Grantee Research Project Results
2000 Progress Report: Investigations of the Chemistry of Secondary Aerosol Formation Using Thermal Desorption Particle Beam Mass Spectrometry
EPA Grant Number: R826235Title: Investigations of the Chemistry of Secondary Aerosol Formation Using Thermal Desorption Particle Beam Mass Spectrometry
Investigators: Ziemann, Paul J.
Institution: University of California - Riverside
EPA Project Officer: Hahn, Intaek
Project Period: December 1, 1997 through November 30, 2000 (Extended to November 30, 2001)
Project Period Covered by this Report: December 1, 1999 through November 30, 2000
Project Amount: $294,762
RFA: Ambient Air Quality (1997) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Air
Objective:
Understanding the effects of fine atmospheric aerosol particles on human health and the environment, and developing strategies for controlling fine particle concentrations, will require much more information on aerosol chemistry than is currently available. In this project, a newly developed thermal desorption particle beam mass spectrometer (TDPBMS) that is capable of real-time, quantitative chemical analysis of particles as small as ~0.01 µm in diameter is being used in conjunction with other tools for environmental chamber studies of the chemistry of secondary aerosol formation. The objectives of the project are to: (1) investigate the products, kinetics, and mechanisms of secondary aerosol formation resulting from the photochemical reactions of selected VOC of anthropogenic and biogenic origin with OH, NO3, and O3; (2) investigate the effects of SO2, NH3, H2O, and seed particles on the chemistry of secondary aerosol formation in these VOC/oxidant systems; and (3) compile a thermal desorption particle beam mass spectral library of compounds found in secondary aerosol.Progress Summary:
In the first 2 years of this project, we developed a thermal desorption particle beam mass spectrometer (TDPBMS) for real-time analysis of organic particles, and a temperature programmed thermal desorption technique for obtaining single-component TDPBMS mass spectra. We then used these techniques to investigate the chemistry of secondary organic aerosol from ozonolysis of normal alkenes in the presence of alcohols, carboxylic acids, and water, in an environmental chamber, and showed that organic hydroperoxides, secondary ozonides, and peroxyhemiacetals are the major aerosol components. This is the first time these types of compounds have been identified in aerosol particles, and they cannot be identified using standard gas chromatography-mass spectrometry techniques, since they thermally decompose to aldehydes and carboxylic acids on the gas chromatographic column.
The mass spectra obtained will be valuable for identifying these types of compounds in laboratory and field studies.
In the past year, we have extended our work on normal alkenes to kinetic studies to determine the importance of such reactions in the atmosphere. Relative rate constants for reactions of alcohols, carboxylic acids, aldehydes, and water with stabilized Criegee biradicals (a key reactive intermediate in ozonolysis) were measured using real-time quantitative TDPBMS for aerosol analysis. The results show that the reactivity of the compounds increases as follows: water << methanol < 2-propanol << formaldehyde < formic acid < heptanoic acid, but that in the ambient atmosphere the major aerosol product should be hydroperoxides or peroxyhemiacetals formed by reaction with water. These rates can probably be applied to reactions of ozone with cyclic alkenes. We also carried out studies of the ozonolysis of cyclohexene, and results indicate that hydroperoxides are also important in aerosol formation for cyclic alkenes, and may provide a mechanism for the formation of dicarboxylic acids. Studies of aerosol formation from reaction of OH radicals with toluene and m-xylene in the absence and presence of NOx are also underway, and preliminary results indicate the presence of organic peroxides and nitrates.
The compounds identified in these studies have sufficiently low vapor pressures to partition completely into aerosol, and will thus accumulate primarily in the fine particle mode. Particles of this size are efficiently respired, and therefore provide a route by which organic hydroperoxides, peroxyhemiacetals, and secondary ozonides can be transported and deposited onto deep-lung surfaces. Because of their oxidizing properties and presence in fine particles, hydroperoxides and peroxides are considered to be one of the possible causative agents for the adverse effects of PM2.5 on human health. The observation that the compounds generated in our environmental chamber reactions are stable for at least hours in the chamber and days in solution indicates that the lifetimes are long enough for transport and deposition to occur. The results of this research are helping to elucidate the fundamental chemical and physical processes involved in secondary aerosol formation in the atmosphere. This knowledge aids in the development of more sophisticated models of secondary aerosol formation and behavior, which can in turn be used in airshed models to estimate the effects of human activities (including pollution control strategies) on air quality. Information on the chemical composition of the aerosol is also valuable for understanding the effects of fine particles on human health by identifying compounds (such as peroxides) that should be screened for potential toxicity.
Future Activities:
Environmental chamber studies using real-time TDPBMS and TPTD will focus on aerosol products of reactions of O3 and NO3 with cyclic alkenes (cyclohexene and a-pinene), and reactions of OH and NO3 with alkanes (pentadecane) and aromatics (toluene and m-xylene). The effects of SO2, NH3, and H2O, and seed particles will also be investigated, and additional TDPBMS mass spectra will be compiled.Journal Articles on this Report : 8 Displayed | Download in RIS Format
Other project views: | All 22 publications | 8 publications in selected types | All 8 journal articles |
---|
Type | Citation | ||
---|---|---|---|
|
Butler EC, Hayes KF. Kinetics of the transformation of trichloroethylene and tetrachloroethylene by iron sulfide. Environmental Science & Technology 1999;33(12):2021-2027. |
R826235 (2000) R825958 (1998) R825958 (2000) R825958 (Final) |
Exit Exit Exit |
|
Chattopadhyay S, Tobias HJ, Ziemann PJ. A method for measuring vapor pressures of low-volatility organic aerosol compounds using a thermal desorption particle beam mass spectrometer. Analytical Chemistry 2001;73(16):3797-3803. |
R826235 (2000) R828173 (2001) R828173 (2002) R828173 (2003) R828173 (Final) |
Exit Exit Exit |
|
Tobias HJ, Ziemann PJ. Compound identification in organic aerosols using temperature-programmed thermal desorption particle beam mass spectrometry. Analytical Chemistry 1999;71(16):3428-3435. |
R826235 (2000) |
Exit Exit Exit |
|
Tobias HJ, Kooiman PM, Docherty KS, Ziemann PJ. Real-time chemical analysis of organic aerosols using a thermal desorption particle beam mass spectrometer. Aerosol Science and Technology 2000;33(1-2):170-190. |
R826235 (2000) |
Exit Exit |
|
Tobias HJ, Docherty KS, Beving DE, Ziemann PJ. Effect of relative humidity on the chemical composition of secondary organic aerosol formed from reactions of 1-tetradecene and O3. Environmental Science & Technology 2000;34(11):2116-2125. |
R826235 (2000) |
Exit Exit Exit |
|
Tobias HJ, Ziemann PJ. Thermal desorption mass spectrometric analysis of organic aerosol formed from reactions of 1-tetradecene and O3 in the presence of alcohols and carboxylic acids. Environmental Science & Technology 2000;34(11):2105-2115. |
R826235 (2000) |
Exit Exit Exit |
|
Tobias HJ, Ziemann PJ. Kinetics of the gas-phase reactions of alcohols, aldehydes, carboxylic acids, and water with the C13 stabilized Criegee intermediate formed from ozonolysis of 1-tetradecene. Journal of Physical Chemistry A 2001;105(25):6129-6135. |
R826235 (2000) |
Exit Exit Exit |
|
Ziemann PJ. Evidence for low-volatility diacyl peroxides as a nucleating agent and major component of aerosol formed from reactions of O3 with cyclohexene and homologous compounds. The Journal of Physical Chemistry A 2002;106(17):4390-4402. |
R826235 (2000) |
Exit Exit Exit |
Supplemental Keywords:
particulates, absorption, adsorption, environmental chemistry, gas-particle partitioning, measurement methods, tropospheric, RFA, Scientific Discipline, Air, Toxics, particulate matter, Chemical Engineering, air toxics, Environmental Chemistry, VOCs, Chemistry, tropospheric ozone, Atmospheric Sciences, Chemistry and Materials Science, Environmental Engineering, ambient air quality, ambient aerosol, particulates, secondary aerosol formation, air pollutants, volatile air toxics, environmental chamber studies, mass spectrometry, air quality models, ambient measurement methods, particle beam mass spectrometry, spectroscopic studies, chemical composition, oxidant gas, aerosol, oxidant precursors, Volatile Organic Compounds (VOCs), atmospheric chemistry, aerosol productionProgress 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.