Origin of Reactive N in Rocky Mountain NP

Transcription

1 Origin of Reactive N in Rocky Mountain NP Bret A. Schichtel 1, William C. Malm 3, Mike Barna 1, Krisiti Gebhart 1, Katie Benedict 2, Anthony Prenni 2, Jr. 2, Christian M. Carrico 2, Ezra Levin 2, Derek Day 3, Doris Chen 2, John Ray 1, Jeffrey L. Collett 2, Sonia M. Kreidenweis 2 1 National Park Service, CSU/CIRA, Fort Collins, Colorado Department of Atmospheric Science, Colorado State University 3 Cooperative Institute for Research in the Atmosphere (CIRA), CSU

2 NOx and NH 3 U.S. Emissions: 2006 verse 2050 Projection It is projected that the U.S. will shifting from oxidized to reduced dominated RN emissions by 2050 Raluca Ellis et al., 2012

3 Rocky Mountain Airborne Nitrogen and Sulfur (RoMANS) Study Objectives Characterize the atmospheric concentrations of sulfur and reactive nitrogen species in gaseous, particulate and aqueous phases along the east and west sides of the Continental Divide Identify the relative contributions to atmospheric sulfur and nitrogen species in RMNP from within and outside of the state of Colorado. from more emission sources along the Colorado Front Range versus other areas within Colorado. from mobile sources, agricultural activities, large and small point sources within the state of Colorado.

4 Rocky Mountain NP Deposition Studies RoMANS I: 2006 March/April (spring) and July/August (summer) RoMANS II: November 2008-November 2009 April September 2010 Particle composition and gases 24 hr PM 2.5 and composition 15 minute PM 2.5 ions (PILS) 24 hr SO 2, NH 3 and HNO 3 (URG) Continuous NO x, NO y, NH 3, O 3, CO Weekly HiVol PM 2.5 Wet deposition Event and sub-event/hourly Ion chromatography Org N = TN inorg N Other measurements Co-located w/ IMPROVE & CASTNet monitors 2006 study had monitors throughtout RMNP and at Colorado borders

5 Rocky Mountain, NP Reactive N Deposition Budget Nov Nov 2009 Annual N dep=3.4 kg/ha/yr Nitrogen Deposition (µg N/m2) Wet ON Wet NH4 Wet NO3 Dry HNO3 Dry NH3 Dry NO3 Dry NH4 Wet organic N + Dry NH3 ~35% of total N deposition Dry organic N is still missing

6 Recall Source Attribution Budgets from 2006 ROMANS I Study Spring N deposition is primarily from northeastern CO and Front Range due to a synoptic upslope event Summer N deposition is from a diverse set of sources Local sources contribute ~25% of summer NH 3 deposition

7 Ambient Ammonia Concentrations Nov 2008 Nov 2009 Synoptic Upslope event April June

8 RMNP RN Apportionment Strategy (Weight of Evidence) Concentration gradients. Which way is the wind coming from? Simple back trajectories. Frequency with which the air mass passes over source areas before it arrives at the receptor - residence time analysis. Receptor models. Trajectory receptor models. Source Oriented Chemical transport models. Hybrid Models.

9 Summer Diurnal Cycles NOx Temperature Wind direction PM1 NH 3 NOy Box and whisker plots with the median, 10, 25, 75, and 90 percentiles shown

10 PILS and Winds, 2009 Spring/Summer o Daily upslope o Increased Concentrations o Generally associated with precipitation. Fall o Fewer events but similar to spring o Important synoptic scale upslope event

11 90 th Percentile of concentrations as a function of wind direction Average Wind Rose, Nov 08 Nov 09

12 The frequency the measured surface winds at RMNP are from a given direction and the average NH 3 concentrations associated with each wind direction The average contribution of the NH 3 concentrations associated with each wind sector to the RMNP annual average NH 3. Sources Winter Spring Summer Fall Annual East 29% 44% 45% 49% 44% West 71% 56% 55% 51% 56% The estimates of the contribution of sources east and west of RMNP to the seasonal and annual measured NH 3 concentrations.

13 Transport Modeling Measured 10-m Wind Rose Vs. WRF 4-km Modeled Nov 2008 Dec 2009 Core Observed wrf 12 km West wrf at Core Site wrf 12 km East

14 Distance Weighted Residence Time Where did the air come from on an average day? Winter Spring me/equal Prob. Sfc. endpts/grid= 1 im e/equal Prob. Sfc. n endpts/grid= 1 < t < t Summer Fall R e s. T im e /E q u a l P ro b M in e n d p ts /g rid = 1 m e/equal Prob. Sfc. endpts/grid= 1 < me/equal Prob. Sfc. endpts/grid= 1 < t < to to to to to to to to > 0.2 5

15 Incremental Probability Transport on High NH3 Days Compared Average Days Winter rential Probability n endpts/grid= 1 Spring ential Probability endpts/grid= 1 < & N o D ata t < & No Data Summer Fall D iffe ren tial P ro b a b ility M in e n d p ts/g rid = 1 rential Probability endpts/grid= 1 < & N o D ata ential Probability endpts/grid= 1 < & No Data < & N o D to -7.5 e e to -5 e-0-5 e to -2.5 e e to 0 0 to 2.5 e e to 5 e e to 7.5 e e to >

16 Regression Techniques of Source Apportionment Assumption: On average, the concentration measured at the receptor is some linear combination of the contributions of several sources. Concentration = a 1 Source 1 + a 2 Source 2 + TrMB (Trajectory Mass Balance) Use many concentrations of 1 species and counts of trajectory endpoints in source regions to predict average attributions over a long period. NH 3 i = j a j # End _ Pts ji + ε i j - Source Regions i - observations Source Regions Src _ Cont j = 1 I i a j # End _ Pts ji

17 TrMB Attributions of Ammonia Concentrations 2006 and 2009 Colorado (%) Eastern U.S. (%) Western U.S. (%) URG 24-hr Conc (ug/m3) Spring ± 5 8 ± 2 35 ± Summer ± 7 21 ± 3 29 ± Winter 2008/09 48 ± 14 5 ± 7 46 ± Spring ± ± 8 46 ± Summer ± 11 8 ± 6 44 ± Fall 2008/09 47 ± ± 7 43 ± Combining both hourly and 24-hour concentrations, 720 trials each for 2008/2009. About half of the NH3 is from Colorado sources Results are inline with ROMANS I

18 TrMB Attributions of Ambient Ammonia Concentrations 2006 (final) and 2009 NE Colorado (%) SE Colorado (%) Front Range (%) W Colorado (%) Spring ± 1 NA 9 ± 3 39 ± 4 Summer ± 5 NA 15 ± 4 24 ± 5 Winter 2008/09 10 ± 8 1 ± 2 5 ± 6 32 ± 14 Spring ± 4 2 ± 3 4 ± 3 26 ± 10 Summer ± 5 1 ± 1 6 ± 3 31 ± 12 Fall 2008/09 16 ± 7 3 ± 5 6 ± 4 22± 11 For 2009 Combed both hourly and 24-hour concentrations, 720 trials each. Northeast CO + Front Range account for 12-22% of NH 3 Western CO contributes 22-32% of NH3 Results are inline with ROMANS I Wind fields likely underestimate contributions from east of ROMO

19 Hybrid Receptor Model: C = a S + ε ki kj ji ik Where j k = 1... m, the number of observations, i = 1... n, the number of sources contributing to receptor, j = 1... N, the number of source region vectors, C ki = concentrations of ammonia from source i for time period k, a kj = time weighting functions, and S ji = source vectors. = error term including random and lack of fit error. ε ik ( C) = α Φ k jk jk j C k = the measured hourly aerosol concentrations Α jk = the regression coefficients Φ jk = the average of modeled concentrations arriving at the receptor from sources areas grouped according to eigenvectors, v Source contributions were estimated by statistically relating transport from source regions to ROMO measurements

20 Hybrid Receptor Model Similar to TRMB model except: Simulated the transport of inert NH 3 emissions to the Rocky Mnt receptor site. E.g. Emission weighted transport Statistically grouped collinear source regions Did not apriori select all source regions Incorporated constant dry NH 3 deposition

21 NH 3 Source regions National scale emissions divided into ~100 source regions Regional scale model used to simulate transport of emissions from each region to Rocky Mountain NP NO x Simulated transport of inert NH 3 emissions from western CO

22 Hybrid Model verse Measured NH3

23 Hybrid modeling ambient NH 3 apportionment results compared to the tracer CAMX concentrations weighted for dry deposition. Inert Tracer + dry deposition Hybrid Model

24 Fraction of ammonia apportioned to sources in and outside Colorado About 55% of the ambient ammonia in all seasons is apportioned to sources inside of Colorado In ROMANS I spring and summer ~70% of ammonia was from Colorado sources

25 Ambient Ammonia Source Apportionment

26 Ambient Ammonia Source Apportionment ROMANS II ROMANS I Source regions are not exactly the same, e.g. Front Range + Northeastern CO = Denver + Northeastern CO Both ROMANS I and II show eastern CO to be a significant contributor RMNP NH 3 ; ROMANS II winds underestimate transport from eastern Colorado ROMANS II shows contributions from broader array of source regions Northern Utah and Snake River Valley were not contributions in ROMANS I

27 Summary About 55% of the NH 3 originates from sources within Colorado Little of the measured ammonia at Rocky Mountain originated from the Midwest, an area with high ammonia emissions. Sources west of Colorado contribute ~35-45% of measured ammonia California ~ 13% Utah ~ 8%, Snake River valley ~ 5-6% Arizona ~ 5-6%. Rocky Mountain NP would benefit from regional reduction in NH 3 emissions

28 Summary Contributions of NH3 from sources within the state of Colorado to Rocky Mountain NP Western Colorado ~ 15% Central Colorado ~ 15% Front range including the Greely area ~ 15%. Northeastern Colorado ~ 6%. The Yampa river valley ~ 4%. CAMx PSAT source apportionment results will be available soon.