Grantee Research Project Results
1999 Progress Report: Transformations of Selected Organic Urban HAPs: Mechanistic and Modeling Studies to Identify Cancer and Non-Cancer Human Health Risk
EPA Grant Number: R826247Title: Transformations of Selected Organic Urban HAPs: Mechanistic and Modeling Studies to Identify Cancer and Non-Cancer Human Health Risk
Investigators: Jeffries, Harvey E. , Chien, Chao-Jung , Sexton, Ken , Liu, Xiaoyu
Current Investigators: Jeffries, Harvey E.
Institution: University of North Carolina at Chapel Hill
EPA Project Officer: Chung, Serena
Project Period: December 8, 1997 through December 7, 2000
Project Period Covered by this Report: December 8, 1998 through December 7,1999
Project Amount: $540,000
RFA: Ambient Air Quality (1997) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Air
Objective:
The three objectives of this project are to: (1) advance fundamental knowledge of atmospheric transformation of organic hazardous air pollutants (HAPs)?initially, 1,3-butadienes, aromatics, and epoxides will be studied and, in subsequent years, this will expand to other HAPs; (2) include the large variety of organic HAPs in modern air quality models by extensions of the newly developed morphecules concept; and (3) design and prepare a HAPs mixture of testing HAPs behavior in an urban-like environment and for evaluating the allomorphic/morphecule representation and other mechanisms for air quality models.Progress Summary:
Additional progress was made in understanding the fate of aromatic hydrocarbon photochemical oxidation and the formation of their products, many of which are toxic and on the EPA HAPs list. Additional experiments were conducted with the important aromatic products belonging to the 1,4-unsatured dicarbonyls (butenedial, 4-oxo-2-penteneal, and 3-hexene-2,5-dione). These compounds are very reactive and help explain the reactivity of the parent aromatics and their rate of degradation in the atmosphere. The products formed and observed in smog chamber experiments include formaldehyde, acrolein, glycolaldehyde, glyoxal, methylglyoxal, malonaldehyde, methylvinylketone, hydroxyacetone, acetaldehyde, and acetone. These products were measured using the O-pentafluorobenzyl-hydroxylamine derivation method, followed by gas chromatography/ion trap mass spectrometry analysis (PFBHA/GC/MS). Rate constants of reactions of these 1,4-unsatured dicarbonyls with ozone were measured. Reaction mechanisms are proposed and discussed.1,3-butadiene is classified as hazardous in the 1990 Clean Air Act Amendments. Smog chamber experiments were conducted with this, and analogs including isoprene and products were measured using the PFBHA/GC/MS method. 1,3-butadiene is shown to be highly reactive, which limits its atmospheric life-time, but is converted to products that also are toxic. The oxidation products observed include formaldehyde, acrolein, glycolaldehyde, glycidaldehyde, 3-hydroxy-propanaldehyde, hydroxy acetone, malonaldehyde, furan, 1,3-buatadiene monoxide, and 1,3-butadiene diepoxide. Various schemes for the reaction mechanism are proposed.
Acrolein and methacrolein are major products of 1,3-butadiene and 2-methyl-1,3-butadiene (isoprene), and both are HAPs. Both compounds were used to conduct additional photochemical chamber experiments to further the understanding of the complete chemistry of these dienes. Acrolein products measured include formaldehyde, glycoladehyde, glycidaldehyde, 3-OH-propanaldehyde, malonaldehyde, glyoxal, and unknown M86 (an unknown which is not 2,3-butanedione). Glycidaldehyde is an epoxy carbonyl and potent mutagen, which can react further yielding additional toxic products such as formic acid and formaldehyde. Methacrolein products include formaldehyde, acetaldehyde, acetone, glycolaldehyde, hydroxyacetone, methylglyoxal, glyoxal, and unknowns M86 and M114 (possibly a C5 epoxy dicarbonyl or C5 trione). Computer simulations were performed for new proposed mechanisms for acrolein and methacrolein: fair success was obtained. OH radical reaction is the major loss process for these compounds.
Because many of these product compounds are polar, studies were conducted to evaluate and test the sample procedures, chamber wall loss, and calibration methods. Because of the large volume of the University of North Carolina (UNC) chamber, gas-phase standards can be prepared more easily from injections, or nebulizing using pure compounds or solutions of pure compounds. These efforts resulted in greatly increased confidence in our measurements.
The smog chamber experiments conducted during the last year are listed in a table located at the UNC Web site listed below. These are daytime experiments starting at sunrise and lasting for about 10 hours, or nighttime experiments to study chemistry without photolytic processes. Experiment results are in a file containing documentation and physical and time-concentration data. Each experiment listed in the tables is linked to a plot of the time-concentration data for NOx and O3, and basic physical data of sunlight, temperature, and dewpoint. The lists of tests evaluating the calibration and sampling procedures will be presented in the final report. The smog chamber facilities are described in another linked and downloadable document.
Future Activities:
Future work will include: additional calibration methods development and intercomparisons for polar compounds; evaluation of different types of samplers; and scheduled smog chamber experiments.Journal Articles on this Report : 1 Displayed | Download in RIS Format
| Other project views: | All 13 publications | 1 publications in selected types | All 1 journal articles |
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Liu X, Jeffries HE, Sexton KG. Atmospheric photochemical degradation of 1,4-unsaturated dicarbonyls. Environmental Science & Technology 1999;33(23):4212-4220. |
R826247 (1999) R826247 (Final) |
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Supplemental Keywords:
atmospheric degradation, oxidation products, polar products, aromatic products, toxic products of atmospheric HAPs, fate of atmospheric HAPs., Health, RFA, Air, Toxics, Risk Assessments, HAPS, tropospheric ozone, air toxics, cancer risk, hazardous air pollutants, health effects, human health, urban air pollution, carcinogens, outdoor smog chamber, epoxides, urban air, aldehydes, ambient monitoring, urban air pollutants, morphecules, air quality data, ketones, air quality criteria, atmospheric chemistry, cancer, human exposure, risk assessment, mechanistic and modeling studies, chemical composition, monitoring, smog, photochemical reaction mechanism, 1, 3-Butadiene, air pollution models, fate and transport, hazardous air pollutants (HAPs), risk, urban air toxics, molecular biology, air pollutants, air quality models, ambient air, cancer risk assessment, ambient air quality, atmospheric transformation, modeling, transport, ketone, atmospheric, environmental effects, modelRelevant Websites:
http://airchem.sph.unc.edu/research/projects/epaprojects/thaps/ Exithttp://toxnet.nlm.nih.gov/ Exit
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.