1998 Progress Report: Transformations of Selected Organic Urban HAPs: Mechanistic and Modeling Studies to Identify Cancer and Non-Cancer Human Health RiskEPA Grant Number: R826247
Title: 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 , Liu, Xiaoyu , Sexton, Ken
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, 1997 through December 7,1998
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:Analytical methods have been developed or improved, and used to measure HAPs degradation and transformation in smog chamber experiments, to measure product formation and estimate yields, and to develop mechanisms for inclusion into air quality and risk models.
We report the development of a new gas chromatography and mass spectrometry (GC/MS) method for the measurement of organic acids and phenols. This derivatization method utilizes pentafluorobenzyl bromide (PFBBr) and pentafluorobenzyl alcohol (PFBOH) as a novel reagent gas for chemical ionization mass spectrometry (CIMS). The PFBOH increases sensitivity and lowers detection limits. Acrylic (one of the EPA's 189 HAPs) and methacrylic acid (also toxic) were detected in isoprene chamber experiments for the first time. Both hydroxyl- and ozone-initiated oxidation experiments were conducted. Organic carboxylic acids and several phenols were measured in toluene chamber experiments. This method allows for measurement of such polar toxic compounds (usually difficult and usually not measured) on a typical GC/MS system, which aids in identification.
To better understand the fates of aromatics in the atmosphere, studies on the transformation chemistry of several unsaturated dicarbonyls, known to be products of aromatic hydrocarbon oxidation, such as 3-hexene-2, 5-dione, 4-oxo-2-pentenal, and butendial were investigated. Several O-initiated and O3-initiated smog chamber experiments under atmospheric conditions were conducted in the University of North Carolina (UNC) smog chamber in 1998. Carbonyl intermediates and products were measured using the O-(2,3,4,5,6-pentafluorobenzyl)-hydroxylamine (PFBHA) derivatization method by GC/ion trap MS analysis. Carbonyl products detected include formaldehyde, OH-acetone, methylglyoxal, methacrolein, glyoxal, malonaldehyde (propanedial), acrolein, glycoladehyde, and other products. Many of these carbonyls are on the EPA's HAPs list or are known to be toxic. It is shown that unsaturated dicarbonyls decay very fast in the OH-initiated reactions, suggesting that they are active intermediates in the aromatics photooxidation. There is a strong correlation between destruction of unsaturated dicarbonyls and formation of products. The reaction mechanisms are being investigated.
The smog chamber experiments conducted during the last year are listed in a table 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. Each experiment's 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 smog chamber facilities are described in another hypertext link, which includes a downloadable document.