The Arizona Wilderness and Urban Visibility Monitoring Networks

The Arizona Wilderness and Urban Visibility Monitoring Networks Paper # 51 Joe Adlhoch Air Resource Specialists, Inc., 191 Sharp Point Dr., Suite E, Fort Collins, CO 8525 Michael Sundblom Arizona Department of Environmental Quality, 111 W. Washington St., Phoenix, AZ, 857 Darcy Anderson Arizona Department of Environmental Quality, 111 W. Washington St., Phoenix, AZ, 857 ABSTRACT The Arizona Department of Environmental Quality (ADEQ) implemented a long-term urban visibility monitoring network in 1992 and a wilderness visibility monitoring network to supplement existing Interagency Monitoring of Protected Visual Environments (IMPROVE) monitoring in 1996. The overall goals of these networks are: to collect data in support of regulatory requirements (nationally, the Regional Haze Rule; locally the Phoenix Brown Cloud Summit recommendations and subsequent legislative directives); increase scientific understanding of visibility in terms of aerosol composition, light scattering and extinction, and hourly time resolution; and support ancillary efforts, including public outreach (real-time data reporting on the internet), AIRNow PM 2.5 reporting, PM 2.5 forecasting, and fire programs. Both networks have developed significantly in size and scope since their inception. ADEQ currently operates over 2 visibility monitoring sites (including nephelometers, transmissometers, high resolution web cameras, and meteorology) which geographically cover much of the state of Arizona. Monitoring occurs in or near each of Arizona s Class I areas. Monitoring is conducted at multiple sites in the metropolitan areas of Phoenix and Tucson. Combined, these two networks provide sufficient data to determine spatial characterization of aerosol and light scattering/extinction budgets and regional variations in agreement between measured and estimated light scattering/extinction, and to capture and illustrate the effects of regional visibility events. Examples of how the data from these networks are used to meet ADEQ s diverse goals are presented. INTRODUCTION The Arizona Department of Environmental Quality (ADEQ) operates visibility monitoring networks to support a diverse set of goals, including: To collect data in support of regulatory requirements (nationally, the Regional Haze Rule; locally the Phoenix Brown Cloud Summit recommendations and subsequent legislative directives) Paper No. 51, The Arizona Wilderness and Urban Visibility Monitoring Networks, Regional and Global Perspectives on Haze: Causes, Consequences and Controversies Visibility Specialty Conference, Air & Waste Management Association, Asheville, NC, October 25-29, 24

To increase scientific understanding of visibility in terms of aerosol composition, light scattering and extinction, and hourly time resolution; and To support ancillary efforts, including public outreach (real-time data reporting on the internet), AIRNow PM 2.5 reporting, PM 2.5 forecasting, and fire programs. ADEQ s urban haze networks are designed to monitor particulate and visibility parameters in the state s two largest metropolitan areas (Phoenix and Tucson). ADEQ s wilderness network focuses on the state s Class I areas and supplements the Interagency Monitoring of Protected Visual Environments (IMPROVE) aerosol network. Urban Haze Networks Detailed studies of the nature and causes of urban hazes were conducted by contractors on behalf of ADEQ in the Phoenix area during the winter of 1989-9 and in the Tucson area during the winter of 1992-93. Each of those studies recommended long-term, year-round monitoring of visibility, and ADEQ then made a commitment to do so, with instrument deployment starting in 1993. Visibility monitoring data from the Tucson and Phoenix long-term urban haze/pm 1 networks are used to: Provide policy-makers and the public with information regarding urban haze levels; Track short-term and long-term urban haze trends; Assess source contributions to urban haze; and Better evaluate the effectiveness of air pollution control strategies on urban haze. After nearly a decade of visibility-related data collection and analysis, Governor Hull of Arizona established the Brown Cloud Summit in 2 to identify strategies to improve visibility in the Phoenix metropolitan area. 1 The Visibility Standards Subcommittee of the Brown Cloud Summit was charged with establishing options for a visibility standard or other method to track progress in improving visibility in the Phoenix area. The Summit concluded a daily Visibility Index for the metropolitan area should have its characteristics defined through a public survey process. This process called for a representative cross-section of residents to determine what visual air qualities are desirable, what visual range is acceptable, and how often the combination of acceptable visual range and air quality is preferred. Through a series of meetings in 22, ADEQ and the Visibility Index Oversight Committee designed the visibility survey, selected a contractor to conduct the survey, and oversaw the completion of the field portion of the survey. Based upon the technical analysis of the survey results, the Committee selected the following category thresholds for the Visibility Index: 1-14 deciviews - excellent; 15-2 deciviews - good; 21-24 deciviews - fair; 25-28 deciviews - poor; and 29 or more deciviews - very poor. 2 The index is not designed to be a tool to affect short term actions because other programs are currently in place to do that in the Phoenix Metropolitan area. The Governor s Brown Cloud Summit also recommended that ADEQ enhance the Phoenix Urban Haze network, both spatially and technologically. The network now includes one additional transmissometer, 4 nephelometers, and 5 digital cameras, all with near real-time posting to a newly designed Web site (www.phoenixvis.net). The Web site is also the primary

means for presenting the daily Visibility Index to the public. The expanded network was deployed to represent the West Valley, Central Phoenix and East Valley as well as views of familiar landmarks such as the White Tank Mountains, Estrella Mountains, Camelback Mountain, Superstition Mountains, and the Downtown Phoenix area. Figure 1 illustrates Phoenix area monitoring locations in the expanded visibility network. The Phoenix and Tucson metropolitan area networks have experienced other recent changes. In Tucson, the visibility network now includes 1 transmissometer and 3 nephelometers. In both cities filter based urban haze measurements with dichotomous samplers were discontinued as of December 31, 23. In the Phoenix area aerosol samples continue to be collected with IMPROVE samplers. Additional filter based sampling will be conducted in the future to allow for historical comparison and trend analysis. Figure 1. Phoenix area monitoring locations. Transmissometer paths are red, nephelometer locations green, and digital camera locations and view angles yellow. Wilderness Visibility Network The 1977 federal Clean Air Act Amendments designated as Class I areas specific federal lands that had earlier been designated wilderness areas, and in which visual air quality was an important resource for visitors. Of the 156 Class I areas designated across the nation, 12 are located in Arizona. From the Class I area designations, EPA initiated a national speciated aerosol monitoring network in 1987 called the Interagency Monitoring of Protected Visual Environments

(IMPROVE) program. The purpose of the IMPROVE network is to characterize broad regional trends and visibility conditions using monitoring data collected in or near Class I Areas across the United States. Originally the national IMPROVE network was made up of approximately 3 sites at Class I areas; during 1999-2 the number of sites increased to approximately 11. In 1996 ADEQ began to add nephelometer monitoring sites in or near Class 1 areas in the state in order to supplement the IMPROVE network. Where feasible, nephelometers were collocated with aerosol samplers. The monitoring sites and represented Class I or other areas are presented in Table 1. Table 1. Visibility Monitoring Site Locations In Arizona Geographic Area Represented Grand Canyon National Park (Class I area) Petrified Forest National Park (Class I area) Sycamore Canyon USFS Wilderness (Class I area) Mazatzal and Pine Mountain USFS Wilderness (Class I areas) Mount Baldy USFS Wilderness (Class I area) Sierra Ancha USFS Wilderness (Class I area) Superstition USFS Wilderness (Class I area) Saguaro National Park (Class I area) Chiricahua National Monument, Chiricahua and Galiuro USFS Wilderness (Class I areas) Background (not Class I areas) Special study site: Naco, AZ (not Class I area) Monitoring Site Name Hance and Indian Gardens Petrified Forest Camp Raymond Humboldt Mountain Ike s Backbone Greer Water Treatment Plant Pleasant Valley Ranger Station McFadden Peak (Deactivated in 2) Tonto National Monument Queen Valley Saguaro East Saguaro West (Tucson Mountain) Chiricahua National Monument Entrance Station Muleshoe Ranch Rucker Canyon (Deactivated in 21) Hillside Meadview Organ Pipe National Monument Naco

REGIONAL VISIBILITY EVENTS A geographically large monitoring network can be used to track regional visibility events. This section describes episodes in which ADEQ relied on visibility data to help interpret visibility events. Wind Event Affecting Southeast Arizona May 23 A high wind event affected several sites in southeastern Arizona beginning on May 2, 23. Elevated concentrations of particulate matter 1 microns or smaller (PM 1 ) were measured in Paul Spur along the Arizona-Mexican border west of Douglas, Arizona. The elevated values were shown to be caused by a regional wind event. Nephelometer data collected throughout southern and central Arizona were used to aid in identifying the extent of the wind blown dust. Figure 2 illustrates the northward progression of the particulate matter over a period of approximately 12 hours. Sites shown in the legend are listed from left to right in order of the time of maximum light scattering (b scat ) occurrence. The Naco and Muleshoe Ranch nephelometers first detected the particulate matter at approximately 8:P.M. on May 2. Tucson Mountain recorded a maximum value at approximately 2:A.M., followed by the Phoenix Supersite at 8:A.M., both on May 21. Elevated scattering was also seen at the Pleasant Valley and Greer sites during this period. This event was also observed and documented with the optical instruments and urban digital cameras in the Phoenix area. Figure 3 shows b scat values recorded at the Phoenix Supersite between May 19 and May 22. An increase in light scattering can be seen during the evening of May 2 and a maximum value early on May 21. Figure 4 presents three images taken with one of ADEQ s digital web cameras. Downtown Phoenix is centered in each image. This series of images depicts the progression of the dust event through the Phoenix area.

Figure 2. Nephelometer timelines for several Southeastern Arizona sites during May 19 22, 23. 25 225 2 175 Timeline of Southern Arizona Nephelometer Data May 19-22, 23 Bscat (Mm-1) 15 125 1 75 5 25 5/2/3 5/21/3 5/22/3 Naco Muleshoe Tucson Mt Phoenix SS Pleasant Valley RS Greer Figure 3. Nephelometer timeline for the Phoenix Supersite during May 19 22, 23. 15 Timeline of Phoenix Supersite Nephelometer Data May 19-22, 23 125 Bscat (Mm-1) 1 75 5 25 5/2/3 5/21/3 5/22/3

Figure 4. Images of downtown Phoenix captured by one of ADEQ s digital web cameras showing the effects of the high wind event in Phoenix. Image 1. 5/2/3 9:15AM Image 2. 5/21/3 9:15AM Image 3. 5/22/3 9:15AM

Asian Dust Event Affecting the Western US April 21 Dust from Asian deserts are periodically transported across the Pacific Ocean, typically in Spring. During April 21 a large Asian dust event affected particulate concentrations across the western and central U.S. The total amount of dust transported over the continental U.S. has been estimated at 1.1 metric tons. 3 This April 21 Asian dust event was observed at wilderness and urban nephelometers throughout Arizona. Figure 5 presents the measured particle scattering (b sp ) at several southern Arizona sites during April, and clearly illustrates the arrival of the Asian dust on April 17-18, 21. Figure 5 compares the April event as measured by the Muleshoe Ranch nephelometer to historical 2% best and 2% worst b sp for the site. Figure 5. Left: Particle scattering at four Southeastern Arizona nephelometer sites during April 21. The dust transported from Asia arrived on April 17-18, 21. Right: Particle scattering at the Muleshoe Ranch nephelometer site during April 21. The historical 2% best and 2% worst b sp for the site are indicated on the plot for reference. SOUTHERN ARIZONA NEPHELOMETER SITES Asian Dust Event, April 21 Tucson Mountain Tucson (Craycroft) Muleshoe Ranch Rucker Canyon 16 14 12 MULESHOE RANCH (GALIURO W.) ADEQ Class I Nephelometer Network Asian Dust Event, April 21 Historical 2% Dirty Particle Scattering Historical 2% Clean 12 1 8 6 4 2 4/1 4/11 4/12 4/13 4/14 Particle Scattering (Mm -1 ) 4/15 4/16 4/17 4/18 4/19 Particle Scattering (Mm -1 ) 4/2 4/21 4/22 4/23 4/24 4/25 1 8 6 4 2 4/1 4/2 4/3 4/4 4/5 4/6 4/7 4/8 4/9 4/1 4/11 4/12 4/13 4/14 4/15 4/16 4/17 4/18 4/19 4/2 4/21 4/22 4/23 4/24 4/25 4/26 4/27 4/28 4/29 4/3 COMPARISONS BETWEEN MEASURED AND ESTIMATED LIGHT SCATTERING Ambient nephelometers are used to measure light scattering of aerosols with minimal changes to the sample aerosol temperature and humidity. This information allows comparison between estimated aerosol scattering based on IMPROVE methodologies 4 and direct measurements of particle scattering. Ambient nephelometer data are screened to identify periods that are not representative of particle scattering (e.g., weather events, insects or other objects in the measurement chamber, etc.). 5 Hourly relative humidity measurements collected at the aerosol sampling sites are used to calculate aerosol scattering. Comparisons between aerosol-based and directly measured light scattering have shown that there is a tendency for high (low) ambient nephelometer scattering to be higher (lower) than aerosol

scattering calculated with the IMPROVE method. This has generally been attributed to limitations in some of the assumptions in the IMPROVE aerosol extinction model. In general, differences between daily estimated and measured scattering may occur due to the following reasons: Differences between assumed and actual aerosol characteristics (size, scattering efficiency, acidity, hygroscopicity, etc.). Nephelometer measurement error (e.g., weather or other interference not caught by screening algorithms; systematic bias in measurement from one instrument to another). Aerosol sample measurement or analysis error (e.g., variable sample flow which affects particle size cut point; contamination of filter sample). Instrument uncertainty associated with the aerosol sample or nephelometer measurement. Figure 6 presents comparisons of estimated and measured particle scattering at two wilderness sites and one urban site in Arizona. The IMPROVE aerosol data were taken from the Visibility Information Exchange Web Site (VIEWS). 6 The Sycamore Canyon site is located near Flagstaff in northern Arizona. The Saguaro National Park West site is located just west of Tucson in southern Arizona. The Phoenix Supersite is located in downtown Phoenix, within the downtown transmissometer path and the South Mountain web camera view. Aerosol scattering data from the all three sites can be seen to generally overestimate the measured nephelometer scattering at low values (~ < 3 Mm -1 ). Data at the Phoenix Supersite shows a trend of overestimating measured scattering at all times. A review of measured fine aerosol mass and reconstructed fine aerosol mass (the sum of calculated ammonium sulfate, ammonium nitrate, organic carbon, elemental carbon, and fine soil) for 22 at these sites reveals that while the reconstructed mass under predicted measured mass by 7 11% at the wilderness sites, it over predicted mass at the Phoenix site by 16%.

Figure 6. Scatterplots comparing estimated aerosol scattering and measured nephelometer scattering at two wilderness sites and one urban site in Arizona. The Sycamore Canyon site is located near Flagstaff in northern Arizona. The Saguaro National Park West site is located outside of Tucson in southern Arizona. The Phoenix Supersite is located in downtown Phoenix, within the downtown transmissometer path and the South Mountain web camera view. Sycamore Canyon 22 Saguaro National Park - West 22 6 6 Estimated Particle Scattering (Mm-1) 5 4 3 2 1 y =.91x + 3.26 R 2 =.68 Estimated Particle Scattering (Mm-1) 5 4 3 2 1 y =.95x + 3.45 R 2 =.86 1 2 3 4 5 6 Measured Particle Scattering (Mm-1) 1 2 3 4 5 6 Measured Particle Scattering (Mm-1) Phoenix Supersite (22) 14 Estimated Particle Scattering (Mm-1) 12 1 8 6 4 2 y = 1.11x + 4.54 R 2 =.91 2 4 6 8 1 12 14 Measured Particle Scattering (Mm-1)

OTHER USES OF ADEQ S VISIBILITY NETWORK DATA Participation in EPA s AIRNow Program The EPA s AIRNow program collects continuous Ozone and PM 2.5 data from across the country to support local and regional applications of the Air Quality Index (AQI). 7 Phoenix began participation in the AIRNow PM 2.5 program in September 23. Data collected with Phoenix area nephelometers are used to estimate PM 2.5 concentrations, and while the algorithm used is not perfect, the results are reasonable and useful due to the generally low relative humidity experienced in Phoenix and the broad categories employed by the AQI. Due to the real-time nature of AIRNow, data are not subjected to strict validation criteria prior to posting. Under contract to the EPA, Battelle assisted ADEQ with developing a relationship between continuous nephelometer scattering and collocated 24-hr federal reference method PM 2.5 monitoring at the Phoenix Supersite. 8 The algorithm developed was implemented at four nephelometer monitoring locations within the Phoenix metropolitan area (indicated by green squares in Figure 1). The estimated PM 2.5 values are reported hourly throughout the year to the EPA AIRNow program. Figure 7 presents a sample AIRNow map showing the reported PM 2.5 values from many monitoring locations across the country for February 18, 24. Figure 8 presents images of downtown Phoenix and Camelback Mountain captured by ADEQ s digital web camera network on the same day. During that period the Phoenix Region Visibility Index reported in the Fair category (21 24 deciviews, calculated over a 4-hour period, measured by the downtown transmissometer). Figure 7. Continental U.S. AIRNow map for February 18, 24, 3pm MST (5pm EST). Taken from the EPA AIRNow web site (http://www.epa.gov/airnow/mapselect.html).

Figure 8. Images of downtown Phoenix (left) and Camelback Mountain (right) captured by ADEQ s digital web cameras on February 18, 24, at 15 MST. Several landmarks in each image and their approximate distances are indicated. The Phoenix Region Visibility Index at the time measured Fair (21 24 deciviews calculated over a 4-hour period, measured by the downtown transmissometer). The EPA AIRNow particulate level (see map in Figure 7) was reported as Moderate (yellow) at most Phoenix sites during this time period. Downtown Phoenix, 2/18/4 @ 15 Camelback Mountain, 2/18/4 @ 15 PM 2.5 Forecasting and Fire Emissions Tracking Hourly data collected for AIRNow are also used to support the weekly and daily air quality forecasting program that ADEQ assumed in cooperation with Maricopa County Department of Environmental Services (MCESD). Prior to October 23, MCESD issued forecasts of CO and PM 1 during the winter season for the Phoenix metropolitan area and continues to have the authority to issue no-burn days when forecasted conditions warrant. ADEQ had conducted the summertime ozone forecasting program. With the new 8-hour ozone and PM 2.5 standards, yearround forecasting for all four pollutants (ozone, carbon monoxide, PM 1 and PM 2.5 ) using the EPA Air Quality Index began in October of 23. These forecasts are linked to EPA s AIRNow and AQI forecast web pages as part of EPA s effort to provide a year-round, national, comprehensive air quality forecast and current air pollutant and health related information to the public. Hourly and even 5-minute nephelometer data is also used to support ADEQ s fire program. Because many of the IMPROVE monitoring sites are located in or near forested areas, ADEQ utilizes near real-time nephelometer scattering data to attempt to track smoke plumes associated with wildfire in Arizona. During the 22 Rodeo-Chedeski fire in northern Arizona, ADEQ utilized the wilderness nephelometer network to provide a qualitative measure of smoke intensity and ground support for tracking smoke plumes.

CONCLUSIONS The Arizona Department of Environmental Quality has developed large, comprehensive visibility monitoring networks within its largest urban areas and its federal Class I areas to support regulatory requirements and increased understanding of the science of visibility, and to support public outreach, pollution forecasting, and fire programs. ADEQ s efforts complement other national and state programs, allowing for a broader understanding of visibility issues within the state. REFERENCES 1. Governor Jane Dee Hull, Executive Order 2-3, Governor s Brown Cloud Summit, 2. 2. Visibility Index Oversight Committee, Final Report Recommendation for a Phoenix Area Visibility Index, March 23. 3. Transport and Impact on Surface Aerosol Concentrations in the U.S., EOS, Transactions, American Geophysical Union, Vol 84, Number 86, Pg 51-516, November 18, 23. 4. Cooperative Institute for Research in the Atmosphere, Colorado State University, Spatial and Seasonal Patterns and Temporal Variability of Haze and Its Constituents in the United States: Report III, ISSN: 737-5352-47, 2. 5. Air Resource Specialists, Inc., Technical Instruction 44-51: Nephelometer Data Reduction and Validation (IMPROVE Protocol), 1994. 6. VIEWS Web site, http://vista.cira.colostate.edu/views/ 7. EPA AIRNow Web site, http://www.epa.gov/airnow/index.html 8. Wendt, D.A., Battelle, Development of Materials and Models for PM Fine Continuous Monitoring to Support AQI and AIRNow for Arizona MSA, 23.