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Regional-scale influences on urban air quality : a field study in Phoenix, Arizona.

Description: Regional air quality can play an important role in determining whether urban ozone or PM-2.5 standards are exceeded. Background levels of nitrogen oxide species (NO{sub x}) and their interactions with natural organics can generate secondary aerosol products via formation of nitric acid and its subsequent reaction with ammonia to form ammonium nitrate. Natural organics and reactive anthropogenic organic compounds, particularly aromatic species and monoterpenes, can also lead to the formation of secondary organic aerosols, contributing to the formation of PM-2.5. Long-range transport and chemical transformation of hydrocarbons and NO{sub x} via both photochemical reactions and nighttime chemistry can yield significant regional levels of ozone and other oxidants, such as peroxyacyl nitrates (R-C=O-O-O-NO{sub 2}; PANs). The PANs are key species in determining the apparent age of an air parcel (Gaffney et al., 1989, 1993, 1997). The most common member of the family is peroxyacetyl nitrate (R=CH3-; PAN), which typically accounts for more than 85% of the PANs found in an urban or rural site. The PANs are in equilibrium with NO{sub 2}. Peroxyacyl radicals (R-C=O-O-O) are typically produced by the photooxidation reactions of organics, particularly those of aldehyde oxidation products with OH radical during the daytime (photochemically active) periods. Proposed mechanisms for nighttime formation of PANs (Gaffney et al., 1989) include abstraction reactions of nitrate radical (NO{sub 3}) and the initiation of OH chemistry by olefin-ozone reactions.
Date: October 12, 1998
Creator: Gaffney, J. S.
Partner: UNT Libraries Government Documents Department

Alcohol fuel use: Implications for atmospheric levels of aldehydes, organic nitrates, pans, and peroxides: Separating sources using carbon isotopes

Description: We have developed DiNitroPhenylHydrazone (DNPH) derivatization--high performance liquid chromatographic methods for measuring aldehydes in ambient samples with detection limits of approximately 1ppbV. These methods can be used for air or precipitation studies, and have been used for indoor measurements at much higher levels using shorter integration times. We are using gas chromatographs with electron capture detection (GCECD) to measure ambient levels of peroxyacyl nitrates and organic nitrates. Diffusion tubes with synthetically produced organic nitrates in n-tridecane solution are used to calibrate these systems. These compounds are important means of transporting NO/sub x/ over large scales due to their reduced tropospheric reactivity, low water solubilities, photolytic, and thermal stability. Their chemistries are coupled to aldehyde chemistry and are important greenhouse gases as well as phytotoxins. We have completed preliminary studies in Rio de Janeiro examining the atmospheric chemistry consequences of ethanol fuel usage. The urban air mass has been effected by the direct uncontrolled usage of ethanolgasoline and ethanoldiesel mixtures. We are exploring the use of luminol chemiluminescent detection of peroxides using gas chromatography to separate the various organic and inorganic peroxides. These compounds are coupled to the aldehyde chemistry, particularly in remote chemistries down-wind of urban sources. 13 refs.
Date: January 1, 1988
Creator: Gaffney, J.S. & Tanner, R.L.
Partner: UNT Libraries Government Documents Department

Longwave radiative forcing by aqueous aerosols

Description: 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.
Date: January 1, 1995
Creator: Gaffney, J.S. & Marley, N.A.
Partner: UNT Libraries Government Documents Department

Potential changes in atmospheric chemistry in the decades ahead: Climate and biosphere interactions and feedbacks

Description: Atmospheric chemistry is a challenging area of research where much knowledge is needed if we are to continue to survive as a species. This paper outlines research needs in the decades ahead in this key area of scientific endeavor. Highlighted are areas of research that are likely to lead to climatic and biospheric impacts and have been given little attention in the past. In particular, the possible organic transformation chemistries that may lead to chemical and physical changes in tropospheric cloud chemistries are highlighted and emphasized as an area where research is needed in the future. 22 refs.
Date: October 1, 1991
Creator: Gaffney, J.S. & Marley, N.A.
Partner: UNT Libraries Government Documents Department

Potential impacts on air quality of the use of ethanol as an alternative fuel. Final report

Description: 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 such 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.
Date: September 1, 1994
Creator: Gaffney, J. S. & Marley, N. A.
Partner: UNT Libraries Government Documents Department

Tropospheric chemistry of natural hydrocarbons, aldehydes, and peroxy radicals: Their connections to sulfuric acid production and climate effects

Description: Recent work has shown that natural hydrocarbon emissions can significantly affect the levels of urban and regional tropospheric ozone. We report on the reactivities of these biogenic trace gases, particularly isoprene, focusing on their importance in the production of aldehydes and peroxy radicals, leading to increased levels of hydrogen over regional forests. Hydrogen peroxide can lead to the wet oxidation of sulfur dioxide to acidic sulfate in aerosols, fogs, and clouds. In turn, acidic sulfate can act to as a light scattering aerosol and a source of cloud condensation nuclei (CCN), potentially leading to global cooling. Aerosol sulfate and other dissolved organic and inorganic compounds can also play important roles as a greenhouse species in the lower troposphere.
Date: May 1, 1993
Creator: Gaffney, J. S. & Marley, N. A.
Partner: UNT Libraries Government Documents Department

Humic and fluvic acids and organic colloidal materials in the environment

Description: Humic substances are ubiquitous in the environment, occurring in all soils, waters, and sediments of the ecosphere. Humic substances arise from the decomposition of plant and animal tissues yet are more stable than their precursors. Their size, molecular weight, elemental composition, structure, and the number and position of functional groups vary, depending on the origin and age of the material. Humic and fulvic substances have been studied extensively for more than 200 years; however, much remains unknown regarding their structure and properties. Humic substances are those organic compounds found in the environment that cannot be classified as any other chemical class of compounds. They are traditionally defined according to their solubilities. Fulvic acids are those organic materials that are soluble in water at all pH values. Humic acids are those materials that are insoluble at acidic pH values (pH < 2) but are soluble at higher pH values. Humin is the fraction of natural organic materials that is insoluble in water at all pH values. These definitions reflect the traditional methods for separating the different fractions from the original mixture. The humic content of soils varies from 0 to almost 10%. In surface waters, the humic content, expressed as dissolved organic carbon (DOC), varies from 0.1 to 50 ppm in dark-water swamps. In ocean waters, the DOC varies from 0.5 to 1.2 ppm at the surface, and the DOC in samples from deep groundwaters varies from 0.1 to 10 ppm. In addition, about 10% of the DOC in surface waters is found in suspended matter, either as organic or organically coated inorganic particulates. Humic materials function as surfactants, with the ability to bind both hydrophobic and hydrophyllic materials, making numic and fluvic materials effective agents in transporting both organic and inorganic contaminants in the environment.
Date: April 1996
Creator: Gaffney, J. S.; Marley, N. A. & Clark, S. B.
Partner: UNT Libraries Government Documents Department

Chemiluminescent detection of organic air pollutants

Description: Chemiluminescent reactions can be used for specific and highly sensitive detection of a number of air pollutants. Among these are chemiluminescent reactions of ozone with NO or organics and reactions of luminol with a variety of oxidants. Reported here are studies exploring (1) the use of the temperature dependence of the chemiluminescent reactions of ozone with organic pollutants as a means of differentiating types of hydrocarbon classes and (2) the use of luminol techniques to monitor atmospheric concentrations of nitrogen dioxide (NO{sub 2}) and organic oxidants, specifically peroxyacyl nitrates (PANs). Coupling gas chromatography to the chemiluminescent detectors allows the measurement of individual species at very low concentrations.
Date: April 1, 1996
Creator: Marley, N.A.; Gaffney, J.S. & Chen, Yu-Harn
Partner: UNT Libraries Government Documents Department

Aircraft measurements of nitrogen dioxide and peroxyacyl nitrates using luminol chemiluminescence with fast capillary gas chromatography

Description: Peroxyacyl nitrates (PANs) and nitrogen dioxide (NO{sub 2}) are important trace gas species associated with photochemical air pollution. The PANs are in thermal equilibrium with the peroxyacetyl radical and NO{sub 2}. Because PANs are trapped peroxy radicals, they are an important indicator species of the photochemical age of an air parcel, as well as being a means of long-range transporting of NO{sub 2}, leading to the formation of regional ozone and other oxidants. Typically, PANs are measured by using a gas chromatograph with electron-capture detection (ECD). Once automated, this method has been shown to be reliable and quite sensitive, allowing the levels of PANs to be measured at low parts per trillion in the troposphere. Unfortunately, a number of other atmospheric gases also have strong ECD signals or act as inferences and limit the speed in which the analysis can be completed. Currently, the shortest analysis time for PAN is approx. 5 minutes with ECD. The authors recent examined the luminol detection of NO{sub 2} and PANs using gas capillary chromatography for rapid monitoring of these important trace gases. Analysis of the PANs (PAN, PPN, and PBN) and NO{sub 2} in one minute has been demonstrated in laboratory studies by using this approach. Reported here are modifications of this instrument for aircraft operation and preliminary results from test flights taken near Pasco, Washington in August of 1997.
Date: September 1997
Creator: Gaffney, J. S.; Marley, N. A. & Drayton, P. J.
Partner: UNT Libraries Government Documents Department

Fast gas chromotography with luminol detection for measurement of nitrogen dioxide and PANs.

Description: Fast capillary gas chromatography has been coupled to a luminol-based chemiluminescence detection system for the rapid monitoring of nitrogen dioxide and peroxyacyl nitrates. A first-generation instrument was described recently (Gaffney et al., 1998). This system is capable of monitoring nitrogen dioxide and peroxyacyl nitrates (PANs; to and including the C4 species) with 1-min time resolution. This is an improvement by a factor of five over gas chromatography methods with electron capture detection. In addition, the luminol method is substantially less expensive than laser fluorescent detection or mass spectroscopic methods. Applications in aircraft-based research have been published electronically and will appear shortly in Environmental Science and Technology (Gaffney et al., 1999a). An improved version of the instrument that has been designed and built makes use of a Hammamatsu photon-counting system. Detection limits of this instrumentation are at the low tens of ppt. The range of the instrument can be adjusted by modifying sampling volumes and detection counting times. A review of past work and of recent application of the instrumentation to field measurements of nitrogen dioxide and PANs is presented. The data clearly indicate that the luminol approach can determine the target species with time resolution of less than 1 min. Examples of applications for estimation of peroxyacetyl radical concentrations and nitrate radical formation rates are also presented. This instrumentation can further be used for evaluation of surfaces for loss of nitrogen dioxide and PANs, phenomena of possible importance for sampling interfaces and chamber wall design. Our high-frequency field data clearly indicate that the ''real world'' is not well mixed and that turbulent mixing and plume-edge chemistries might play an important role in urban- and regional-scale interactions. Dynamic flow systems might be required to evaluate such effects in new-generation chamber studies.
Date: September 30, 1999
Creator: Gaffney, J. S.; Marley, N. A. & Drayton, P. J.
Partner: UNT Libraries Government Documents Department

Improved instrumentation for near-real-time measurement of reactive hydrocarbons, NO{sub 2}, and peroxyacyl nitrates.

Description: The measurement of reactive hydrocarbons and associated nitrogen oxides, NO{sub 2}, and peroxyacyl nitrates (PANs) is of key importance to unraveling the complex chemistries involved in daytime photochemical oxidant formation and nighttime chemistry driven by the nitrate radical. Recent work has demonstrated that chemiluminescent reactions of ozone with hydrocarbons (and the temperature dependence of the reactions) can be used as a means of detecting a wide variety of organic compounds in the gas phase with sensitivity comparable to or better than that of the conventional flame ionization detection method (Marley and Gaffney, 1998). We have implemented a new design and built a new instrument to evaluate this approach for the monitoring of alkenes. This instrument makes use of a computer-controlled photon-counting system with a reaction chamber operated at room temperature. Signals are compared to those for an ethene standard to estimate relative reactivity. The instrument is described in detail here, along with a new version of a luminol-based chemiluminescence detection system with fast gas chromatography for measurement of NO{sub 2} and PANs. The photon-counting system, the reaction chamber, and the luminol detection system have been combined on one instrument rack for field use on both ground-based and aircraft platforms. Data presented show the response times of the instruments and indicate applications for examining reactive hydrocarbon emissions from both vegetation and anthropogenic sources. In addition, the luminol chemiluminescence instrument was field tested, and the data obtained are compared with data from a commercial NO{sub x} analyzer. Preliminary results demonstrating the potential use of this instrumentation for rapid measurement of key tropospheric trace species are presented and discussed.
Date: October 6, 1999
Creator: Drayton, P. J.; Blazer, C. A.; Gaffney, J. S. & Marley, N. A.
Partner: UNT Libraries Government Documents Department

Application of natural radionuclides for determination of tropospheric ozone and aerosol transport.

Description: Natural radionuclides have been proposed for use in assessing the transport of ozone and aerosols in the troposphere. For example, {sup 7}Be is known to be produced in the upper troposphere and lower stratosphere by interactions with cosmogenic particles. Beryllium-7 has a 53.28-day half-life and is a gamma emitter that attaches itself to fine particles in the atmosphere once it is formed. Indeed, in tropospheric aerosol samples TBe is typically found in association with aerosol particles that are 0.3 {micro}m in diameter. Some investigators have asserted that ozone from aloft can be transported into rural and urban regions during stratospheric/tropospheric folding events, leading to increased background levels of ozone. During the Texas 2000 Air Quality study, aerosol samples with a 2.5-{micro}m cutoff were collected during 12-hour cycles (day/night) for a 30-day period at the Deer Park, Texas, field site in August-September 2000. To monitor {sup 7}Be levels, high-volume samples were collected on glass fiber filters on Julian dates 225-259. Sample collection was at a field site near a city park, away from any nearby traffic. This site is under routine operation by the Texas Natural Resource Conservation Commission. Instruments operated at this same site during the study period included an ozone monitor (Dasibi), a nitrogen oxides instrument (API), a CO instrument (API), a nephelometer, a UV-B meter (Richardson-Berger), and a multifilter rotating shadow band radiometer (MFRSR, Yankee Environmental Systems). In addition, we made modified fast-response NO{sub 2} and peroxyacetyl nitrate (PAN) measurements by using a fast gas chromatography with luminol detection, to be described at this meeting (3). The results for {sup 7}Be (mBq m{sup {minus}3})are compared in Figure 1 with the maximum and average ozone values (ppb) observed at the site to identify potential correlations. In Figure 2, all of the {sup 7}Be data are plotted against the maximum ...
Date: December 6, 2000
Creator: Gaffney, J. S.; Marley, N. A.; Drayton, P. J. & Orlandini, K. A.
Partner: UNT Libraries Government Documents Department

Short-Time-Response measurements of nitrogen dioxide and peroxyacetyl nitrate by fast capillary gas chromatography with luminol detection.

Description: The interaction of hydrocarbons and nitrogen oxides in sunlight to produce photochemical smog has been well studied over the years. In the past, the workhorse for the measurement of NO{sub 2}and NO was the chemiluminescent reaction with ozone. This method has detection limits of approximately 0.5 ppb in most commercial instruments, but it cannot detect NO{sub 2} directly; the instrument detects NO and uses hot catalytic surfaces to decompose all other nitrogen oxides (including NO{sub 2}) to NO for detection (l). The main problem with the method is the inherent difficulty in detecting excited NO{sub 2}, which emits over a broad region beginning at approximately 660 nm and has a maximum at 1270 nm, thus requiring a red-shifted photomultiplier for detection. The use of luminol for direct chemiluminescent detection of NO{sub 2} was demonstrated to have greater inherent sensitivity (detection limits of 5 ppt) than the indirect ozone chemiluminescence detection (2). In the luminol system, a gas-liquid reaction leads to light emission with a maximum at approximately 425 nm, at the maximum sensitivity for most photomultiplier tubes. This emission is responsible for the increased detection sensitivities. The biggest problem with this method for direct measurement of NO{sub 2} has been interference due to other soluble oxidants, particularly peroxyacyl nitrates (PANs).
Date: December 7, 2000
Creator: Marley, N. A.; Gaffney, J. S. & Drayton, P. J.
Partner: UNT Libraries Government Documents Department

Puerto Rico - 2002 : field studies to resolve aerosol processes.

Description: A number of questions remain concerning homogeneous aerosol formation by natural organics interacting with anthropogenic pollutants. For example, chlorine has been proposed as a potential oxidant in the troposphere because of its very high reactivity with a wide range of organics (Finlayson-Pitts, 1993). Indeed, sea salt aerosol in the presence of ozone has been shown to produce chlorine atoms in heterogeneous photochemical reactions under laboratory conditions. Whether chlorine can initiate oxidation of natural organics such as monoterpene hydrocarbons and can generate homogeneous nucleation or condensable material that contributes to aerosol loadings needs to be assessed. The nighttime reactions of ozone and nitrate radical can also result in monoterpene reactions that contribute to aerosol mass. We are currently planning field studies in Puerto Rico to assess these aerosol issues and other atmospheric chemistry questions. Puerto Rico has a number of key features that make it very attractive for a field study of this sort. The principal feature is the island's very regular meteorology and its position in the Caribbean Sea relative to the easterly trade winds. This meteorology and the island's rectangular shape (100 x 35 miles) make it highly suitable for simplification of boundary layer conditions. In addition, the long stretch between Puerto Rico and the nearest pollution sources in Africa and southern Europe make the incoming background air relatively clean and constant. Furthermore, Puerto Rico has approximately 3.5 million people with a very well defined source region and a central area of rain forest vegetation. These features make Puerto Rico an ideal locale for assessing aerosol processes. The following sections describe specific areas of atmospheric chemistry that can be explored during the proposed field study.
Date: October 5, 1999
Creator: Gaffney, J. S.; Marley, N. A. & Ravelo, R.
Partner: UNT Libraries Government Documents Department

Ozone chemiluminescent detection of olefins: Potential applications for real-time measurements of natural hydrocarbon emissions

Description: A chemiluminescence analyzer has been constructed that takes advantage of the temperature dependence of the ozone-hydrocarbon reaction. When operated at a temperature of 170 C, the analyzer functions as a total nonmethane hydrocarbon analyzer with sensitivities 10--1,000 times better than a conventional FID. However, with operation at varying temperatures, the chemiluminescent signal reflects the differences in rates of reaction of the hydrocarbons with ozone. Preliminary studies at room temperature indicated that the relative rates of reaction of isoprene, {alpha}-pinene, {beta}-pinene, and limonene with ozone correlated with the observed chemiluminescence signal. When hydrocarbons are grouped in classes of similar structure, their rates of reaction with electrophilic atmospheric oxidants (e.g., OH, O{sub 3}, NO{sub 3}) can be correlated with each other. By varying the temperature of the reaction chamber, the chemiluminescence analyzer can be tuned to more reactive classes of hydrocarbons. Therefore, the chemiluminescence analyzer has the ability to determine atmospheric hydrocarbon concentrations as a function of class and will also provide a measure of the atmospheric reactivity of the hydrocarbons.
Date: October 1, 1997
Creator: Marley, N.A.; Gaffney, J.S. & Cunningham, M.M.
Partner: UNT Libraries Government Documents Department

Real-time instrument for ambient monitoring of hydrogen sulfide, dimethyl sulfide, and other reduced organosulfur species using ozone chemiluminescent detection

Description: The chemiluminescent reactions of H/sup 2/S and other gaseous sulfides with ozone at 298/sup 0/K have been investigated, with the aim of developing a simple, selective, real-time monitor for these naturally emitted compounds. A commercial chemiluminescent ozone monitor has been adapted, for detection of the ozone/sulfide chemiluminescence between 300 and 400 nm wavelenght. Excess ozone was supplied to the reaction chamber from an electrical discharge ozone source. Response to dimethyl sulfide was enhanced by the use of air in the ozone source rather than oxygen. This effect was found to be caused by the presence of oxides of nitrogen produced in the ozonizer; a similar enhancement was not observed for the other sulfide compounds studied. Observed chemiluminescence signal decreased in the order CH/sub 3/SH > CH/sub 3/SCH/sub 3/ > H/sub 2/S > thiophene, with detection limits of 0.1, 0.3, 4, and 12 ppb respectively, at an instrument time constant of 60 sec. Calibration plots were linear at low sulfide concentrations, and showed less-than-first order dependence on sulfide at higher concentrations. A very small signal from ethylene was the only interference found from several compounds tested; sample air humidity has a small but significant effect on the instrument response.
Date: January 1, 1982
Creator: Kelly, T.J.; Phillips, M.F.; Tanner, R.L. & Gaffney, J.S.
Partner: UNT Libraries Government Documents Department

Conformational changes in polyelectrolytes and the effect on metal binding

Description: There has been considerable interest in the complexation of metals and other cations by natural humic and fulvic acids, as well as synthetic polyelectrolytes. In order to explain the binding observed for metals, and other species by organic polyelectrolytes, steric effects have been proposed. In this work, the effects of pH changes in aqueous solution on two synthetic polyelectrolytes, polymaleic acid (PMA) and polyacrylic acid (PAA), have been examined by laser Raman spectroscopy and turbidity measurements. These results are compared to Fourier-transform infrared (FTIR) and (/sup 13/C) nuclear magnetic resonance (NMR) spectra for solid samples of PMA, PAA, and fulvic and humic acids. Two types of carboxylic acid groups were detected for PMA in aqueous solution. Crystallization of PMA in a narrow pH range was observed. These data are consistent with strong intramolecular hydrogen bonding occurring in PMA at a pH of approximately 4. This implication of these results on the use of these compounds as models for fulvic and humic acids is discussed. 27 refs., 3 figs., 1 tab.
Date: September 1, 1988
Creator: Marley, N.A.; Gaffney, J.S.; Minai, Y. & Choppin, G.R.
Partner: UNT Libraries Government Documents Department