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Air Quality Study Provides Insights Into Air Pollution On Front Range

Monday, May 4, 1998

FORT COLLINS--Colorado State University today released the preliminary findings from the $4 million Northern Front Range Air Quality Study, the largest study of its kind in state history, and opened the results of the study for public comment.

The study was mandated by the state legislature and governor and funded by nearly 40 state government, industry and trade associations and research institutions. The extent of chemical and meteorological analyses in the Northern Front Range Air Quality Study was more extensive than past studies, said Ralph Smith, associate vice president for research at Colorado State, which oversaw the study. Smith also said the analysis of sources of air pollution, including emissions from cars, trucks, meat cooking and wood burning, was more comprehensive than in past studies. Another unique feature of the study was how the various sites were selected, using meteorological and topographical principles, which researchers believed would produce a more accurate study.

The study focuses on air pollution particles that are less than 2.5 microns in diameter (PM-2.5) - a target for the study because of the impact of these particles on human health and on visibility, including the Denver "brown cloud." The study area extended from Chatfield Reservoir in southwest Denver north to Fort Collins and east to Brush.

The three goals of the study were: to determine the sources of carbon particles in the atmosphere (the largest component of PM-2.5 particles in the Denver area); to understand which pollutants are the most important in formation of airborne ammonium nitrate and ammonium sulfate particles; and to determine the sources of ammonium nitrate and ammonium sulfate in the atmosphere.

Doug Lawson, technical project manager for the study, said the study was successful in achieving its goals. He said, however, additional work must be done on identifying the sources of pollution that lead to the formation of ammonium nitrate and ammonium sulfate.

The report will be open for public comment beginning today and until May 28. Then, it will be revised to reflect public input and will be presented to the state July 1. Complete copies of the study are available on the Internet at http://charon.cira.colostate.edu, Colorado State's Morgan Library and the Denver Public Library and other locations around the state (see attached list.)

The report shows that although central Denver is still one of the highest spots for PM-2.5 air pollution along the Front Range, two other locations also were high in these particles during the testing period: Evans, near Greeley; and Masters, a rural location on U.S. 34 between Greeley and Fort Morgan.

"The study was designed to meet the objectives of the legislation by using the best science possible," Lawson said.

The research indicated the following.

* There were no violations of the national ambient air quality standards during the study period; however, the state visiblity standard was exceeded on 54 percent of the days when measurements were taken in the winter of 1996-97.

* PM-2.5 is a complex mixture of pollutants arising from a variety of mobile, industrial and area sources; its composition varies greatly throughout the Front Range. The study showed that these particles are primarily elemental carbon, organic carbon, ammonium nitrate, ammonium sulfate and soil-like material.

* Pollution caused by mobile sources, in the form of direct emissions and road dust, contributes more than 50 percent of the PM-2.5 particles.

* A relatively small percentage of cars and trucks may produce a disproportionate amount of the PM-2.5 pollution from gasoline powered vehicles.

* Gasoline-powered vehicles produce nearly three times more PM-2.5 than diesel-powered vehicles along the Front Range, although on a per-vehicle basis, diesel-powered vehicles create more pollution. This is because about 95 percent of the miles driven each day are by gasoline vehicles.

* Road dust contributes about 15 percent of the PM-2.5 at urban locations, with a larger contribution in the non-urban areas away from Denver. In the urban area, much of this comes from street sand and dust from paved roadways.

* The contribution of 2.5 micron-sized wood-smoke particles has dropped significantly since 1987 to only 5 percent of the present total, due to control programs and new technology.

* Charbroiling meat appears to have a negligible effect on overall air quality.

* For the first time in the Denver area, ammonia was studied as a pollutant. The study concluded that ammonia emissions from agricultural operations are an important contributor to secondary particles of ammonium nitrate and ammonium sulfate.

* The study provided information on the relative effectiveness of reducing ammonia and nitrogen oxide emissions on ambient ammonium nitrate concentrations.

* For the first time, this study was able to separate nitrogen oxide emissions from power plants from those emitted from ground-level sources such as cars and trucks. Study results suggest that most of the particulate nitrate is formed by nitrogen oxide emissions from mobile sources.

* The study demonstrated a new method for distinguishing sulfur dioxide emitted by power plants from other sources of sulfur dioxide. The results showed the Cherokee power plant was found to be a significant source of sulfur dioxide. More data are needed, however, to define the relative importance of all sulfur dioxide sources in different locations in the Front Range region and their impact on airborne particulate sulfate.

Public comments, which will be taken at Colorado State until May 28, will be included along with the final report which will be given to the governor and state legislature July 1. The draft final report has been peer reviewed by a scientific panel and will be published in scientific journals.

Smith, of Colorado State, said researchers were surprised to find the high levels of 2.5 micron particles at the Evans and Masters sites. The sites were tested last winter and the results are based on the average levels of these particles during days when air pollution was the highest during the testing.

Masters, Evans and central Denver experienced the highest average concentrations on the episode days. Monitoring sites in Fort Collins, Welby (in northeast metro Denver) and near Longmont had intermediate PM-2.5 average levels, and Brighton, Highlands Ranch and Chatfield Reservoir had the lowest average values during the winter study period.

The relative contribution of pollutant species varied at the different sampling locations. Downtown Denver's PM-2.5 was dominated by mobile source-related emissions, while the northern, non-urban sites were dominated by ammonium nitrate. The high concentrations at Evans and Masters were caused by the stagnant, high humidity conditions from wintertime inversions along the South Platte River. Locations away from the river had lower PM-2.5 concentrations.

Another part of the study broke down the sources of the 2.5 micron particles in air pollution. To do that, the study did a comprehensive chemical analysis at sites in Welby, in the metro Denver area and at Brighton.

The Welby site showed the following breakdown:

Source of Pollution Percentage of 2.5

micron particles

Primary particles emitted directly from sources

Gasoline-powered vehicles (Includes all cars and trucks that burn gasoline. 29% Most of the pollution comes from poorly maintained vehicles, cold starts and older vehicles. Because a large fraction of the total PM-2.5 comes from these vehicles, further research is needed to verify these results and to quantify how many vehicles on the road belong to each subcategory below. Contributions to the total are listed, along with confidence levels.)

* Gasoline-powered vehicles operating in a hot, 3% + or - 1% stabilized mode (PM-2.5 emissions from these well-maintained vehicles are low when they are warmed up.)

* Intermittent smoking gasoline-powered vehicles 13% + or - 7% and cold starts (PM-2.5 emissions are high from vehicles when they are started cold and also from poorly maintained vehicles that may emit a puff of smoke upon acceleration. These vehicles occasionally emit visible smoke.)

* Smoking gasoline-powered vehicles (This group of 13% + or - 9% vehicles emits visible smoke much of the time. These vehicles are less than 2.5% of the fleet, and they may emit as much or more particulate matter than the average light-duty diesel vehicle.)

Diesel vehicles (Four to 5 percent of vehicles on 10% the road, as well as other construction equipment and industrial diesel-powered engines)

Geological sources, including paved road dust 17%

Wood Burning 5%

Meat Cooking (Mostly restaurant cooking - the 3% study was conducted in winter when little outdoor barbecuing took place)

Secondary particles formed in the atmosphere

Ammonium Nitrate (Formed when ammonia and 24% nitrogen oxides combine in the atmosphere. About 90 percent of the ammonia comes from agricultural sources. The majority of nitrogen oxides is produced from motor vehicles with moderate contributions from industrial sources.)

Ammonium Sulfate (Formed when ammonia and sulfur 10% dioxide combine in the atmosphere. Sulfur dioxide is produced by power plants, refineries and other industrial uses as well as mobile sources.)

Colorado Senate President Tom Norton (R-Greeley), a legislative sponsor of the study and professional engineer, said once the study is made final, lawmakers will use the data to help form public policy based on sound scientific research.

"We're pleased to see that this study was successful, and it will provide the state with very useful information on air quality issues," Norton said. "This technical data will be a valuable tool for us in the future. As a state, we value our natural environment, and this study will help us develop effective policies to preserve our environment."

Rep. Shirleen Tucker (R-Lakewood), an original sponsor of the legislation to create the study, said, "In the future, we're going to face some critical decisions concerning air quality. This study gives us the data to ensure that we make those decisions based on science. This was a good study, a lot of care went into this and now its our job to use this information to create good policies for our state."

Gov. Roy Romer, said, "This study shows we've made a lot of progress over the years, but that we still have to work hard to alleviate the Brown Cloud. The problem is complex--there is no single cause and there will be no single solution. I hope that everyone--citizens, businesses and government agencies--continues to work together to ensure that we have clean air for the next 20 to 30 years."

Smith said the study successfully incorporated contributions from a large number of highly dedicated organizations. The study includes data gathered at the Colorado Department of Public Health and Environment's Aurora Emissions Technical Center and the Colorado School of Mines' Institute for Fuels and High Altitude Research. Colorado State University served as study contractor and provided technical management.

The study's Technical Advisory Panel, co-chaired by Sen. Norton and Rep. Tucker, provided project oversight.

Study scientists included the Desert Research Institute of the University of Nevada system; Sonoma Technology Inc. from Santa Rosa, Calif.; the National Oceanic and Atmospheric Administration in Boulder; the National Institute of Standards and Technology from Maryland; Air Resource Specialists Inc. from Fort Collins; and Aerosol Dynamics Inc. and ENSR Consulting from California.

EPRI, the Electric Power Research Institute of Palo Alto, Calif., General Motors Research and Development from Michigan, and the U.S. Environmental Protection Agency from North Carolina took part in several phases of the program. Officials from the Colorado Department of Public Health and Environment and the Regional Air Quality Council also participated in the study.

A complete list of sponsoring organizations follows.

Northern Front Range Air Quality Study Sponsoring Organizations

ARCO Coal Company Associated Governments of Northwest Colorado Center for Energy and Economic Development City and County of Denver Colorado Office of Energy Conservation Colorado Interstate Gas Company Conoco, Inc. Coordinating Research Council Coors Brewing Company Cyprus Amax Mineral Company Denver Nuggets Limited Eastman Kodak Co. Englewood/Littleton Wastewater EPRI (Electric Power Research Institute) Kennecott Energy Company KN Energy Kodak Colorado Division Fort Collins, Colorado Consortium

Anheuser Busch

City of Fort Collins

Colorado State University/CIRA


Larimer County Lockheed Martin Metro Denver Wastewater Reclamation District Pacific Power Corporation Phillips Petroleum Co. Platte River Power Authority Public Service Company of Colorado Regional Air Quality Council Rocky Mountain Hearth Products Association Seneca Coal Company State of Colorado Total Petroleum Trigen Colorado Energy Company Ultramar/Diamond Shamrock U.S. Department of Energy U.S. Environmental Protection Agency

Locations where the public may see the NFRAQS report


Joint Legislative Library Room 048 State Capitol Building Basement Denver, CO 80203-1784 Contact: Delores Lanier, Librarian (303) 866-4799

Information Center Colorado Department of Public Health and Environment 4300 Cherry Greek Drive South Denver, CO 80222-1530 Contact: Kay Juricek, Librarian (303) 692-2037

Denver Public Library General Reference and Nonfiction Department 10 West 14th Avenue Parkway Denver, CO 80204 Contact: Rob Jackson, Head, Government Publications Division (303) 640-6226


Morgan Library Loan Desk Colorado State University Fort Collins, CO 80523 Contact: Fred Schmidt, Government Documents (970) 491-1881


Penrose Public Library Local History Section 20 North Cascade Avenue Colorado Springs, CO 80903


James A. Michener Library Government Documents Reference Desk University of Northern Colorado Greeley, CO 80639 Contact: Mark Anderson, Government Publications Librarian (970) 351-2987


Mesa County Public Library District Mesa County Public Library 530 Grand Avenue P.O. Box 20000-5019 Grand Junction, CO 81502-5019 Contact: Kay Oxer, Head Reference Librarian (970) 241-5251

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