Intercontinental influence of NO x and CO emissions on particulate matter air quality

Transcription

1 Intercontinental influence of NO x and CO emissions on particulate matter air quality Eric M. Leibensperger a, Loretta J. Mickley a, Daniel J. Jacob a, and Steven R. H. Barrett b a School of Engineering and Applied Sciences, Harvard University, Cambridge, MA USA b Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, MA USA Submitted October 8, 2010 Corresponding Author: Eric Leibensperger 110J Pierce Hall 29 Oxford St. Cambridge, MA Phone: Fax: eleibens@fas.harvard.edu

2 Abstract We conduct sensitivity simulations with the GEOS-Chem chemical transport model to quantify the intercontinental influence of anthropogenic NO x and CO emissions (2000 levels) on particulate matter (PM) air quality. We find that US NO x and CO emissions each increase PM in Europe and East Asia by up to 0.25 µg m -3. East Asian NO x and CO emissions have nearly as great an effect on PM abundances in Europe and up to 0.1 µg m -3 in the US. These effects are driven by background increases in oxidants and are largest in population centers with high domestic SO 2, NO x, and ammonia emissions. They are comparable to or greater than the intercontinental effect of SO 2 emissions. These effects add to the magnitude of previous intercontinental transport estimates that focus on SO 2 emissions and are largest in population centers with high domestic SO 2, NO x, and ammonia emissions. Sensitivity to changes in background oxidant levels can be decreased through reductions in domestic emissions of PM precursors. 34

3 Introduction Many countries are currently regulating their sources of particulate matter (PM) to meet air quality goals. Aerosols and their precursors can be transported across oceans and affect air quality downwind. As a result, there has been much recent interest in quantifying the effect of intercontinental transport of pollution (Park et al., 2004; Heald et al., 2006; Chin et al., 2007; Task Force on Hemispheric Transport of Air Pollutants, 2007; Liu et al., 2009b). Intercontinental transport of dust has long been recognized as a contributor to surface PM levels (Prospero, 1999; Husar et al., 2001; Fairlie et al., 2007). More recently, surface, aircraft, and satellite observations have identified episodic transport of anthropogenic PM across the Pacific (Jaffe et al., 1999; Jaffe et al., 2003; Yu et al., 2008). Global models indicate annual mean sulfate enhancements in the US of up to 0.2 µg m -3 from Asian emissions (Park et al., 2004; Heald et al., 2006; Chin et al., 2007). Additional components of PM, including anthropogenic organic and nitrate aerosols, appear to be far less important for intercontinental transport (Heald et al., 2006; van Donkelaar et al., 2008) Sulfate, nitrate, and organic aerosol form in the atmosphere by oxidation of their precursor gases SO 2, NO x, and volatile organic compounds (VOCs). Oxidant levels affect the rate of aerosol production. Previous global model studies have found that changes in the emissions of ozone precursors (NO x, CO, VOCs) affect surface PM concentrations and radiative forcing by perturbing background concentrations of the oxidants OH, H 2 O 2, and ozone (Unger et al., 2006; Rae et al., 2007; Kloster et al., 2008; Shindell et al., 2008; Shindell et al., 2009). A recent study by Barrett et al. (2010) found that NO x emissions from aircraft at cruising altitudes can affect surface air quality by enhancing surface sulfate and nitrate PM. 3

4 International reports have been produced to quantify and address the uncertainties of intercontinental transport of PM (Task Force on Hemispheric Transport of Air Pollutants, 2007). The studies cited within these assessments typically have diagnosed relationships between dust, black carbon (BC), and SO 2 emissions of a source region to an intercontinental downwind receptor region. This perspective emphasizes the transport of unreactive components such as dust and BC, and the formation of sulfate from source region SO 2, but does not account for the intercontinental effects of oxidant perturbations. Here we apply a source-receptor analysis using the GEOS-Chem global chemical transport model (Park et al., 2004; Park et al., 2006; Liao et al., 2007) to estimate the sensitivity of PM surface air quality to anthropogenic NO x and CO emissions from other continents Model Simulations We conducted detailed tropospheric chemistry simulations with the GEOS-Chem chemical transport model (version ; driven by assimilated meteorological data from the Goddard Earth Observing System (GEOS)-4. The model has a horizontal resolution of 2 latitude x 2.5 longitude and 30 vertical levels. The model forms sulfate aerosol from SO 2 through gas-phase oxidation by OH and in-cloud oxidation by H 2 O 2 and ozone. The MARS-A aerosol thermodynamic equilibrium model is used to calculate sulfate-nitrateammonium aerosol formation (Binkowski and Roselle, 2003). Nitric acid is formed by the gas phase reaction of NO 2 with OH and the hydrolysis of N 2 O 5 in aqueous aerosol (Evans and Jacob, 2005). Secondary organic aerosols are formed by oxidation of volatile organic compounds (VOCs) by ozone and OH, following the work of Chung and Seinfeld (2002), as implemented by 4

5 Liao et al. (2007). Earlier versions of GEOS-Chem have been used in similar configurations to investigate intercontinental influences on PM air quality (Park et al., 2004; Heald et al., 2006; van Donkelaar et al., 2008), although never separating out the effect of oxidants Our six sensitivity simulations were conducted by individually removing sources of fossil fuel and biofuel CO, NO x, and SO 2 emissions from the contiguous US and East Asia. We define East Asia as the emission inventory domain of Streets et al. (2003), which extends from Pakistan to Japan in the west-east direction and from Indonesia to Mongolia in the south-north direction. Each simulation used the meteorology of The first year is used for model initialization and analysis is conducted on the second year Fossil fuel and biofuel emissions of NO x and SO 2 are from the EDGAR 3.2 FT inventory for 2000 (Olivier and Berdowski, 2001). These include 4.8 Tg N a -1 and 7.5 Tg S a -1 from the contiguous US and 10.0 Tg N a -1 and 27.4 Tg S a -1 from East Asia. US fossil fuel and biofuel emissions of CO are from the EPA National Emissions Inventory 1999 (NEI99; and amount to 81.6 Tg CO a -1. East Asian fossil fuel and biofuel emissions of CO are from Streets et al. (2006), and amount to Tg CO a -1. Ammonia emissions are from Bouwman et al. (1997). Additional sources are described by van Donkelaar et al. (2008) Results and Discussion Figure 1 shows the annual mean PM enhancements in Europe and Asia from US anthropogenic sources of SO 2, NO x, and CO as calculated by GEOS-Chem. PM enhancements are diagnosed as 5

6 the differences in surface air concentrations of dry sulfate, nitrate, ammonium, and organic aerosol between a present-day simulation and a simulation with the corresponding emissions shut off. Changes in organic aerosol concentrations are small (< 5 ng m -3 ) and will not be discussed further. The intercontinental effects of SO 2 arise from the transport of sulfate and thus decrease with distance downwind. US SO 2 emissions mainly influence Europe, by up to 0.2 µg m -3 in the west. This enhancement is comparable to the results of Park et al. (2004), but larger than the increases found by Chin et al. (2007) and Liu et al. (2009b) US NO x emissions enhance European and Asian PM concentrations by up to 0.25 µg m -3 on an annual basis. This is due not to direct transport of nitrate, which is negligibly small, but to increases in oxidants. US NO x emissions increase tropospheric ozone by 3.5%, OH by 3.8%, and H 2 O 2 by 0.3% in the Northern Hemisphere. These increases promote formation of sulfate and nitrate. Most of the PM enhancement in Europe is due to sulfate. By contrast, most of the PM enhancement in eastern China and northern India is due to nitrate because of large local sources of NO x and ammonia CO emissions in the US decrease tropospheric OH by 2.1%, but increase ozone by 1.3% and H 2 O 2 by 4% in the Northern Hemisphere. The net effect of US emissions is an increase in sulfate and nitrate over polluted regions of Europe and Asia (Figure 1). The enhancement of PM is not as large as from NO x emissions, partially due to the decrease in OH concentrations Figure 2 shows the intercontinental increases in PM from Asian emissions. The intercontinental influence of Asian SO 2 emissions is the strongest in the western US where subsidence from the 6

7 free troposphere brings Asian outflow to the surface. The enhancement of µg m -3 in this region is comparable to the results of Park et al. (2004), Heald et al. (2006), and Chin et al. (2007). The enhancements from Asian NO x and CO are weaker than the previously discussed intercontinental influence of US emissions on Europe and Asia, and this is because of the weaker domestic US emissions of ammonia and SO 2. The largest influence of Asian NO x is in the Midwest where ammonia emissions are large. Asian NO x and CO each cause PM enhancements of similar magnitude in Europe, but Asian CO forms more sulfate while Asian NO x forms more nitrate We thus find that intercontinental PM enhancements from US and Asian sources of NO x and CO are comparable to or greater than those from sources of SO 2. Furthermore, they peak in densely populated regions with high domestic emissions of PM precursors and that already experience high PM concentrations. Reductions in domestic emissions of PM precursors have the added benefit of reducing exposure to intercontinental enhancements mediated by oxidants. Nitrate enhancements are largest in the fall and winter when cold temperatures promote nitrate aerosol formation. Sulfate increases maximize in the fall and spring The intercontinental effects of NO x and CO emissions on PM are small compared to regulatory standards but still of some relevance. In a global model study with non-dust PM tagged by continent of origin, Liu et al. (2009a) found that intercontinental transport of non-dust PM causes 90,000 premature deaths globally. That study did not include the effects of oxidant perturbations, which would be largest in populated areas. The effect of anthropogenic emissions on background oxidant concentrations needs to be better understood in light of our work. A model 7

8 intercomparison of intercontinental influence on surface ozone has been completed (Fiore et al., 2009), but no such intercomparison has been conducted for OH and H 2 O 2, which are additionally important for the effects reported here Our study used emission inventories for Emissions have changed over the past decade and also have some uncertainty. The more recent EPA NEI 2005 inventory for the US ( includes 2% more NO x, 20% less CO, and 57% less SO 2 than used in this work, while the East Asian 2006 inventory of Zhang et al. (Zhang et al., 2009) include 12% more NO x, 19% more CO, and 14% less SO 2. These differences arise from both trends and improved emission accounting. Changes in regional emissions could affect the relative intercontinental influence of NO x and CO compared to SO 2, as well as the relative importance of Asian vs. US emissions

9 162 References Barrett, S.R.H., Britter, R.E., Waitz, I.A., Global Mortality Attributable to Aircraft Cruise Emissions. Environ. Sci. Technol. 44, Binkowski, F., Roselle, S., Models-3 community multiscale air quality (CMAQ) model aerosol component - 1. Model description. J. Geophys. Res. 108, Bouwman, A., Lee, D., Asman, W., Dentener, F., Van Der Hoek, K., Olivier, J., A global high-resolution emission inventory for ammonia. Global Biogeochem. Cy. 11. Chin, M., Diehl, T., Ginoux, P., Malm, W., Intercontinental transport of pollution and dust aerosols: implications for regional air quality. Atmos. Chem. Phys. 7, Chung, S., Seinfeld, J., Global distribution and climate forcing of carbonaceous aerosols. J. Geophys. Res. 107, Evans, M., Jacob, D., Impact of new laboratory studies of N 2 O 5 hydrolysis on global model budgets of tropospheric nitrogen oxides, ozone, and OH. Geophys. Res. Lett. 32, L Fairlie, T.D., Jacob, D.J., Park, R.J., The impact of transpacific transport of mineral dust in the United States. Atmos. Environ. 41, Fiore, A.M., Dentener, F.J., Wild, O., Cuvelier, C., Schultz, M.G., Hess, P., Textor, C., Schulz, M., Doherty, R.M., Horowitz, L.W., Mackenzie, I.A., Sanderson, M.G., Shindell, D.T., Stevenson, D.S., Szopa, S., Van Dingenen, R., Zeng, G., Atherton, C., Bergmann, D., Bey, I., Carmichael, G., Collins, W.J., Duncan, B.N., Faluvegi, G., Folberth, G., Gauss, M., Gong, S., Hauglustaine, D., Holloway, T., Isaksen, I.S.A., Jacob, D.J., Jonson, J.E., Kaminski, J.W., Keating, T.J., Lupu, A., Marmer, E., Montanaro, V., Park, R.J., Pitari, G., Pringle, K.J., Pyle, J.A., Schroeder, S., Vivanco, M.G., Wind, P., Wojcik, G., Wu, S., Zuber, A., Multimodel estimates of intercontinental source-receptor relationships for ozone pollution. J. Geophys. Res. 114, D Heald, C.L., Jacob, D.J., Park, R.J., Alexander, B., Fairlie, T.D., Yantosca, R.M., Chu, D.A., Transpacific transport of Asian anthropogenic aerosols and its impact on surface air quality in the United States. J. Geophys. Res. 111, 13. Husar, R., Tratt, D., Schichtel, B., Falke, S., Li, F., Jaffe, D., Gasso, S., Gill, T., Laulainen, N., Lu, F., Reheis, M., Chun, Y., Westphal, D., Holben, B., Gueymard, C., McKendry, I., Kuring, N., Feldman, G., McClain, C., Frouin, R., Merrill, J., DuBois, D., Vignola, F., Murayama, T., Nickovic, S., Wilson, W., Sassen, K., Sugimoto, N., Malm, W., Asian dust events of April J. Geophys. Res. 106, Jaffe, D., Anderson, T., Covert, D., Kotchenruther, R., Trost, B., Danielson, J., Simpson, W., Berntsen, T., Karlsdottir, S., Blake, D., Harris, J., Carmichael, G., Uno, I., Transport of Asian air pollution to North America. Geophys. Res. Lett. 26,

10 Jaffe, D., McKendry, I., Anderson, T., Price, H., Six 'new' episodes of trans-pacific transport of air pollutants. Atmos. Environ. 37, Kloster, S., Dentener, F., Feichter, J., Raes, F., van Aardenne, J., Roeckner, E., Lohmann, U., Stier, P., Swart, R., Influence of future air pollution mitigation strategies on total aerosol radiative forcing. Atmos. Chem. Phys. 8, Liao, H., Henze, D.K., Seinfeld, J.H., Wu, S., Mickley, L.J., Biogenic secondary organic aerosol over the United States: Comparison of climatological simulations with observations. J. Geophys. Res. 112, 19. Liu, J., Mauzerall, D.L., Horowitz, L.W., 2009a. Evaluating inter-continental transport of fine aerosols:(2) Global health impact. Atmos. Environ. 43, Liu, J., Mauzerall, D.L., Horowitz, L.W., Ginoux, P., Fiore, A.M., 2009b. Evaluating intercontinental transport of fine aerosols: (1) Methodology, global aerosol distribution and optical depth. Atmos. Environ. 43, Olivier, J.G.J., Berdowski, J.J.M., Global emissions sources and sinks, in: al., J.B.e. (Ed.), The Climate System. A. A. Balkema Publishers/Swets and Zeitliner Publishers, Lisse, Netherlands, pp Park, R., Jacob, D., Field, B., Yantosca, R., Chin, M., Natural and transboundary pollution influences on sulfate-nitrate-ammonium aerosols in the United States: Implications for policy. J. Geophys. Res. Park, R., Jacob, D., Kumar, N., Yantosca, R., Regional visibility statistics in the United States: Natural and transboundary pollution influences, and implications for the Regional Haze Rule. Atmos. Environ. 40, Prospero, J., Long-term measurements of the transport of African mineral dust to the southeastern United States: Implications for regional air quality. J. Geophys. Res. 104, Rae, J.G.L., Johnson, C.E., Bellouin, N., Boucher, O., Haywood, J.M., Jones, A., Sensitivity of global sulphate aerosol production to changes in oxidant concentrations and climate. J. Geophys. Res. 112, D Shindell, D., Lamarque, J.-F., Unger, N., Koch, D., Faluvegi, G., Bauer, S., Ammann, M., Cofala, J., Teich, H., Climate forcing and air quality change due to regional emissions reductions by economic sector. Atmos. Chem. Phys. 8, Shindell, D.T., Faluvegi, G., Koch, D.M., Schmidt, G.A., Unger, N., Bauer, S.E., Improved Attribution of Climate Forcing to Emissions. Science 326,

11 Streets, D., Bond, T., Carmichael, G., Fernandes, S., Fu, Q., He, D., Klimont, Z., Nelson, S., Tsai, N., Wang, M., Woo, J., Yarber, K., An inventory of gaseous and primary aerosol emissions in Asia in the year J. Geophys. Res. 108, Streets, D.G., Zhang, Q., Wang, L., He, K., Hao, J., Wu, Y., Tang, Y., Carmichael, G.R., Revisiting China's CO emissions after the Transport and Chemical Evolution over the Pacific (TRACE-P) mission: Synthesis of inventories, atmospheric modeling, and observations. J. Geophys. Res. 111, D Task Force on Hemispheric Transport of Air Pollutants, Hemispheric transport of air pollution 2007 interim report, in: Keating, T.J., Zuber, A. (Eds.), Air Pollut. Stud. 16. U.N. Econ. Comm. for Europe, New York. Unger, N., Shindell, D., Koch, D., Streets, D., Cross influences of ozone and sulfate precursor emissions changes on air quality and climate. P. Natl. Acad. Sci. USA 103, van Donkelaar, A., Martin, R.V., Leaitch, W.R., Macdonald, A.M., Walker, T.W., Streets, D.G., Zhang, Q., Dunlea, E.J., Jimenez, J.L., Dibb, J.E., Huey, L.G., Weber, R., Andreae, M.O., Analysis of aircraft and satellite measurements from the Intercontinental Chemical Transport Experiment (INTEX-B) to quantify long-range transport of East Asian sulfur to Canada. Atmos. Chem. Phys. 8, Yu, H., Remer, L.A., Chin, M., Bian, H., Kleidman, R.G., Diehl, T., A satellite-based assessment of transpacific transport of pollution aerosol. J. Geophys. Res. 113, D14S12. Zhang, Q., Streets, D.G., Carmichael, G.R., He, K.B., Huo, H., Kannari, A., Klimont, Z., Park, I.S., Reddy, S., Fu, J.S., Chen, D., Duan, L., Lei, Y., Wang, L.T., Yao, Z.L., Asian emissions in 2006 for the NASA INTEX-B mission. Atmos. Chem. Phys. 9, Acknowledgements This work was supported by the Electric Power Research Institute (EPRI) and an Environmental Protection Agency Science to Achieve Results (EPA-STAR) Program Graduate Fellowship to Eric Leibensperger. EPRI and EPA have not officially reviewed or endorsed this publication and the views expressed herein may not reflect those of EPRI and EPA. This work has benefitted from discussions with Jenny Fisher, Christopher Holmes, Eloïse Marais, and Lin Zhang and useful comments from Naresh Kumar and Eladio Knipping

12 Figure Captions Figure 1 - Annual mean enhancements of surface PM air concentrations over Europe and Asia from US anthropogenic emissions of SO 2 (top), NO x (middle), and CO (bottom). Figure 2 - Annual mean enhancements of surface PM air concentrations over the US and Europe from East Asian anthropogenic emissions of SO 2 (top), NO x (middle), and CO (bottom)

13 PM 2.5 Enhancement from US SO PM 2.5 Enhancement from US NO x x PM 2.5 Enhancement from US CO μg m -3

14 PM 2.5 Enhancement from Asian SO PM 2.5 Enhancement from Asian NO x PM 2.5 Enhancement from Asian CO μg m -3