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Figure E1. Typical flow diagram. APPENDIX F-REFERENCE METHOD FOR THE dioxide concentrations of 140 mg./m.3 (0.072

DETERMINATION OF NITROGEN DIOXIDE IN THE p.p.m.) and 200 ug./m.3 (0.108 p.p.m.), respecATMOSPHERE (24-HOUR SAMPLING METHOD) tively, based on an automated analysis of 1. Principle and Applicability.

samples collected from a standard test at1.1 Nitrogen dioxide is collected by bub

mosphere. Precision would probably be dif

ferent when the analysis is performed bling air through a sodium hydroxide solution to form a stable solution of sodium


4.2 No accuracy data are available. nitrite. The nitrite ion produced during sampling is determined colorimetrically by react

4.3 Samples are stable for at least 6 weeks.

5. Apparatus. ing the exposed absorbing reagent with

5.1 Sampling. See Figure F1. phosphoric acid, sulfanilamide, and N-lnaphthylethylenediamine dihydrochloride.

5.1.1 Absorber. Polypropylene tubes 164 X

32 mm., equipped with polypropylene two1.2 The method is applicable to collection of 24-hour samples in the field and sub

port closures.* Rubber stoppers cause high sequent analysis in the laboratory.

and varying blank values and should not be 2. Range and Sensitivity.

used. A gas dispersion tube with a fritted 2.1 The range of the analysis is 0.04 to 1.5 end of porosity B (70–100 um. maximum pore ug. NO,/ml. With 50 ml. absorbing reagent diameter) is used. and a sampling rate of 200 ml./min. for 24 Measurement of Maximum Pore hours, the range of the method is 20–740 Diameter of Frit. Carefully clean the frit with ug./m.: (0.01-0.4 p.p.m.) nitrogen dioxide.

dichromate-concentrated sulfuric acid clean2.2 A concentration of 0.04 ug. NOz/ml. ing solution and rinse well with distilled will produce an absorbance of 0.02 using

water. Insert through one hole of a two-hole 1-cm, cells.

rubber stopper and install in a test tube con3. Interferences.

taining sufficient distilled water to cover the 3.1 The interference of sulfur dioxide is

fritted portion. Attach a vacuum source to eliminated by converting it to sulfuric acid the other hole of the rubber stopper and with hydrogen peroxide before analysis. (1) measure the vacuum required to draw the

4. Precision, Accuracy, and Stability.

4.1 The relative standard deviations are *Available from Bel-Art Products, Pequan. 14.4 percent and 21.5 percent at nitrogen nock, N.J.

first perceptible stream of air bubbles through the frit. Apply the following equation:

30s maximum pore diameter, um.

P s=Surface tension of water in dynes/cm.

at the test temperature (73 at 18° C.,

72 at 25° C., and 71 at 31° C.). P=Measured vacuum, mm. Hg.

5.1.2 Probe. Teflon, polypropylene, or glass tube with a polypropylene or glass funnel at the end and a membrane filter to protect the frit. Replace filter after collecting five samples, or more often as indicated by visual observation of the loading.

5.1.3 Flow Control Device. Calibrated 27gauge hypodermic needle, three-eighths of an inch long to maintain a flow of approximately 0.2 liter/minute. The needle should be protected by a membrane filter. Change filter after collecting 10 samples.

5.1.4 Air Pump. Capable of maintaining a flow of 0.2 liter/minute through the absorber, and a vacuum of 0.7 atmosphere.

5.1.5 Calibration Equipment. Glass flowmeter for measuring airflows up to approximately 275 ml./min. within +2 percent, stopwatch, and precision wet test meter (1 liter/revolution).

5.2 Analysis.

5.2.1 Volumetric Flasks. 50, 100, 200, 250, 500, 1,000 ml.

5.2.2 Graduated Cylinder. 1,000 ml.

5.2.3 Pipets. 1, 2, 5, 10, 15 ml. volumetric; 2 ml., graduated in 1/10 ml. intervals.

5.2.4 Test Tube.

5.2.5. Spectrophotometer or Colorimeter. Capable of measuring absorbance at 540 nm. Bandwidth is not critical.

6. Reagents.
6.1 Sampling.

6.1.1 Absorbing Reagent. Dissolve 4.0 g. sodium hydroxide in distilled water and dilute to 1,000 ml.

6.2 Analysis.

6.2.1 Sulfanilamide. Dissolve 20 g. sulfanilamide in 700 ml. distilled water. Add, with mixing, 50 ml. concentrated phosphoric acid (85 percent) and dilute to 1,000 mi. This solution is stable for a month if refrigerated.

6.2.2 NEDA Solution. Dissolve 0.5 g. N-1naphthylethylenediamine dihydrochloride in 500 ml. of distilled water. This solution is stable for a month if refrigerated and protected from light.

6.2.3 Hydrogen peroxide. Dilute 0.2 ml. 30 percent hydrogen peroxide to 250 ml. with distilled water. This solution may be used for a month if protected from light.

6.2.4 Standard Nitrite Solution. Dissolve sufficient desiccated sodium nitrite (NaNO2, assay of 97 percent or greater) and dilute with distilled water to 1,000 ml. so that a solution containing 1,000 ug. NO,/ml. is obtained. The amount of NaNO2 to use is calculated as follows:

G=Amount of NaNO,, 8.
1.500=Gravimetric factor in converting

NO, into NaNO,.
A=Assay, percent.
7. Procedure.

7.1 Sampling. Assemble the sampling train as shown in Figure F1. Add 50 ml. absorbing reagent to the absorber. Disconnect funnel, insert calibrated flowmeter, and measure flow before sampling. If flow rate before sampling is less than 85 percent of needle callbration, check for leak or change filters as necessary. Remove flowmeter and replace funnel. Sample for 24 hours from midnight to midnight and measure flow at end of sampling period.

7.2 Analysis. Replace any water lost by evaporation during sampling. Pipet 10 ml. of the collected sample into a test tube. Add 1.0 ml. hydrogen peroxide solution, 10.0 ml. sulfanilamide solution, and 1.4 ml. NEDA solution with thorough mixing after the addition of each reagent. Prepare a blank in the same manner using 10 ml. absorbing reagent. After a 10-minute color-development interval, measure the absorbance at 540 nm. against the blank. Read ug. NO:/ml. from standard curve (Section 8.2).

8. Calibration and Efficiencies.
8.1 Sampling.

8.1.1 Calibration of Flowmeter. Using a wet test meter and a stopwatch, determine the rates of air flow (ml./min.) through the flowmeter at several ball positions. Plot ball positions versus flow rates.

8.1.2 Calibration of Hypodermic Needle. Connect the calibrated flowmeter, the needle to be calibrated, and the source of vacuum in such a way that the direction of airflow through the needle is the same as in the sampling train. Read the position of the ball and determine flow rate in ml./min. from the calibration chart prepared in 8.1.1. Reject all needles not having flow rates of 190 to 210 ml./min. before sampling.

8.2 Calibration Curve. Dilute 5.0 ml. of the 1,000 ug. NOz/ml. solution to 200 ml. with absorbing reagent. This solution contains 25 ug. NOz/ml. Pipet 1, 2, 5, and 15 ml. of the 25 ug. NO,/ml. solution into 50-, 50-, 100-, and 250-ml. volumetric flasks and dilute to the mark with absorbing reagent. The solutions contain 0.50, 1.00, 1.25, and 1.50 Mg. NOz/ml., respectively. Run standards as instructed in 7.2. Plot absorbance vs. ug, NO,/ml.

8.3 Efficiencies. An overall average efficiency of 35 per cent was obtained from test atmospheres having nitrogen dioxide concentrations of 140 ug./m.3 and 200 ug./m. by automated analysis.(2)

9. Calculation.
9.1 Sampling.
9.1.1 Calculate volume of air sampled.

F: +F,
V= 2 XTX 10-6



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V=Volume of air sampled, m.3

Fi=Measured flow rate before sampling,

ml./min. F,=Measured flow rate after sampling,

ml./min. T=Time of sampling, min. 10-6=Conversion of ml. to m.;

9.2 Calculate the concentration of nitrogen dioxide as ug. NO,/m.3

(ug. NOz/ml.) x 50 ug. NO,/m.:=

VX 0.35
(ug. NO;/ml.) X 143

50=Volume of absorbing reagent used in

sampling, ml.

V=Volume of air sampled, m. 0.35=Efficiency.

9.2.1 If desired, concentration of nitrogen dioxide may be calculated as p.p.m. NO,.

p.p.m.= (ug. NO,/m.3) X 5.32 X 10-2 10. References. (1) Jacobs, M. B., and Hochheiser, S., "Con

tinuous Sampling and Ultramicrodetermination of Nitrogen Dioxide in

Air", Anal. Chem., 30 426 (1958).
(2) Purdue, L. J., Dudley, J. E., Clements,

J. B., and Thompson, R. J., "Studies in
Air Sampling for Nitrogen Dioxide,"
I. A reinvestigation of the Jacobs-
Hochheiser Reagent. In Preparation.

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PART 51—REQUIREMENTS FOR PREP. Subpart B-Plan Content and Requirements


51.10 General requirements.

51.11 Legal authority. PLANS

51.12 Control strategy: General, Subpart A-General Provisions

51.13 Control strategy: Sulfur oxides and Sec.

particulate matter. 51.1 Definitions.

51.14 Control strategy: Carbon monoxide, 51.2 Stipulations,

hydrocarbons, photochemical oxi51.3 Classification of regions.

dants and nitrogen dioxide. 51.4 Public hearings.

51.15 Compliance schedules. 51.5 Submittal of plans; preliminary re- 51.16 Prevention of air pollution emerview of plans.

gency episodes. 51.6 Revisions.

51.17 Air quality surveillance. 51.7 Reports.

51.18 Review of new sources and modifica51.8 Approval of plans.



51.19 Source surveillance.
51.20 Resources,
51.21 Intergovernmental cooperation.
51.22 Rules and regulations.

Subpart C-Extensions 51.30 Request for 2-year extension, 51.31 Request for 18-month extension. 51.32 Request for 1-year postponement. Appendix A-Air Quality Estimation. Appendix B_Examples of Emission Limita

tions Attainable with Reasonably

Available Technology. Appendix C—Major Pollutant Sources. Appendix D-Emissions Inventory Summary

(Examples Regions). Appendix E—Point Source Data. Appendix F-Area Source Data. Appendix G-Emmissions Inventory Sum

mary (Other Regions). Appendix H-Air Quality Data Summary. Appendix I-Projected Motor Vehicle Emis

sions. Appendix J—Required Hydrocarbon Emis

sion Control a Function of Photochemical Oxidant Concen

trations, Appendix K—Control Agency Functions. Appendix 1—Example Regulations for Pre

vention of Air Pollution Emergency

Episodes. AUTHORITY: The provisions of this part 51 issued under section 301 (a) of the Clean Air Act (42 U.S.C. 1857(a), as amended by section 15(c) (2) of Public Law 91-604, 84 Stat. 1713.

SOURCE: The provisions of this part 51 appear at 36 F.R. 22398, Nov. 25, 1971, unless otherwise noted.

Subpart A-General Provisions $ 51.1 Definitions.

As used in this part, all terms not defined herein shall have the meaning given them in the Act:

(a) “Act" means the Clean Air Act (42 U.S.C. 1857-18571, as amended by Public Law 91-604, 84 Stat. 1676).

(b) “Administrator" means the Administrator of the Environmental Protection Agency (EPA) or his authorized representative.

(c) “Primary standard means a national primary ambient air quality standard promulgated pursuant to section 109 of the Act.

(d) “Secondary standard' means a national secondary ambient air quality standard promulgated pursuant to section 109 of the Act.

(e) “National standard” means either a primary or a secondary standard.

(f) "Plan” means an implementation plan, under section 110 of the Act, to attain and maintain a national standard.

(g) “Applicable plan” means a plan or portion thereof, or the most recent revision of such plan or portion thereof, which has been approved or promulgated by the Administrator pursuant to section 110 of the Act.

(h) “Regional Office" means one of the ten (10) EPA Regional Offices.

(i) “State agency” means the air pollution control agency primarily responsible for development and implementation of a plan under the Act.

(j) “Local agency” means any air pollution control agency other than a State agency, which is charged with responsibility for carrying out a portion of a plan.

(k) “Point source” means:

(1) Any stationary source causing emissions in excess of 100 tons (90.7 metric tons) per year of any pollutant for which there is a national standard in a region containing an area whose 1970 “urban place” population, as defined by the Bureau of Census, was equal to or greater than 1 million or

(2) Any stationary source causing emissions in excess of 25 tons (22,7 metric tons) per year of any pollutant for which there is a national standard in a region containing an area whose 1970 “urban place” population, as defined by the U.S. Bureau of the Census, was less than 1 million and

(3) Without regard to amount of emissions, stationary sources such as those listed in Appendix C to this part.

(1) "Area source" means any small residential, governmental, institutional, commercial, or industrial fuel combustion operations: onsite solid waste disposal facility; motor vehicles, aircraft, vessels, or other transportation facilities; or other miscellaneous sources such as those listed in Appendix D to this part, as identified through inventory techniques similar to those described in: “A Rapid Survey Technique for Estimating Community Air Pollution Emissions," Public Health Service Publication No. 999-AP-29, October 1966.

(m) “Region” means (1) an air quality control region designated by the Secretary of Health, Education, and Welfare or the Administrator, (2) any


area designated by a State agency as an air quality control region and approved by the Administrator, or (3) any area of a State not designated as an air quality control region under subparagraph (1) or (2) of this paragraph.

(n) "Control strategy” means a combination of measures designated to achieve the aggregate reduction of emissions necessary for attainment and maintenance of a national standard, including, but not limited to, measures such as:

(1) Emission limitations.

(2) Federal or State emission charges or taxes or other economic incentives or disincentives.

(3) Closing or relocation of residential, commercial,

industrial facilities.

(4) Changes in schedules or methods of operation of commercial or industrial facilities or transportation systems, including, but not limited to, short-term changes made in accordance with standby plans.

(5) Periodic inspection and testing of motor vehicle emission control systems, at such time as the Administrator determines that such programs are feasible and practicable.

(6) Emission control measures applicable to in-use motor vehicles, including, but not limited to, measures such as mandatory maintenance, installation of emission control devices, and conversion to gaseous fuels.

(7) Measures to reduce motor vehicle traffic, including, but not limited to, measures such

as commuter taxes, gasoline rationing; parking restrictions, or staggered working hours.

(8) Expansion or promotion of the use of mass transportation facilities through measures such as increases in the frequency, convenience, and passengercarrying capacity of mass transportation systems or providing for special bus lanes on major streets and highways.

(9) Any land use or transportation control measures not specifically delineated herein.

(10) Any variation of, or alternative to, any measure delineated herein.

(0) "Reasonably available control technology" means devices, systems, process modifications, or other apparatus or techniques, the application of which

will permit attainment of the emission limitations set forth in Appendix B to this part, provided that Appendix B to this part is not intended, and shall not be construed, to require or encourage State agencies to adopt such emission limitations without due consideration of (1) the necessity of imposing such emission limitations in order to attain and maintain a national standard, (2) the social and economic impact of such emission limitations, and (3) alternative means of providing for attainment and maintenance of such national standard. $ 51.2 Stipulations.

Nothing in this part shall be construed in any manner:

(a) To encourage a State to prepare, adopt, or submit a plan which does not provide for the protection and enhancement of air quality so as to promote the public health and welfare and productive capacity.

(b) To encourage a State to adopt any particular control strategy without taking into consideration the cost-effectiveness of such control strategy in relation to that of alternative control strategies.

(c) To preclude a State from employing techniques other than those specified in this part for purposes of estimating air quality or demonstrating the adequacy of a control strategy, provided that such other techniques are shown to be adequate and appropriate for such purposes.

(d) To encourage a State to prepare, adopt, or submit a plan without taking into consideration the social and economic impact of the control strategy set forth in such plan, including, but not limited to, impact on availability of fuels, energy, transportation, and employment.

(e) To preclude a State from preparing, adopting, or submitting a plan which provides for attainment and maintenance of a national standard through the application of a control strategy not specifically identified or described in this part.

(f) To preclude a State or political subdivision thereof from adopting or enforcing any emission limitations or other measures or combinations thereof to attain and maintain air quality better than that required by a national standard.

(g) To encourage a State to adopt a control strategy uniformly applicable throughout a region unless there is no

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