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where:

y = ml of concentrated HCl required.
x = molarity of HCl in 6.2.6.
0.15 = dilution factor in 7.2.2.

6.2.8 Lead nitrate, Pb(NO,).. ACS reagent grade, purity 99.0 percent. Heat for 4 hours at 120° C and cool in a desiccator.

6.3 Calibration standards.

6.3.1 Master standard, 1000 ug Pb/ml in HNO,. Dissolve 1.598 g of Pb(NO3), in 0.45 M HNO, contained in a 1 l volumetric flask and dilute to volume with 0.45 M HNO3.

6.3.2 Master standard, 1000 ug Pb/ml in HNO,/HCI. Prepare as in section 6.3.1 except use the HNO,/HCl solution in section 6.2.7

Store standards in a polyethylene bottle. Commercially available certified lead standard solutions may also be used.

7. Procedure.

7.1 Sampling. Collect samples for 24 hours using the procedure described in reference 10 with glass-fiber filters meeting the specifications in section 6.1.1. Transport collected samples to the laboratory taking care to minimize contamination and loss of sample. (16).

7.2 Sample preparation.
7.2.1 Hot extraction procedure.

7.2.1.1 Cut a " X 8" strip from the exposed filter using a template and a pizza cutter as described in Figures 1 and 2. Other cutting procedures may be used.

Lead in ambient particulate matter collected on glass fiber filters has been shown to be uniformly distributed across the filter. " 3" Another study 12 has shown that when sampling near a roadway, strip position contributes significantly to the overall variability associated with lead analyses. Therefore, when sampling near a roadway, additional strips should be analyzed to minimize this variability.

7.2.1.2 Fold the strip in half twice and place in a 150-ml beaker. Add 15 ml of 3 M HNO, to cover the sample. The acid should completely cover the sample. Cover the beaker with a watch glass.

7.2.1.3 Place beaker on the hot-plate. contained in a fume hood, and boil gently for 30 min. Do not let the sample evaporate to dryness. Caution: Nitric acid fumes are toxic.

7.2.1.4 Remove beaker from hot plate and cool to near room temperature.

7.2.1.5 Quantitatively transfer the sample as follows:

7.2.1.5.1 Rinse watch glass and sides of beaker with D.I. water.

7.2.1.5.2 Decant extract and rinsings into a 100-ml volumetric flask.

7.2.1.5.3 Add D.I. water to 40 ml mark on beaker, cover with watch glass, and set aside for a minimum of 30 minutes. This is a critical step and cannot be omitted since it allows the HNO, trapped in the filter to diffuse into the rinse water.

7.2.1.5.4 Decant the water from the filter into the volumetric flask.

7.2.1.5.5 Rinse filter and beaker twice with D.I. water and add rinsings to volumetric flask until total volume is 80 to 85 ml.

7.2.1.5.6 Stopper flask and shake vigorously. Set aside for approximately 5 minutes or until foam has dissipated.

7.2.1.5.7 Bring solution to volume with D.I. water. Mix thoroughly.

7.2.1.5.8 Allow solution to settle for one hour before proceeding with analysis.

7.2.1.5.9 If sample is to be stored for subsequent analysis, transfer to a linear polyethylene bottle.

7.2.2 Ultrasonic extraction procedure.

7.2.2.1 Cut a %" x 8" strip from the exposed filter as described in section 7.2.1.1.

7.2.2.2 Fold the strip in half twice and place in a 30 ml beaker. Add 15 ml of the HNO,/HCI solution in section 6.2.6. The acid should completely cover the sample. Cover the beaker with parafilm.

The parafilm should be placed over the beaker such that none of the parafilm is in contact with water in the ultrasonic bath. Otherwise, rinsing of the parafilm (section 7.2.2.4.1) may contaminate the sample.

7.2.2.3 Place the beaker in the ultrasonication bath and operate for 30 minutes.

7.2.2.4 Quantitatively transfer the sample as follows:

7.2.2.4.1 Rinse parafilm and sides of beaker with D.I. water.

7.2.2.4.2 Decant extract and rinsings into a 100 ml volumetric flask.

7.2.2.4.3 Add 20 ml D.I. water to cover the filter strip, cover with parafilm, and set aside for a minimum of 30 minutes. This is a critical step and cannot be omitted. The sample is then processed as in sections 7.2.1.5.4 through 7.2.1.5.9.

NOTE: Samples prepared by the hot extraction procedure are now in 0.45 M HNO3. Samples prepared by the ultrasonication procedure are in 0.40 M HNO, + X M HCI.

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8. Analysis.

8.1 Set the wavelength of the monochromator at 283.3 or 217.0 nm. Set or align other instrumental operating conditions as recommended by the manufacturer.

8.2 The sample can be analyzed directly from the volumetric flask, or an appropriate amount of sample decanted into a sample analysis tube. In either case, care should be taken not to disturb the settled solids.

8.3 Aspirate samples, calibration standards and blanks (section 9.2) into the flame and record the equilibrium absorbance.

8.4 Determine the lead concentration in ug Pb/ml, from the calibration curve, section 9.3.

8.5 Samples that exceed the linear calibration range should be diluted with acid of the same concentration as the calibration standards and reanalyzed.

9. Calibration.

9.1 Working standard, 20 ug Pb/ml. Prepared by diluting 2.0 ml of the master standard (section 6.3.1 if the hot acid extraction was used or section 6.3.2 if the ultrasonic extraction procedure was used) to 100 ml with acid of the same concentration as used in preparing the master standard.

9.2 Calibration standards. Prepare daily by diluting the working standard, with the same acid matrix, as indicated below. Other lead concentrations may be used.

9.3 Preparation of calibration curve. Since the working range of analysis will vary depending on which lead line is used and the type of instrument, no one set of instructions for preparation of a calibration curve can be given. Select standards (plus the reagent blank), in the same acid concentration as the samples, to cover the linear absorption range indicated by the instrument manufacturer. Measure the absorbance of the blank and standards as in section 8.0. Repeat until good agreement is obtained between replicates. Plot absorbance (y-axis) versus concentration in ug Pb/ml (x-axis). Draw (or compute) a straight line through the linear portion of the curve. Do not force the calibration curve through zero. Other calibration procedures may be used.

To determine stability of the calibration curve, remeasure-alternately-one of the following calibration standards for every 10th sample analyzed: Concentration lug Pb/ml; concentration 10 ug Pb/ml. If either standard deviates by more than 5 percent from the value predicted by the calibration curve, recalibrate and repeat the previous 10 analyses.

10. Calculation.

10.1 Measured air volume. Calculate the measured air volume at Standard Temperature and Pressure as described in Reference 10.

10.2 Lead concentration. Calculate lead concentration in the air sample.

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where:

%" X 8" glass fiber filter strips containing C=Concentration, ug Pb/sm?

80 to 2000 ug Pb/strip (as lead salts) and ug Pb/ml=Lead concentration determined

blank strips with zero Pb content should be

used to determine if the method as being from section 8. 100 ml/strip=Total sample volume.

used-has any bias. Quality control charts

should be established to monitor differences 12 strips = Total useable filter area, 8" x 9". Exposed area of one strip, %" x 7".

between measured and true values. The fre

quency of such checks will depend on the Filter=Total area of one strip, %" x 8". Fo=Lead concentration of blank filter, ug,

local quality control program.

To minimize the possibility of generating from section 6.1.1.2.3.

unreliable data, the user should follow pracVstp=Air volume from section 10.2.

tices established for assuring the quality of 11. Quality control.

air pollution data, (13) and take part in

EPA's semiannual audit program for lead analyses.

12. Trouble shooting.

1. During extraction of lead by the hot extraction procedure, it is important to keep the sample covered so that corrosion prod. ucts-formed on fume hood surfaces which may contain lead-are not deposited in the extract.

2. The sample acid concentration should minimize corrosion of the nebulizer. However, different nebulizers may require lower acid concentrations. Lower concentrations can be used provided samples and standards have the same acid concentration.

3. Ashing of particulate samples has been found, by EPA and contractor laboratories, to be unnecessary in lead analyses by atomic absorption. Therefore, this step was omitted from the method.

4. Filtration of extracted samples, to remove particulate matter, was specifically excluded from sample preparation, because some analysts have observed losses of lead due to filtration.

5. If suspended solids should clog the nebulizer during analysis of samples, centrifuge the sample to remove the solids.

13. Authority.

(Secs. 109 and 301(a), Clean Air Act as amended, (42 U.S.C. 7409, 7601(a)).)

14. References.

1. Scott, D. R. et al. "Atomic Absorption and Optical Emission Analysis of NASN Atmospheric Particulate Samples for Lead." Envir. Sci. and Tech., 10, 877-880 (1976).

2. Skogerboe, R. K. et al. "Monitoring for Lead in the Environment." pp. 57-66, Department of Chemistry, Colorado State University, Fort Collins, Colo. 80523. Submitted to National Science Foundation for publications, 1976.

3. Zdrojewski, A. et al. “The Accurate Measurement of Lead in Airborne Particulates." Inter. J. Environ. Anal. Chem., 2, 6377 (1972).

4. Slavin, W., "Atomic Absorption Spectroscopy." Published by Interscience Company, New York, N.Y. (1968).

5. Kirkbright, G. F., and Sargent, M. "Atomic Absorption and Fluorescence Spectroscopy." Published by Academic Press, New York, N.Y. 1974.

6. Burnham, C. D. et al., *Determination of Lead in Airborne Particulates in Chicago and Cook County, Ill. by Atomic Absorption Spectroscopy." Envir. Sci. and Tech., 3. 472475 (1969).

7. “Proposed Recommended Practices for Atomic Absorption Spectrometry.” ASTM Book of Standards, part 30, pp. 1596-1608 (July 1973).

8. Koirttyohann, S. R. and Wen, J. W.. "Critical Study of the APCD-MIBK Extraction System for Atomic Absorption." Anal Chem., 45, 1986-1989 (1973).

9. Collaborative Study of Reference Method for the Determination of Suspended Particulates in the Atmosphere (High Volume Method). Obtainable from National Technical Information Service, Department of Commerce, Port Royal Road, Springfield, Va. 22151, as PB-205-891.

10. “Reference Method for the Determination of Suspended Particulates in the Atmosphere (High Volume Method)." Code of Federal Regulations, Title 40, Part 50, Appendix B, pp. 12-16 (July 1, 1975).

11. Dubois, L., et al., "The Metal Content of Urban Air." JAPCA, 16, 77-78 (1966).

12. EPA Report No. 600/4-77-034, June 1977, “Los Angeles Catalyst Study Sympo. sium." Page 223.

13. Quality Assurance Handbook for Air Pollution Measurement System. Volume 1Principles. EPA-600/9-76-005, March 1976.

14. Thompson, R. J. et al., "Analysis of Selected Elements in Atmospheric Particulate Matter by Atomic Absorption." Atomic ADsorption Newsletter, 9, No. 3, May-June 1970.

15. To be published. EPA, QAB, EMSL, RTP, N.C. 27711

16. Quality Assurance Handbook for Air Pollution Measurement Systems. Volume II-Ambient Air Specific Methods. EPA-600/ 4-77/027a, May 1977.

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(Secs. 109, 301(a) of the Clean Air Act, as amended (42 U.S.C. 7409, 7601(a); secs. 110, 301(a) and 319 of the Clean Air Act (42 U.S.C. 7410, 7601(a), 7619) [43 FR 46258, Oct. 5, 1978, as amended at 44 FR 37915, June 29, 1979; 46 FR 44163, Sept. 3, 1981)

APPENDIX H-INTERPRETATION OF THE
NATIONAL AMBIENT AIR QUALITY
STANDARDS FOR OZONE

endar year with maximum hourly average concentrations above 0.12 ppm (235 ug/m") is equal to or less than 1. An expanded discussion of these procedures and associated examples are contained in the “Guideline for Interpretation of Ozone Air Quality

1. General

This appendix explains how to determine when the expected number of days per cal.

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