Grantee Research Project Results
Final Report: Oxygenated Volatile Organic Compounds Elucidation of Atmospheric Sources
EPA Grant Number: R825257Title: Oxygenated Volatile Organic Compounds Elucidation of Atmospheric Sources
Investigators: Zika, Rod G.
Institution: University of Miami
EPA Project Officer: Hahn, Intaek
Project Period: October 21, 1996 through October 20, 1999
Project Amount: $481,115
RFA: Air Quality (1996) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Air
Objective:
A considerable portion of the burden of volatile organic compounds (VOCs) in the rural and urban troposphere is comprised of a range of oxygenated VOCs, primarily carbonyls and alcohols. The importance of these compounds is evident from their participation in photochemical oxidant formation and their ability to serve as markers for atmospheric oxidation processes of both natural and anthropogenic VOCs. During summer 1995, a comprehensive measurement campaign at a rural site in Tennessee was completed as part of the 1995 SOS Nashville intensive study. An intercomparison of a variety of measurement techniques was made for a similar set of oxygenated compounds. This preliminary campaign served as an ideal situation to identify many of the problems inherent with the measurement of oxygenated compounds and probably represents one of the only multi-institutional, multimethod ambient air intercomparisons for a variety of oxygenated compounds.
As a result of this intercomparison and observations made over the past several years, the objectives of this project were to resolve several important issues regarding the accurate measurement of oxygenated compounds. Rapid analysis techniques involving gas chromatography with mass spectrometric detection and more robust standardization techniques are needed to accomplish these objectives. The first phase of this approach involved an extensive series of laboratory experiments to develop and test the analytical methodology. The second and subsequent phases of the approach utilized these improved techniques to conduct field studies on the dynamics of these compounds on rapid timescales. Studies were conducted at established field sites where long-term monitoring for other associated parameters (i.e., O3, NOx, CO, etc.) were being measured.
Specific objectives we planned to accomplish over the course of our investigation were to:
• Increase the Confidence With Which Oxygenated VOCs Can Be Measured. A fully automated concentration and analysis system was assembled using highly inert materials. Intercomparison studies and standard evaluations conducted in conjunction with th National Center for Atmospheric Research (NCAR) during the Program for Research on Oxidants: Photochemistry, Emissions, and Transport (PROPHET), 1998 study indicated that the system is capable of measuring low part per trillion levels of the compounds studied.
• Create More Reliable Techniques for the Calibration of These Compounds. High pressure gas standards for oxygenated volatile organic compounds (OVOCs) were developed with assistance from Air Environmental, and utilized for standardization of the analytical system for the three field studies.
• Increase Time Resolution of Direct Sampling. The time required for the analysis of ambient air samples is directly proportional to the complexity of the list of compounds desired. During the PROPHET 1998 study, using a target list of 20 compounds, samples were analyzed every 30 minutes. By the 1999 studies the target list had grown to 85 compounds, requiring 60 minutes for the analysis. Rapid GC techniques were not developed for this analysis; the GC/MSD system required for this development was/is not available.
• Identify Causes of Several Problems Apparent with Current Analytical Techniques. Reactive surfaces within the analytical system have been shown to be responsible for the low recovery of reactive volatile species. Silcosteel and Teflon surfaces were used in the concentrator to minimize these loses.
• Utilize These Improved Techniques During an Ongoing Study of Oxygenated VOC Chemistry at Shenandoah National Park, Virginia, A Site Which is Impacted by a Variety of Atmospheric Transport Patterns. The system was used during three field studies, Pellston, MI, PROPHET 1998; Shenandoah National Park, VA, 1999; and Atlanta, GA, SuperSite 1999, to measure a variety of VOCs, OVOCs, and halogenated VOCs. The target list for the 1999 studies is presented in Table 1.
| OVOC Analysis | GC/MSD | |
| TO-15A Standard | ||
| Freon-12 | Chloroform | Dibromochloromethane |
| Freon-114 | Ethyl Acetate | 1,2-Dibromoethane |
| Chloromethane | 1,1,1-Trichloroethane | Methyl Butyl Ketone (MBK) |
| Vinyl Chloride | Cyclohexane | Chlorobenzene |
| Propylene | Methyl Ethyl Ketone (MEK) | Ethylbenzene |
| 1,3-Butadiene | Tetrahydrofuran (THF) | m&p-Xylene |
| Bromomethane | Carbon Tetrachloride | o-Xylene |
| Chloroethane | Benzene | Styrene |
| Freon-11 | 1,2-Dichloroethane | Bromoform |
| 1,1-Dichloroethene | 2-Butanol | 1,1,2,2-Tetrachloroethane |
| Freon-113 | Heptane | 4-Ethyltoluene |
| Carbon Disulfide | Trichloroethylene | 1,3,5-Trimethylbenzene |
| Ethanol | 1,2-Dichloropropane | 1,2,4-Trimethylbenzene |
| Methylene Chloride | Bromodichloromethane | 1,3-Dichlorobenzene |
| trans-1,2-Dichloroethene | 1,4-Dioxane | 1,4-Dichlorobenzene |
| Acetone | trans-1,3-Dichloropropene | Benzyl Chloride |
| Hexane | Toluene | 1,2-Dichlorobenzene |
| 1,1-Dichloroethane | Methyl Isobutyl Ketone (MIBK) | 1,2,4-Trichlorobenzene |
| Methyl Tertbutyl Ether (MTBE) | cis-1,3-Dichloropropene | Hexachloro-1,3-Butadiene |
| Vinyl Acetate | 1,1,2-Trichloroethane | |
| cis-1,2-Dichloroethene | Tetrachloroethylene | |
| Oxygenated VOC Standard | ||
| Acetaldehyde | Methyl Vinyl Ketone (MVK) | Heptanal |
| Methanol | Methyl Ethyl Ketone (MEK) | β-Pinene |
| Isoprene | Benzene | 2-Ethyl-1-Hexanal |
| Propanal | 1-Butanol | Benzealdehyde |
| Ethanol | Pentanal | Limonene |
| Acetone | 2-Pentanone | Octanal |
| Isopropyl Alcohol | Methyl Methacrylate | Nonanal |
| Methacrolein (MACR) | Methyl Isobutyl Ketone (MIBK) | Decanal |
| 3-Methylfuran | Hexanal | |
| Butanal | α-Pinene |
Summary/Accomplishments (Outputs/Outcomes):
The first year of the study, 1996-1997, the system was designed and fabrication of the concentration system was begun. The specific questions addressed in the design of the system were maximizing the sample throughput while minimizing the amount of liquid Nitrogen (LN2) used by the concentrator, and ensuring that the surfaces contacted by the sample were as inert as possible. Several trap designs were evaluated before choosing the final configuration. Several pressure cap and channel designs also were evaluated. During the second year, 1997-1998, three different assemblies were constructed, the circuitry needed to control/automate sample collection, and the software to monitor/control the sample concentration process were assembled and testing of the system was begun. The third channel/pressure cap design was used during the PROPHET study in Pellston, Michigan, in summer 1998, where ambient samples were analyzed and an intercomparison of the system was performed against a concentration system developed by NCAR. Several problems with the design of the channel/pressure cap became evident during that study, resulting in a fourth design incorporating the information gained from the PROPHET study. During the third year, 1998-1999, the system design was finalized. The system, Figure 1, consists of a 25-liter Taylor-Whorton model 25LD dewar, the trap channel, a pressure cap, a trap plate, and two interface boxes-one containing the electronics, the other containing the hardware (solenoid valves, mass flow controllers, etc.) used to manage the collection of the samples. The trap channel was constructed by welding two 25-mm square pieces of aluminum tubing together and to a top flange, which was designed to fit into a recess in the pressure cap. The channel facilitated independent cooling of either the cryotrap or the cryofocusser, by varying the pressure in the dewar and, thus, the level of the LN2 within each of the tubes. The pressure cap has four threaded ports along the side of the cap. One port is used to pressurize the dewar, one port is used to fill the dewar with LN2, and the final two ports are used to vent the dewar. The vent and pressurizing ports are connected to solenoid valves in the interface box with 0.25-inch Teflon tubing. The cryotrap and cryofocussing trap were constructed using ¼-inch Teflon tubing and were connected to the trap plate using compression fittings. The Teflon tubing acted as a conduit for a thermocouple and a length of SilcoSteel tubing. The SilcoSteel tubing was used as the trapping substrate, and the thermocouple was used to monitor the temperature of the SilcoSteel tubing. This tubing consists of stainless steel tubing that has been coated with fused silica, giving the internal surfaces the inertness of glass, and the tubing the strength and durability of stainless steel. The entire system was monitored and controlled by an IBM compatible computer with software developed using LabView. This system was used to collect ambient air samples at two sites in summer 1999. The first was at Big Meadows in Shenandoah National Park, and the second was at the Atlanta Georgia SuperSite. During both of these studies, the system ran 24 hours per day, 7 days per week without a major failure. We analyzed 1,198 samples during the months of July and August. Currently, data analysis and interpretation are underway in the laboratory, and is expected continue for the next few years.
This program resulted in guidelines for more confident determination of oxygenated compounds in the atmosphere and, thus, better constraint on the chemical climatologies of these compounds. The information gained and methodology developed through this research have been applied to field programs and will continue to be used in future studies. The research group will continue to participate in open dialog and information exchange with other researchers resulting in a community-wide improvement in the understanding of the cycling and the analysis of oxygenated volatile organic compounds.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
| Other project views: | All 16 publications | 1 publications in selected types | All 1 journal articles |
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| Type | Citation | ||
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Barket Jr. DJ, Hurst JM, Couch TL, Colorado A, Shepson PB, Riemer DD, Hills AJ, Apel EC, Hafer R, Lamb BK, Westberg HH, Farmer CT, Stabenau ER, Zika RG. Intercomparison of automated methodologies for determination of ambient isoprene during the PROPHET 1998 summer campaign. Journal of Geophysical Research–Atmospheres 2001;106(D20):24301-24313. |
R825257 (Final) R825256 (1999) R825256 (Final) R825419 (Final) |
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Supplemental Keywords:
ambient air, measurements, VOCs, volatile organics compounds., RFA, Air, Scientific Discipline, Geographic Area, EPA Region, State, Environmental Chemistry, tropospheric ozone, Atmospheric Sciences, air toxics, alcohols, photochemistry, urban air, FLA, air quality data, air sampling, gas chromatography, mass spectrometry, Florida, measurement of oxygenated compounds, atmospheric monitoring, region 4, photochemical oxidant formation, VOCs, ambient air, chemical kinetics, aerosol sampling, carbonylsProgress 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.