1. 2/5/2016 Anthropogenic Impacts on Organic Aerosol during the 2007 BAQS-Met Field Study Craig Stroud, Michael Moran, Paul Makar, Junhua Zhang, Wanmin Gong, Sunling Gong, Jeff Brook Air Quality Research Division, Environment Canada Jonathan Abbatt, Jay Slowik, Steve Sjosted University of Toronto, Department of Chemistry CMAS, 2009

2. 2/5/2016 Outline Motivation AURAMS description Model evaluation for STN sites Model evaluation for BAQS-Met supersites “Zero out” sensitivity runs OA/CO ratios Conclusions

3. 2/5/2016 Motivation Sources of organic aerosol (OA) are poorly understood (primary vs. secondary, anthropogenic vs. biogenic). Air quality models do not reproduce the high levels of OA observed in polluted environments. Recent measurements suggest rapid growth of oxygenated OA occurs in urban plumes (e.g. NEAQS,MILAGRO). SVOCs and IVOCs are postulated to be important precursors to this rapid production.

4. 2/5/2016 BAQS-Met Study (summer 2007) Border Air Quality and Meteorology Study provided an opportunity to examine SOA production in the Detroit/Windsor air shed and plume.

5. 2/5/2016 A Unified Regional Air-Quality Modelling System (AURAMS) Population data Econometric data Land-use data Geophysical data National Emission Inventories (Cdn, U.S.) Meteorological observations (OA) PM2.5, PM10, etc., Concentration Fields Regional PM Model (CHRONOS+ADOM+CAM+new) Advection/diffusion (of 29 gaseous and 8x12 aerosol tracers), emission (including gaseous precursors and size-segregated and chemically-resolved PM), dry deposition of gaseous tracer, coupled gaseous, aqueous-phase, aerosol/heterogeneous chemistry, secondary organic aerosol formation, aerosol microphysics (nucleation, condensation/evaporation, coagulation, CCN activation), size-dependent scavenging/wet deposition, size-dependent dry deposition of aerosols, gravitational settling/sedimentation. Regional PM Model (CHRONOS+ADOM+CAM+new) Advection/diffusion (of 29 gaseous and 8x12 aerosol tracers), emission (including gaseous precursors and size-segregated and chemically-resolved PM), dry deposition of gaseous tracer, coupled gaseous, aqueous-phase, aerosol/heterogeneous chemistry, secondary organic aerosol formation, aerosol microphysics (nucleation, condensation/evaporation, coagulation, CCN activation), size-dependent scavenging/wet deposition, size-dependent dry deposition of aerosols, gravitational settling/sedimentation. SMOKE point mobile area biogenics SMOKE point mobile area biogenics GEM/GEM-LAM (prognostic meteorological model) GEM/GEM-LAM (prognostic meteorological model)

6. 2/5/2016 SOA Formation in AURAMS SOA precursors include TOLU, AROM, BENZ, ALKA, ALKE, IVOCs, PINE, ISOP, SESQ. SOA yields for each VOC precursor are calculated as a function of organic aerosol loading and temperature (updated to literature yields as of 2008). IVOC emissions calculated as 1.5x POA emissions (as in Robinson et al., Science, 2007). IVOCs are assumed to react with OH and form SOA in one reaction step (upper limit). POA emissions were modified to represent volatility at grid-scale concentrations (75% went to SOA and 25% remained as POA). This split was calculated using the volatility basis set parameterization (Robinson et al., Science, 2007) at a representative OA grid cell loadings of 10  g/m 3. Assume volatilization and re- condensation is a sub-grid scale process. SOA yields are also calculated depending on the grid-cell VOC/NOx regimes. Incremental increase in SOA mass calculated from yields under high NOx and low NOx conditions; actual incremental increase is calculated from a linear interpolation between limits based on the fraction of RO 2 radicals which react with NOx vs HOx. Algorithm is computationally efficient and can be used in an operational air quality model

7. 2/5/2016 AURAMS Nested Modelling Domains

8. 2/5/2016 STN Comparison “urban sites” N=946 pts June-July 2007 AURAMS V1.4.0 AURAMS V1.4.0 beta Model OA Average3.8±2.44.8±2.7 Data OA Average6.5±2.9 Slope0.32±0.020.49±0.03 Intercept1.1±0.21.7±0.2 Mean Bias-2.7-1.7 RMSE3.83.2 Correlation, R0.500.51 15km resolution ● Improved bias and error

9. 2/5/2016 Differences between AMS OOA at Harrow and Bear Creek SW flow from Detroit to Bear Creek NNW flow from Sarnia to Bear Creek NW flow from Detroit to Harrow

10. 2/5/2016 AURAMS SOA at Harrow and Bear Creek AURAMS predicts multiple peaks at Bear Creek on July 4 and a broad peak on July 5 AURAMS misses the differences between the sites at Harrow peak ● AURAMS generally captures transition from a clean air mass to a regionally polluted air mass over the 5-day period

11. 2/5/2016 Map of AURAMS SOA Predictions on July 4, 2007 (13-17Z) Flow from Detroit/Windsor goes out over Lake St. Clair where SOA production continues before arriving at Bear Creek

12. 2/5/2016 Zero VOC Precursor Pathways to SOA at Bear Creek ● IVOC, PINE and AROM are all important precursors for July 4 event ● Regionally polluted air mass on July 7 was biogenic in origin

13. 2/5/2016 July 4 Precursor Contributions to SOA: Blue is Biogenic and Red is Anthropogenic ● Background air from the mid-west U.S. ● Values close to unity represent anthropogenic-dominated SOA (e.g. Toronto) 70-80% Anthro. SOA

14. 2/5/2016 AURAMS SOA at Harrow and Bear Creek AURAMS predicts multiple peaks at Bear Creek on July 4 and a broad peak on July 5 AURAMS misses the differences between the sites at Harrow peak ● AURAMS generally captures transition from a clean air mass to a regionally polluted air mass over the 5-day period

15. 2/5/2016 Maps for AURAMS SOA on July 6 (18-21Z) ● In the model, the Detroit/Windsor plume goes east of Harrow due to influence of the lake breeze. Difficulty in capturing urban plumes with model. High background entering domain

16. 2/5/2016 July 6: Precursor VOC Contributions: Blue is Biogenic and Red is Anthropogenic Background air was biogenic Mixed sources in study area

17. 2/5/2016 OA/CO ratio as a measure of extent of urban VOC processing to form SOA (de Gouw et al., 2008) Empirical parameterization to fit NEAQ 2002 data for urban plume aging of ΔOA/ Δ CO ratios Max ~0.07 ug/m 3 /ppbv after several days of processing ICARTT data de Gouw 2005 de Gouw 2008

18. 2/5/2016 SOA/CO ratio as a measure of extent of urban VOC processing to form SOA (de Gouw et al., 2008) Harrow average age=17 hr (from TOLU/BENZ) Eq. (5) Δt=17 hr primary ● Large spread to the model correlation

19. 2/5/2016 Harrow data shows higher AMS OM than predicted by the de Gouw parameterization Harrow average age=17 hr (from TOLU/BENZ) Eq. (5) Δt=17 hr primary Harrow average age=14 hr (from TOLU/BENZ) Eq. (5) Δt=14 hr AURAMS AMS Some large slopes not consistent with de Gouw parameterization

20. 2/5/2016 Harrow background concentrations change due to biogenic regional event AMS OM and CO correlation shows periods with different slopes representing: - biogenic SOA production (steepest slopes) are consistent with Slowik et al (2009) - anthropogenic SOA production (intermediate slopes) - primary emission (lowest slope) biogenic slopes primary slope

21. 2/5/2016 July 4: max OA/CO ratios in modelled urban plume at Bear Creek near 0.07 ug/m 3 /ppbv (13-23Z) ● CO distribution shows a max for areas of local emissions (e.g. Detroit, Sarnia). ● SOA distribution is complex with urban-scale to regional-scale production (<1 day) ● OA/CO is a measure of SOA production as the urban air mass ages ● Slope of 0.07 ug/m 3 /ppbv (70 ug/m 3 /ppmv) is consistent with de Gouw parameterization Cleaner background

22. 2/5/2016 Conclusions urban SOA enhancement in Detroit/Windsor plume measured at Bear Creek was ΔSOA~10  g/m 3 on July 4 (relative to Harrow) Model captured urban plume SOA at Bear Creek; IVOCs, PINE and AROM were all important VOC precursors. Model OA/CO ratios consistent with de Gouw parameterization on July 4. IVOC contribution is an upper limit estimate. Model missed urban plume on July 6 at Harrow due to influence/complexity of lake breeze circulation Measured OA/CO ratios at Harrow were much higher than the de Gouw parameterization on July 6 suggesting Harrow was influenced by mix of biogenic and anthropogenic sources

23. 2/5/2016 Thank you for your attention! craig.stroud@ec.gc.ca

24. 2/5/2016 Impact of Model Resolution at Bear Creek ● 15km grid spacing captures background levels well, but sometimes misses peak max. 42km underestimates the regional build-up of SOA on July 6-7