1. www.epa.gov/airscience AIR CLIMATE & ENERGY RESEARCH PROGRAM B U I L D I N G A S C I E N T I F I C F O U N D A T I O N F O R S O U N D E N V I R O N M E N T A L D E C I S I O N S U.S. Environmental Protection Agency Office of Research and Development Ultrafine particle measurement and related EPA research studies Presentation to 2013 MARAMA Monitoring Committee, December 11 Gayle Hagler and Sue Kimbrough EPA Office of Research and Development

2. 2 U.S. Environmental Protection Agency Office of Research and Development UFPs are an integral measurement for many EPA research studies Emissions characterization - e.g., how do driving conditions affect UFP emissions? Near-source air quality and mitigation – e.g., how do roadside barriers affect near- road UFP concentrations? Exposure – e.g., what sources contribute to personal exposure? Health – e.g., what health effects are related to UFPs? Seinfeld and Pandis, 2 nd Ed., 2006 Mass Surface Area Number

3. 3 U.S. Environmental Protection Agency Office of Research and Development As a highly dynamic pollutant, measurement approach is important Production: nucleation, condensation, coagulation Emissions Condensational growth Zhang et al., 2004 Dilution: Factor of ~10,000 from tailpipe to near- road areas

4. 4 U.S. Environmental Protection Agency Office of Research and Development As a highly dynamic pollutant, measurement approach is important Significant variability in the urban environment: factor of ~5 difference from “urban background” to “roadside” Morawska et al., 2008

5. 5 U.S. Environmental Protection Agency Office of Research and Development As a highly dynamic pollutant, measurement approach is important Several factors affect measurement strategy: Size detection: Do you care to know the size distribution or maximum particle size? What is the minimum acceptable size? Count/particle detection: What is the acceptable upper/lower detection limit for your measurement environment Resolution: what time resolution is acceptable? What about spatial resolution? Seinfeld and Pandis, 2 nd Ed., 2006 Mass Surface Area Number e.g., Atmospheric particle size distribution

6. 6 U.S. Environmental Protection Agency Office of Research and Development One way to think about UFP measurement technologies Measurement speed Slower (min) Fast (s) Sizing No bins Many bins eUFP sizer (Chen et al., in development) Other factors: Portability Cost Sensitivity (LOD) Data logging

7. 7 U.S. Environmental Protection Agency Office of Research and Development 7 P P P P P 50 m 0 N P-Trak Open path samples: NO, CO A B SMPS + CPC (UFPs) Aethelometer (BC) Jet-REMPI (air toxics) CEMS (NOx, CO) GRIMM (PM 2.5, PM 10 ) Wind speed/direction CEMS (NOx, CO) Wind speed/direction B A I-440 Near-Road Site in Raleigh, NC Near-source / personal exposure push towards greater spatial coverage of data

8. 8 U.S. Environmental Protection Agency Office of Research and Development 8 Concentration gradient: e.g. Monday rush hour (Hagler et al., 2008)  Gradient strongest during morning rush hour – UFPs elevated even at 300 m downwind of road. Near-source / personal exposure push towards greater spatial coverage of data

9. 9 U.S. Environmental Protection Agency Office of Research and Development 9 UFP concentration gradient: Up to 100 m, linearly approximate ~5-12% (avg. 8.5%) drop per 10 m Downwind morning rush hr avg (7 days) Normalized results for this and other near-road studies Near-source / personal exposure push towards greater spatial coverage of data

10. 10 U.S. Environmental Protection Agency Office of Research and Development 10 Near-source / personal exposure push towards greater spatial coverage of data Ideal: Data quality and utility DurationSpatial coverage Cost high low Mobile monitoring: Data quality and utility DurationSpatial coverage Cost high low Hybrid stationary monitoring + modeling: Data quality and utility DurationSpatial coverage Cost high low Lower cost, wireless air monitoring stations Data quality and utility DurationSpatial coverage Cost high low ?

11. 11 U.S. Environmental Protection Agency Office of Research and Development Mobile monitoring – time resolution and portability are key Measurement speed Slower (min) Fast (s) Sizing No bins Many bins eUFP sizer (Chen et al., in development) Other factors: Portability Cost Sensitivity (LOD) Data logging Mobile monitoring (fast data collection priority)

12. 12 U.S. Environmental Protection Agency Office of Research and Development Mobile monitoring: maximum range and time resolution key Engine Exhaust Particle Sizer on EPA’s GMAP platform: Sizes using sequential electrometer rings Counts via electrometer Time resolution: Very high (s) Size resolution: high (>30 bins) Sensitivity: lower than CPC – upper and lower detection limits Operating complexity: Low (no operating fluid) Cost: High

13. 13 U.S. Environmental Protection Agency Office of Research and Development 13 Sampling and data- processing Mobile monitoring: complex data analysis

14. 14 U.S. Environmental Protection Agency Office of Research and Development Measuring roadside barrier effect on near-road UFPs Field data: Mobile sampling study at three sites in North Carolina Two sites had tree stands One site had a solid brick barrier Mebane Raleigh Chapel Hill 14

15. 15 U.S. Environmental Protection Agency Office of Research and Development Chapel Hill: porous evergreen stand Lower concentrations behind noise barrier (avg. 47% lower traffic-related ultrafine particles) Variable results seen for thin tree stand Hagler, G.S.W., Lin, M-Y., Khlystov, A., Baldauf, R.W., Isakov, V., Faircloth, J., Jackson, L. Roadside vegetative and structural barrier impact on near-road ultrafine particle concentrations under a variety of wind conditions Science of the Total Environment. Measuring roadside barrier effect on near-road UFPs

16. 16 U.S. Environmental Protection Agency Office of Research and Development Long-term UFP monitoring at roadside stations: low-maintenance and longevity key Measurement speed Slower (min) Fast (s) Sizing No bins Many bins eUFP sizer (Chen et al., in development) Other factors: Portability Cost Sensitivity (LOD) Data logging Which are most cost-effective, reliable, and easy to operate?

17. 17 U.S. Environmental Protection Agency Office of Research and Development In the near-source environment Trade-off of cost, complexity, time resolution, size resolution UFP 3031 (TSI, Inc) Time resolution: 15 min Cost: high Size bins: 6 Complexity: low Reliability: High (1 repair in ~4 yrs)

18. 18 U.S. Environmental Protection Agency Office of Research and Development In the near-source environment Trade-off of cost, complexity, time resolution, size resolution EPC 3783 (TSI) or TAPI (Teledyne) Time resolution: seconds to minutes Cost: Moderate Size bins: No sizing Complexity: Low (operating fluid = ultrapure water) Reliability: Moderate (multiple repairs in ~4 yrs)

19. 19 U.S. Environmental Protection Agency Office of Research and Development 19 Intercomparison of instruments Only had a brief opportunity to compare side-by-side, indoor levels in Las Vegas and Detroit Longer-term ambient intercomparison ongoing at a site in Durham, NC. e.g., Las Vegas (#/cm 3 )

20. 20 U.S. Environmental Protection Agency Office of Research and Development 20 Ambient monitoring site on EPA-RTP campus Intercomparison of instruments

21. 21 U.S. Environmental Protection Agency Office of Research and Development 21 1 month of data (March- April, 2012); hourly average Intercomparison of instruments

22. 22 U.S. Environmental Protection Agency Office of Research and Development 22 Intercomparison of instruments 1 month of data (March- April, 2012), hourly average R = 0.992 Mean(Y./X) = 1.46 R = 0.991 Mean(Y./X) = 1.20 R = 0.988 Mean(Y./X) = 1.11 R = 0.994 Mean(Y./X) = 1.06 R = 0.994 Mean(Y./X) = 0.984 R = 0.868 Mean(Y./X) = 3.62

23. 23 U.S. Environmental Protection Agency Office of Research and Development Interesting wildfire event effecting UFP levels – made possible through the size information Las Vegas: Aug 30-Sept 1 23 Kimbrough et al., in review

24. 24 U.S. Environmental Protection Agency Office of Research and Development Intercomparison of EPCs Indoors and outdoor sampling at EPA-RTP facility

25. 25 U.S. Environmental Protection Agency Office of Research and Development Intercomparison of EPCs Example intercomparison time series

26. 26 U.S. Environmental Protection Agency Office of Research and Development Intercomparison of EPCs Indoors and outdoor sampling at EPA-RTP facility 15041601Regression Insidelpms sslope: 1504/1601R2R2 B131310.960.99 B23103 0.960.95 B33603 0.950.99 B inside average0.96.98 Outside B131310.940.99 B23103 0.940.999 B33603 0.930.999 B outside average0.94.999

27. 27 U.S. Environmental Protection Agency Office of Research and Development Emerging techniques: concept of tiered systems Emerging air monitoring systems (informal classification) Group 1: Regulatory or regulatory- equivalent air monitoring stations Cost: 100Ks (in thousands), Data reliability = A+ Group 2: Smaller-footprint monitoring systems for community screening and research studies Cost: 1-10Ks, Data reliability = B+ (target) Group 3: Very small, very low cost systems enabling dense sensor networks, citizen science Cost: 0.1-1Ks, Data reliability = ? existing emerging 27

28. 28 U.S. Environmental Protection Agency Office of Research and Development Emerging new techniques supporting saturation or personal monitoring (EPA has not yet tested) DiSCmini

29. 29 U.S. Environmental Protection Agency Office of Research and Development Recent EPA grant recipient: Da-Ren Chen (Virginia Commonwealth University) “Development of Cost- effective, Compact Electrical Ultrafine Particle (eUFP) Sizers and Wireless eUFP Sensor Network” (Chen et al., 2013) Emerging new techniques supporting saturation or personal monitoring (EPA has not yet tested)

30. 30 U.S. Environmental Protection Agency Office of Research and Development Acknowledgements EPA Office of Research and Development staff: Rich Snow, Bill Squier, Bill Mitchell, Richard Shores, Robert Wright, EPA Air, Climate, and Energy program TSI support of UFP3031 and EPC3783