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The search for cleaner air has led us to examine alternative hydrocarbon fuels. In particular, alcohol and oxygenated blends have been proposed as panaceas for our urban air pollution problems, especially ozone. Discussed here is the alternative fuel issue as it relates to alcohol fuel usage, and an examination of the key issues that have to be addressed in considering adoption of any alternative energy strategy for controlling atmospheric pollution. Tradeoffs must be considered, including economic, safety, and potential water pollution problems.

Recently, a great deal of interest has been focused on the role of aerosols in climatic change because of their potential cooling impacts due to light scattering. Recent advances in infrared spectroscopy using cylindrical internal reflectance have allowed the longwave absorption of dissolved aerosol species and the associated liquid water to be accurately determined and evaluated. Experimental measurements using these techniques have shown that dissolved sulfate, nitrate, and numerous other aerosol species will act to cause greenhouse effects. Preliminary calculations indicate that the longwave climate forcing (i.e., heating) for sulfate aerosol will be comparable in magnitude to the cooling effect produced by light scattering. However, more detailed modeling will clearly be needed to address the impact of the longwave forcing due to aerosols as a function of atmospheric height and composition. Their work has shown that aerosol composition will be important in determining longwave forcing, while shortwave forcing will be more related to the physical size of the aerosol droplets. On the basis of these studies, it is increasingly apparent that aerosols, fogs, and clouds play a key role in determining the radiative balance of the atmosphere and in controlling regional and global climates.

The use of ethanol/gasoline mixtures in motor vehicles has been proposed as an alternative fuel strategy that might improve air quality while minimizing US dependence on foreign oil. New enzymatic production methodologies are being explored to develop ethanol as a viable, economic fuel. In an attempt to reduce urban carbon monoxide (CO) and ozone levels, a number of cities are currently mandating the use of ethanol/gasoline blends. However, it is not at all clear that these blended fuels will help to abate urban pollution. In fact, the use of these fuels may lead to increased levels of other air pollutants, specifically aldehydes and peroxyacyl nitrates. Although these pollutants are not currently regulated, their potential health and environmental impacts must be considered when assessing the impacts of alternative fuels on air quality. Indeed, formaldehyde has been identified as an important air pollutant that is currently being considered for control strategies by the State of California. This report focuses on measurements taken in Albuquerque, New Mexico during the summer of 1993 and the winter of 1994 as an initial attempt to evaluate the air quality effects of ethanol/gasoline mixtures. The results of this study have direct implications for the use of suchmore » fuel mixtures as a means to reduce CO emissions and ozone in a number of major cities and to bring these urban centers into compliance with the Clean Air Act.« less

Source fingerprints for 18 nonmethane hydrocarbons (NMHCS) containing 2-8 carbon atoms are currently used to apportion NMHC sources by chemical mass balance (CMB) modeling approaches. The source profiles must be stable in the troposphere to obtain accurate CMB model predictions. The NMHC source apportionment compounds are susceptible to gas phase oxidation in the atmosphere by hydroxyl radical (OH). Expected tropospheric lifetimes for peak concentrations of OH in typical urban air range from an hour to over 100 hours. When OH oxidation of a source profile for vehicle tailpipe emissions is simulated, significant changes occur in the distribution of the source apportionment compounds after a reaction time of 2-4 hr. These calculations indicate that sampling strategies to define source-receptor relationships of NMHCs by CMB modeling techniques must be carefully designed to minimize the possibility of NMHC oxidation by OH.

Recently, there has been considerable interest regarding possible greenhouse effects due to combustion and energy-related pollution. This concern has been due to the release and secondary production of greenhouse gases such as carbon dioxide, freons, methane, nitrous oxide, and ozone. These gases can absorb infrared radiation as it comes back from the heated ground and therefore effectively trap the infrared radiation in the troposphere, leading to climatic change. Beyond these gases, clouds, aerosols, and fogs may also play important roles in affecting, the radiation balance by scattering incoming radiation. This work describes the measurement of water soluble infrared absorbers that are known to be derived from pollution. Polluted precipitation is likely to be an important contributor to radiation balance that is currently being neglected. Pollutants characterized include sulfate, nitrate, formate, acetate, oxalate, phenol, p-nitrophenol, ammonium, carbonate, bicarbonate, formaldehyde (dihydroxy methane), methanol, and ethanol. Band positions and band strengths have been determined. These species show measurable infrared absorption bands in the atmospheric window regions (i.e., 900--1600 cm{sup {minus}1}). These data are discussed with regard to the reported discrepancies in the radiatively important water infrared absorption region commonly referred to as the ``foreign broadened continuum.``

Increased solubility of quartz and mobilization in contaminated groundwater due to the complexation with dissolved organic acids has been recently proposed [Bennett and Siegel, Nature 326 , 684–686 (1987)]. Using laser Raman and Fourier transform infrared spectroscopies, we have examined mixed solutions of oxalic and silicic acids at near neutral pH in the tenth molar concentration ranges in an attempt to directly observe the proposed organo-silicate complexes. In both laser Raman and infrared spectra, product bands were observed that indicate an oxalate/silicic acid ester is being formed in the reaction. These data support the observation that organic diacids can lead to enhanced solubility of quartz in hydrogeological systems.

Sulfur isotope analyses have been completed for twelve samples of marine Jurassic oils from a single basin, and are presented along with previous chemical analyses of the same oils (Seifert and Moldowan, 1978). Two isotopic anomalies are discussed in light of correlational analyses, and show that sulfur isotope ratios, when used with other chemical variables, are sensitive indicators of subtle changes in initial source input. Measurements of δ34S in correlational studies of crude oil characterization and identification are recommended.

Ammonia chemical ionization mass spectra of rapidly heated free amino acids and peptides provide an opportunity for a study of the competition between gas-phase solvation and association reactions of these biochemically interesting species. Compounds investigated include methionine, phenylalanine, tryptophan, and peptides; AlaAla, PheAla, AlaAlaAla, AlaPheGly, GlyAlaPhe, tetraAla and PCAHisProNH 2 (thyrotropin releasing hormone). Extensive formation of solvated-protonated species were observed and associated protonated peptides up to (4 M + 1) + in some cases. The observation of association reactions with rapidly heated samples presents problems in the analytical use of this technique. Investigation of the kinetic order of reactions leading to association of protonated species reveals a significantly more effective energy transfer process in collisions of protonated peptides with parent neutral molecules than with neutral solvent gas.

Sulfur isotopic analyses have been completed for eight Triassic, Jurassic and Lower Cretaceous oils from the Prudhoe Bay field, Alaska. Results presented complement earlier work and further indicate the diagnostic importance of δ 34S values in correlation studies of crude oils. The present work supports an earlier contention that Kuparuk River, Sadlerochit and Lisburne crude oils have a similar source of origin, distinct from that of Kingak oil. If Kingak and Shublik Formations contribute to the Sag River Sand crude oil in the Prudhoe Bay area of Alaska, the same may not be the case for Sag River Sand oil in the Point Barrow area which apparently originated from a different source or combination of sources.

A novel gas chromatographic detector is described which measures the infrared absorption of an eluting molecule by monitoring the photothermal perturbation in an intracavity laser. Laser intracavity photothermal spectroscopy is a non-destructive technique which can be highly selective by using specific infrared absorptions which are characteristic of the molecule or class of compounds of interest to the analyst. Gas chromatography—laser intracavity photothermal spectroscopy detection has comparable sensitivity and selectivity to the previously reported gas chromatographic use of phase-fluctuation optical heterodyne spectroscopy. Thus, absorption sensitivity of ca . 10 −8 cm −1 and detection limits of ca . 1.0 pg s −1 (30 cc min −1 ) are anticipated for species with absorption cross-sections of 10 cm −1 atm −1 (a typical absorption coefficient for the strongest infrared bands of most molecules). Analyses of sulfur hexafluoride and ethylene are presented which demonstrate the capabilities of this technique: the simplicity of the detector makes it attractive for non-destructive analyses, especially in the area of atmospheric trace gas analysis.

The vibration-rotation bands (Meinel bands) of OH (2Πi) have been observed in the chemiluminescent gas phase reaction of ozone with acetaldehyde at a total pressure of 3 torr at room temperature; a weaker emission in the visible region is tentatively identified as formaldehyde fluorescence.

The UV absorption spectrum was measured for peroxyacetyl nitrate (PAN) and peroxypropionyl nitrate (PPN) at 298 +/- 1 K in the 200-400-nm wavelength region. From this, the absorption cross sections for PAN and PPN have been calculated. Solar photolysis rates for PAN and PPN are estimated on the basis of the measured and extrapolated cross sections. 2 tables.