1、Designation: D2914 15Standard Test Methods forSulfur Dioxide Content of the Atmosphere (West-GaekeMethod)1This standard is issued under the fixed designation D2914; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last r
2、evision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.1 These test methods cover the bubbler c
3、ollection 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 0.03 gSO2/mL to 1.3
4、 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),2representing 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 These test methods i
5、ncorporate 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. Manual Method Bis pH-
6、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 described in Annex A4
7、.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 The values stated in SI units are to be regarded asstandard. No other units of measurement
8、 are included in thisstandard.1.8 WarningMercury has been designated by many regu-latory agencies as a hazardous material that can cause seriousmedical issues. Mercury, or its vapor, has been demonstrated tobe hazardous to health and corrosive to materials. Cautionshould be taken when handling mercu
9、ry and mercury contain-ing products. See the applicable product Safety Data Sheet(SDS) for additional information. Users should be aware thatselling mercury and/or mercury containing products into yourstate or country may be prohibited by law.1.9 This standard does not purport to address all of thes
10、afety 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 limitations prior to use. For specificprecautionary statements, see 8.3.1, Section 9, and A3.1.3.
11、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 AmbientAtmosphereD1914 Practice for Conversion Units and Factors Relating toSampling and Analysis of Atmosp
12、heresD3195 Practice for Rotameter CalibrationD3609 Practice for Calibration Techniques Using Perme-ation TubesD3631 Test Methods for Measuring Surface AtmosphericPressureE1 Specification for ASTM Liquid-in-Glass ThermometersE2251 Specification for Liquid-in-Glass ASTM Thermom-eters with Low-Hazard P
13、recision LiquidsE275 Practice for Describing and Measuring Performance ofUltraviolet and Visible Spectrophotometers1These 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.Cu
14、rrent edition approved July 1, 2015. Published July 2015. Originally approvedin 1970. Last previous edition approved in 2007 as D2914 01 (2007).DOI:10.1520/D2914-15.2The boldface numbers in parentheses refer to a list of references at the end ofthis standard.3For referenced ASTM standards, visit the
15、 ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. Un
16、ited States12.2 Other Standards:40 CFR Part 58 Probe and Monitoring Path Siting Criteriafrom Ambient Air Quality Monitoring, Appendix E43. Terminology3.1 For definitions of terms used in this method, refer toTerminology D1356.4. Summary of Test Methods4.1 Sulfur dioxide (SO2) is absorbed by aspirati
17、ng a mea-sured air sample through a tetrachloromercurate (TCM)solution, resulting in the formation of a dichlorosulfonatomer-curate complex (2, 3). Ethylenediaminetetraacetic acid diso-dium salt (EDTA) is added to this solution to complex heavymetals that interfere with this method (4).Dichlorosulfo
18、natomercurate, once formed, is stable to strongoxidants (for example, ozone and oxides of nitrogen) (2).Afterthe absorption is completed, any ozone in the solution isallowed to decay (5). The liquid is treated first with a solutionof sulfamic acid to destroy the nitrite anion formed from theabsorpti
19、on of oxides of nitrogen present in the atmosphere (6).It is treated next with solutions of formaldehyde and speciallypurified acid-bleached pararosaniline containing phosphoricacid (H3PO4) to control pH. Pararosaniline, formaldehyde, andthe bisulfite anion react to form the intensely colored pararo
20、-saniline methyl sulfonic acid which behaves as a two-color pHindicator (2). The pH of the final solution is adjusted to thedesired value by the addition of prescribed amounts of 3 NH3PO4to the pararosaniline reagent (5).5. Significance and Use5.1 Sulfur dioxide is a major air pollutant, commonlyfor
21、med by the combustion of sulfur-bearing fuels. The Envi-ronmental Protection Agency (EPA) has set primary andsecondary 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 s
22、ulfur dioxide inworkplace atmospheres (8).5.3 These methods have been found satisfactory for mea-suring sulfur dioxide 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 determina
23、tionof sulfur dioxide.6. Interferences6.1 The interferences of oxides of nitrogen are eliminatedby sulfamic acid (5, 6), of ozone by time delay (5), and ofheavy metals by EDTA and phosphoric acid (4, 5). At least 60g of Fe(III), 10 g of Mn(II), and 10 g of Cr(III), 10 gofCu(II) and 22 g of V(V) in 1
24、0 mLof absorbing reagent can betolerated in the procedure. No significant interference wasfound with 2.3 gofNH3(9).7. 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 ves
25、sel is usedfor sampling periods of 30 min and 1 h (or any periodconsiderably less than 24 h).7.1.2 Absorber, 24-h SamplingA glass or polypropylenetube 32 mm in diameter and 164 mm long with a polypropyl-ene two-port cap (rubber stoppers are unacceptable because theabsorbing reagent can react with th
26、e stopper to yield errone-ously high SO2concentrations, and cause high and variableblank values). Insert a glass impinger stem, 6 mm insidediameter and 158 mm long, into one port of the absorber cap.Taper the tip of the stem to a small diameter orifice (0.4 6 0.1mm) such that a No. 79 jewelers drill
27、 bit will pass through theopening but a No. 78 drill bit will not. Clearance from thebottom of the absorber to the tip 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 Probe
28、A sample probe meeting the re-quirements of Section 7 of 40 CFR Part 58, Appendix E,(TFE-fluorocarbon, polypropylene, or 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 precipi
29、tation, large particles, etc.7.1.4 Moisture TrapGlass or polypropylene trap as shownin Fig. 1, placed between the absorber 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. Ch
30、arcoal is preferred whencollecting long-term samples (1 h or more) if flow changes areroutinely encountered.7.1.5 Cap SealsSeal 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.
31、7.1.6 Filter, membrane, of 0.8 to 2.0 m porosity, with filterholder, to protect the flow controller from particles duringlong-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 spec
32、ifiedflow rate across the flow control device.7.1.8 Flow Control and Measurement Devices:7.1.8.1 Flow Control DeviceA calibrated 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
33、-term sampling. Acritical orifice can be used for regulating flow rate for bothlong-term and short-term sampling. Use a 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 hypoder
34、mic needle 16 mm in4Available from U.S. Government Printing Office Superintendent of Documents,732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401, http:/www.access.gpo.gov.D2914 152length to provide a flow rate of approximately 0.5 L/min.Provide a flow control for a 24h sample by a 27gageh
35、ypodermic 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, meeting therequirem
36、ents of Specification E1 will meet the requirements ofmost applications in this method. A comparable precisionlow-hazard liquid thermometer, ASTM Thermometer S33C,meeting the requirements of Specification E2251, may also beused.7.1.10 Barograph or Barometer, capable of measuring at-mospheric pressur
37、e to 60.5 kPa (5 torr). (See Test MethodsD3631.)7.1.11 Temperature Control DeviceTo maintain the tem-perature of the absorbing solution during sampling at 15 610C. Maintain the temperature of the collected sample at 5 65C, as soon as possible following sampling and until analysis.Where an extended p
38、eriod of time may elapse before thecollected sample can be moved to the lower storagetemperature, use a collection temperature near the lower limitof the 15 6 10C range to minimize losses during this period.Thermoelectric coolers specifically designed for this tempera-ture control are available comm
39、ercially and normally operatein the range of 5 to 15C. Small refrigerators can be modifiedto provide the required temperature control; however, insulatethe inlet lines from the lower temperatures to prevent conden-sation when sampling under humid conditions.Asmall heatingpad may be necessary when sa
40、mpling at low temperatures(10 mL of absorbing solution was used, bringthe absorber solution in each impinger to original volume withdistilled 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
41、sampling, storethe solutions at 5 6 5C. Calculate the total mass of SO2ineach solution as follows:M 5Ca3 Qs3 t 3 Va31023Vb(A4.2)where:M = 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,FIG. A4.1 Gas Dilut
42、ion System for Preparation of Standard Concentrations of Sulfur Dioxide for Laboratory Use by the PermeationTube MethodD2914 1513Va= volume of absorbing solution used for color develop-ment (10 mL), andVb= volume of absorbing solution used for sampling, mL.Add the remaining reagents for color develo
43、pment 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 calculate theexact
44、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 vented atatmosp
45、heric 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 Qs31023(A4.3)where:t = sampling time, min,Vb=
46、volume of absorbing solution used for sampling (50mL),Cs= desired concentration of SO2in the absorbing solution,g/mL,Ca= concentration of the standard atmosphere calculated inaccordance with equation A4.1, gSO2/m3, andQs= sampling flow rate, L/min.At the completion of sampling, bring the absorber so
47、lutionsto 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 development in the s
48、amemanner 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, O., Jr., “Collabo
49、rativeStudy of Reference Method for Determination of Sulfur Dioxide inthe Atmosphere (Pararosaniline Method),” September 1971,EPAAPTD-0903, U.S. Environmental Protection Agency, ResearchTriangle Park, NC 27711.(2) West, P. W., and Gaeke, G. C., “Fixation of Sulfur Dioxide asSulfitomercurate 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-romercura
