1	Visual Air Quality Big Bend National Park
2	Big Bend – A Land of Borders One of the largest and least-visited national parks, Big Bend encompasses over 800,000 acres in southwest Texas. Situated on the northern banks of the Rio Grande it is the meeting place of nations and cultures. Three states come together at Big Bend: Texas in the United States, and Coahuila and Chihuahua in Mexico. Because of it’s unique character, Big Bend was designated a Desert Biosphere Reserve in 1976.
3	Big Bend – A Land of Panoramic Views
4	Big Bend – A Land of Panoramic Views
5	Big Bend – A Land of Panoramic Views
6	Big Bend – A Land of Panoramic Views
7	Big Bend – A Land of Panoramic Views
8	"Visibility" Visibility: Defining the Problem
9	Big Bend – Air Pollution
10	Big Bend – Air Pollution
11	Big Bend – Air Pollution
12	It’s Hazy and Getting Hazier
13	Most visitors believe the haze is natural. It’s not. The primary cause is human activity.
14	It’s Hazy and Getting Hazier
15	Park managers began monitoring the air at Big Bend in 1978.
16	It’s Hazy and Getting Hazier
17	How Far Can You See? Good Day – over 100 miles (this good or better 10% of the time)
18	"Visibility" Visibility Concepts
19	What is Visibility? Visibility is historically defined as: “the farthest distance one can see a large black object against the background sky.”
20	What is Visibility? Molecules in the earth’s atmosphere scatter light, limiting the maximum distance you can see even under under natural conditions. The scattering of light by air molecules is called “blue sky” or “Rayleigh” scattering.
21	What is Visibility? Visibility is more than just how far we can see. It is better described as how “well” we can see and appreciate the colors, textures, forms, and detail in distant landscape features.
22	How impairment manifests itself depends upon the extent and distribution of particles and gases in the atmosphere.
23	Particles and gases in the atmosphere can scatter or redirect image-forming light as it travels to the eye. Through scattering, some image-forming light is removed from the view path. In addition, extra light, sunlight, and light reflected from the clouds and ground are added to the sight path, which interferes with the ability to view the scene.
24	Another cause of visibility impairment is absorption. Particles and gases in the atmosphere absorb or remove image-forming light before it ever reaches the viewer’s eye. Although significant, absorption usually is less important than scattering processes when we talk about visibility impairment.
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26	Parameters Describing Visual Air Quality 1. Visual Range 2. Extinction 3. Deciview
27	Examples of particles that affect visibility
28	Particle Size Matters
29	Five Particle Types that Reduce Visibility
30	Secondary Particle Formation
31	Sulfate Formation and Growth Nitrate particles are created in much the same way from nitrogen oxide gases. Organic particles similarly evolve from gaseous emissions of hydrocarbon gases.
32	Relative Humidity Affects Visibility
33	Sources of Visibility Reducing Pollutants
34	"Policies Aimed at" Policies Aimed at Improving Visibility
35	National Park Service Organic Act August 26, 1916 “… to conserve the scenery and the natural and historic objects and the wildlife therein and to provide for the enjoyment of the same in such manner and by such means as will leave them unimpaired for the enjoyment of future generations.”
36	Big Bend National Park Authorized by Congressional Act June 20, 1935 “…lands…as necessary for recreational park purposes...are hereby established, dedicated, and set apart as a public park for the benefit and enjoyment of the people.”
37	Clean Air Act
38	Regional Haze Rule April 1999 Addresses visibility impairment in the form of “regional haze”. The rule calls for states to work together to improve visibility in all mandatory Class I national parks and wilderness areas. States are encouraged to work together in regional partnerships to develop and implement multi-state strategies to reduce emissions of visibility-impairing fine particle pollution. Additionally, states must determine whether or how much emissions from sources in a given area affect visibility in a downwind Class I area.
39	"What is the" What is the Park Doing?
40	IMPROVE Big Bend has been part of the IMPROVE national monitoring program since 1981.
41	Visibility Monitoring - Optical
42	Visibility Monitoring - Aerosol
43	Visibility Monitoring - View Photography documents the changing appearance of a scene as visibility levels vary, documenting changes in haze levels, lighting conditions, vegetative cover, and cloud effects.
44	Other Air Quality Monitoring
45	"Monitoring Results" Monitoring Results
46	National Visibility Trends 1990–1999
47	Annual Aerosol Extinction, 1996–1998
48	Fine Mass
49	Sulfate Mass
50	Organic Mass
51	Soil Mass
52	"Monitoring Trends" Monitoring Trends at Big Bend National Park
53	Trends in Extinction at Big Bend from 1990–2002
54	Big Bend Extinction Budget – 1998–2002
55	Big Bend Extinction Budget – 1998–2002
56	"Special" Special Study
57	BRAVO Study (July–October, 1999)
58	BRAVO Study Objectives Understand the long-range trans-boundary transport of haze from regional sources in the U.S. and Mexico Determine the role of meteorology on Big Bend haze Identify the most likely pollutant transport corridors associated with Big Bend haze Quantify (model) the contribution of specific U.S. and Mexican source regions and source types responsible for Big Bend’s haze Mexican Carbón I/II power plants Industrial source areas on the Texas gulf coast and in Monterrey and Tula, Mexico Coal-fired power plants and refineries in Texas (Lignite Belt) Large SO₂ source regions in the southeastern and midwestern U.S.
59	Potential Source Areas of Haze at Big Bend
60	BRAVO Network Configuration Tracer Release and Monitoring Sites
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62	BRAVO Study Site at KBar
63	BRAVO Emissions Inventory – U.S. / Mexico
64	BRAVO Emissions By Source Region
65	Newly Built and Proposed New Power Plants in Texas
66	Local, Regional, and International Transport
67	Models: Linking Emissions to Measured Pollutants Pollutants are emitted from a source, transformed in the atmosphere, and transported with the winds. Along the way they become diluted or may deposit out as dry particles, or in rain, fog, or snow.
68	Models: Transport Pathways
69	Simulated Tracer Release Regional transport results in the mixing of emissions from distant sources which can be more than 1000 km apart. The highest concentrations from a single source region often occur under stagnant winds which allow the emissions to accumulate near the sources. Re-circulating transport patterns and flow reversals also allow for the accumulation and mixing of emissions from multiple source regions. Pollutants can then be transported to downwind receptor sites, resulting in elevated pollutant concentrations. This animation illustrates the transport and diffusion of plumes from four Texas source regions. This event demonstrates how southerly flow transports the plumes north, mixing them together. The flow reverses, passing over the sources again and allowing the pollutants to accumulate. The pollutants are then transported to Big Bend National Park.
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71	Big Bend’s Sulfate Haze Source Attribution
72	Big Bend’s Sulfate Haze Source Attribution
73	Clear Day – Pollution Free
74	Average Low Haze Day - BRAVO
75	Average High Haze Day - BRAVO
76	What is Causing Big Bend’s Haze?
77	What is Causing Big Bend’s Haze? Sulfate is the single largest contributor to haze at Big Bend NP. Big Bend is one of the only national parks where sulfates are increasing. Some of the highest haze episodes during the spring season are caused by international transport of dust and smoke.
78	What Are the Common Transport Pathways… Throughout the year air masses en route to Big Bend frequently reside over Mexico, particularly northern Mexico. Airflow from eastern Texas and the eastern U.S. is most frequent during late summer and fall months, during the period with the greatest contribution to haze by sulfate particles. Airflow from the western U.S. to Big Bend is greatest in the winter months when haze levels at the park are lowest. The highest sulfate haze periods during BRAVO were associated with low speed and low level transport from the the eastern U.S., eastern Texas, and northeastern Mexico. The lowest sulfate haze periods during BRAVO were associated with higher speed transport from the Gulf of Mexico up along the Mexican/Texas border to Big Bend and from the western U.S.
79	Where Does the Sulfate Haze Come From… At any given time, over half of the sulfate haze can come from either the eastern U.S., eastern Texas, or Mexico. During the BRAVO study period, the eastern U.S. and eastern Texas are responsible for ~50% on average and more on the high sulfate days of Big Bend’s sulfate haze during the BRAVO study period. At 20%, the Carbón power plant is the single largest contributor to Big Bend’s sulfate haze, during the BRAVO study period. On the clear days, Mexico and the western U.S. are the largest contributors.
80	How Can Visibility Be Improved… Control SO₂ emissions from the Carbón power plants. Significantly reduce SO₂ emissions in both east Texas and the eastern U.S. Reductions in SO₂ emissions in northern Mexico and the western U.S. can significantly improve Big Bend’s clear days. To address the U.S. regional haze rule, Texas will need to seek agreements for sulfur oxide reductions regionally within the U.S. and with Mexico in addition to achieving SO₂ reductions within the state. As SO₂emissions are reduced, the role of organic carbon and coarse soil in reducing visibility will become increasingly important.
81	What Can You Do? Stay informed about air quality issues that may affect the park. Let federal, state, and local government officials know that air quality is important to you. Support ballot measures and candidates sensitive to air quality issues. Learn about local efforts to see what is being done in your area. During your visit to Big Bend, join a ranger for a guided walk or evening presentation to learn more about other issues affecting park resources. Conserve energy at home and at work. Use energy efficient appliances and lighting when possible. Ask your utility company about its customer energy conservation program Keep your car engine tuned and maintain the correct tire pressure. Use an energy-conserving grade motor oil and “clean” fuels. Drive at a medium speed; most cars operate most efficiently between 35–55 miles per hour.
82	What Can You Do?