6th FECS Conference 1998
VOC
Kinetic Studies on the Reaction of Chlorine Atoms and Hydroxyl Radicals with Aromatic Compounds 1
John Wenger, 1Howard Sidebottom, 2 Paul Chadwick, 2Barbara O'Leary, 2Jack Treacy
1
Department of Chemistry, University College Dublin, Dublin 4, Ireland 'School of Chemistry, Dublin Institute of Technology, Dublin 8, Ireland
Aromatic compounds when released into the atmosphere can have a direct effect on health as well as comributing to the formation of secondary air pollutants including ozone. Commercial uses of aromatic hydrocatbons inelude use as solvents, in paints and polymer manufacture. Single ring compounds are constituents of petrol and this is a large source of their release to the atmosphere. Reaction with OH radicals is believed to be the dominant loss process for aromatic compounds in the troposphere and has been the subject of numerous kinetic studies with rate data being now well established. However, there have been few systematic studies carried out to date on substituted aromatics. Structure activity trends have shown that increased degree of alkyl substitution leacis to enhanced reactivity of the ring towards the electrophilic OH radical, while increasing the length of the alkyl side chain appears to show no trend among investigations. There have been relatively few kinetic studies on reactions of OH with halogenared aromatics, in particular fluorinared aromatics which
are used as intetmediates in the chemieal industry. lt has recently been suggested that Cl atoms may play a
significant role in the gas phase degradation of volatile organic compounds in marine air masses. Measurements of the ambient concentrations of alkanes and alkyl nitrates in the lower troposphere during the Aretic springtime also provide evidence for the importance of Cl atom reactions in the atmosphere. A growing body of evidence from field experiments, labaratory studies and model calculations suggest that, in addition to HC!, highly reactive chlorine-eontaining species, suehas Cl" HOC!and C!NO, also volatilise from sea salt aerosol in d1e marine boundary layer. Subsequent photolysis of these eompounds mayprovide relative!y high levels of Cl in various regions of the troposphere. This work involves a systematic study on the kinetics of the reaction of OH radicals and Cl atoms with aromatic compounds. The results are compared with previous litetature values and discussed in terms of struerure activity relationships.
Indoor Air Chemistry: Enhanced Airway Irritation by (+)-α-Pinene/Ozone Mixtures Peder Wolkoff, Per A. Clausen, Cornelius K. Wilkins, Karin S. Hougaard, Gunnar D. Nielsen National Institute of Occupational Health, Lersø Parkalle 105, DK-2100 Capenhagen Ø, Denmark
In a recent review, it was proposed that atmospheric reactions between unsaturated VOCs and oxidants (e.g., terpenes and 03 ) may produce chemically reactive produets more likely to be responsible for eye and airway irritation than the chemically unreactive VOCs usually measmed indoors (WOLKOFF et al., 1997). lt was also postulared that intermediate species (e.g., hydroperoxides or radicals) formed in the reactions could be strong irritants. The reaction between terpenes and 0 3 under realistic indoor conditions occurs within minutes), while saturated hydrocarbons are chemically non-reactive. The purpose of this project was to find experimental evidence for the existence of highly irritating substances in mixtures of 0 3 and α-pinene using the ASTM mouse bioassay. This assay analyzes the respiratory pattern of mice in an exposure chamber. When exposed to airway irritants, the respiratory rate is reduced by stimulation of the nasal trigeminal nerve (by holding the breath after inhalation). When exposed to pulmonary irritants, the vagal nerve is stimulated, and this either results in a reduction of the respiratory rate (by holding the breath before inhalation),
ESPR- Environ. Sci. & Pollut. Res. 5 (3) 1998
or in increase of the respiratory rate, in addition to a reduction of the tidal volume. These effeets are dose dependent over a wide concentration range. These effects are distinguished by analysis of the respiratory pattern. No effeet levels were established for both 03 and (+)-apinene. A mixture of 03 and extess (+ )-α-pinene (ratio 1:15) at these levels resulted in a significant airway irritation (reduction of mean respiratory rate > 30% ). In addition to unreacted (+)-α-pinene, there was about 15% unreacted ozone. The major reaction produets identified in air samples concentrated on Tenax TA followed bythermal desorption and gas chromatography were: pinonaldehyde, a-pinene oxide, acetone and mesityl oxide. None of these produets can cause a reduetion of the respiratory rate at the concentrations observed. Because the resulting 03 concentration was far below no effect level and the reduc uction was significant (p < 10-7 ), the results suggest strong airway irritants has been formed. The effect has not yet been optimized with regard to starting concentrations of 03 and (+)-αpinene, reaction time, and the relative humidity.
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VOC The potential health impact of indoor oxidation reactions of common naturally occurring compounds (e.g. terpenes) with 03 ,in addition to the possible effects of nitrogen dioxide and UV light will be investigated in greater detail. Acknowledgernents This project was financially supported by the Center for Indoor Air
6th FECS Conference 1998 Research (Award No. 98-11). Wethank Mrs. M. Hammer, Mrs. V. Hansen, and Mr. K. Larsen for excellent technical assistance.
References Wolkoff, P., Clausen, P.A., Jensen, B., Nielsen, G.D., Wilkins, C.K. (1997): "Are We Measuring the Relevant Indoor Pollutants? ", Indoor Air, 7, 92-106
The Qualitative and Quantitative Analysis of VOCs in Arnbient Air using Mobile Laboratory with TD/GC/MS Equipment Viktors Zilinskis, Guntis Jansons, Aigars Peksens, Agris Lazdins Latvian Environment Data Centre, Labaratory Department, Osu street 5, Jurmala, LV-2015, Latvia; E-Mai!:
[email protected]
The analysis of VOCs in air was performed to determine the influence of some air pollution sources on the air quality. The main results of this work are connected with the project "Preliminary investigations of transboundary pollution transfer in southern region of Latvia ". The possible sources of pollution Iie in Latvia and Lithuania. The monitoring of the composition and concentrations of VOCs in ambient air is a difficult task requiring the special sample concentration and analysis technique. For this purpose Latvian Environment Data Centre has a mobile labaratory (ML) basedon MERCEDES BENZ 914. This labaratory has foliowing equipment:
temperature, atmospheric pressure, air humidity can be measured) •
Air sampling systems, instalied in the ML and portable air sampling pumps for independent sampling
• Energy source - on-board batteries, invertors and battery charger. ML was used in two ways: •
as a stationary laboratory, when samples were collected by means of portable sampling pumps and transporred to labaratory for analysis
• directly at the measurement place.
• Zero gas generator for calibration systems •
Permcation calibration systems UPK 1000 and UPK lOOOHT and dilution calibration system UPK 1010-C-3
•
Gas Chromatograph HP 5890 with mass selective derector HP 5971
•
TEKMAR Model 5010 Automatie Desorber and PERKIN ELMER Automatie Thermal Desorption System ATD 400
•
Meteorological station (wind velocity and direction,
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US EPA Method TO l was used for sampling and analyses. A large number of VOCs were found in the air, and quantiration of a number of VOCs was made. A correlation between VOC concentration levels and weather conditions was investigated. The influence of possible pollution sources on the transboundary pollution transfer is discussed.
ESPR- Environ. Sci. & Pollut. Res. 5 (3) 1998
