2014-15 UINTAH BASIN WINTER OZONE STUDY - USU...3 2. List of Tables Table 1. Air quality monitoring stations, winter 2014‐15..... 6 Table 2. 8‐hour average ozone concentrations

320 North Aggie Blvd Vernal, UT 84078 [email protected] o: 435.722.1740 m: 435.630.1433 rd.usu.edu

FINAL REPORT

2014-15 UINTAH BASIN WINTER OZONE STUDY Submitted to:

Paul Hacking Uintah Impact Mitigation Special Service District 320 N Aggie Blvd Vernal, UT 84078

Submitted by:

Seth Lyman Bingham Entrepreneurship and Energy Research Center Office of Commercialization and Regional Development Utah State University 320 N Aggie Blvd Vernal, UT 84078

DOCUMENT NUMBER: BRC_151031A REVISION: ORIGINAL RELEASE DATE: OCTOBER 31, 2015

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1. Contents

1. Contents ................................................................................................................................................ 2

2. List of Tables ......................................................................................................................................... 3

3. List of Figures ........................................................................................................................................ 4

4. Background ........................................................................................................................................... 5

5. Air Quality and Meteorology During Winter 2014‐15 .......................................................................... 5

5.1. Introduction ................................................................................................................................... 5

5.2. Methods ........................................................................................................................................ 5

5.3. Results and Discussion .................................................................................................................. 7

6. Air Quality Modeling ........................................................................................................................... 21

6.1. Meteorological Models ............................................................................................................... 21

6.2. Emissions Modeling ..................................................................................................................... 22

6.3. Chemistry Modeling .................................................................................................................... 23

7. Acknowledgements ............................................................................................................................. 24

8. Additional Reports .............................................................................................................................. 24

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2. List of Tables

Table 1. Air quality monitoring stations, winter 2014‐15. ............................................................................ 6

Table 2. 8‐hour average ozone concentrations around the Uintah Basin, winter 2014‐15. ........................ 9

Table 3. Ozone summary statistics for five sites in the Uintah Basin over seven calendar years. All values were calculated from daily maximum 8‐hour average concentrations. ..................................................... 15

Table 4. PM2.5 summary statistics for the Uintah Basin over six calendar years. All values shown were calculated from daily 24‐hour average concentrations. ............................................................................. 17

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3. List of Figures

Figure 1. Snow depth time series at Roosevelt and Horsepool, winter 2014‐15. ........................................ 8

Figure 2. Time series of 8‐hour average ozone concentrations at all monitoring sites in the Uintah Basin, winter 2014‐15. The EPA NAAQS of 70 ppb is shown as a red dashed line. ................................................ 8

Figure 3. Time series of daily average snow depth, total UV albedo, and wind speed at Horsepool, winter 2014‐15. ........................................................................................................................................................ 9

Figure 4. Daily maximum 8‐hour average ozone for 5 January 2015. ........................................................ 10




Figure 8. Maximum 8‐hour average ozone on 7 January versus site elevation for all sites in the Uintah Basin, winter 2014‐15. ................................................................................................................................ 13

Figure 9. Time series of daily maximum 8‐hour average ozone concentration at five sites in the Uintah Basin, July 2009 through September 2015. The red dashed line shows 70 ppb, the EPA NAAQS for ozone. .................................................................................................................................................................... 14

Figure 10. Time series of daily 24‐hour average PM2.5 concentrations at nine sites in the Uintah Basin, October 2009‐March 2015. The red dashed line shows 35 μg m‐3, the EPA standard for PM2.5. .............. 16

Figure 11. 98th percentile of 24‐hour average PM2.5 concentrations for all sites in the Uintah Basin, winter 2014‐15. ........................................................................................................................................... 17

Figure 12. Time Series of NOx at Horsepool and Roosevelt, winter 2014‐15. ........................................... 19

Figure 13. Time Series of NOy at Horsepool and Roosevelt, winter 2014‐15. ........................................... 20

Figure 14. Time Series of NOz at Horsepool and Roosevelt, winter 2014‐15. ........................................... 20

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4. Background

Ozone has been measured continuously in the Uintah Basin since summer 2009. During winter 2009‐10 ozone concentrations measured at Ouray and Red Wash exceeded Environmental Protection Agency (EPA) standards. Following the discovery of this new phenomenon, stakeholder concern led to the establishment of several additional air quality monitoring stations to support subsequent studies. Seventeen stations operated around the Uintah Basin during winter 2010‐11, 30 operated during winter 2011‐12, 20 operated during winter 2012‐13, and 19 operated during winter 2014‐15. The results of these studies can be found in reports available at rd.usu.edu.

In general, wintertime air quality in the Uintah Basin becomes impaired when strong, multi‐day inversion events occur. Strong, multi‐day inversions only occur when (1) stagnant, high pressure meteorological conditions exist and (2) sufficient snow cover exists to reflect incoming sunlight, which keeps the ground from absorbing sunlight and warming. Snow also increases the amount of available sunlight to provide energy for the chemical reactions that form ozone. Numerous exceedances of EPA’s ozone standard have occurred during winters with adequate snow cover and sustained high pressure conditions, and no wintertime exceedances have ever been observed without snow cover.

During strong, multi‐day inversion episodes, high ozone first forms in the low‐elevation center of the Basin, and builds day‐upon‐day in concentration while expanding towards the Basin’s margins. In general, longer episodes and episodes that occur late in the winter season lead to higher ozone.

This report provides information about Uintah Basin air quality research conducted by Utah State University during 2014 and 2015. Section 5 of this report provides information about air quality measurements collected in the Uintah Basin during winter 2014‐15. Sections 6 and 7 provide summaries of emissions measurements and air quality model development carried out over the past year by Utah State University.

5. Air Quality and Meteorology During Winter 2014‐15

5.1. Introduction

This section provides an analysis of ozone, precursor, and meteorology data from air quality monitoring sites that operated around the Basin during winter 2014‐15, and an analysis of variability across all years of available ozone data. In this chapter, “winter 2014‐15,” “winter,” “winter season,” or other similar phrases refer to the period from November 15 through March 31.

5.2. Methods

5.2.1. Ozone Measurements

During winter 2014‐15, 20 air quality monitoring stations were operated in the Uintah Basin. Table 1 contains a list of all monitoring stations, including locations, elevations, and responsible operators. Data and methods used for stations operated by organizations other than USU were obtained from EPA’s AQS

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database (https://ofmext.epa.gov/AQDMRS/aqdmrs.html) or from http://airnowtech.org. We utilized 2B Technology Model 205 or 202 ozone monitors at most stations operated by USU, but an Ecotech Model 9810 ozone analyzer and a Thermo 49i were used at the Horsepool and Rabbit Mountain sites, respectively. We performed calibration checks at all USU stations at least every other week using NIST‐traceable ozone standards. Calibration checks passed if monitors reported in the range of ±5 ppb when exposed to 0 ppb ozone, and if monitors were within ±7% deviation from expected values when exposed to higher concentrations of ozone. We only included data bracketed by successful calibration checks in the final dataset.

Table 1. Air quality monitoring stations, winter 2014‐15. All stations except Randlett measured at least ozone and meteorology. Stations that measured VOC, NOx, and/or PM2.5 are indicated. NOx* signifies NO2 measured with a photolytic NO2 (rather than molybdenum) converter. Ute is the Ute Indian Tribe. NPS is the National Park Service. UDAQ is the Utah Division of Air Quality. BLM is the Bureau of Land Management. AQS is the EPA AQS air quality database (https://ofmext.epa.gov/AQDMRS/aqdmrs.html). Airnow is the EPA real time air quality database (http://www.airnowtech.org).

Operator Latitude Longitude Elev. (m) VOC NOx, PM2.5 Data Origin

Duchesne USU 40.162 ‐110.401 1682 N/A N/A USU

Flat Rock Ute/USU 39.547 ‐109.675 2274 N/A PM2.5 USU

Mtn. Home Ute/USU 40.432 ‐110.382 2234 N/A N/A USU

Seep Ridge USU 39.754 ‐109.546 1975 N/A N/A USU

Seven Sisters USU 39.981 ‐109.345 1618 N/A N/A USU

Castle Peak USU 40.051 ‐110.020 1605 N/A NOx USU

Rabbit Mtn. USU 39.869 ‐109.097 1879 N/A NOx USU

Dinosaur NPS 40.437 ‐109.305 1463 N/A N/A AQS

Red Wash Ute Tribe 40.204 ‐109.352 1689 N/A NOx Airnow

Vernal UDAQ 40.453 ‐109.510 1606 N/A NOx, PM2.5 Airnow

Whiterocks Ute Tribe 40.484 ‐109.906 1893 N/A NOx Airnow

Ouray Ute Tribe 40.055 ‐109.688 1464 N/A NOx Airnow

Roosevelt UDAQ 40.294 ‐110.009 1587 VOC NOx*, PM2.5 Airnow/USU

Myton Ute/USU 40.217 ‐110.182 1610 N/A NOx, PM2.5 Airnow/USU

Fruitland UDAQ 40.209 ‐110.840 2021 N/A NOx Airnow

Horsepool USU 40.144 ‐109.467 1569 VOC NOx*, PM2.5 USU

Ft. Duchesne Ute/USU 40.282 ‐109.870 1559 N/A PM2.5 USU

Dry Fork USU 40.565 ‐109.691 2030 N/A N/A USU

Rangely NPS/BLM 40.087 ‐108.762 1648 N/A NOx AQS

Randlett Ute/USU 40.232 ‐109.845 1482 N/A PM2.5 USU

5.2.2. Ozone Precursor Measurements

We measured NO, true NO2 (via a photolytic converter), and NOy (sum of NO, NO2, and other reactive nitrogen compounds) at Roosevelt and Horsepool with AQD/Teledyne‐API and Ecotech systems, respectively, and calibrated the systems weekly with NO standards, monthly with NO2 standards via gas phase titration, and once during the campaign with nitric acid and n‐butyl nitrate permeation tubes to calibrate for NOy (the sum of NOx and other reactive nitrogen compounds). All sites operated by other

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organizations measured NO and NO2 via a molybdenum converter‐based system, a method known to bias NO2 and NOx results high due to NOy interference.

We measured 57 ozone‐forming nonmethane hydrocarbons (NMHC) in 30‐minute and hourly samples at Horsepool and Roosevelt, respectively, during January and February. NMHC were analyzed by sample concentration on activated carbon traps, followed by desorption into automated gas chromatography‐flame ionization detection systems. Methane and total non‐methane hydrocarbons were measured at Horsepool and Roosevelt with gas chromatograph‐based instruments. We calibrated these systems every week with certified gas standards. EPA C2‐C12 PAMS compounds (EPA, 2003) were measured by the automated systems at Horsepool and Roosevelt.

5.2.3. Particulate Matter Measurements

We measured particulate matter with diameter smaller than 2.5 micrometers (PM2.5) at Horsepool and Rabbit Mountain with BAM 1020 monitors. We measured PM2.5 and PM10 at Myton with a Thermo TEOM DF‐1450 monitor. We collected filter‐based PM2.5 samples at Fort Duchesne and Randlett using BGI PQ200 instruments and determined PM2.5 gravimetrically in our laboratory. PM2.5 at Fort Duchesne and Randlett was measured with 24‐hour filter samples every 6th day. Instruments were operated according to manufacturer protocols, with leak checks, flow calibrations, and cleanings performed at regular intervals. Particulate matter values from other sites were extracted from the EPA AQS database (https://ofmext.epa.gov/AQDMRS/aqdmrs.html).

5.2.4. Meteorological Measurements

We deployed solar radiation sensors at Horsepool (incoming and outgoing short wave, long wave, UV‐A, and UV‐B radiation) and at Roosevelt (incoming and outgoing shortwave radiation). We operated a suite of comprehensive, research grade meteorological instruments at Horsepool, and more cost‐effective instruments (Davis VantagePro) at other sites. We also obtained shared meteorological data from the EPA AQS database and mesowest.utah.edu. We check wind speed and direction, temperature, and humidity against a calibration standard once annually. We check radiation measurements against calibration standards once every three years.

5.3. Results and Discussion

5.3.1. Ozone

Little snow fell in the Uintah Basin during winter 2014‐15, and the snow that did fall melted quickly (Figure 1). Enough snow persisted in the central Basin in the first week of January to lead to weak multi‐day inversions and some ozone buildup, though no exceedances of the EPA standard of 70 ppb were observed (Figure 2). This snow melted in the second week of January, and without persistent snow local ozone production was insignificant for the remainder of the winter.

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Figure 1. Snow depth time series at Roosevelt and Horsepool, winter 2014‐15.

Figure 2. Time series of 8‐hour average ozone concentrations at all monitoring sites in the Uintah Basin, winter 2014‐15. The EPA NAAQS of 70 ppb is shown as a red dashed line.

Because the lack of persistent snow cover prevented the formation of strong, sustained inversion episodes, no ozone exceedances were observed at any site during winter 2014‐15 (Figure 2, Table 2). Figure 3 shows that snow cover, high reflectivity (i.e, albedo) of UV light, and low winds all persisted at the Horsepool site during the first week of January, allowing a weak inversion to build up over a few days and lead to some ozone production. A brief snow event around the first of March led to another increase in UV albedo, but the snow melted rapidly and did not lead to a high ozone episode.

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Table 2. 8‐hour average ozone concentrations around the Uintah Basin, winter 2014‐15.

Mean Maximum Minimum

4th Highest Daily Maximum

Number of Exceedances

Duchesne 26.0 57.4 2.4 54.5 0Flat Rock 42.1 59.2 19.1 56.9 0Mtn. Home 40.4 59.6 17.9 56.5 0Seep Ridge 40.9 58.5 22.8 57.5 0Seven Sisters 32.1 53.8 10.7 52.9 0Castle Peak 31.5 55.9 12.2 53.3 0Rabbit Mtn. 33.2 52.3 13.7 51.1 0Dinosaur 27.3 53.1 3.6 51.1 0Red Wash 32.7 59.1 6.6 54.5 0Vernal 27.2 56.4 2.0 50.9 0Whiterocks 35.4 57.1 16.8 55.0 0Ouray 27.6 67.3 2.4 53.9 0Roosevelt 26.5 54.5 4.6 53.4 0Myton 30.0 54.9 6.3 54.6 0Fruitland 30.3 57.5 1.6 52.1 0Horsepool 34.9 63.1 12.6 58.5 0Ft. Duchesne 27.8 56.1 6.6 53.8 0Dry Fork 38.8 58.3 14.4 54.8 0Rangely 28.1 54.4 2.0 50.9 0

Figure 3. Time series of daily average snow depth, total UV albedo, and wind speed at Horsepool, winter 2014‐15.

Figures 4 through 7 show the spatial distribution of ozone during the weak multi‐day inversion episode that occurred from 5‐8 January. As has been observed consistently during the five years of available

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ozone measurements in the Uintah Basin, the highest ozone concentrations were at sites in the center of the Basin during this episode. Inversion conditions tend to appear first at lower elevations and persist longest there, allowing more time for ozone to build. Also, lower elevations are more insulated from the clean, upper atmosphere air above the inversion, helping to keep ozone and precursors trapped near the surface. Elevation and ozone have been strongly inversely correlated in years with many high ozone days, but Figure 8 shows that there was only a weak relationship between elevation and ozone during winter 2014‐15.

Little or no snow cover existed at Roosevelt during the early January inversion episode, but several centimeters of snow existed at Horsepool (Figure 1), indicating that snow cover in the Basin was not uniform. By 9 January, ozone returned to background or near‐background levels (Figure 7), even though full snow melt didn’t occur at Horsepool until a week later. Low winds on and around 9 January at Horsepool provide evidence against a strong storm breaking up the inversion, as has commonly occurred during previous years. However, the snow level and UV albedo at Horsepool were decreasing by 9 January, and warm temperatures that led to melting snow likely ended the inversion episode.

Figure 4. Daily maximum 8‐hour average ozone for 5 January 2015.

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Figure 8. Maximum 8‐hour average ozone on 7 January versus site elevation for all sites in the Uintah Basin, winter 2014‐15.

Figure 9 shows a time series of ozone concentrations at several sites in the Uintah Basin from July 2009 through September 2015. The Ouray air quality monitoring station began operation in July 2009.

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During winter 2009‐10, Ouray experienced multiple exceedances of the NAAQS for ozone (70 ppb). Subsequently, regulatory monitors in Roosevelt, Vernal, Fruitland, and Rangely were added. As Figure 9 shows, exceedances of the NAAQS have been observed during four of the six winters in the Uintah Basin for which continuous ozone monitoring data is available. The Utah Department of Environmental Quality also measured ozone in Vernal during 2006 and 2007, but those data are not publicly available and are not included here. No wintertime exceedances of the NAAQS were measured in Vernal during that period.

Figure 9. Time series of daily maximum 8‐hour average ozone concentration at five sites in the Uintah Basin, July 2009 through September 2015. The red dashed line shows 70 ppb, the EPA NAAQS for ozone.

Table 3 summarizes ozone statistics from the five sites shown in Figure 9 for each of the years that data are available. Data are organized by calendar year rather than by winter season, since summertime exceedances have also occurred (albeit rarely) and since a nonattainment designation, if made by EPA, will be based on the average of the annual fourth highest daily maximum 8‐hour average concentration averaged over three consecutive calendar years (i.e., the “ozone design value”).

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Table 3. Ozone summary statistics for five sites in the Uintah Basin over seven calendar years. All values were calculated from daily maximum 8‐hour average concentrations.

Year Site Mean Median Max Min 4th High Daily Max

Exceedance Days (>70.9 ppb)

2009 (July‐Dec)

Ouray 47.2 47.9 101.5 23.4 67.4 1

Fruitland ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

Vernal ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

Roosevelt ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

Rangely ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

2010 Ouray 56.7 54.5 123.6 20.3 117.3 45

Fruitland ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

Vernal ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

Roosevelt ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

Rangely 42.3 42.2 67.2 11.1 58.8 ‐‐

2011 Ouray 54.0 52.8 138.6 18.1 119.6 28

Fruitland 49.3 50.6 71.6 24.0 65.3 1

Vernal 55.5 55.6 95.1 33.1 84.9 12

Roosevelt 56.2 54.7 116.3 29.3 103.6 21

Rangely 48.6 50.0 88.6 21.9 73.4 4

2012 Ouray 49.3 50.5 76.5 18.8 67.6 1

Fruitland 49.9 49.6 71.9 26.1 70.3 3

Vernal 45.7 46.8 68.9 14.5 64.8 0

Roosevelt 50.3 51.6 70.9 14.6 67.0 0

Rangely 46.7 47.4 71.9 15.9 69.6 2

2013 Ouray 58.3 54.6 141.6 24.0 132.4 52

Fruitland 50.1 50.0 75.1 18.6 69.8 2

Vernal 53.2 52.9 114.9 20.5 102.1 32

Roosevelt 50.5 51.8 110.8 13.6 104.0 35

Rangely 50.8 50.7 106.1 22.3 91.0 13

2014

Ouray 52.1 47.0 91.9 28.5 79.8 8

Fruitland 48.4 49.7 65.6 16.0 64.1 0

Vernal 42.3 42.6 57.5 28.0 54.3 0

Roosevelt 45.3 45.0 63.8 25.0 58.3 0

Rangely 42.4 42.3 51.8 30.0 49.7 0

2015 (Jan‐Sep)

Ouray 48.8 50.2 71.4 21.8 68.5 2

Fruitland 49.0 50.1 77.9 23.5 69.8 3

Vernal 47.3 48.5 66.5 10.5 63.5 0

Roosevelt 46.3 48.5 66.6 14.3 63.8 0

Rangely 46.8 47.8 70.8 15.1 66.9 0

5.3.2. Particulate Matter

As has been typical in previous years, PM2.5 concentrations tended to be higher on the west side of the Uintah Basin than on the east side during winter 2014‐15, and concentrations in populated areas tended to be higher than in more remote areas (Figures 10 and 11). The only site to exceed the EPA standard

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for PM2.5 was Roosevelt (though monitors at Vernal, Ouray, and Red Wash were not operational). It is not clear why the west side of the Basin has higher PM2.5. The western Uintah Basin has more oil wells and few gas wells, and combustion emissions from pumpjack engines and other combustion devices that are common at oil wells could be at least partly responsible.

Summertime PM2.5 exceedances were observed in the Uintah Basin during summer 2012, and spikes in PM2.5 have been observed during every summer (Figure 10). These summertime spikes in PM2.5 concentrations have likely been due to wildfire smoke.

Figure 10. Time series of daily 24‐hour average PM2.5 concentrations at nine sites in the Uintah Basin, October 2009‐March 2015. The red dashed line shows 35 μg m‐3, the EPA standard for PM2.5.

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Figure 11. 98th percentile of 24‐hour average PM2.5 concentrations for all sites in the Uintah Basin, winter 2014‐15.

PM2.5 values in Vernal and Roosevelt have exceeded EPA standards more than other sites, including Ouray, which has the highest ozone (Table 4). While PM2.5 increases at all sites during winter inversion episodes, and while those values can be near or sometimes exceed EPA standards, urban sources (which might include wood smoke, traffic‐related emissions, or other sources) apparently add additional PM2.5, making urban areas more likely to experience exceedances of the standard. Table 4 is a summary of PM2.5 values at sites around the Uintah Basin from 2010 through March 2015.

Table 4. PM2.5 summary statistics for the Uintah Basin over six calendar years. All values shown were calculated from daily 24‐hour average concentrations.

Year Site Winter Mean

Winter Median

Winter Max

Winter Min

Annual # of Exceedance Days

Annual 98th Percentile Value

2010 Roosevelt ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

Vernal ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

Ouray 8.8 5.2 22.5 0.0 0 19.0

Red Wash 7.2 5.8 22.7 0.0 0 16.0

Myton ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

Rabbit Mtn ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

Horsepool ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

2011 Roosevelt ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

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Year Site Winter Mean

Winter Median

Winter Max

Winter Min

Annual # of Exceedance Days

Annual 98th Percentile Value

Vernal ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

Ouray 9.8 8.6 29.9 1.1 0 22.5

Red Wash 7.8 6.5 23.6 1.0 0 17.7

Myton 11.8 6.9 48.1 0.0 8 36.7

Rabbit Mtn ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

Horsepool ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

2012 Roosevelt 5.6 2.7 22.2 0.0 3 28.2

Vernal 7.9 7.1 25.6 1.2 0 22.0

Ouray 6.1 5.9 13.9 1.2 3 27.4

Red Wash 4.8 4.4 10.6 0.0 0 15.9

Myton ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

Rabbit Mtn 2.7 2.5 10.7 0.0 4 20.2

Horsepool 3.9 2.5 10.7 0.0 0 10.3

2013 Roosevelt 18.6 12.1 41.7 0.0 5 35.1

Vernal 19.9 15.4 55.7 2.6 18 42.1

Ouray 13.3 11.5 32.0 2.2 0 26.5

Red Wash 10.8 8 26.6 3.0 0 25.9

Myton ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

Rabbit Mtn 4.9 3.7 13.9 0.0 0 18.0

Horsepool 13.6 8.4 28.3 0.0 0 27.8

2014

Roosevelt 8.1 4.1 35.3 0.0 1 29.8

Vernal 9.5 6.6 32.1 2.2 0 30.3

Ouray 9.2 6.8 34.3 2.3 0 31.6

Red Wash 5.9 3.4 26.8 0.0 0 15.1

Myton ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

Rabbit Mtn 2.0 1.5 5.0 0.0 0 5.1

Horsepool 5.5 4.0 22.3 0.0 0 21.6

2015 thru Mar 31

Roosevelt 8.2 4.4 46.7 0.0 1 29.1

Vernal ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

Ouray ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

Red Wash ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

Myton 6.5 3.6 25.5 0.1 0 23.6

Rabbit Mtn 1.7 1.6 3.8 0.0 0 3.6

Horsepool 6.9 6.1 15.2 3.0 0 14.1

Ft Duchesne 7.5 4.1 18.0 1.8 0 11.1

Randlett 10.5 3.8 34.6 2.2 0 18.5

5.3.3. Reactive Nitrogen

NO2 measurements at regulatory monitoring stations do not reflect true NO2 values. NOx measurements at these stations use molybdenum oxide catalysts to convert NO2 to NO. Because the catalysts also convert other reactive nitrogen compounds (e.g., nitric acid, nitrous acid, peroxyacetyl

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nitrate, etc.) to NO, and because concentrations of these other compounds tend to be greater than concentrations of NO2, NO2 and NOx values measured at regulatory monitoring stations are biased high when concentrations of non‐NOx reactive nitrogen are high. The ratio of NO2 to other reactive nitrogen compounds is likely to vary from site to site, so estimating true NO2 concentrations (and true NOx concentrations) from measured NO2 values is problematic. NO values at regulatory monitors are not biased.

This section only discusses reactive nitrogen data collected by USU from Roosevelt and Horsepool. These sites have NOx monitors that utilize photolytic NO2 converters that do not suffer from the NOy bias to which molybdenum oxide converters are subject. During winter 2014‐15, as observed in previous years, NOx was consistently higher at Roosevelt (4.8 [mean] ± 6.0 ppb [st. deviation]) than at Horsepool (3.0 ± 4.3 ppb), with more variability and a higher average for the season (Figure 12). The difference is likely due to urban NOx sources that are more abundant in Roosevelt. Figure 13 shows that NOy (i.e., the sum of all reactive nitrogen compounds, including NOx, nitric acid, organic nitrates, etc.) likewise was more abundant at Roosevelt (7.4 ± 7.4) than at Horsepool (5.4 ± 5.3).

The difference between NOy and NOx, often termed NOz, is a measure of the amount of non‐NOx reactive nitrogen in the atmosphere. NOz is made up of nitric acid, nitrous acid, peroxyacetyl nitrate, and other byproducts and end products of the photochemistry that also produces ozone. NOz concentrations at the two sites were similar (2.8 ± 2.7 at Roosevelt, 2.5 ± 2.1 at Horsepool), indicating similar levels of photochemical activity at the two sites (Figure 14). NOz concentrations at both sites were higher during the first week of January when significant local photochemistry also led to increases in ozone (Figure 2, Figure 14).

Figure 12. Time Series of NOx at Horsepool and Roosevelt, winter 2014‐15.

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Figure 13. Time Series of NOy at Horsepool and Roosevelt, winter 2014‐15.

Figure 14. Time Series of NOz at Horsepool and Roosevelt, winter 2014‐15.

5.3.4. Organic Compounds

Methane, total nonmethane hydrocarbons, and speciated nonmethane hydrocarbons were measured at Horsepool and Roosevelt during winter 2014‐15. Analysis of these measurements is still underway, however, and will be reported separately.

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6. Air Quality Modeling

Ozone modeling generally consists of three separate stages: (1) meteorology, in which we model the dynamics of the atmosphere; (2) emissions, in which we try to account for all of the pollutants entering the atmosphere; and (3) chemistry, in which we model the chemical reactions by which the primary pollutants entering at stage 2 (e.g., ozone precursors) are transformed into secondary pollutants (including ozone). We have made a number of improvements in the capability of these modeling platforms for winter ozone events in the Uintah Basin. The following paragraphs highlight the accomplishments over the previous year. Many of these model development projects have been carried out in cooperation with scientists at the University of Utah, Brigham Young University, and the Utah Division of Air Quality.

6.1. Meteorological Models

Following are the areas of focus for meteorological models.

6.1.1. Snow cover and vegetation

The default snow cover and vegetation parameterizations have proved to be defective. Snow cover plays a role in stabilizing inversions; it keeps the surface layer cold by reflecting most of the solar radiation. For the snow cover to be completely effective, it must be deep enough to cover surface vegetation. We modified the models, first, to use actual observational snow depth data, and second, we used a higher resolution vegetation dataset available from the US Geological Survey. With these modifications, the reflectivity of the snowpack during modeled events changed from about 55% to about 80%.

6.1.2. Cloud cover

The meteorological models tend to over‐estimate cloud cover, which makes them under‐predict solar radiation and ozone production. We applied modifications designed by John Horel’s group at the University of Utah to the cloud physics package, and saw significant improvements in the stability and duration of thermal inversions.

6.1.3. Model initialization

The timing of the start‐up of a simulation run relative to the beginning of the thermal inversion is crucial. To avoid the “butterfly effect,” (the effect in which model predictions deteriorate after several days) a common practice in modeling long‐term events has been to reinitialize the simulation after every few days. However, we have found that the model performance can be very poor if we reinitialize in the middle of an inversion. It is better not to reinitialize during the course of an inversion, even if this means going a week or more between reinitializations.

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6.1.4. Observational Nudging

The meteorological packages allow a technique called “observational nudging,” in which real‐life observational data like wind speed or temperature is used to “nudge” the models and bring them closer to reality. We have made the counter‐intuitive finding that nudging degrades the quality of the Uintah Basin wintertime models. In particular, it tends to underestimate the depth and strength of the inversion layer.

6.2. Emissions Modeling

6.2.1. Available emissions inventories

An estimate of emissions into the atmosphere, or an emissions inventory, broken down by time and location, is an obvious requirement for doing air quality modeling. So‐called “bottom‐up” inventories attempt to determine emissions by accounting for all possible sources, while “top‐down” inventories are intended to be more global, and are often based on aircraft flyovers or satellite measurements. We have studied four different inventories of the Uintah Basin. The first bottom‐up inventory is the National Emissions Inventory (NEI), prepared by EPA using data supplied by the states, and is updated every few years. The second bottom‐up inventory is iteration three of an inventory prepared by the Western Regional Air Partnership, a private consortium working with an environmental consulting firm (Environ); it is the so‐called WRAP‐III inventory, and only includes data from the oil and gas production industry. The third bottom‐up inventory is the BLM‐ARM inventory, which was sponsored by the Air Resources Management program of BLM and performed by another consulting firm (AECOM), which also includes only oil and gas data. The fourth inventory we have considered is top‐down, developed by NOAA and University of Colorado researchers based on an aircraft flyover that occurred in February 2013. The flyover only detected methane emissions, so emissions of other VOCs were scaled in proportion to total methane.

6.2.2. VOC speciation profiles and missing formaldehyde

Often, the inventories only specify total VOC emissions, without breaking the total down into contributions from individual species. Therefore, as part of the emissions modeling, a “VOC speciation profile” must be combined with the inventory. We examined a number of different VOC speciation profiles that are currently in use. The most significant difference is the amount of formaldehyde and other carbonyls that each contains, and without high formaldehyde, we find that the chemistry models always under‐predict ozone. (This coincides with findings from NOAA researchers indicating that formaldehyde plays a crucial role in Uintah Basin ozone formation.) However, we have examined in detail why some profiles have more formaldehyde than others, and always find it is there for a wrong reason. The default profile provided by EPA assumes more flaring than actually occurs in the Uintah Basin. Another profile has mistakenly double‐counted sources of formaldehyde. A third has formaldehyde set artificially high to test the sensitivity of the models to total formaldehyde. When we try to make our speciation profiles reflect the best available observational data, we never have enough formaldehyde to predict high ozone. This means either that there is an unknown formaldehyde source, or that there are aspects of low‐temperature, low‐humidity ozone chemistry that are poorly understood and unaccounted for in the models. Assuming the former to be true, then finding the missing formaldehyde is an ongoing problem for both the BRC modeling and measuring teams, and may be

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crucial to solving the winter ozone problem. Obviously, if we can locate the source or sources, we have a chance of knowing how to control them.

6.3. Chemistry Modeling

Over the past year we have made a number of important improvements to the chemistry models, as explained below.

6.3.1. Surface Reflectivity

The modifications to the snow cover and vegetation parameterizations discussed above have also had a big impact on the chemistry models, by assuring that the models properly reflect the amount of solar energy available for ozone formation.

6.3.2. Dry Deposition of Chemical Species

Ozone can be removed from the atmosphere by settling out and absorbing onto the snow surface. We modified the dry deposition rate of ozone in the models to be consistent with the latest measurements.

6.3.3. Source Apportionment Methods

One advantage of computer modeling is it lets us estimate the impact of any given emission source or emission category. The chemistry models include two applications for doing this, and these were applied to a study of the impact of the Bonanza Power Plant. One application asks how total ozone would change if the plant were completely shut down. The other asks for the impact of incremental changes, say if plant emissions were to increase or decrease by 10%. Our finding was that the power plant has minimal impact on winter ozone in the basin for two reasons, one, because it emits only NOx but not VOC, and two, because the NOx is injected by a tall stack above the inversion layer.

6.3.4. Modifications to the chemistry models to reflect issues specific to the Uintah Basin ozone system

If you set out to model urban summer ozone caused mainly by vehicular emissions you are justified in making certain assumptions. However, the resulting model may be less than optimal for winter ozone in the Uintah Basin. We have applied many modifications to the chemistry models to rectify these issues. The modifications fall into four categories: corrections for conditions of (1) low temperature, (2) low humidity, (3) high methane, and (4) incorporating the most up‐to‐date chemical measurements. This effort included collaboration with Jaron Hansen’s group at BYU, who identified many of the changes that needed to be made. At USU, we did the code modifications and testing. The methane modifications led to a net increase in predicted ozone of about 6 to 7 ppb, an important finding since it has always been assumed that methane is not important for ozone formation. However, when all modifications are applied, the predicted ozone decreases, which we attribute mainly to the effect of lower temperature.

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7. Acknowledgements

We are grateful to the Uintah Impact Mitigation Special Service District, the Ute Indian Tribe, and the Utah Science, Technology, and Research Initiative for financial support of this work. We thank the Bureau of Land Management for providing equipment for remote ozone monitoring. We are also grateful to the Utah Department of Environmental Quality for providing space, shelter, and power for our instruments at Roosevelt, to QEP Resources for providing space and power for the Horsepool station, to Enefit American Oil for allowing us to operate their Rabbit Mountain station, and to Newfield for providing space and power for the Castle Peak station.

8. Additional Reports

A number of additional reports and papers regarding Uintah Basin Air Quality were produced during the past year. These are listed below, and links are provided. Results from many of the reports are in various stages of preparation and review for publication and will be made available as soon as possible.

Annual Performance Report: Measurement of Methane and Non‐methane Soil Flux Near Oil and Gas Wells in Utah. CRD_14364A. December 2014. Available at https://usu.box.com/shared/static/dqvby4bwoh6hbhq4vbiv0wnjpwjnu9fq.pdf.

Final Report: Bonanza Power Plant Emissions Model. BRC_15009A. January 2015. Available at https://usu.box.com/shared/static/yiq8ub9gvonk5d3b8lqr8bzp9ekq3jlu.pdf.

Final Report: Computer Modeling of Winter Ozone Formation in the Uintah Basin. BRC.15090A. March 2015. Available at https://usu.box.com/shared/static/dhix4rdgimbo2ry0fxi4vky0htuvsd5t.pdf.

Annual Report: Measurements of Air Quality on Ute Tribal Lands. CRD_150531A. May 2015. Available at https://usu.box.com/shared/static/gdg9k16r4i4mof96a7zsvv6h0k32kp2y.pdf.

Final Report: Measurement of Carbonyl Emissions From Oil and Gas Sources in the Uintah Basin. CRD_150731A. July 2015. Available at https://usu.box.com/shared/static/mj00rz4j520sauy7buovgf992kxgf87e.pdf.

Final Report: Adapting the SAPRC Chemistry Mechanism for Low Temperature Conditions. BRC_NNNNN. September 2015. Available at https://usu.box.com/shared/static/vtzj3rj4z0iax4rm8y9kbnkm80s0vnfx.pdf.

Annual Report: Establishment of the USU‐Uintah Basin Air Quality Modeling Center. September 2015. Available at https://usu.box.com/shared/static/7taofaecxma816w51j1bx5qzmh5sm729.pdf.

Inversion Structure and Winter Ozone Distribution in the Uintah Basin, Utah, U.S.A. October 2015. Accepted for publication in Atmospheric Environment. Final manuscript available at https://usu.box.com/shared/static/eilraap3romw5ifq41ino7j48lpktm2v.pdf.

2014-15 UINTAH BASIN WINTER OZONE STUDY - USU...3 2. List of Tables Table 1. Air quality monitoring stations, winter 2014‐15..... 6 Table 2. 8‐hour average ozone concentrations

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