1、Designation: D7535 09 (Reapproved 2015)Standard Test Method forLead-210 in Water1This standard is issued under the fixed designation D7535; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in pare
2、ntheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of radioac-tive210Pb in environmental water samples (for example,drinking, non-process and effluent waters)
3、 in the range of 37mBq/L (1.0 pCi/L) or greater.1.2 The values stated in SI units are to be regarded asstandard. The values given in parentheses are provided forinformation purposes only.1.3 This method has been used successfully with tap water.It is the users responsibility to ensure the validity o
4、f this testmethod for samples larger than 500 mL and for waters ofuntested matrices.1.4 This standard does not purport to address all of thesafety 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
5、 determine the applica-bility of regulatory limitations prior to use. For specific hazardsstatements, see Section 9.2. Referenced Documents2.1 ASTM Standards:2D1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD2777 Practice for Determination of Precision and Bias ofApplicable T
6、est Methods of Committee D19 on WaterD3370 Practices for Sampling Water from Closed ConduitsD4448 Guide for Sampling Ground-Water Monitoring WellsD5847 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Water AnalysisD6001 Guide for Direct-Push Groundwater Sampling forE
7、nvironmental Site CharacterizationD7282 Practice for Set-up, Calibration, and Quality Controlof Instruments Used for Radioactivity MeasurementsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 DefinitionsFor definitions of terms used in
8、 this testmethod, refer to Terminology D1129.4. Summary of Test Method4.1 This test method is based on the utilization of solidphase extraction of lead from water samples with detection ofthe radioactive lead by beta gas flow proportional counting.Analiquot of the sample is measured into a beaker; i
9、ron carrier andlead carrier are added. Lead is scavenged by an iron hydroxideprecipitation. Lead is then selectively sorbed on a solid phaseextraction column and eluted with water. Lead is precipitatedas lead sulfate and is collected on a filter paper.The lead sulfateprecipitate is covered with alum
10、inum foil and held for 5 daysor longer for210Bi ingrowth. It is then counted for betaradiation on a gas flow proportional counter.5. Significance and Use5.1 This test method was developed to measure the concen-tration of210Pb in nonprocess water samples. This test methodmay be used to determine the
11、concentration of210Pb inenvironmental samples.6. Interferences6.1 Significant amounts of stable lead (0.3 mg/L) presentin the sample will interfere with the chemical yielddetermination, leading to positive bias in the yield. If it isknown or suspected that natural lead is present in the sample,blank
12、 sample aliquots to which no lead carrier content is addedshould be analyzed. The amount of natural lead contained inthe sample shall be used to correct the yield.6.2 In most cases measurable amounts of210Pb will bepresent in the Pb carrier used in 12.1. This additional contri-bution to the measured
13、 sample activity must be determined andtreated as additional background activity. For each new carriersolution, the inherent210Pb in the carrier must be measured. Abrief description of this additional background calibration isgiven in 11.2. Accurate determination of the combined stan-dard uncertaint
14、y and the minimum detectable concentrationshould include this additional activity in the method back-ground count rate.1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.04 on Methods of Radiochemi-cal Analysis.Current editi
15、on approved Jan. 1, 2015. Published January 2015. Originallyapproved in 2009. Last previous edition approved in 2009 as D7535 091. DOI:10.1520/D7535-09E01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTM
16、Standards 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. United States16.3 Previous experimental data suggests that barium con-centrations of approximately 30 ppm
17、can be a source ofinterference, leading to chemical yield determinations that maybe non-representative and outside normal acceptance criteria.7. Apparatus7.1 Analytical Balance, 0.0001 g.NOTE 1A thickness of aluminum of approximately 0.003 in. (arealdensity of approximately 0.02 mg/cm2) is needed to
18、 effectively eliminatethe 60 keV beta particles from210Pb.3The thickness of aluminum foilused during calibration of the detector and measurement samples must beheld constant to maintain self-absorption of210Pb and210Bi beta particlesat a constant level.7.2 Aluminum foil.7.3 Centrifuge.7.4 Centrifuge
19、 tubes (50 mL plastic).7.5 Filters, 25 mm polypropylene, 0.1 m, with polycarbon-ate base and metal screen.7.6 Filter apparatus, polysulfone funnel and 100 mL poly-propylene flask.7.7 Beta Gas Flow Proportional Counting System, (1.0cpm beta), low background.7.8 Glass stir rods.7.9 Glass beakers.7.10
20、Hot plate.7.11 Petri dish.7.12 Planchets, stainless steel, flat, with diameter largeenough to hold the 25 mm filter.7.13 Tweezers.7.14 Watch glass.8. Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reag
21、ents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available. Other grades may beused, provided that the reagent is of sufficiently high purity topermit its use without increasing the background of themeasu
22、rement. Some reagents, even those of high purity, maycontain naturally occurring radioactivity, such as isotopes ofuranium, radium, actinium, thorium, rare earths and potassiumcompounds and/or artificially produced radionuclides.Consequently, when such reagents are used in the analysis oflow-radioac
23、tivity samples, the activity of the reagents shall bedetermined under analytical conditions that are identical tothose used for the sample. The activity contributed by thereagents may be considered to be a component of backgroundand applied as a correction when calculating the test sampleresult. Thi
24、s increased background reduces the sensitivity of themeasurement.8.2 Purity of WaterUnless otherwise indicated, referenceto water shall be understood to mean reagent water conformingto Specification D1193, Type III.8.3 Ammonium hydroxide15MNH4OH, (concentratedreagent).8.4 Iron Carrier (20 mg/mL)Diss
25、olve 9.6 g of ferricchloride (FeCl36H2O) in 70 mL of 0.5 M HCl and dilute to100 mL with 0.5 M HCl.8.5 Nitric Acid, 16 M HNO3(concentrated reagent) (sp gr1.42).8.5.1 Nitric Acid,8MHNO3Add 500 mL of concentratednitric acid to 400 mL water. Dilute to 1 L with water and mixwell.8.5.2 Nitric Acid,1MHNO3A
26、dd 63 mL of concentratednitric acid to 800 mL water. Dilute to 1 L with water and mixwell.8.5.3 Nitric Acid, 0.1 M HNO3Add 6.4 mL of concen-trated nitric acid to 600 mL water. Dilute to 1 L with water andmix well.8.6 Lead Carrier (10 grams Pb/L)Dissolve 1.60 g of leadnitrate in water and dilute to 1
27、00 mL with water.8.7 Lead Extraction Chromatography Column, 2-mL bedvolume, 100150 m particle size.48.8 Pb-210 Standardizing SolutionTraceable to a nationalstandardizing laboratory such as National Institute of Standardsand Technology, Gaithersburg, MD, USA (NIST) or NationalPhysical Laboratory, Ted
28、dington, Middlesex, UK, (NPL) withless than 0.1 mg of stable lead per mL of final solution with atypical210Pb concentration range from 85 to 125 Bq/mL.The210Pb calibration source should be in equilibrium with itsprogeny210Bi.8.9 Sulfuric Acid, 18 M H2SO4concentrated reagent (sp gr1.84).9. Hazards9.1
29、 Use extreme caution when handling all acids. They areextremely corrosive, and skin contact could result in severeburns.9.2 When diluting concentrated acids, always use safetyglasses and protective clothing, and add the acid to the water.10. Sampling10.1 Collect a sample in accordance with Guides D4
30、448 andD6001 and Practice D3370, or other documented procedure asappropriate.11. Calibration11.1 Detection Effciency Calibration (see also PracticeD7282):3Radiological Health Handbook, Revised Editions January 1970, Compiled andEdited by the Bureau of Radiological Health and the Training Institute E
31、nviron-mental Control Administration, US Department of Health, Education and Welfare.4Resin available in bulk form and in prepacked columns or cartridges fromEichrom Technologies LLC, Lisle, IL 60532. If you are aware of alternativesuppliers, please provide this information to ASTM International Hea
32、dquarters.Your comments will receive careful consideration at a meeting of the responsibletechnical committee,1which you may attend.D7535 09 (2015)211.1.1 Prepare a set of three working calibration sourcesaccording to the calibration procedure outlined in the subse-quent steps.11.1.2 Pipet 1.0 mL of
33、 lead carrier into a small beaker.11.1.3 Add 1.0 mL of210Pb standardizing solution to thebeaker and evaporate to near dryness on a hot plate at a lowsetting.11.1.4 Redissolve the residue in 10 mL of1MHNO3.11.1.5 Follow the steps described in 12.9 through 12.28.11.1.6 Count to amass at least 10 000 c
34、ounts. Record thetime and date of the midpoint of this counting period as tm.11.1.7 Detection Effciency CalculationCalculate the de-tection efficiency for210Bi for each calibration source and eachdetector using Eq 1.Bi5Ra2 Rbcs3Vs3DF 3IF 3YPb(1)where:Bi= detection efficiency for210Bi,Ra= total count
35、 rate (s1) for calibration source, (countsdivided by count time (s)Rb= count rate (s1) for blank or background source,(counts divided by count time (s)IF = correction factor for ingrowth of210Bi from210Pbbetween the time of the bismuth separation to themidpoint of counting, 12e2Bitm2ts!, where:Bi= d
36、ecay constant for210Bi, (1.60 106s1),ts= date and time of210Bi separation, andtm= midpoint of count of calibration mount (date andtime).DF = correction factor for decay of210Pb in the carriersolution from the carrier activity reference date to thetime of the bismuth separation,e2Pbts2tr!, where:Pb=
37、decay constant for210Pb, (9.85 1010s1),tr= reference date and time of210Pb calibration oflead carrier, andts= date and time of210Bi separation.cs= activity concentration (or massic activity) of thecalibration standard solution (Bq/unit),Vs= volume (or mass) of standard solution used (mLor g),YPb= ch
38、emical yield of lead (see 13.1 and 13.2); YPb5ms/cc3Vc!, where:ms= net mass (mg) of lead sulfate found in thesource, equal to mF+PmF, where mF+Pis the totalmass of the filter plus precipitate and mFis the taremass (filter only),cc= mass concentration (mg/mL) of lead (as sulfate)in the carrier soluti
39、on (see Eq 5), andVc= volume of carrier solution added (mL).Eq 1 assumes that any210Pb activity contamination in the Pbcarrier is insignificant compared to the amount of210Pb activityin the calibration source spike.11.1.8 The variance in the210Bi detector efficiency, Bi, (notthe average) is calculat
40、ed by Eq 2:uc2Bi! 5 Su2Ra!1u2Rb!ms23IF21SRa2 Rbms3IFD23u2ms!ms21u2Fc! 3DFc2D3cc23Vc2cs23Vs23DF21Bi23Su2cs!cs21u2Vs!Vs21u2cc!cc21u2Vc!Vc2 D(2)where u() denotes standard uncertainty; for example, u(Vs)is the standard uncertainty of Vs.11.1.8.1 Eq 2 omits the uncertainties due to the activityconcentrat
41、ion of the calibration standard solution, cs, and theconcentration of the carrier solution, cc. These uncertaintycomponents are accounted for when the average efficiency isdetermined (below).11.1.8.2 The procedure requires an average of (at least)three efficiencies (N = 3) measured using three calib
42、rationsources on each detector. For this purpose, calculate 1, 2, 3for each source, and use Eq 3 to calculate the weightedaverage:HBi51N(i51Ni(3)11.1.8.3 To calculate the uncertainty of the average, includ-ing uncertainty components due to systematic errors, Eq 4 isused:uHBi! 5 1N2 (i51Nuc2i!1HBi23S
43、u2cs!cs21u2cc!cc2 D(4)11.2 Determination of Inherent210Pb in Pb Carrier:11.2.1 As noted in 6.2, in cases where the Pb carrier used inthis procedure has not been determined to be free of210Pb,the210Pb content inherent in the lead carrier used in thismethod must be evaluated. Each new carrier solution
44、 must bemeasured for210Pb prior to use. Once the210Pb content of thelead carrier is known, the210Pb count rate from the recoveredlead carrier can be calculated for each sample analyzed. Thefollowing step provides a protocol to determine the inherent210Pb in the lead carrier and Section 13 provides t
45、he equationsneeded to correct for the210Pb inherent in the lead carrier. Thespecific number of samples, as well as acceptance criteria forthe data and statistical tests to determine detectable210Pb inthe lead carrier, should be specified in the laboratorys QualitySystems Manual.11.2.2 To a minimum o
46、f five 50 mL centrifuge tubes, add 1mL of the Pb carrier solution.11.2.3 Add 20 mL of water and 4 mL concentrated sulfuricacid to each centrifuge tube.11.2.4 Continue with the normal sample preparation, begin-ning at 12.16.11.2.5 After counting, calculate for each sample the210Pbconcentration and as
47、sociated uncertainty according to Section13. Calculate the weighted average acand standard uncertaintyu(ac) of the210Pb concentration using the calculated sampleresults from the data set using the equations in 13.3.12. ProcedureNOTE 2See Fig. 1 for a diagram of the procedure.12.1 Add 1.0 mL of lead
48、carrier and 1.0 mL of iron carrierto a maximum 500 mL of sample. Acidify sample with nitricacid to pH 2.12.2 Cover beaker with a watch glass and heat at nearboiling for an hour. Reduce heat.D7535 09 (2015)312.3 Remove watch glass. Carefully, with stirring, addapproximately 12 mL of concentrated ammo
49、nium hydroxide toprecipitate iron hydroxide. Add more if necessary to form aprecipitate.12.4 Heat the sample without boiling for another 30 min-utes.12.5 Let the precipitate settle for at least 2 hours (preferablyovernight). Decant the supernatant. Transfer the remainingsample along with the precipitate into a 50 mL plasticcentrifuge tube.12.6 Centrifuge at approximately 3500 RPM for approxi-mately 15 minutes and discard the supernatant.12.7 Wash the precipitate with 10 mL of water. Centrifugeand discard th
