Potential Air Quality Effects of Using Ethanol -Gasoline Fuel Blends: A Field Study in Albuquerque, New Mexico JEFFREY S. GAFFNEY* AND NANCY A. MARLEY Environm ental Research Division, Building 203, 9700 South Cass Avenue, Argonne National Laboratory, Argonne, Illinois 60439 RANDAL S. MARTIN, † ROY W. DIXON, ‡ LUIS G. REYES, ‡ AND CARL J. POPP ‡ Department of Mineral and Environmental Engineering and Department of Chemistry, New Mexico Institute of Mining and Technology, Socorro, New Mexico 87801 The use of alternate fuels has been proposed as a method of improving urban air quality by reducing combustion- related pollution. One such program mandates the use of oxygenates in the wintertime to reduce CO emissions in cities such as Albuquerque,NM. A field study was conducted in Albuquerque to determine the atmospheric impacts of the use of ethanol fuels. Atmospheric concentrations of ozone,oxides of nitrogen,CO,peroxyacetyl nitrate (PAN), aldehydes, and organic acids were measured in the summer of 1993, before the use of ethanol fuels, and in the winters of 1994 and 1995, during the use of 10% ethanol fuel (>99%). Data showed increased levels of peroxyacetyl nitrate (PAN) and aldehydes in winter. The formaldehyde/ acetaldehyde ratio was 1.4, indicating an anthropogenic source,and PAN and acetaldehyde levels were anti-correlated over short time periods, indicating primary acetaldehyde emissions. A comparison of data taken at rural sites south of the city indicates that although there is a significant anthropogenic component to the aldehyde concentrations during the winter, there are also contributions from the photochemical oxidation of natural hydrocarbons. Introduction The use of alternative fuels has been proposed as a method of improving urban air quality by reducing combustion- related pollution and minimizingU.S.dependence on foreign oil (1). In an attempt to speed progress toward urban attainment of the National Ambient Air Quality Standards, oxygenated and reformulated gasoline programs were man- dated by the 1990 Clean Air Act Amendments in the worst nonattainment areas. Specifically, the oxygenated fuels program requires the use of fuels containing 2.7% oxygen by weight (e.g., methanol, ethanol, methyl tert -butyl ether [MTBE]) in the wintertime to reduce CO emissions while the reformulated gasoline program requires fuels containing 2% oxygen in the summer to reduce ozone formation (2). However,it is not completelycertain that these blended fuels will help to abate urban air pollution (1-7). The effects of oxygenated fuels on ambient CO concentrations are smallat best. Studies have shown reductions in wintertime CO concentrations to vary from as high as 10% to as low as zero (3). In addition,some evidence indicatesthat the use ofthese fuels may lead to increased ambient levels of other air pollutants,specificallyaldehydesand peroxyacylnitrates(4- 8), which are both toxic and possible animal carcinogens (9, 10). Although these pollutants are not currently regulated, their potential health and environmental effects should be considered in assessments ofthe impacts ofalternative fuels on air quality. The use of oxygenated fuels in motor vehicles generally decreases the total hydrocarbon and CO emissions under moderate temperatures,although the totalmagnitude ofthis reduction is uncertain (3, 7, 11). However, the 1990 Clean Air Act Amendments also directed the U.S. Environmental Protection Agency (EPA) to consider not only the total mass but also the reactivity of hydrocarbon emissions in defining low-pollution fuels (12). The combustion of ethanol and methanol in spark-ignition engines results in increased emissions of primary acetaldehyde and formaldehyde, both of which are much more reactive in the atmosphere than their parent alcohols (13). The reaction ofacetaldehyde with the OH free radical in urban atmospheres leads directly to the formation of the peroxyacetyl radical, which can react with NO 2 to form PAN. Increased concentrations of PAN have been observed in Rio de Janeiro, Brazil (5, 8), and in preliminary studies in Albuquerque (6) during periods of increased use of ethanol-gasoline blends. Currently, PAN is not a criteria pollutant, nor are aldehydes; however, these compounds are known to be potent lachrymators and mutagens. In addition, PAN is a plant toxin more potent than ozone (10). The data taken at both Rio de Janeiro and Albuquerque also indicate that peroxypropionylnitrate (PPN), a larger peroxyacyl nitrate, is apparently produced at higher levels when ethanol or MTBE is used as an oxygenated fuel (3, 4). PPN has been found to be more toxic than PAN. It is a storage medium for NO 2 and will lead to the formation of PAN,peroxides,and aldehydesupon thermaldecomposition as the air mass is transported downwind. Regional ozone levels can also be affected by changes in these emissions downwind of the urban center. Albuquerque,NM,waschosen asa field studysite because itiscurrentlymandated,likeincreasingnumbersofU.S.urban areas, to use ethanol-gasoline fuel blends and to institute bans on wood burning in an attempt to maintain air quality duringthe winter months. Although the use ofblended fuels containing 10% alcohol is >99% in the winter, in the summertime the use is substantially less (<5% statewide) (14). This pattern makes Albuquerque an ideal site for studying the urban and downwind effects of alternative fuel usage. Atmospheric concentrations of ozone, oxides of nitrogen, CO, peroxyacetyl nitrate (PAN), aldehydes, and organic acids were measured in the summer of 1993, before the use of ethanol fuels, and in the winters of 1994 and 1995, during the use of 10% ethanol fuel. This paper focuses on measurements of the non-criteria pollutants (PAN and aldehydes)in an initialattempt to evaluate the totalair quality effects of the combustion of ethanol-gasoline mixtures in motor vehicles. The results of this study have direct implica- tions for the use of such fuel mixtures to reduce carbon monoxide emissions and ozone formation in a number of major cities and to bringthese urban centers into compliance with the Clean Air Act. *Corresponding author telephone: 630-252-5178; fax: 630-252- 8895; e-mail: jeff_gaffney@qmgate.anl.gov. † Department of Mineral and Environmental Engineering. ‡ Department of Chemistry. Environ. Sci. Technol. 1997, 31, 3053-3061 S0013-936X(96)01038-3 CCC: $14.00  1997 American Chemical Society VOL. 31, NO. 11, 1997 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 3053