Atmospheric Environment 34 (2000) 35}43 The gas phase reaction of ozone with 1,3-butadiene: formation yields of some toxic products Franz Kramp!, Suzanne E. Paulson",* !Forschungszentrum Ju( lich, Institut fu( r Chemie und Dynamik der Geospha( re (ICG-2), P.O. Box 1913, 52425 Ju( lich, Germany "Department of Atmospheric Sciences, University of California at Los Angeles, Los Angeles, CA 90095}1565, USA Received 23 April 1999; received in revised form 7 July 1999; accepted 9 July 1999 Abstract The formation yields of acrolein, 1,2-epoxy-3-butene and OH radicals have been measured from reaction of ozone with 1,3-butadiene at room temperature and atmosphere pressure. 1,3,5-Trimethyl benzene was added to scavenge OH radicals in measurements of product yields. In separate experiments, small quantities of 1,3,5-trimethyl benzene were added as a tracer for OH. Formation yields of acrolein of (52$7)%, 1,2-epoxy-3-butene of (3.1$0.5)% and OH radicals of (13$3)% were observed. In addition, the rate coe$cient of the gas-phase reaction of ozone with 1,2-epoxy-3-butene was measured both directly and relative to propene, "nding an average of (1.6$0.4)]10~18 cm3 molecule~1 s~1, respectively, at 296$2 K. The results are brie#y discussed in terms of the e!ect of atmospheric processing on the toxicity of 1,3-butadiene. ( 1999 Elsevier Science Ltd. All rights reserved. Keywords: 1,2-Epoxy-3-butene; Ozone rate constant 1. Introduction Air Act. The ozone reaction also produces 1,2-epoxy-3- butene (Atkinson et al., 1994). Even though this epoxide 1,3-Butadiene is a common atmospheric pollutant that is only formed in yields of a few percent, because of its has been found to be carcinogenic due to its epoxide mutagenic potential, the epoxide could contribute to the metabolites (Himmelstein et al., 1997). It was identi"ed risk due to butadiene inhalation for human health in both as a Hazardous Air Pollutant in the 1990 Clean Air smoggy cities. Act (US public law 101}549) and as a Toxic Air Con- Ozone reacts with alkenes by adding across the taminant under California's air toxics program (AB 1807) double bond to form a primary ozonide which rapidly in 1992. Butadiene is a very volatile and widely used decomposes to a carbonyl compound and a vibrationally industrial chemical as well as a product of the incomplete excited carbonyl oxide (see Scheme 1). combustion of gasoline and diesel fuels, and is widely Butadiene also generates some 1,2-epoxy-3-butane, observed in ambient air at concentrations in the low ppt probably via pathway (R1c), (Atkinson et al., 1994). In the to low ppb range, with an average around 0.2 ppb (subur- gas phase, carbonyl oxides can then be collisionally sta- ban air, (EPA, 1993; Schmitz et al., 1997). In-vehicle bilized or undergo decomposition and/or isomerization exposures are typically higher; around 1.3 ppb (EPA, (e.g., Herron and Huie, 1977; Su et al., 1980; Horie and 1993). It reacts in the atmosphere with OH, O3 and NO3 Moortgat, 1991). For the C carbonyl oxide: to produce a number of potentially toxic products. All 1 t P(M) ** ++ # three reactions produce acrolein and formaldehyde, [H2COO] H2COO ( Thermalized ) M (R2a) which are also considered air toxics under the 1990 Clean HC(O)OH#M (R2b) P # 2H CO2 (R2c) # * Corresponding author. H2O CO (R2d) # E-mail addresses: [email protected] (F. Kramp), paul- CO2 H2 (R2e) [email protected] (S.E. Paulson) OH#HCO. (R2f) 1352-2310/99/$- see front matter ( 1999 Elsevier Science Ltd. All rights reserved. PII: S 1 3 5 2 - 2 3 1 0 ( 9 9 ) 0 0 3 2 7 - 1 36 F. Kramp, S.E. Paulson / Atmospheric Environment 34 (2000) 35}43 Scheme 1. Table 1 Summary of product yields from the O3 reaction with 1,3-butadiene under atmospheric conditions Compound Yield (%) Yield (%) Yield (%) Yield (%) Yield (%) (this work) (a)! (b) (c) (d)! Acrolein 52$6 51 Observed Formaldehyde (HCHO) 65 Observed Ethylene (19 Acetylene (19 b-Propiolactone (1 2,5-Dihydrofuran (0.5 Trace 1,2-Epoxy-3-butene 3.1$0.5 2.3$0.4! Observed 1,2,3,4-Diepoxybutane (1 Trace OH radicals 13$38(#4!3) CO 47 CO2 23 Formic anhydride 9 !Study did not use an OH scavenger. (a) Niki et al. (1983); (b) Atkinson et al. (1994); (c) Atkinson and Aschmann (1993), (d) Liu et al. (1999). Also observed (at low levels): glycolaldehyde, glycidaldehyde, hydroxy acetone, glyoxal, methylglyoxal, malonaldehyde, 2,3-butanedione, butenedial, and several C3 and C4 compounds with multiple carbonyl and/or hydroxy groups. Several recent studies have investigated OH formation (probably minor) products that are not observable with from ozone}alkene reactions (e.g., Atkinson and Asch- gas chromatography or FTIR. mann, 1993; Paulson et al., 1997; Gutbrod et al., 1997; In this study we report formation yields for acrolein, Donahue et al., 1998). For many alkenes, OH yields are 1,2-epoxy-3-butene, the OH radical, and upper limits for large and as such, these reactions are a signi"cant source the yields of several minor products of the ozone}bu- of the chain-initiating radicals that drive oxidizing tadiene reaction. The rate constant for the reaction of photochemistry in urban and rural air (Paulson and 1,2-epoxy-3-butene with O3 was also measured using Orlando, 1996). both absolute and relative rate techniques. Su$cient The results of previous studies on the butadiene reac- concentrations of 1,3,5-trimethylbenzene (TMB) or di-n- tion with O3 are summarized in Table 1. Using Fourier butylether (DBE) were added to scavenge OH in the transform infrared spectroscopy (FTIR), Niki et al. (1983) product studies. The results are discussed in terms of the observed acrolein, formaldehyde, CO, and CO2 together reaction mechanism and the e!ect of atmospheric pro- with small quantities of ethene, acetylene, and formic cessing on the toxicological potency of 1,3-butadiene. anhydride from the 1,3-butadiene ozone reaction, but did not use an OH scavenger. Atkinson et al. (1994) mea- sured an 1,2-epoxy-3-butene yield (using an OH scaven- 2. Experimental description ger), and Atkinson and Aschmann (1993) estimated the OH formation yield. Recently, Liu et al. (1999) used Experiments were carried out in 250 l Te#on chambers a semi-quantitative derivatization technique to investi- at atmospheric pressure (760$10 Torr) and 296$2K. gate formation of carbonyls, including multi-functionals. Liquid compounds were evaporated into a stream of In addition to the above carbonyls, they observed several puri"ed air (Thermo Environmental Model 111) as the F. Kramp, S.E. Paulson / Atmospheric Environment 34 (2000) 35}43 37 chamber was "lled; gasses were added directly using other loss process for TMB (apart from a small amount graduated micro syringes. The quality of the zero air was of wall loss, (1.5%) is unlikely. Rate constants show 1 3 checked periodically and concentrations of hydrocar- that H atoms rapidly combine with O2,O( D) and O( P) bons, nitrogen oxides and ozone were always below the rapidly react to form O3, and while it is conceivable that detection limits (about 15, 3 and 5 ppb, respectively). the carbonyl oxides may react with TMB, the alkene is Once the gas mixture was prepared, the chamber was a far more likely target, as are water, organic acids and mixed by moving the walls and left to stand for at least aldehydes. Relative loss of tracer pairs including TMB, 1 h to allow the reactant concentrations to stabilize. di-n-butyl ether, m-xylene and several other tracers in Several measurements of the organic compounds in the the presence of ozone and alkenes have been studied dark chamber were made to establish the initial concen- by Paulson et al. (1997) and Marston et al. (1998); trations before addition of ozone. All organic compounds both studies are completely consistent with the tracers (DBE, TMB, 1,3-butadiene, acrolein, and 1,2-epoxy-3- reacting with OH. butene, Aldrich stated purity, 99, 98, 99, 96, and 98%, The rate coe$cient of the reaction between 1,2-epoxy- respectively), were used without further puri"cation. 3-butene and ozone was measured both directly and Ozone was generated by #owing pure oxygen relative to propene (Table 3). All experiments had added (150 ml/min) through a mercury lamp generator (JeLight, excess TMB to scavenge OH. For the relative measure- Model 600) and the ozone concentration inside the ments, ozone was added in three aliquots of about 2 ppm chamber was measured with UV absorption (Dasibi, each. In the direct measurements, O3 was added once Model 1003RS). and analyses of the hydrocarbon and ozone concentra- Experiments to investigate products of the 1,3-buta- tions were made every half hour during the 4}5 h experi- diene reaction with ozone are summarized in Fig. 3. ments. TMB or DBE were added in su$cient excess to trap Samples of organic compounds were drawn through more than 95% of the OH radicals formed. Ozone a heated Te#on line and analyzed with GC/#ame ioniz- was added every 30}60 min in aliquots, each resulting in ation detection (Hewlett-Packard 5890) equipped with l 0.5 to 2 ppm O3 inside the chamber. Analyses of a 30 m DB-1 column (J&W, ID 0.32 mm, 1 m "lm). The the composition of the reacting mixture were made every GC was calibrated daily using a 20.2$0.4 ppm n-hexane 30 min just before addition of the next ozone aliquot.