ASTM D5015-02

Standard Test Method for pH of Atmospheric Wet Deposition Samples by Electrometric Determination

SIGNIFICANCE AND USE
The accurate measurement of pH in atmospheric wet deposition is an essential and critically important component in the monitoring of atmospheric wet deposition for trends in the acidity and overall air quality. Atmospheric wet deposition is, in general, a low ionic strength, unbuffered solution. Special precautions, as detailed in this test method, are necessary to ensure accurate pH measurements (1).3 Special emphasis must be placed on minimizing the effect of the residual liquid junction potential bias.
This test method is applicable only to the measurement of pH in atmospheric wet deposition. Its use in other applications may result in inaccuracies.
Fig. 1 provides a frequency distribution of precipitation pH values measured in conjunction with a national monitoring program within the United States. These data are an indication of the range of pH values common to atmospheric wet deposition.
FIG. 1 Frequency Distribution of Measured Laboratory pH of Atmospheric Wet Deposition From the 1984 National Atmospheric Deposition Program (NADP)/National Trends Network (NTN)
SCOPE
1.1 This test method is applicable to the determination of pH in atmospheric wet deposition samples by electrometric measurement using either a pH half cell with a reference probe or a combination electrode as the sensor.
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 09-Oct-2002
• ICS: 71.040.50 - Physicochemical methods of analysis
• Technical Committee: D22 - Air Quality
• Drafting Committee: D22.03 - Ambient Atmospheres and Source Emissions

Relations

• Replaces: ASTM D5015-95 - Standard Test Method for pH of Atmospheric Wet Deposition Samples by Electrometric Determination
• Effective Date: 10-Oct-2002
• Replaced By: ASTM D5015-02(2008) - Standard Test Method for pH of Atmospheric Wet Deposition Samples by Electrometric Determination
• Effective Date: 01-Aug-2008
• Referred By: ASTM D6328-18 - Standard Guide for Quality Assurance Protocols for Chemical Analysis of Atmospheric Wet Deposition
• Effective Date: 10-Oct-2002
• Referred By: ASTM D1356-20a - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 10-Oct-2002

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:D5015–02
Standard Test Method for
pH of Atmospheric Wet Deposition Samples by
1
Electrometric Determination
This standard is issued under the fixed designation D5015; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3.1.2 Fordefinitionsofothertermsusedinthistestmethod,
refer to Terminology D1129 and D1356. For an explanation
1.1 This test method is applicable to the determination of
of the metric system including units, symbols, and conversion
pH in atmospheric wet deposition samples by electrometric
factors, see Practice E380.
measurementusingeitherapHhalfcellwithareferenceprobe
or a combination electrode as the sensor.
4. Summary of Test Method
1.2 This standard does not purport to address all of the
4.1 The pH meter and the associated electrodes are cali-
safety concerns, if any, associated with its use. It is the
brated with two reference buffer solutions that bracket the
responsibility of the user of this standard to establish appro-
anticipatedsamplepH.ThepHofthewetdepositionsampleis
priate safety and health practices and determine the applica-
determinedfromthiscalibrationandaqualitycontrolstandard.
bility of regulatory limitations prior to use.
The quality control standard is necessary in this application to
2. Referenced Documents evaluate the bias due to residual liquid junction potentials and
2
to correct for this bias.
2.1 ASTM Standards:
4.2 The pH of a solution is related to the EMF (millivolts)
D1129 Terminology Relating to Water
ofapHelectrodesystemaccordingtotheoperationaldefinition
D1193 Specification for Reagent Water
for a two-point calibration:
D1356 Terminology Relating to Sampling andAnalysis of
Atmospheres E 2 E
X S
1
pH ~X! 5pH ~S ! 1 [pH ~S ! 2pH ~S !# (1)
1 2 1
D2777 Practice for Determination of Precision and Bias of E 2 E
S S
2 1
Applicable Methods of Committee D19 on Water
D5012 Guide for Preparation of Materials Used for the
where:
Collection and Preservation of Atmospheric Wet Deposi-
pH(X) = pH of an unknown sample,
tion
pH (S ) = pH of a Standard Solution 1,
1
D 5111 Guide for Choosing Locations and Sampling Meth-
pH (S ) = pH of a Standard Solution 2,
2
ods to Monitor Atmospheric Deposition at Non-Urban
E = EMF (mV) measured in an unknown sample,
X
Locations
E = EMF (mV) measured in Standard Solution 1,
S
1
E1 Specification for ASTM Thermometers
and
E380 Practice for Use of the International System of Units
E = EMF (mV) measured in Standard Solution 2.
S
2
(SI) (the Modernized Metric System)
5. Significance and Use
3. Terminology
5.1 The accurate measurement of pH in atmospheric wet
3.1 Definitions:
depositionisanessentialandcriticallyimportantcomponentin
3.1.1 pH—the negative logarithm to the base ten of the
the monitoring of atmospheric wet deposition for trends in the
conventional hydrogen ion activity.
acidity and overall air quality. Atmospheric wet deposition is,
in general, a low ionic strength, unbuffered solution. Special
1
This test method is under the jurisdiction of ASTM Committee D22 on Air precautions, as detailed in this test method, are necessary to
3
Quality and is the direct responsibility of Subcommittee D22.03 on Ambient
ensure accurate pH measurements (1). Special emphasis must
Atmospheres and Source Emissions.
be placed on minimizing the effect of the residual liquid
Current edition approved October 10, 2002. Published December 2002. Origi-
junction potential bias.
nally published as D5015–89. Last previous edition D5015–95.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
3
Standards volume information, refer to the standard’s Document Summary page on Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
the ASTM website. this standard.
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D5015–02
between the stirred and unstirred pH of the sample (4). The
magnitude of the streaming potential is dependent on the
electrodesandonthestirringrate.DifferencesinpHforstirred
and unstirred wet deposition samples when the electrode
assembly has been calibrated only with quiescent reference
standards average 0.05 pH units at a stirring rate of four
revolutions per second.
6.5.1 Eliminate the errors associated with residual stream-
ing potentials by agitating all calibration standards and wet
deposition samples thoroughly to speed electrode equilibration
and then allowing each aliquot to become quiescent bef
...