David Parrish - NOAA Aeronomy Laboratory Review “Section 6.4: Evaluation of the strengths and weaknesses of current inventories and models.” Please feel free to provide critiques and feedback!!! Today: Preview of NARSTO Emission Inventory Assessment EMIS Meeting, Portsmouth NH, August 3, 2004

1.0 Introduction 2.0 Overview of Emissions Inventories Provide an emissions inventory primer for decision makers 3.0 Vision for Future North American Emission Inventory Programs Set the target: define where we need to be in future years. 4.0 North American Emission Inventories List what currently exists 5.0 Inventory Tools Describe how are inventories constructed 6.0 Strengths and Weaknesses of Current Inventories and Models: Sensitivities, Uncertainties, and Applicability Describe how to evaluate Provide an evaluation of important sectors 7.0 Evolving Tools for Determining Emissions Describe advanced methods and methodologies 8.0 Roadmap for Future Emission Inventory Application and Development NARSTO Emission Inventory Assessment

Emission Inventory Development Emission Factors and Models Databases for Source Activity Levels Defaults for Emissions Related Variables Point and Non Point Source Data Growth Factors Starting Point for EI Factor and Model Improvements Regional/State/Local/Tribe/Provincial Improvements EI Applications Forecasting Measurement Methods Field Testing and Sampling Local Activity Levels & Variables Preliminary EI for Base 20xx States and Other Stakeholders Improved EI for Base Year 20xx Emissions Processor Speciation Factors Temporal Factors Spatial Factors Tests, Evaluations and Reviews

Emission Inventory Development Emission Factors and Models Databases for Source Activity Levels Defaults for Emissions Related Variables Point and Non Point Source Data Growth Factors Starting Point for EI Factor and Model Improvements Regional/State/Local/Tribe/Provincial Improvements EI Applications Forecasting Measurement Methods Field Testing and Sampling Local Activity Levels & Variables Preliminary EI for Base 20xx States and Other Stakeholders Improved EI for Base Year 20xx Emissions Processor Speciation Factors Temporal Factors Spatial Factors Tests, Evaluations and Reviews

Evaluations of Road Transport Emissions: U.S. EPA emissions estimates have changed drastically. Danger Sign!! Most recent emissions estimates are uncertain by at least ~10% for VOC and NO x and ~50% for CO = MOBILE = MOBILE 6 For 1985 the 2003 estimate is higher than previous estimates by factors of up to 1.35, 1.6 and 2.5 for NO x, VOC, and CO History of temporal trends of road transport emissions in NEI

Rural U.S. CO levels have also decreased, but at a rate of only about 3%/yr. [Hallock-Waters et al., GRL, 26, , 1999] Evaluations of Road Transport Emissions: Temporal trend of CO emissions in NEI compared to ambient levels Trends in 2003 Report agree well with trend of ambient levels, but not 2000 Repoprt. Exception is latest 2 years. No information regarding the accuracy of the absolute emissions = MOBILE = MOBILE 6 Urban %/yr %/yr %/yr

Evaluations of Road Transport Emissions: Temporal trend of CO/NO x ratio in NEI compared to ambient ratios Neither Trends Report matches recent low observed CO/NO x ratios, and 2003 is worse than Disagreement a factor > 2 by (Parrish et al., JGR, 107, 4140, doi: /2001JD000720, 2002) Neither Trends Report captures rapid decrease in CO/NO x ratios. Current U.S. emissions estimates are too high for CO, and/or too low for NO x.

Evaluations of Road Transport Emissions: Comparison of fuel-based and mileage-based emissions estimates (Harley et al., JGR, 106, , 2001) VOC agree well. CO ≈ 40% high Nashville 1995 Road Transport Sources Fuel-based emissions agree with ambient CO/NO x NO x agree well, but not partitioning EPA equivalent to 2000 Trends Report MOBILE 5B emissions vs. Fuel-based in 1995: MOBILE 6 emissions (2003 Trends Report) would degrade CO comparison

Evaluations of Road Transport Emissions: Reconciliation of estimated emissions with ambient measurements CO emissions trend assumed to be %/yr ( temporal trend of ambient CO levels). CO to NO x emission ratio trend assumed to be %/yr (temporal trend for L.A. Nashville) NO x emissions from the 2000 Trends Report are assumed to be accurate. Assumptions: CO emissions in the 2003 Trends Report are over estimated by a factor of 2 for (worse lately). Conclusions: NO x emissions are within 20% of the 2003 Trends Report values for all years after 1993, but are increasing rather than decreasing. Interestingly, the inferred NO x temporal trend closely follows the increasing trend of the first 5 years of the 1990s in the 2000 Trends Report.

Evaluations of Road Transport Emissions: Reconciliation of estimated emissions with ambient measurements No substantial inconsistencies have been identified in the VOC emissions. Conclusions: VOC emissions trend for (2003 Trends Report) is %/yr, very close to %/yr trend of ambient CO levels. VOC emissions do not increase recently as CO.

Evaluations of Road Transport Emissions: Evaluation of VOC speciation are from road transport Conclusions: Benzene / acetylene ratio: exhibits long-term trends in response to VOC emission control measures Mean Benzene/Acetylene Ratio Assumptions: Benzene & acetylene: react slowly in the atmosphere - ambient benzene to acetylene ratio reflects emission ratio The inventory values are a factor of 3 to 4 higher than ambient, and trends do not agree. There is a critical need for a re- evaluation of the VOC speciation in the NEI.

Evaluations of Power Plant Emissions: Nearly 50 plume studies on over 30 CEMS-equipped power plants (1995, 1997, 1999, 2000, and 2002). Flux ratios agree on average within estimated uncertainty of ambient determinations (± 10%). There are occasional significant discrepancies.

Absolute NO x, SO 2 and CO 2 fluxes agree with CEMS data within the estimated uncertainty (±20% for optimum conditions). CEMS data are accurate Conclusions: CEMS data are accurately integrated into the NEI CO emissions can be more than a factor 10 higher than inventoried. Evaluations of Power Plant Emissions: emission tabulated / flux measured There are occasional significant discrepancies.

Inventory alkene emissions are low by the following factors: Sweeny Freeport Choc. Bayou Ethene: Propene Coincident, highly elevated levels of NO x and reactive VOCs lead to rapid formation of high O 3 levels. Models using inventoried emissions of VOCs fail. Evaluation of Emissions from Texas Petrochemical Facilities (Ryerson et.al., JGR, 108, 4249, doi: /2002JD003070, 2003)

PM 2.5 source apportionment from chemical mass balance compared to the emission inventory in Denver, CO  Showed nearly twice the fractional contribution from fugitive dust emissions.  Did not include cold start gasoline vehicle exhaust, which makes a substantial contribution in the CMB analysis.  Underrepresented high emitter (i.e. poorly-maintained) gasoline vehicles. Compared to emission inventory, CMB showed: Inverse modeling application to ammonia emission inventory  Showed 40% lower average annual emissions with strong seasonal cycle.  Dramatic improvement in aerosol nitrate simulation (not included in inverse optimization) Compared to emission inventory, inverse modeling showed:

Conclusions Recommendations Challenge inventories with ambient measurements. Increase interaction and feedback between inventory and measurement folks. (Appropriate sites, measurement techniques, data analysis.) “Top down” tests do provide valuable evaluations of current inventories. It is not yet possible to develop “bottom up” inventories that are accurate enough for many scientific uses without support of direct measurements (e.g. CEMS) Still, “bottom up” inventories are indispensable

Global CO Emissions Inventory Enigmas: Compared to U.S., Western Europe emits factor of 2 less with 40% more population. Lifestyle! Western Europe emissions decreasing significantly while U.S. emissions nearly constant? Road transportation emissions in U.S.: ≈ 2/3 of total. Really increasing?

“Everyone knows” that CO emissions have decreased dramatically over the last couple of decades “National Vehicle Emissions Policies and Practices and Declining US Carbon Monoxide-Related Mortality”, J.A. Mott et al., J. Amer. Med. Assoc., 288, , ≈ 12,000 deaths avoided in U.S. ≈ 86% increase in vehicle miles traveled Death rates from CO Poisoning

U.S. National CO Emissions Inventory Enigmas: U.S. EPA emissions estimates have changed drastically. Danger Sign!! Looking at history of current estimates gives impression of increasing emissions. (Road Transport Sources)

U.S. National CO Emissions Inventory Enigmas: U.S. EPA emissions estimates have changed drastically. Danger Sign!! Looking at history of current estimates gives impression of increasing emissions. EDGAR EDGAR inventory may be affected by this changing of models (Road Transport Sources)

CO to NOx Ratio in Urban Vehicle Exhaust Ambient CO and NOy correlate well during morning rush hour. Ambient measurements characterize CO/NOy emission ratio in vehicle exhaust.

CO to NO x automotive exhaust emission ratios Ratio of CO to NO x in vehicle exhaust has decreased dramatically at these two sites from 1989 to 1999.

Comparison to Emission Inventories VOC emissions parallel CO emissions. The character of urban photochemistry must have changed as well. National inventory does not accurately reflect observed decrease. (National Air Pollutant Emission Trends, 2000) Colorado inventory does reflect Boulder decrease. (Colorado Department of Public Health and Environment) CO to NO x Ratio

Emissions ratios:from near-field aircraft transects in mixed layer

slopes from multiple transects vary by ±2% combined instrumental uncertainties typ. ± 10% provides an exacting test of inventory ratios

Absolute emission rates: calculate flux across plume transect White et al., Science, 194, , 1976.

Absolute emission rates: calculate flux across plume transect Thomas Hill plant Randolph County, MO July 7, km/1.5 hrs downwind Estimated uncertainty of ±20% in flux calculation under optimal conditions

Application to CO emissions from power plants: Power plant combustion is carefully monitored for maximum efficiency; most power plants emit undetectable amounts of CO, most of the time Martin Lake (TX) Monticello (TX) Three out of four lignite-coal-fueled power plants showed substantially enhanced CO emissions, up to factors of 30 greater than inventory values; also observed in bituminous- and gas-fired electric utility power plants. J. Environ. Monit., 5, (2003) expected slopes, from inventory ratios

Application to petrochemical industrial emissions: Houston, TX Compare measured (alkene/NO x ) to inventory (alkene/NO x ) Electra NO x and VOC measurements accurate to ±10% 2000 PSDB inventory NO x data are accurate to ± 30% any larger discrepancies in (alkene/NO x ) comparison attributed to errors in the alkene emissions inventory

Application to petrochemical industrial emissions: Houston, TX Inventory alkene emissions are low by the following factors: Sweeny FreeportChoc. Bayou Ethene: Propene (JGR, 108(D8), 4249, doi: /2002JD003070, 2003)

Nashville and Boulder are representative