Center for Global and Regional Environmental Research, University of Iowa

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Reaction # Reaction Equations 1 NO2 + hv  NO + O3P 2 O3P + O2 O3 Cloud field Dobson O3 Gaseous Reactions SAPRC-99 7 O3 + NO  NO2 + O2 Gas-phase absorption Tropospheric O3 8 O3 + NO2 NO3 + O2 Gaseous Loss 9 NO + NO3 2NO2 Photolysis Rates On-line TUV Heterogeneous Reactions (Dust) Gas-Aerosol Equilibrium interaction 17 O3 + hv  O2 + O3P 18 O3 + hv  O2 + O1D Dust surface saturation Aerosol Production Aerosol Optical Properties 19 O1D + H2O  2OH Aerosol Equilibrium Module SCAPE 21 OH + NO  HONO Four aerosol size bins are used: 0.1µm-0.3µm, 0.3µm-1.0µm, 1.0µm-2.5µm, and 2.5µm-10µm (referred to as bins 1 to 4, respectively). 22 HONO + hv  OH + NO 25 OH + NO2 HNO3 29 OH + CO + O2 HO2 + CO2 To represent the involvement of dust in heterogeneous chemistry we define the dust surface fresh ratio as 30 OH + O3 HO2 + O2 31 HO2 + NO  NO2 + OH where Caactive is the amount of dust active calcium that is available for heterogeneous reactions: 32 HO2 + NO2 HNO4 41 H2O2 + hv  2OH Simulated dust influences below 1 km averaged for April 4-14, 2001 show OH is mainly affected (up to 20% reduction) by dust reducing photolysis rates, which also results in O3 decrease in polluted areas and downwind sites. In clean areas dust radiative influence tends to increase O3 by decreasing its photolytic loss. On average during this period, dust heterogeneous reactions have stronger impacts on O3 than its radiative influence. The regional O3 decrease due to heterogeneous reactions also affects other species, like NO2, through photochemical reactions. 44 OH + SO2 + H2O + O2 H2SO4 + HO2 125 OH + HCHO  HO2 + CO 236 NO2 + Dust  0.5Nitrate + 0.5 Nitrite 237 O3 + Dust  1.5O2 Averaged Dust Radiative Impact on OH (%) below 1 km Averaged Dust Radiative Impact on O3 (%) below 1 km Averaged Dust Heterogeneous Impact (%) on O3 (left) and NO2 (right) below 1 km Chemical budget when trajectory A passed over the polluted region, Beijing Simulated Total Dust below 3 km with Weather Stations where Dust Were Reported Simulated Sulfate (contour, µg/m3) and its Coarse Ratio (color-coded) Simulated Dust Fresh Ratio Dfresh GMS-5 Dust-Enhanced Image C-130 Flight 8 encountered aged dust Dust did not influence the sub-micron sulfate, but significantly increased the super-micron sulfate concentration. Sub-micron dust ages faster than the super-micron dust. Apr 7 Extracted model results along trajectory B (shown left) illustrating the dust aging process and composition variation. Apr 9 Simulated Total Ca (µg/std m3) TAS Total Ca (µg/std m3) Irregular Points Measurements Compared to the Simulations with and without Dust along C-130 Flight 6 Trajectory A Ca Increase Ca Increase Apr 11 C-130 Flight 6 & 7 Trajectory B Dust influences on Gaseous Species along C-130 Flight 6 Apr 13 C-130 Flight 8 The model simulations (FULL, NORMAL and NODUST) extracted along trajectory A (see map in left corner) show the impacts of dust heterogeneous and radiative processes on gaseous species and photochemistry. The main influence of dust heterogeneous reactions is to reduce O3 concentrations, which decrease NO2/NO ratio, but increase HONO concentrations. The O3 difference was nearly linearly correlated with O3-Dust heterogeneous reactions, except over heavily polluted areas. Simulations with and without dust clearly show the dust influence on secondary aerosols. Dust increased total sulfate and nitrate concentrations, especially increased their coarse portions, but the high Ca loading repelled ammonia uptake. The dust storms also significantly increased aerosol extinction. Simulated Dust Fresh Ratio in the 400m level Simulated Sulfate Coarse Ratio in the 400m level Averaged Dust Concentration (µg/m3) Averaged in the layers below 3km Three Simulations: NODUST: without dust NORMAL: consider dust radiative impact FULL: consider both heterogeneous and radiative impacts The dust storms that occurred from April 4-14, 2001 in East Asia were named “perfect storm”by some ACE-Asia investigators. These dust storms accompanied with cold-air outbreak and were transported eastward. Dusts became aged (shown by dust fresh ratio) when passing over polluted areas and sulfate in the coarse fraction increased (i.e., coarse ratio). The interaction of dust, secondary aerosols and gaseous species through equilibria and heterogeneous processes significantly affected related species and aerosol size distributions, which was verified by aircrafts (C-130 and Twin Otter), NOAA ship (Ronald H. Brown), and ground measurements. The C-130 flight 6 encountered the strongest dust events. Framework of Chemical Interactions Aerosol Outflow and Their Interactions with Gaseous Species in East Asia during Springtime, 2001: Three-Dimensional Model Study Combining Observations Youhua Tang1, Gregory R. Carmichael1, John H. Seinfeld2, Donald Dabdub3, Rodney J. Weber4, Barry Huebert5, Antony D. Clarke5, Gakuji Kurata6, Itsushi Uno7, Jung-Hun Woo1, David G. Streets8, Chul-Han Song4, Adrian Sandu9, Theodore L. Anderson10, Robert W. Talbot11 and Jack E. Dibb11 Re-Colored by Coarse Dust Fresh Ratio The C-130 measurements of sulfate and nitrate coarse ratios show different correlations under different dust loading, represented by the Ca concentrations. When dust loading increased, the correlations show less variation and converge to a certain point related to dust coarse ratio. Both model and measurements show similar trends. The simulations also show some points that do not follow this trend. For these points, nitrate and sulfate coarse ratios are linearly related. Re-colored by the coarse dust fresh ratio, these points were identified as fresh (un-aged) dust. When dust was very fresh, both nitrate and sulfate increase since they follow similar uptake mechanisms. • Dept. of Ecological Engineering, Toyohashi University of Technology, Japan • Research Institute for Applied Mechanics, Kyushu University, Japan • Decision and Information Sciences Division, Argonne National Laboratory • Dept. of Computer Science, Virginia Technical University • Dept. of Atmospheric Science, University of Washington at Seattle • Dept. of Earth Sciences, University of New Hampshire • Center for Global and Regional Environmental Research, University of Iowa • Dept. of Chemical Engineering and Environmental Science Engineering, California Institute of Technology • Dept. of Mechanical and Aerospace Engineering, U. of California at Irvine • School of Earth and Atmospheric Sciences, Georgia Institute of Technology • School of Ocean and Earth Science and Technology, University of Hawaii Thank you for your attention For further information, please check our papers: Tang, Y., et al. The impacts of dust on regional tropospheric chemistry during the ACE-Asia experiment: a model study with observations, J. Geophys. Res., doi: 10.1029/2003JD003806, in press, 2003. Tang, Y., et al. Three-dimensional studies of aerosol ions and their Size Distribution in East Asia during spring 2001, submitted to J. Geophys. Res.. Or contact us : Youhua Tang (ytang@cgrer.uiowa.edu) Greg Carmichael (gcarmich@engineering.uiowa.edu) Trajectory A passed over the polluted area J. Geophys. Res., C-130 flight 6 encountered the strongest dust storm during ACE-Asia campaign, which strongly affected both aerosol (left) and gaseous (up) species via equalibria, heterogeneous and radiative processes.