-shrinkmaterial to prevent the caps coming loose during sampling,shipment, or storage.7.1.6 Filter, membrane, of 0.8 to 2.0 m porosity, with filterholder, to protect the flow controller from particles durin
30、glong-term sampling. This item is optional for short-termsampling.7.1.7 Pump, equipped with vacuum gauge, capable of main-taining a vacuum greater than 70 kPa (0.7 atm) at the specifiedflow rate across the flow control device.7.1.8 Flow Control and Measurement Devices:7.1.8.1 Flow Control DeviceA ca
31、librated rotameter andneedle valve combination capable of maintaining and measur-ing air flow to within 62 percent is suitable for short-termsampling but shall not be used for long-term sampling. Acritical orifice can be used for regulating flow rate for bothlong-term and short-term sampling. Use a
32、22-gage hypodermicneedle 25 mm long as a critical orifice (10) to yield a flow rateof approximately 1 L/min for a 30min sampling period. Whensampling for 1 h, use a 23-gage hypodermic needle 16 mm inlength to provide a flow rate of approximately 0.5 L/min.Provide a flow control for a 24h sample by a
33、 27gagehypodermic needle critical orifice that is 9.5 mm in length sothat the flow rate is in the range of 0.18 to 0.22 L/min.7.1.8.2 Flow Measurement Devicecalibrated as specifiedin 11.1.1, and used to measure sample flow rate at themonitoring site.7.1.9 ThermometerASTM Thermometer 33C, meetingthe
34、requirements of Specification E1will meet the require-ments of most applications in this method.7.1.10 Barograph or Barometer, capable of measuring at-mospheric pressure to 60.5 kPa (5 torr).7.1.11 Temperature Control DeviceTo maintain the tem-perature of the absorbing solution during sampling at 15
35、 6D 2914 01 (2007)210C. Maintain the temperature of the collected sample at 5 65C, as soon as possible following sampling and until analysis.Where an extended period of time may elapse before thecollected sample can be moved to the lower storage tempera-ture, use a collection temperature near the lo
36、wer limit of the 156 10C range to minimize losses during this period. Thermo-electric coolers specifically designed for this temperaturecontrol are available commercially and normally operate in therange of 5 to 15C. Small refrigerators can be modified toprovide the required temperature control; how
37、ever, insulate theinlet lines from the lower temperatures to prevent condensationwhen sampling under humid conditions. A small heating padmay be necessary when sampling at low temperatures (10 mL of absorbing solution was used, bringthe absorber solution in each impinger to original volume withdisti
38、lled H2O and pipet 10 mL portions from each impingerinto a series of 25 mL volumetric flasks. If the color develop-ment steps are not to be started within 12 h of sampling, storethe solutions at 5 6 5C. Calculate the total mass of SO2ineach solution as follows:M 5Ca3 Qs3 t 3 Va3 1023Vb(A4.2)where:M
39、= mass of SO2in each solution, in g,Ca= concentration of SO2in the standard atmosphere,g/m3,s = sampling flow rate, L/min,t = sampling time, min,Va= volume of absorbing solution used for color develop-ment (10 mL), andVb= volume of absorbing solution used for sampling, mL.Add the remaining reagents
40、for color development in thesame manner as in Annex A2 for static solutions. Calculate acalibration equation and a calibration factor (Bg) in accordancewith Annex A2, adhering to all the specified criteria.A4.1.2 24 h SamplesGenerate a standard atmospherecontaining approximately 1,050 gSO2/m3and cal
41、culate theexact concentration in accordance with EqA4.1. Set up a seriesof six absorbers in accordance with Fig. 1 and connect to acommon manifold for sampling the standard atmosphere. Besure that the total flow rate of the standard exceeds the flowdemand at the sample manifold, with the excess flow
42、 vented atatmospheric pressure. Sample the standard atmosphere forvarying time periods to yield solutions containing 0, 0.2, 0.6,1.0, 1.4, 1.8, and 2.2 gSO2/mL solution. Calculate thesampling times required to attain these solution concentrationsas follows:t 5Vb3 CsCa3 Qs3 1023(A4.3)where:t = sampli
43、ng time, min,Vb= volume of absorbing solution used for sampling (50mL),Cs= desired concentration of SO2in the absorbing solu-tion, g/mL,Ca= concentration of the standard atmosphere calculatedin accordance with equation A4.1, gSO2/m3, andQs= sampling flow rate, L/min.At the completion of sampling, br
44、ing the absorber solutionsto original volume with distilled water. Pipet a 10 mL portionfrom each absorber into one of a series of 25 mL volumetricflasks. If the color development steps are not to be startedwithin 12 h of sampling, store the solutions at 5 6 5C. Addthe remaining reagents for color d
45、evelopment in the samemanner as in 10.2 for static solutions. Calculate the mass ofSO2in each standard, using Eq A4.2.Calculate a calibration equation and a calibration factor (Bt)in accordance with Annex A2 adhering to all the specifiedcriteria.REFERENCES(1) McKee, H. C., Childers, R. E., and Saenz
46、, O., Jr., “Collaborative Studyof Reference Method for Determination of Sulfur Dioxide in theAtmosphere (Pararosaniline Method),” September 1971, EPAAPTD-0903, U.S. Environmental ProtectionAgency, Research Triangle Park,NC 27711.(2) West, P. W., and Gaeke, G. C., “Fixation of Sulfur Dioxide asSulfit
47、omercurate III and Subsequent Colorimetric Determination,”Analytical Chemistry, Vol 28, 1956, p. 1816.(3) Dasgupta, P. K., and DeCesare, K. B., “Stability of Sulfur Dioxide inFormaldehyde Absorber and Its Anomalous Behaviour in Tetrachlo-romercurate II,” Atmospheric Environment, Vol 16 (12), 2927293
48、4,(1982).(4) Zurlo, N., and Griffini, A. M.,“ Measurement of the SO2Content ofAir in the Presence of Oxides of Nitrogen and Heavy Metals,”Medicina del Lavoro, Vol 53, 1962, p. 330.(5) Scaringelli, F. P., Saltzman, B. E., and Frey, A. A.,“Spectrophotomet-ric Determination of Atmospheric Sulfur Dioxid
49、e,” Analytical Chem-istry, Vol 39, 1967, p. 1709.(6) Pate, J. B., Ammons, B. E., Swanson, G. A., and Lodge, J. P., Jr.,“Nitrite Interference in Spectrophotometric Determination of Atmo-spheric Sulfur Dioxide,” Analytical Chemistry, Vol 39, 1965, p. 942.(7) Federal Register, 40 CFR Part 50.(8) Federal Register, 29 CFR Part 1910.(9) Rehme, K. A., and Scaringelli, F. P., “Effect of Ammonia on theSpectrophotometric Determination of Atmospheric Concentrations ofSulfur Dioxide,” Analytical Chemistry, Vol 47, p. 2474, 1995.(10) Lodge,
