Optical Measurements of PM2.5 Collected on Teflon Filters to Estimate Elemental Carbon. Neil Frank ( 尼尔 弗兰克 ) Joann Rice Joe Tikvart US EPA / OAQPS

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1 Optical Measurements of PM. Collected on Teflon Filters to Estimate Elemental Carbon Neil Frank ( 尼尔 弗兰克 ) Joann Rice Joe Tikvart US EPA / OAQPS For Presentation at A&WMA Conference, Xi an China May,

2 Findings Many Benefits of Optical Measurements Inexpensive utilization of archived PM. filters Can predict EC by measuring the darkness of the filters Better and more consistent relationship with IMPROVE protocol carbon method Opportunity to cost effectively expand existing thermal optical carbon monitoring networks to support Health researchers Climate-related purposes Emission and modeling efforts QA

3 Background Optical measurements of filters used for decades The U.S. IMPROVE Network has been doing optical measurements for a long time (for QC of thermal EC), using HIPS British Smoke with Reflectometer widely used in Europe Why is EPA now interested? EPA transitioned the OC-EC protocol from the NIOSH-type method [with.7 LPM & 7mm quartz filters] to IMPROVE protocol [with. LPM & mm quartz] Health researchers expressed concern about possible discontinuity in EPA s s EC time series New EC ~.*Old EC (network median) Mostly May-June data

4 Optical Measurements highly correlate with EC Smoke Stain Reflectometer recently used with Teflon Filters Cyrys et. al., Site-specific calibration with EC is necessary. Thurston et al. South Bronx Environmental Health Policy Study (7) Sometimes EC calibrated optical measurements are reported as BC Thurston (summer-time Cyrys

5 Other Optical Measurements of PM. Filters Using the Tobias Densitometer Comparison filter carbon measurements at the Fresno Supersite John G. Watson and Judith C. Chow () Linear up to ug/m EC EC=~ (Filter absorption) / Tobias Densitometer (white light source with a peak intensity at nm)

6 Optical measurements of PM. teflon filters can increase existing EC spatial resolution Elizabeth NJ S. Bronx NY NYC area and, provide daily EC at PM. sites which sample every day! PM. sites for potential expansion of EC measurements

7 NYC Heath Department BC Study using portable PM. samplers Source: The New York City Community Air Survey, Results from Winter Monitoring 8-9 7

8 Study of Magee (OT) Transmissometer Teflon filters from 7 CSN sites (.7 LPM) Representing different emission influences sites ( )which switched TOA protocol in May 7 To permit comparisons to new EC_TOR and old EC_CSN in day filters were selected per site from 7 sampling Subset of sites with collocated FRM filters (.7 LPM) Tacoma Gary Bronx Sacramento Elizabeth, NJ Atlanta Birmingham 8

9 CSN Teflon Filters This is a non-destructive procedure - can be used on archived PM. filters 9

10 Magee Transmissometer Study EPA s NIOSH-type EC vs. Optical Measurements (7 sites) EC, ug/m (Old CSN Method) EC r =.89 (n=) Non-Wood Smoke sites ATN = * ln ( Io / I) (precision = ± ) Wood Smoke sites (Sacramento and Tacoma) - 7 Optical Measurement (Attenuation ATN, IR units, IR channel) The OT measures at wave lengths (7 and 88nm). I only present results for the infra-red channel.

11 ec_old 7 Optical attenuation vs. EPA s NIOSH-type EC The wood smoke areas are different! (more absorption per measured ug/m EC) SITE=7 SITE=7 SITE=89 ec_old ec_old 7 7 Sacramento EC, Old (ug/m) ATN, IR ATN, IR ATN, IR OPTICAL, ATN Regression Equation: Regression Equation: ec_old = *ATN_IR ec_old = *ATN_IR Regression Equation: Similar ec_old =.77 site-specific +.7*ATN_IR relationships in East SITE=889 SITE=9 AIRS Site Code=9 ec_old ec_old ec_old 7 7 Strong correlations mostly >.9 Birmingham Tacoma Atlanta Regression Equation: ec_old =.7 +.*ATN_IR ATN, IR Gary Regression Equation: ec_old = *ATN_IR ATN, IR Elizabeth ATN IR

12 More Consistent Filter Absorption Relationship among sites with IMPROVE EC Elemental Carbon, ug/m Normalized Filter Absorption, Fabs Fabs=(A/V) x ATN, where A= PM. Filter Area (m ) and V=sample volume (m ) (A/V)=. for EPA FRM - Fabs=(A/V) x ATN Fabs PM. FRM sites Tacoma, WA (wood smoke) Gary, IN Bronx, NY

13 ... PM. Filter Absorption (Fabs) is much more precise than thermal EC field blanks Fabs =.±. EC, ug/m Fabs ATN IR.. IMPROVE EC = ~ ATN/ = ~ Fabs /... Filter Absorption Coefficient (σ) - Tacoma Bronx Gary Fabs=(A/V) ABS_IR x ATN Possible non-linear saturation effect at higher EC concentrations, say > ug/m

14 Elemental Carbon, ug/m EC-Filter absorption relationship Varies with wavelength 88 nm EC= ~ Fabs/ σ = ~- m g - Fresno at nm (σ = ~) 7 nm EC= ~Fabs/8 σ = ~8 m g Fabs No apparent 7 nm absorption enhancement at wood smoke location

15 PM. Filter Absorption Coefficients using Magee Transmissometer (at 88nm) Aerosol and carbon-protocol specific differences Carbon Protocol (Quartz filters) IMPROVE_A (TOR). LPM sampler mm filter EPA NIOSH-Type (TOT).7 LPM sampler 7mm filter CSN / FRM Networks (Teflon Filters) Wood Smoke - m g - - m g - Non-Wood Smoke - m g - - m g - Old EPA NIOSH-type EC may not include some Wood smoke LAC Literature reports coefficients ranging from to > m/g-

16 Estimated EC using FRM Filter Absorption with single nation-wide equation, EC=Fabs/ Gary, IN Predicted EC using Attenuation of FRM filters and single national equation AIRS Site Code=889 Old EC New (IMPROVE)EC These graphs show that predicted EC with single equation tracks the IMPROVE measurements EC, ug/m Date Fabs/ can also help identify potential outliers in measured EC with old EPA protocol. EC_ratio = predicted IMPROVE protocol EC / measured EC Bronx, NY Predicted EC using Attenuation of FRM filters and single national equation AIRS Site Code= Tacoma, WA Predicted EC using Attenuation of FRM filters and single national equation AIRS Site Code=9 EC, ug/m EC, ug/m Date EC_ratio = predicted IMPROVE protocol EC / measured EC Date EC_ratio = predicted IMPROVE protocol EC / measured EC

17 Summary EC can be estimated without speciation sampling Calibrated EC derived from PM. Teflon filter absorption can depend on Optical wavelength Thermal optical and quartz filter C sampling protocols Aerosol composition Optical Measurements of PM. filters can Help QA thermal EC Establish higher EC spatial resolution Produce daily EC when PM. filters are available Provide opportunity to compare world-wide wide EC 7

18 总结 EC 可以估计, 不用物种形成采样 从 PM. 聚四氟乙烯过滤器吸收获得的被校准的 EC 可能依靠 光学波长 热量光学和石英过滤器碳采样协议 湿剂构成 PM. 过滤器的光学测量能 帮助质量保证热量 EC 测量 建立更高的 EC 空间分辨率 当 PM. 过滤器是可利用的时, 导致每日 EC 提供机会比较 光引人入胜的湿剂,, 全世界 Translated using Yahoo Babel Fish 8