The Regional Atmospheric Chemistry Mechanism, version 2 (RACM2)

Transcription

1 The Regional Atmospheric Chemistry Mechanism, version 2 (RACM2) William R. Stockwell 1,2 and Wendy S. Goliff 2 1 Department of Chemistry, Howard University 2 Division of Atmospheric Sciences, Desert Research Institute

2 Mechanism Ancestry RADM2 Regional Acid Deposition Mechanism, version 2 (Stockwell et al., 1990): Developed to predict regional atmospheric chemistry and acid rain formation. RACM1 Regional Atmospheric Chemistry Mechanism, version 1 (Stockwell et al., 1997): The aromatic chemistry scheme was improved using available laboratory data. Included reaction schemes for biogenic compounds such as isoprene, limonene and α-pinene.

3 RACM2 RACM2 is being developed from RACM1. It contains a new schemes for: Acetone Aromatic compounds (based upon Calvert et al. (02)) Isoprene (based upon Geiger et al. (03) and improved by adding methyl vinyl ketone explicitly) α-pinene d-limonene About 1 Chemical Species in 300 Reactions

4 ISO + HO ISOP ISOP + NO 0.95 HO2 + HCHO MACR MVK ISON NO2 ISOP + HO2 ISHP MCAR ISOP + MO HCHO HO MVK MACR ISOP + ACO HO MO ORA2 + HCHO MACR MVK ISOP + NO3 GEIGER ET AL. 03 Isoprene HO2 + HCHO MACR 0.58 MVK + NO2

5 α-pinene API + HO APIP APIP + NO 0.82 HO HCHO ALD ACT KET ORA ONIT NO2 APIP + HO2 APIP + MO2 APIP + ACO3 APIP + NO3 OP2! --- ATKINSON 1994, 03 2 HO2 + HCHO + ALD + KET HO2 + MO2 + ALD + KET HO2 + ALD + KET + NO2

6 LIM + HO LIMP + NO LIMP + HO2 d-limonene LIMP 0.90 HO ACT KET 0.25 MACR + 0. ONIT NO2 OP2 LIMP + MO2 2 HO MACR + 0. OLI + 1. HCHO LIMP + ACO3 HO MACR + 0. OLI + 0. HCHO + MO2 LIMP + NO3 HO OLI + 0. HCHO MACR + NO2 GILL AND HITES 02; ATKINSON 03

7 Walker Branch Forest Oak Ridge National Laboratory, Oak Ridge, TN J.D. Fuentes

8 Thesis Forested ecosystems capable of high rates (> 50 nmoles m -2 s -1 ) of biogenic hydrocarbon emissions, and in the vicinity of modest rates of nitrogen oxide emissions from suburban automobile traffic, can support a unique and active photochemistry. Regional air quality models will likely need to include the in canopy processing of biogenic hydrocarbons, if they intend to accurately represent the photochemical production of pollutants.

9 Biosphere - Atmospheric Interactions Simulations of Biogenic Emission Measurements Climate Change Light Scattering Carbon Assimilation Air Quality Forecasting Ozone Aerosol Particles Emissions from Canopy Deposition Surface Emissions Emissions In Canopy Chemical Processing

10 Simulations Based on Oak Ridge Measurement Data for July, Sampling Heights (m)

11 Diurnal variations of photosynthetically active radiation (PAR) above and below the forest canopy. 1 s 2 moles mpar in PAR (µmoles m -2 s -1 ) Above canopy Below canopy Time (hours) C o

12 oles mpar in Measured at 36.6 m above a mixed deciduous forest canopy at Oak Ridge, TN on July Temperature ( C) C o Air temperature in Time in hours

13 Diurnal variations of ozone mixing ratios measured within and above a mixed deciduous forest canopy at Oak Ridge, TN on July Ozone (ppbv) ]i [O b m 39.8 m Time in hours

14 Diurnal variations of nitrogen oxide mixing ratios measured within and above a mixed deciduous forest canopy at Oak Ridge, TN on July m 0.2 m NO x (ppbv) X ]i [NO b Time in hours

15 Averaged vertical variations of (a) ozone, (b) nitrogen oxide, and (c) isoprene mixing ratios within and above a mixed deciduous forest canopy at Oak Ridge, TN on July 1999 during 14:00 to 19:00 hours (local time). The horizontal bars denote one standard deviation from the mean mixing ratios. H i h i [Isoprene] in ppbv [O 3 ] in ppbv [NO X ] in ppbv

16 α-pinene Methyl-vinyl-ketone Methacrolein Isoprene Relative VOC Speciation (by Carbon Number) d-limonene Below Canopy HCHO C3-Alkane C5-Alkane C8-Alkane Methyl-vinyl-ketone Methacrolein Isoprene HCHO HC3 Terminal Alkenes HC5 HC8 d-limonene α-pinene Internal Alkenes OLT Dienes OLI Toluene DIEN Xylene TOL XYL ISO MACR MVK API HCHO LIM Above Canopy C3-Alkane C5-Alkane C8-Alkane Terminal Alkenes Internal Alkenes Dienes Toluene Xylene HCHO Alkane C3 Alkane C5 Alkane C8 Termaina Alkene Internal Alkene Diene Toluene Xylene Isoprene MACR MVK API LIM

17 Initial Conditions Ozone and NOx Hour Ozone (ppb) (ppb) 5 NO x (ppb) A

18 Initial Conditions VOC and VOC/NOx Hour VOC VOC/NO x (ppbc) (ppbc/ppb) A

19 Simulated HO Radical Hour Series1 RACM1 RACM2 Series E E E E E E E-04 (ppb)

20 Simulated NO 3 Radical Hour RACM1 Series1 RACM2 Series E E E E E-04 (ppb)

21 Simulated NO 3 Radical 0% ([RACM2] - [RACM1])/[RACM1] 35 Hour Series % 0% 5% % 15% % E-04 (%)

22 HNO3 Hour RACM1 Series1 RACM2 Series E E E E E E-01 (ppb) 5.0E-01

23 HCHO Hour RACM1 Series1 Series1 RACM (ppb) 6.0

24 HNO 3 /HCHO Hour Series RACM1 RACM2 Series

25 PAN Hour RACM1 Series1 RACM2 Series E E E E E-01 (ppb)

26 H2O2 Hour RACM1 Series1 RACM2 Series E E E E E-01 (ppb) 2.0E-01

27 HNO3/H2O2 Hour RACM1 Series RACM2 Series

28 Organic Peroxide Hour RACM1 Series1 RACM2 Series E E E E E E E E E E E E E-02 (ppb) 6.0E-02

29 Organic Acids Hour RACM1 Series1 RACM2 Series (ppb) 0.4

30 Averaged HO X radical production rate modeled within and above a mixed deciduous forest canopy at Oak Ridge, TN on July 1999 during 14:00 to 19:00 hours (local time). The dash line on the y-axis denotes the canopy height. H i ht i 30 Ozone Formaldehyde BVOCs x 6 HO X radicals cm -3 s -1

31 Averaged vertical variations of nitrate and hydroxyl radicals modeled within and above a mixed deciduous forest canopy at Oak Ridge, TN on July 1999 during 14:00 to 19:00 hours (local time). [NO 3 ] [HO]*0.1 H i ht i NO 3 and HO mixing ratio in pptv

32 Averaged vertical variations of (a) isoprene, (b) a-pinene, and (c) d-limonene loss modeled within and above a mixed deciduous forest canopy at Oak Ridge, TN on July 1999 during 14:00 to 19:00 hours (local time). A B C HO HO NO 3 NO 3 O 3 O 3 HO NO 3 O 3 H i ht i 30 H i ht i 30 H i ht i Isoprene loss (molec s -1 ) * α-pinene loss (molec s -1 ) * Limonene loss (molec s -1 ) * 5 Figure 9a Figure 9b Figure 9c

33 Averaged methacrolein and methyl vinyl ketone production rate modeled within and above a mixed deciduous forest canopy at Oak Ridge, TN on July 1999 during 14:00 to 19:00 hours (local time). MACR MVK H i ht i Ppbv per hour

34 The Fifteen Worst American Regions for Ozone 1) Los Angeles/Riverside/Orange County, California 2) Fresno, California 3) Bakersfield, California 4) Visalia/Porterville, California 5) Houston/Baytown/Huntsville, Texas 6) Merced, California 7) Sacramento/Arden/Arcade/Truckee, California, Nevada 8) Hanford/Corcoran, California 9) Knoxville/Sevierville/La Follette, Tennessee ) Dallas/Fort Worth Texas 11) Washington/Baltimore/North Virginia, DC., MD., VA. 12) Philadelphia/Wilmington/Atlantic City, PA.,DE.,MD. 13) New York/Newark/Bridgeport, NY., NJ., CN., PA. 14) Charlotte/Gastonia/Salisbury, NC., SC. 15) Cleveland/Akron/Elyria, Ohio The Wall Street Journal, November 17, 04

35 Beltsville Location

36 Beltsville

37 Air Quality Forecast Evaluation Beltsville Series1 9:00 AM 11:00 AM 1:00 PM 3:00 PM 5:00 PM 7:00 PM 9:00 PM 11:00 PM 1:00 AM 3:00 AM 5:00 AM 7:00 AM Ozone July 18-19, 06 5:00 AM 7:00 AM ppbv

38 Beltsville Meteorological Tower

39 Collection Points for VOC Samples

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43 Conclusions - I Simulations of measurements from a forest canopy were made with the RACM1 and RACM2 mechanisms. RACM1 and RACM2 forecast similar HO and NO 3. RACM1 and RACM2 forecast similar relative reaction rates of HO, O 3 and NO 3 with isoprene, α-pinene and d-limonene. The two mechanisms forecast different concentrations of HNO 3, PAN, HCHO, H 2 O 2, organic peroxides and organic acids. Ratios HNO 3 /HCHO and HNO 3 /H 2 O 2 similar.

44 Conclusions - II Substantial nitrate (NO 3 ) and hydroxyl (HO) radical formation occurred within the forest canopy, with maximum NO 3 and HO levels approaching 1 part per trillion on a volume basis (pptv) and 0.05 pptv, respectively. These NO 3 and HO levels, combined with within-canopy ozone (O 3 ) molar mixing ratios of 60 parts per billion (ppbv), reacted with biogenic hydrocarbons and produced substantial amounts (0.6 ppbv) of peroxy radicals.

45 Acknowledgements Dr. Jose D. Fuentes (University of Virginia) and Dr. Daniel Wang (Environment Canada) for sharing ozone, NOx, and VOC data. Support: NASA under the Experimental Program to Stimulate Competitive Research (EPSCoR), grant number NCC5-583 NOAA Center for Atmospheric Sciences Howard University

46 See our session: Advertisement Want more Beltsville? More suburban sites? Atmospheric Chemistry at the Interface between Rural and Urban Regions All Day Monday 11, 06 at the Fall American Geophysical Meeting