Evolving Understanding of Pollutant Transport from Asia to North America Richard (Tony) VanCuren Research Division, California Air Resources Board Department of Applied Science, UCD WRAP

TransPacific Transport to North America: The contradiction of gas and aerosol data MOPITT CO 2000 TOMS Aerosol April15-May61998

The April 1998 Asian Dust Storms: a Natural Experiment Image after Husar, R. B. et al., J. Geophys. Res. 106: 18,317 – 18,330, 2000.

Asian Dust is Ubiquitous Around the Northeastern Pacific VanCuren & Cahill, 2002

Comparative Frequencies of Asian Dust Across North America

Asian Aerosol Chemistry at Western Cordillera Sampling Sites Two Asian components: Primary - Dust & combustion Mass correlation 0.87 (<2.5um) Secondary - Aged biomass smoke Mass correlation 0.17 (<2.5um) Mean Asian aerosol fraction: 75% of Fines (<2.5  m dia.) 60% of Total (<10  m dia.) Principal Components from: 1234 IMPROVE 24-hr filters March - October Crater Lake, OR and Mt. Lassen, CA VanCuren, 2003

Dusty Asian Plume Siberian(?) Biomass Smoke Aerosol Composition March – October (Transport Season) Crater Lake / Mt. Lassen COARSE 2.9 ± 1.9  g/m 3 FINE 3.8 ± 2.0  g/m3 CARBONACEOUS SO4= SOILNO3- OTHER Mean Asian fraction: 75% of Fines (<2.5  m) 60% of Total (<10  m)

ITCT-2K2 Aerosol Sampling Sites

Trinidad Head Aerosol Composition Modes Marine mode –Medium to coarse sea salt (2-6  g/m 3 ) –Weak sulfur (.2-.4  g/m 3 ) Continental mode –Coarse Si, Fe, Ca, Al, Na, K –Strong fine sulfur (1-2  g/m 3 ) –Mineral & reacted Na –Weak sea salt (.2-.6  g/m 3 ) MARINE 5/19 CONTINENTAL 4/22

Back Trajectory 4/23/02 - Trinidad Head

Trinidad Head, Trinity Alps, & Mauna Loa Continental Aerosols’ Al - Elemental Ratios Trinidad Head, Trinity Alps, & Mauna Loa Continental Aerosols’ Al - Elemental Ratios (Holmes & Zoller, 1996) Trinidad HeadTrinity Alps

ITCT-2K2 Findings: 1 - Dominant Modes Concordant Montane Aerosol Single dominant aerosol Asian origin confirmed by soil element profiles Concentration varies but continuously present MBL Disconnects Coastal Site from Free Troposphere Sea salt & local combustion – infrequent tropospheric mixing

ITCT-2K2 Findings: 2 - Air Mass Mixing State Soil Mixing Model Air Mass Influence

Diurnal oscillation of sources Coarse - strong local sources and upslope transport Fine - dominated by tropospheric fumigation ITCT-2K2 Findings: 3 - Soil Mixing State

Asian Sources Explain “Anomalous” Regional Aerosol Events 2/24/1996

Regional Aerosol Chemistry: Feb 21 & 24, /24/96 2/21/96

Back-trajectories - 2/24/96 Craters of the Moon Bryce Canyon Grand Canyon

Sample Global Model Results Cameron-Smith, P. et al., (2005), Impact of Long-Range Dust Transport on Northern California in Spring 2002, Internal Report Lawrence Livermore Lab Holzer, M., T. M. Hall, and R. B. Stull (2005), Seasonality and weather-driven variability of transpacific transport, J. Geophys. Res., 110, D23103, doi: /2005JD Park, R. J. et al. (2004), Natural and transboundary pollution influences on sulfate-nitrate-ammonium aerosols in the United States: Implications for policy, J. Geophys. Res., 109, D15204, doi: /2003JD Heald et al. Transpacific transport of Asian anthropogenic aerosols and its impact on surface air quality in the United States, Submitted to J. Geophys. Res.

Cameron-Smith, P. et al., (2005), Impact of Long-Range Dust Transport on Northern California in Spring 2002, Internal Report Lawrence Livermore Lab

Holzer, M., T. M. Hall, and R. B. Stull (2005), Seasonality and weather-driven variability of transpacific transport, J. Geophys. Res., 110, D23103, doi: /2005JD

Park, R. J., D. J. Jacob, B. D. Field, R. M. Yantosca, and M. Chin (2004), Natural and transboundary pollution influences on sulfate-nitrate-ammonium aerosols in the United States: Implications for policy, J. Geophys. Res., 109, D15204, doi: /2003JD “Bulk aerosol measurements from the DC-8 aircraft indicate that 40% of non- sea-salt sulfate (nss-SO4=) on average was incorporated in dust particles [Jordan et al., 2003]…. “The observation shows strong outflow in the 0- to 5-km column. The model also shows an enhancement in that column but is lower than observations by up to a factor of 2.

Heald et al. Transpacific transport of Asian anthropogenic aerosols and its impact on surface air quality in the United States, Submitted to J. Geophys. Res.

Concluding Thoughts The coast ranges and Sierra-Cascade generally prevent Pacific marine boundary layer air from reaching the continental interior of North America. TransPacific Transport is strongest in spring, but occurs year- round. The free troposphere “background” aerosol contains “natural” desert dust, anthropogenic dust, and combustion products from Asia: ¼ soil; ¼ SO4=; 2/5 carbonaceous aerosol. North-westerly winds associated with “clean air corridors” commonly carry Asian aerosols, thus the “clean 20%” in the West is significantly influenced by global pollution levels. At “clean” western IMPROVE sites, as much as 3/4 of PM2.5 and 2/3 of Coarse Particles may come from Asia. Emissions growth and control efforts in Asia may modify visibility in North America.