SANDWICH Material BalanceApproach for PM2.5Data AnalysisNeil Frank OAQPS/USEPAFor Presentation at2006 National Air Monitoring ConferenceLas Vegas, NevadaNovember 6-9, 2006Outline• What is “SANDWICH”, why it is good wayto describe PM2.5composition• How it can help with PM2.5 data QC• Examples using STN dataIntroduction• What is theSANDWICHApproach?–Sulfate,AdjustedNitrate,DerivedWater,InferredCarbonHybrid material balanceapproach• for estimating PM2.5 mass composition producedby the PM2.5 FRM.– The approach uses a combination ofspeciation measurements and modeledspeciation estimates to represent FRM PM2.5.Introduction (cont.)• Why is it needed?– The FRM defines the regulatory indicatorof PM2.5.– FRM mass may not retain all nitrate, and includesparticle bound water and other components notestimated directly with STN measurements.– To estimate FRM PM2.5composition including FRMcarbonaceous mass without“fudge” factors.– To help QC speciation measurements• SANDWICH is the default method in EPAmodeling guidance to define baseline PM2.5– for SMAT (speciation modeled attainment test)Old Practice:Use STN measurements todirectlycharacterize PM2.5These represent a subset of STN speciation measurementsFRM and STN measurementsPM2.5 massSO42-NH4+NO3-{Al SI Ca Fe Ti}OCECSulfateAmmoniumNitrateAluminum Silicon Calcium Iron TitaniumOrganicand Elemental CarbonOld Practice:Use STN measurements todirectlycharacterize PM2.5FRM and STN measurementsPM2.5 massSO42-NH4+NO3-{Al SI Ca Fe Ti}OCEC(Teflon filter)FRM sampler(Nylon following denuder) (Teflon)(Quartz)Various Speciation Samplers** Various STN speciation samplers,with different design and flow rates compared to FRM:MetOne (SASS), Anderson (RASS), URG (MASS), R&PFRM and STN measurementsPM2.5 massSO4NH4NO3{Al SI Ca Fe Ti}OCECOld Practice:Use STN measurements todirectlycharacterize PM2.5FRM and speciation samplers have different flow rates,face velocity and monitoring protocols.Constructed Mass using STN measurementsSulfateNitrate{Crustal}OCMECCreate estimates of major componentsOld Practice: Use STN measurements to directly characterize PM2.5with limited consideration of the different monitoring protocolsFRM and STN measurementsPM2.5 massSO4NH4NO3{Al SI Ca Fe Ti}OCECAmmoniumSulfate*(NH4)2SO4AmmoniumNitrate*NH4NO3Cr = 2.2*Al +2.49*Si+1.63*Ca + 2.42*Fe+1.94*TiOCM=1.4*(OC-b)Typical formulas to estimate major componentsOld Practice: Use STN measurements to directly characterize PM2.5Create estimates of major componentsFRM and STN measurementsPM2.5 massSO4NH4NO3{Al SI Ca Fe Ti}OCECConstructed Mass using STN measurements (RCFM)Sulfate +Nitrate+ {Crustal} +OCM+ ECAmmoniumSulfate*(NH4)2SO4AmmoniumNitrate*NH4NO3Cr = 2.2*Al +2.49*Si+1.63*Ca + 2.42*Fe+1.94*TiOCM=1.4*(OC-b)Old Practice: Use STN measurements to directly characterize PM2.5Constructed Mass using STN measurementsSulfate +Nitrate+ {Crustal} +OCM+ ECCreate estimates of major componentsFRM and STN measurementsPM2.5 massSO4NH4NO3{Al SI Ca Fe Ti}OCECto account for O, H, N in C compoundsFrom STN field blanks. Imperfect methodCarbonaceous Massfrom measured C datais a very uncertain calculationk*(OC-b)+EC, e.g. k=1.4 or 1.8Many Sources of error• Analytical uncertainty• Blank correction (avg value ~1-1.5ug/m3 OC, STNsites)– Varies among our 5 different EPA urban speciation samplers– We can’t do site or seasonal adjustments– NOTE: this is a minor issue with IMPROVE dataug C/ filter ug C/m3MetOne (SASS) 9.6 14.8 1.5Anderson (RAAS) 10.4 13.5 1.3R&P 2300 14.4 16.1 1.1URG (MASS) 24 7.7 0.3NetworkAverageTotalCarbon on STN BlankFilters*24-hrsampleVolume(m3)STN sampler5thspeciation sampleris the PM2.5FRMUncertainty of k*(OC-b), continued• Conversion of OC to OCM (+33%), varies withaerosol type and mix– 1.4 < k < 1.8 ("typical" urban)– 2.0 < k < 2.4 ("typical" rural)• Weighted average for mixed urban/regional aerosol– Turpin's estimates based on limited speciation data• OC- EC split (and unaccounted mass for “EC”)• Retainedcarbon mass on FRM teflon vs STNquartz– Volatile or other OC may pass thru Teflon• FRM has higherface velocitythan many STN samplers– Water [20-24% of measured PM2.5 water]Constructed Mass using STN measurements (RCFM)PM2.5 mass=Sulfate +Nitrate+ {Crustal} +OCM+ ECBottom line: Measurement data with standard adjustment does not add up to PM2.5A better use ofthe STN speciation data to support the PM2.5program is neededOld Practice: Use STN measurements to directly characterize PM2.5Approach usingmeasurementsand simple calculatedvaluesDistributeunknown(or scale alldown) equallySO4UnknownCrustalOCMNO3ECFRM and STN measurementsPM2.5 massSO4NH4NO3{Al SI Ca Fe Ti}OCECNow, letsmodifythe STN measurements usingSANDWICHFRM and STN measurementsPM2.5 massSO4NH4NO3{Al SI Ca Fe Ti}OCECNow, letsmodifythe STN measurements usingSANDWICHFRM and STN measurementsPM2.5 massSO4NH4NO3{Al SI Ca Fe Ti}OCECPM2.5= “Gravimetric” mass• Teflon filters are equilibrated at ~21deg C and 35% RH• Net weight and sample volume are used to produce ug/m3The SANDWICH approach considers samplingartifacts and idiosyncrasies of FRM’s gravimetricmass and STN’s monitoring protocolsFRM and STN measurementsPM2.5 massSO4NH4NO3{Al SI Ca Fe Ti}OCECEst.H2O(withAIM)Reduced NO3(using hourlytemp and RHfrom nearby metstation)Crustal(alternativeformulawhich does notuse Al)EC,as reportedFRM Mass(incl. passive,Pa, based onblank=0.5μg/m3)SO4NH4asreportedUse SANDWICH to characterize PM2.5SANDWICH doesnot directly use OCAIM (thermodynamic model)or with our response surface equationSee:http://oaqpswww.epa.gov/tom/wiki/pmteam/index.cfm?doc=Water_CalculationsEvaporation modeldescribed in my JAWMA paperFrank, N. Retained Nitrate, Hydrated Sulfates, and Carbonaceous Massin Federal Reference Method Fine Particulate Matter for Six Eastern U.S. Cities,J. Air & Waste Manage. Assoc.56:500–511FRM and STN measurementsPM2.5 massSO4NH4NO3{Al SI Ca Fe Ti}OCECEst.H2O(withAIM)Reduced NO3(using hourlytemp and RHfrom nearbymet station)Crustal(alternativeformulawhich does notuse Al)Use SANDWICH to characterize PM2.5For particlebound waterwhich is part ofgravimetric massFor losses of semivolatile nitrate onFRM filters duringsamplingFor detectionproblemswith AlFor filtercontamination(not affectedby emissions)FRM Mass(incl. passive,Pa, based onblank=0.5μg/m3)EC,as reportedSO4NH4asreportedFRM and STN measurementsPM2.5 massSO4NH4NO3{Al SI Ca Fe Ti}OCECEst.H2OReduced NO3(using hourlytemp and RHfrom nearbymet station)Crustal(alternativeformulawhich does notuse Al)OCMmb= FRM – (SO4+NH4+NO3r+H2O+EC+Cr+Pa)FRM Mass(includespassive, Pa,based onblank=0.5ug/m3)Use SANDWICH to characterize PM2.5EC,as reportedSO4NH4asreportedOCMmbexplicitly accounts for blank correction (sampling artifact), fudge factor toaccount for OC to OCM conversion, H2O & less (non-volatile) OC retained on Teflon.Cleveland, OH

NO3 Concentration0.02.04.06.08.0J FMAMJ J ASONDannavgBirmingham, ALJ FMAMJ J ASONDannavg6 Nitrate Study Sites, 2003FRM doesn’t retain all ambient nitratesMonthly and AnnualAverage NO3, 2003STN (Measured)FRM (Measured)Sulfate Nitrate TCM Crustal PassiveRCFM(reflects ambient)SANDWICH(reflects FRM PM2.5)0.00.51.01.52.02.50.0 0.5 1.0 1.5 2.0 2.5Measured FRM NO3

Calculated FRM NO3Chicago(URG*)

1 : 1 L i n e* Note: Chicago has URG sampler whose data may underestimateambient nitrates. URG has 2 filters to collect nitrates (Teflonfollowed by nylon). The teflon may loose nitrates when it is firstused by XRF under vacuum prior to non-volatile nitratedetermination.FRM (calculated)Ann Avgratio of H2O to SO4+NO3+NH4 mass0.00.10.20.30.40.50.60.70.80.91.0molar ratio of NH4 to SO40.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0NO3 to SO4 mass ratio0 to 0.10.2 to 0.30.4 to 0.50.6 to 0.70.8 to 0.91.0 to 1.11.5 to 3 Monthly Average Water, ug/m301234Monthly Average Sulfates + Total Ammonium , ug/m30 3 6 9 12 15Regression Equation:zh2Omod0=0+0.241578*zso4plusnh4 mod0PM2.5 Water Estimated with AIM, using SO4, NO3 and NH4Monthly Average Watertracks Sulfate plus Total Ammoniumfor 6 study sites, 2003 dataDegree of NeutralizationUsing Aerosol Inorganics Model (AIM) at 35% RH and 21oC (no solids are allowed to form).http://www.hpc1.uea.ac.uk/~e770/aim.htmlMore waterwith higher % of Sulfatesor More Acidic AerosolEQUATION TO ESTIMATE WATER(replicates AIM at FRM equilibration conditions)Let D = NH4s/ SO4, 0<D<0.375, where NH4sis the amount associated with SO4.[The corresponding DON ('degree of neutralization', molar) varies from 0 to 2.]Define relative amounts ofSO4, NO3 (reduced) and NH4:S=SO4/(SO4+NO3+NH4); N=NO3/(SO4+NO3+NH4); A=NH4/(SO4+NO3+NH4);Eliminate any excess NH4 notneeded to fully neutralize SO4High acidity:DON <1.2 (D < 0.225 )Water= [ 595.56 - 1440.58*S - 1126.49*N + 283.91*(S**1.5) - 13.38*(N**1.5)- 1486.71*(A**1.5) + 764.23*(S**2)+ 1502.00*(N * S) + 451.87*(N**2)- 185.18*(S**2.5) - 375.98*(S**1.5) *N - 16.90*(S**3) - 65.81*(N**1.5) * S+ 96.83*(N**2.5) + 83.04*(N**1.5) *( S**1.5) - 4.42*(N**3)+ 1720.82*(A**1.5) * S + 1220.38*(A**1.5) * N - 311.50*(A**1.5) * (S**1.5)+ 148.77*(A**1.5) * (N**1.5) + 1151.65*(A**3)] * (SO4+NO3+NH4)Low acidity:DON>1.2 (D>0.225)Water= [ 202049.0 - 391494.6*S - 390912.1*N + 442.4*(S**1.5) - 155.3*(N**1.5)- 293406.8*(A**1.5)+189277.5*(S**2)+377992.6*N*S +188636.8*N**2- 447.1*S**2.5 -507.2*S**1.5*N -12.8*S**3 +146.2*N**1.5*S +217.2*N**2.5+ 30.0*N**1.5*S**1.5 - 18.6*N**3+ 216267.0*A**1.5*S + 215419.9*A**1.5*N- 621.8*A**1.5*S**1.5 +239.1*A**1.5*N**1.5+95413.1*A**3] * (SO4+NO3+NH4)New Development (included in Draft Modeling Guidance)measurements and modeled estimatesSO4NH4NO3rH2OCrustalOCMmbEC PaUse SANDWICH to characterize PM2.5estimates of speciated FRMcomponentsFRM and STN measurementsPM2.5 massSO4NH4NO3{Al SI Ca Fe Ti}OCECFRM and STN measurementsPM2.5 massSO4NH4NO3{Al SI Ca Fe Ti}OCECPM2.5 mass =SO4+NH4+NO3r +H2O+Crustal +OCMmb+EC + PaUse SANDWICH to characterize PM2.5By design, perfect mass balanceSulfate,AdjustedNitrate,DerivedWater,InferredCarbonHybrid Material Balance Approach(SANDWICH)FRM and STN measurementsPM2.5 massSO4NH4NO3{Al SI Ca Fe Ti}OCECSANDWICH and STN measurementsPM2.5 mass =SO4+NH4+NO3r +H2O+Crustal +OCMmb+EC + PaSANDWICH and STN measurementsPM2.5 mass =Sulfate +Nitrate+Crustal +TCMmb+ PaUse SANDWICH to characterize PM2.5Simpler representation of major componentsBy design, perfect mass balanceSANDWICH and STN measurementsPM2.5_mass =SO4+NH4+NO3r +H2O+Crustal +OCMmb+EC +PaSANDWICH and STN measurementsPM2.5 mass =Sulfate +Nitrate+Crustal +TCMmb+ PaUse SANDWICH to characterize PM2.5For Data Presention Purposes:Simplify components of PM2.5into Sulfate and Nitrate portions,the NH4and estimated H2O must be partitioned.Carbon can be represented as Total Carbonaceous Mass.PartitionNH4andH20CombineOCM and ECFor further datadetails, See:http://www.epa.gov/airexplorer/(a) W. Reduced Nitrates(b) With added waterSO4UnknownCrustalpassiveTCMNO3(c) Plus passive PM2.5(= FRM blank)(d) Remaining unknown massis assigned to carbon(1) Approachusing measurementsand calculated valuesConceptual Overview of Mass Balance Approaches*Distributeunknown(or scale alldown) equally* Default SANDWICH can be modified to considerother components, like salt. This reduces estimate of TCM.(2) SANDWICHSulfate mass increasesUncertainties, Caveats and Data Use• Assumptions:– Reduced nitrate and enhanced sulfate are more reflective ofwhat might be measured by the FRM– OCM is the most uncertain mass component• TCMmb is upper estimate and subject to errors in thenon-C components• Inclusion of all “known” components is good– E.g. Salt for coastal areas or urban wintertime• Sometimes, TCMmbcan be negative– But, so can measurement derived “OC-b”– So, modified SANDWICH uses measurement data as an“OCM floor” (See discussion on Air Explorer)• TCMmbcan be used to ground truth k*(OC-b) +ECApplication of SANDWICH to STN DataandSome examples of SANDWICH for QCRCFM SANDWICHAnnual Average Composition (2002-04) in East NA areasLess nitrate and more sulfate mass with SANDWICHNA area without STN data (02-04)Black outlined pies have collocated FRM and speciationarea area_annual_dvNA area: Johnstown, PA 15.3NA area: Martinsburg, WV-Hagerstown, MD 16.1NA area: Parkersburg-Marietta, WV-OH 15.2NA area: Reading, PA 16.1NA area: Steubenville-Weirton, OH-WV 17NA area: Wheeling, WV-OH 15.1RCFMSANDWICHAnnual Average Composition (2002-04) in West NA areasLess nitrate and more carbon mass with SANDWICHBlack outlined pies have collocated FRM and speciationQ1Q3Q2Q4Sulfate_mass Nitrate_mass TCMUnknown_at_DV_site Crustal PassiveQuarterly PM2.5 Composition in Eastern NA areas, 2002-04Seattle-Bellevue-Everett,WA site=530330080Chicago,IL site=170310076Riverside-San Bernardino,CA site=0606580012002 2003 2004 2005Sulfate_mass Nitrate_mass ECOCM Crustal

PM2.5 and Components, ug/m3 0 60 0 60Seattle ChicagoBirmingham2002 2003 2004 2005Rubidoux, CAFRM PM2.5Chicago,IL site=170310076Seattle-Bellevue-Everett,WA site=530330080Birmingham,AL site=010730023Riverside-San Bernardino,CA site=060658001Sulfate_mass Nitrate_mass ECOCMmb Crustal PassiveSeattle ChicagoRubidoux, CA2002 2003 2004 2005

PM2.5 and Components, ug/m3 0 60 0 60Birmingham(More sulfate massand OCM)2002 2003 2004 2005(More OCM)(Less nitrate, moresulfate mass and OCM)(More sulfate mass, less nitrate,more OCM)2 3 4 5 6 7 8 9 10 11 12Riverside-San Bernardino,CA site= 060658001 (2005)2 3 4 5 6 7 8 9 10 11 12

PM2.5 and Components, ug/m3 0 60Rubidoux, CA (2005)RCFMSANDWICHFRM PM2.5 massLess nitrate massMore sulfate and carbonGray line shows {OCMmb - OCM14}Chem Sulfate_mass Nitrate_mass ECOCMmb Crustal PassiveOver-estimates FRM massBirmingham,AL site= 010732003 (2005)0.05.010152025303540455055601 2 3 4 5 6 7 8 9 10 11 12Grayline shows{OCMmb - OCM14}Chem Sulfate_mass Nitrate_mass ECOCMmb Crustal Passive1 2 3 4 5 6 7 8 9 10 11 12RCFMSANDWICHFRM PM2.5 mass

PM2.5 and Components, ug/m3 0 60Less nitrate massMore sulfate and carbonBirmingham, AL (2005)Under-estimates FRM massHow to Use SANDWICH for QC• Comparisons of Constructed Fine Mass withmeasured FRM mass– Using reduced nitrate and hydrated sulfateInstead of CFM=[SO4]+[NO3]+[NH4]+ [TCM14]+[Cr]Use CFM=[SO4]+[NO3r]+[NH4]+[H2O] [TCM14]+[Cr]• Examine TCMmb vs. [k*(OC-b)+EC]– Negative numbers and large deviations can beinformative.– Three examples• Use time series and scatter plots• Preliminary QC findings are presentedHuntington-Ashland,WV-KY-OHKentucky 210190017 SASS 2005PLOT tcm sulfate nitratecr tcm14 mf2

PM2.5 and chemical component mass, ug/m3-10010203040date01JAN05 01MAR05 01MAY05 01JUL05 01SEP05 01NOV05 01JAN06

TCMmb, ug/m3-100102030405060tcm14-10 0 10 20 30 40 50 60FRM PM2.5=4.3(Too Low!)SO4=5.9TCM1.4= 3.8 ug/m3TCMmb= -6.9 ug/m3PM2.5SO4Ashland KY, 2002-05TCMmb vs TCM1.4TCM14=1.4(OC-1.5)+ECGreenville-Spartanburg-Anderson,SCSouth Carolina450450009SASS2003PLOT tcm sulfate nitratecr tcm14 mf2

PM2.5 and chemical component mass, ug/m301020304050date01JAN03 01MAR03 01MAY03 01JUL03 01SEP03 01NOV03 01JAN04

TCMmb, ug/m3-100102030405060tcm14-10 0 10 20 30 40 50 60PM2.5=40.1 ug/m3TCMmb= 39.2 ug/m3SO4=0.1 ug/m3Greenville SC 20032002-05Seattle-Bellevue-Everett,WA Washington530330024 RAAS 2002PLOT tcm sulfate nitratecr tcm14 mf2

PM2.5 and chemical component mass, ug/m3-10010203040date01JAN02 01MAR02 01MAY02 01JUL02 01SEP02 01NOV02 01JAN03TCMmb=25.1TCM1.4=8.9Seattle,WA 2002PM2.5= 29.1(Mar3)TCMmbTCM1.4

TCMmb, ug/m3-100102030405060tcm14-10 0 10 20 30 40 50 602002-05TCM14=1.4(OC-1.3)+ECSeattle-Bellevue-Everett,WA Washington530330024 RAAS 2004PLOT tcm sulfate nitratecr tcm14 mf2

PM2.5 and chemical component mass, ug/m301020304050date01JAN04 01MAR04 01MAY04 01JUL04 01SEP04 01NOV04 01JAN05TCMmbTCM1.4Seattle,WA 2004PM2.5Measurement Program Implications:TCM can be estimatedfrom PM2.5, sulfate and nitrateSeattle-Bellevue-Everett,WA Washington 530330024 RAASPLOT tcm tcm14 TCMplus TCMminus

TCMmb, ug/m3-100102030405060tcm14-10 0 10 20 30 40 50 60Seattle-Bellevue-Everett,WA Washington 530330057 RAASPLOT tcm tcm14 TCMplus TCMminus

TCMmb, ug/m3-100102030405060tcm14-10 0 10 20 30 40 50 60Seattle-Bellevue-Everett,WA Washington 530330080 MASSPLOT tcm tcm14 TCMplus TCMminus

TCMmb, ug/m3-100102030405060tcm14-10 0 10 20 30 40 50 60TCMmbvs TCM1.4for 3 sites in Seattle (2002-05)Site 024 RAAS Site 057 RAASSite 080 MASS MASS sampler appears to require differentcombination of “k” and “b” to attainconsistency between TCMmb and k*(OC-b)Higher “k” =1.8 more consistent withwoodsmoke aerosolÆsuggests that SASS sampler may retainadd’l artifact in proportion to particle OC (thisis offset by “k=1.4”)See TCM poster (for further discussion)TCM14=1.4(OC-0.3)+ECTCM14=1.4(OC-1.3)+EC TCM14=1.4(OC-1.3)+ECSANDWICH data are now available on Air Explorerhttp://www.epa.gov/airexplorer/See Mark Schmidt’s Demo, Wednesday 3:30pmA Few Summary Points• Adjustments to STN speciationmeasurements are needed to representFRM PM2.5mass• SANDWICH estimates composition asmight have been measured by the FRM• TCMmb– helps evaluate C fudge factors (k & b) andvalidate C measurements– Use it to estimate TCM without measured CQuestions?Now or at Tomorrow's Poster SessionI hear they will be serving Frank Sandwiches!Summary and Next StepsInferred carbon by mass balance(TCMmb, using SANDWICH)• Directly accounts for• Adsorbed organic gases and carbon-particle water (positive artifacts)• Volatilized OCand other carbonaceous particlesnot retained on Teflon (negativeartifacts);• Total FRM mass associated with carbon.• Eliminates need for blank corrections or site/season-specific multipliers to account for noncarbon elements associated with measured organic or elemental carbon.• Can be used to corroborate measurement derived carbon mass and visa versa.Comparison of TCMmbwith k*(OC-b)+EC• The correct combination of “k” and “b” is critical for calculating TCM from measurementdata.• With STN’s Met One (SASS) and Anderson (RAAS) data in urban samplingenvironments, TCMmbgenerally agrees best with k=1.4 and year specific blank corrections.Assuming that k=1.8 would be more appropriate for a mixed urban-regional aerosol, thenhigher blank correction (b) would be needed tomaintain mass balance. This suggests thatbackup filters behind Teflon might record higher values than quartz field blanks .• For sites with the URG MASS sampler, higher “k” appears to be needed. This isconsistent with published values. Data from these higher flow rate samplers require smallerblank correction & are more sensitive to “k” for calculating mass.Next Steps• For national consistency in ambient carbonmonitoring, EPA is switching the STN carbonprotocol to the IMPROVE method. STN’s newIMPROVE like samplers (22 Lpm flow rate)to be phased in over three years will also likely have less carbon samplingartifact than currentSTN data from SASS and RAAS samplers.•EPA has funded DRI to recommend procedures to estimate sampling artifact for the newurban samplers (using backupfilters) and to develop appropriate factors for estimatingIM W N ot in a M SA site= 550270007 SA SSPLOT tcm tcm14 tcmtcm14 tcm14_new tcm14_newec tcm18_new tcm18_newtcm012345time2002 2003 2004 2005 2006Trends in Carbonaceous PM2.5using Measured STN Carbon and “SANDWICH”Neil FrankOffice of Air Quality Planning and Standards, USEPA Research Triangle ParkNC 27711BackgroundCarbonaceous mass is one of the largest PM2.5chemicalcomponents, but is the most challenging to estimate. The typicalmethod to calculate total carbonaceous mass (TCM) involvescorrecting measured organic carbon (OC) for positive sampling artifact(blank correction), multiplying the result by a simple factor (e.g. 1.4) toaccount for oxygen, hydrogen and other elements in ambient carboncompounds and then adding measured EC. Neither of these OCadjustments can be accurately estimated from existing STNmeasurements or data. The STN program does not currently utilizebackup filters; therefore, field and trip blanks together with samplerflow rate permit at best a crude estimate of the OC artifact. EPA hasused a single network wide value derived from 2001-02 STN data. Forthe multiplier to create OCM, generic values are usually taken fromthe literature; but in reality vary with the mix of particulate OCcompounds and could therefore vary by location, season and evenday. To estimate FRM PM2.5(retained on Teflon with typically higherface velocity), different adjustments are probably needed. This posterprovides estimates of TCM by material balance with FRM mass andits non-C components. These “SANDWICH” results are compared tomeasurement derived TCM. Trends in STN blank values are alsoconsidered.Nov 1, 2006 Email:frank.neil@epa.govSources of error in TCM =k*(OC-b)+EC•Analytical uncertainty•Blank correctionto account for positive sampling artifact•With STN field blanks, no dynamic back up filters.•Differs among urban STN speciation samplers•Conversion of OC to OC mass (OCM)(+33%)•1.4 < k < 1.8 ("typical" urban)ref: Turpin (2001)•2.0 < k < 2.4 ("typical" rural)•Weighted average needed for mixed urban/regional aerosol•Turpin's revised estimates based on limited speciation data•OC- EC split(and unaccounted mass for “EC”)•Retainedcarbon mass on FRM Teflon vs STN quartz•Less volatile OC may be retained on Teflon **•Water [= ~10-24% of PM2.5water]** Volatile OC can vary by location and sampling day. Retained particulate OCdepends on filter face velocity."SANDWICH“ ApproachQSulfate, Adjusted Nitrate, Derived Water, Inferred Carbonaceousmass Hybrid material balance approach•TCMmb= PM2.5- { [SO4] + [NO3FRM] +[NH4] +[water]+ [Crustal] + [FRM blank]}•OCMmb= [TCMmb]– [EC]•Water and reduced FRM NO3 are estimated by models.•Other PM2.5constituents eg. salt, could also be considered•TCMmbexplicitly accounts for positive and negative samplingartifacts, OC hydration,and mass multipliers for carbonaceousmaterial retained on FRM Teflon.•TCMmbis upper estimate for TCM and is subject to error in non-Ccomponents.Reference:Frank, N. Retained Nitrate, Hydrated Sulfates, and Carbonaceous Mass in FederalReference Method Fine Particulate Matter for Six Eastern U.S. Cities,J. Air & Waste Manage. Assoc.56: 500–511 (2006)Example Site-Specific TCM Trends, 2002-2005Monthly Average TCM(TCMmb nicely tracks k*(OC-b))ug C/ filter ug C/m3MetOne (SASS) 9.6 14.8 1.5Anderson (RAAS) 10.4 13.5 1.3R&P 2300 14.4 16.1 1.1URG (MASS) 24 7.7 0.3NetworkAverageTotalCarbon on STN BlankFilters*24-hrsampleVolume(m3)STN sampler*Network-wide valuesfrom 2001-02 data asreported by RTI andpreviously used byEPA to adjust OCsam pler_type=A nderson RA S S

filter blank, total carbon (expressed as ug/m3)0123456time2001 2002 2003 2004 2005 2006sampler_type=METONE SASS

filter blank, total carbon (expressed as ug/m3)0123456time2000 2001 2002 2003 2004 2005 2006sampler_type=URG MAAS

filter blank, total carbon (expressed as ug/m3)0123456time2000 2001 2002 2003 2004 2005 2006Samplersites20012002200320042005Anderson RASS22 1.19 1.50 1.03 0.90 0.99METONE SASS 140 1.53 1.63 1.21 1.01 1.09URG MAAS 5 0.29 0.34 0.25 0.26 0.43Since 2002, STN field and trip blanksvalues forSASSand RAAS samplershave decreased 33% and values forMASS samplers have increased 25%.Reasons for the change are not known atthis timeSite Specific Differences in STN Field BlanksNo apparent consistent difference in TC field blank values among sites.Mostsite average values for Met-One SASS (2004-5) range from 0.75-1.5 ug/m3 as shown.. .tc_conc (ug/m3): <=0.75 >0.75 to 1 >1 to 1.25 >1.25-1.5>1.5. .tc_conc (ug/m 3): <=0.75 >0.75 to 1 >1 to 1.25 >1.25-1.5>1.5Regional Trends in TCM, 2002-2005S EPLOT tcm tcm14 tcmtcm14 tcm14_new tcm14_newtcm23456789101112time2002 2003 2004 2005 2006N EPLOT tcm tcm14 tcmtcm14 tcm14_new tcm14_newtcm0123456789101112tim e2002 2003 2004 2005 2006IMWPLOT tcm tcm14 tcmtcm14 tcm14_new tcm14_newtcm012345678910tim e2002 2003 2004 2005 2006Regional average values of TCM agree wellwith k*(OC-b) using k=1.4 and year specificb values. For some US Regions and sites, theold b values seem better. The successfulchoice of k to represent retained FRM mass(on Teflon) appears to depend on the selectedvalue for “b”. The value for “k” may alsodepend on the particular thermal analyticaltechnique and OC-EC split. Distribution ofsite-quarterly averages of TCM are shown.Similarly, no apparent pattern was observed among TC field blank values by calendar quarter(preliminary analysis). Due to large within-site and between year variability and few samples, multiyear network-wide values seem reasonable to use.N W S eattle-B ellevue-Everett,W A site= 530330080 M A S SPLOT tcm tcm14 tcmtcm14 tcm14_new tcm14_newec tcm18_new tcm18_newtcm0123456789time2002 2003 2004 2005 2006NE W as hington,D C-M D-V A -W V site= 110010043 R AA SPLOT tcm tcm14 tcmtcm14 tcm14_new tcm14_newec tcm18_new tcm18_newtcm012345678910tim e2002 2003 2004 2005 2006IM W Ham ilton-M iddletow n,O H site= 390171004 SA S SPLOT tcm tcm14 tcmtcm14 tcm14_new tcm14_newec tcm18_new tcm18_newtcm012345678tim e2002 2003 2004 2005 2006S E Birmingham,AL site= 010730023 S A SSPLOT tcm tcm14 tcmtcm14 tcm14_new tcm14_newec tcm18_new tcm18_newtcm12345678910111213tim e2002 2003 2004 2005 2006IM W C hicago,IL site= 170310076 M A SSPLOT tcm tcm14 tcmtcm14 tcm14_new tcm14_newec tcm18_new tcm18_newtcm012345678910tim e2002 2003 2004 2005 2006IM W Ham ilton-M iddletown,OH site= 390171004 S ASSPLOT tcm tcm14 tcm14_newtcm tcm14 tcm14_newec tcm18_new tcm18_newtcm0123456789time2002 2003 2004 2005 2006IM W Not in a M SA site= 550270007 SASSPLO T tcm tcm14 tcm14_newtcm tcm14 tcm14_newec tcm18_new tcm18_newtcm012345678time2002 2003 2004 2005 2006Chicago, ILHigher “k” needed for FRM balance (resulting from local highway work whichstarted in 2004).20042005IM W Chicago,IL site= 170310076 M ASSPLOT tcm tcm14 tcm14_newtcm tcm14 tcm14_newec tcm18_new tcm18_newtcm012345678910111213time2002 2003 2004 2005 2006Local emission increase orunderestimate of NO3?Cincinnati, OHTCMmb agrees with k=1.4 and new blanksMayville, WIRural OC needs k >1.8, esp in 2004Seattle, WATCMmb agrees with k=1.8 (MASS sampler & woodsmoke influence)Birmingham, ALTCMmb matches trends with k=1.4 and new blanksWashington, DCTCMmb matches trends with k=1.4 and old blanks

TCM, ug/m3Is all extra mass really OCM?TCMmbTCM1.4(old b)TCM1.4(new b)

TCM, ug/m3NE W ashington,DC-M D-VA-W V site= 110010043 R AASPLOT tcm tcm14 tcm14_newtcm tcm14 tcm14_newec tcm18_new tcm18_newtcm01234567891011121314time2002 2003 2004 2005 2006Mayville, WIHigher “k” or lower “b” is needed for mass balanceDuring the winter season (woodsmoke?)Cincinnati, OH Consistent relationship with k=1.4 and new “b”Chicago, ILWashington, DCECTCMmbTCM1.8(new b)Average Total Carbon Blank by year, ug/m3Industrial MidWest, 11 sitesNortheast, 10 sitesSoutheast, 11 sitesTCMmbTCM1.4(old blank)TCM1.4(new blank)TCM1.4(old b)TCM1.4(new b)TCMmbTCMmb is comparable to TCM withk=1.4 and the old or new b.Note: Winter differences between TCMmband TCM1.8could represent unmeasured NO3 by MASS sampling systemTCMmbTCMmbTrends in STN TC field blanks