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1、8/1/20248/1/20241 1AirPollutionMeasurements,EmissionEstimatesLecture Lecture 4 4 Air Pollution Measurements, Emission Estimates The components of monitoring or sampling device How to get a representative sample? How to determine the concentration correctly? How to selecting the sampling flow rate? H
2、ow to selecting correct analytical methods? How to estimate emissions? The components of monitoring or sampling deviceq Two kinds of air pollution measurements methodsambient monitoringconcentrations of pollutants in the air the public breathessource monitoringconcentration and emission rates from a
3、ir pollution sources, for regulation purposesDetector to quantify instantaneous or cumulative amount of pollutantGas meterSample GasflowInlet device to exclude unwantedsampling probe heated to prevent condensationDevices for positioning the sampling probeAir mover(pump)Vent to airGas sourcesamplingd
4、eterminingpowerFlow rateThe components of monitoring or sampling device How to get a representative sample?(1) selecting a suitable sampler siteGenerally the ambient air sampler should be located at the place to which the public has free access where the pollutants concentration is the highest.q For
5、 ambient sampling How to get a representative sample? How to get a representative sample?q For source testingIn source testing , for most such stacks the velocity and concentration in the stack vary from point to point and from time to time , so that many separate measurements must be made and avera
6、ged. How to get a representative sample?The section near the bend, less uniformThe section far away the bend, more uniform How to get a representative sample? How to get a representative sample?(2)Excludingunwantedmaterialsv a bug screen (昆虫网）昆虫网）v TSP ( particulate matter 50 microns or smaller )v P
7、M10 ( particulate matter 10 microns or smaller )v PM2.5 (particulate matter 2.5 microns or smaller ) How to get a representative sample?(3)Gases(somesemivolatile)maycondenseinthesamplingdevice.Manycombustionstackgaseshaveahighwatercontentandwillcondenseonthewallsofanunheatedsamplingprobe.Probesareno
8、rmallyheatedtopreventcondensationofgasesonthewallsofsamplingprobe How to get a representative sample? How to determine the concentration correctly?(1) Eliminating the interference effectFor example Determining SO2 concentration passes the gas through a dilute solution of NaOH. if not considering of
9、CO2 , Cdeterming CtrueMeasuring the change in NaOH concentration by simple acid-base titration.SO2 + NaOH NaSO3 +H2OCO2 + 2NaOH Na2CO3 + H20(2)Averagingtheconcentration How to determine the concentration correctly?v Real time instruments can memorize a lot of values during a period of time .Time 0tC
10、oncentrationAverage concentration =Cavg = (1/t)CdtC=area of the shadow t = the time of measurement(2)Averagingtheconcentrationv Averaging instruments of the concentration of particles.Average C = Cavg =Total volumeTotal massA PM2.5 sampler ran for 24 hours, average flow of 16.7 L /min , fresh filter
11、 : 0.1400 g , gross weight of used filter : 0.1405 g , what is the average PM2.5 concentration ?Only 0.5mg change How to selecting the sampling flow rate?isokinetic flowsampling for particulates in stack.Vn : gas velocity inside the sampling probe Vs : gas velocity in the stackVn= Vs nozzlestack(1)V
12、sVnDensity of particulate is much larger than density of air, so particulates are more inertial and keep direct.Cdeterming VsC =mass flow nozzle volume(2)VsVnC =mass flow nozzle volumeMass keep constant, Vn Ctrue How to selecting correct analytical methods?Air Quality Monitoring8/1/202419Air Quality
13、 MonitoringqMonitoring ConsiderationsManualvs.automated(real-time,continuous)monitoringSamplingtimeFederalreferencemethod(FRM)vs.equivalentmethod(EM)qMonitoring of Ambient Air PollutantsSO2,NOx,CO,O3HydrocarbonsPM10,PM2.5qSource Sampling and MonitoringSamplingtrainIsokineticsamplingqQuality Assuranc
14、e ProgramsQualityAssuranceQualityControlqAir Quality Monitoring Network8/1/202420Whats the use of ambient air quality monitoring data?Monitoring ConsiderationsSamplinglocation:limitednumberoffixedsitemonitorswhoselocationsreflectobjectivesofairqualitymonitoringprogramLowerlimitofdetection(LOD):asuff
15、icientamountofpollutantmustbecollected,f(samplingrate,duration)Integratedsamplingvs.real-timesamplingAreasamplingvs.personalsamplingCollectionefficiencyoftheinstrument:Lowflowrateforgas-phasecontaminants(10mbyimpactiononagreasedsurfaceParticles10mcollectedonaquartzglassfiberfilterWhatdoesthePM10samp
16、lermeasure?Numberormassconcentrationofparticles?8/1/202433Dichotomous Samplerhttp:/crac.ucc.ie/images/sampler1.jpgHowcanaDichotomoussamplermeasurecoarse(PM2.5-10) andfine(PM2.5)particles?TEOM Series 1400abAmbient Particulate MonitorThermo Electron Co. Equivalent method: TEOMMeasurePM10,PM2.5,TSPTape
17、redelementoscillatingmicrobalanceReal-timemeasurementofparticlemasscollectedonafilter8/1/202434Cascade ImpactorHowcanwecollectdifferentsizesofparticlesusingcascadeimpactor?Aerosol flow InClean air out8/1/202435Source Sampling and MonitoringStack Sampling of PM1)Probeinsertedintothestack2)Temperature
18、sensor3)Pitottubegasvelocityandflowrate4)Two-modulesamplingunitIsokinetic Sampling1)Particlesinertialforces2)Samplesmustbecollectedatthesamerateoflowasthestackgas8/1/202436Whats the use of source emission data?Accuracy, Precision and Bias8/1/202437Relative Error:Coefficient of variation: Bias Precis
19、ionHigh biasHigh precisionLow accuracyLow biasLow precisionLow accuracyLow biasHigh precisionHigh accuracyAccuracy, Precision and BiasCalibrationOftenusedforadjustingbias-typeerrorsMeasuredvaluesarecomparedtostandardreferencevalues(forpollutantconcentration)orstandardairflowmeasuringtechniques/devic
20、es(forvolumeairflow)Primaryvs.secondarystandardforflow:traceabletotheNationalInstituteofStandardsandTechnology(NIST)Primary:bubblemeterSecondary:wetordrytestmeterscalibratedbybubblemeterGasstandards:traceabletoaNISTreferencematerialCO,SO2,NO2,NO:availableincylindergasorpermeationtubesO3:NISTcertifie
21、dO3generator8/1/202439Quality Assurance ProgramsQuality Assurance (QA)SettingpolicyandoverseeingmanagementcontrolsPlanning,reviewofdatacollectionactivitiesanddatauseSettingdataqualityobjectives,assigningresponsibilities,conductingreviews,andimplementingcorrectiveactionsGoal: Valid and reliable air quality monitoring dataQuality Control (QC)TechnicalaspectsofdataqualityprogramsImplementationofspecificQCprocedures:calibrations,checks,replicatesamples,routineself-assessment,andauditsIt is federal rule to document QA/QC efforts !8/1/202440
