Lecture 4 Air pollution Measurements

Lecture4AirPollutionMeasurements,EmissionEstimatesⅠThecomponentsofmonitoringorsamplingdeviceⅡHowtogetarepresentativesample?ⅢHowtodeterminetheconcentrationcorrectly?ⅣHowtoselectingthesamplingflowrate?ⅤHowtoselectingcorrectanalyticalmethods?ⅥHowtoestimateemissions?ⅠThecomponentsofmonitoringorsamplingdeviceTwokindsofairpollutionmeasurementsmethodsambientmonitoringconcentrationsofpollutantsintheairthepublicbreathessourcetestingconcentrationandemissionratesfromairpollutionsourcesⅠThecomponentsofmonitoringorsamplingdeviceDetectortoquantifyinstantaneousorcumulativeamountofpollutantGasmeterSampleGasflowInletdevicetoexcludeunwantedsamplingprobeheatedtopreventcondensationDevicesforpositioningthesamplingprobeAirmover(pump)VenttoairGassourcesamplingdeterminingpowerFlowrateⅡHowtogetarepresentativesample?(1)selectingasuitablesamplersiteGenerallytheambientairsamplershouldbelocatedattheplacetowhichthepublichasfreeaccesswherethepollutantsconcentrationisthehighest.ForambientsamplingⅡHowtogetarepresentativesample?ForsourcetestingInsourcetesting,formostsuchstacksthevelocityandconcentrationinthestackvaryfrompointtopointandfromtimetotime,sothatmanyseparatemeasurementsmustbemadeandaveraged.Thesectionnearthebend,lessuniformThesectionfarawaythebend,moreuniformⅡHowtogetarepresentativesample?ForsourcetestingPage66,Figure4.3(2)Excludingunwantedmaterialsabugscreen(昆虫网）PM10(particulatematter10micronsorsmaller)PM2.5(particulatematter2.5micronsorsmaller)ⅡHowtogetarepresentativesample?(3)ProbesarenormallyheatedtopreventcondensationofgasesonthewallsofsamplingprobeⅡHowtogetarepresentativesample?ⅢHowtodeterminetheconcentrationcorrectly?(1)EliminatingtheinterferenceeffectForexampleDeterminingSO2concentrationpassesthegasthroughadilutesolutionofNaOH.ifnotconsideringofCO2,CdetermingCtrueMeasuringthechangeinNaOHconcentrationbysimpleacid-basetitration.SO2+NaOHNaSO3+H2OCO2+2NaOHNa2CO3+H20(2)AveragingtheconcentrationⅢHowtodeterminetheconcentrationcorrectly?Real–timeinstrumentscanmemorizealotofvaluesduringaperiodoftime.Time0tConcentrationAverageconcentration=Cavg=(1/t)∫CdtC=areaoftheshadowt=thetimeofmeasurement(2)AveragingtheconcentrationAveraginginstrumentsoftheconcentrationofparticles.AverageC=Cavg=TotalvolumeTotalmassExample4.2Page69APM2.5samplerranfor24hours,averageflowof16.7L/min,freshfilter:0.1400g,grossweightofusedfilter:0.1405g,whatistheaveragePM2.5concentration?335338.201008.2min6024min)107.16()1400.01405.0(mgmgmgCavgⅣHowtoselectingthesamplingflowrate?isokineticflowsamplingforparticulatesinstack.Vn:gasvelocityinsidethesamplingprobeVs:gasvelocityinthestackVn=Vsnozzlestack(1)VsVnDensityofparticulateismuchlargerthandensityofair,soparticulatesaremoreinertialandkeepdirect.CdetermingCtrueMasskeepconstant,VnVsC=massflownozzlevolume(2)VsVnMasskeepconstant,VnVsC=massflownozzlevolumeCdetermingCtrueⅤHowtoselectingcorrectanalyticalmethods?P27,Table4.1AccordingtostandardsamplingmethodsbyEPATestmethodsformajorairpollutantsinambientair.AirQualityMonitoring2/5/202016MonitoringConsiderations•Manualvs.automated(real-time,continuous)monitoring•Samplingtime•Federalreferencemethod(FRM)vs.equivalentmethod(EM)MonitoringofAmbientAirPollutants•SO2,NOx,CO,O3•Hydrocarbons•PM10,PM2.5SourceSamplingandMonitoring•Samplingtrain•IsokineticsamplingQualityAssurancePrograms•QualityAssurance•QualityControlAirQualityMonitoringNetwork2/5/202017What’stheuseofambientairqualitymonitoringdata?MonitoringConsiderations•Samplinglocation:limitednumberoffixedsitemonitorswhoselocationsreflectobjectivesofairqualitymonitoringprogram•Lowerlimitofdetection(LOD):asufficientamountofpollutantmustbecollected,f(samplingrate,duration)–Integratedsamplingvs.real-timesampling–Areasamplingvs.personalsampling•Collectionefficiencyoftheinstrument:–Lowflowrateforgas-phasecontaminants(1L/min)2/5/202018Examplesofcriteriaforselectingambientsamplinglocations?Whataretheobjectives?19Differencesinaveragingtimesassociatedwithreal-timedata2/5/2020Whichdurationshouldyouuse?20NationalAmbientAirQualityStandardsPollutantPrimaryStds.AveragingTimesSecondaryStds.CO9ppm(10mg/m3)8-hour(1)None35ppm(40mg/m3)1-hour(1)NonePb1.5µg/m3QuarterlyAveSameasPrimaryNO20.053ppm(100µg/m3)Annual(Arith.Mean)SameasPrimaryPM10Revoked(2)Annual(2)(Arith.Mean)150µg/m324-hour(3)PM2.515.0µg/m3Annual(4)(Arith.Mean)SameasPrimary35µg/m324-hour(5)O30.08ppm8-hour(6)SameasPrimary0.12ppm1-hour(7)(Appliesonlyinlimitedareas)SameasPrimarySO20.03ppmAnnual(Arith.Mean)-------0.14ppm24-hour(1)--------------3-hour(1)0.5ppm(1300µg/m3)(pararosanilnemethod)NO2Gas-phasechemiluminescenceCONondispersiveinfraredphotometryO3ChemiluminescenceNMHCsGaschromatography–FID(flameionizationdetection)PM10Performance-approvedproductPM2.5Performance-approvedproduct2/5/202021SO2FRM-Spectrophotometr