Effects of Ambient Temperature on Aspects of Airborne Polycyclic Aromatic Hydrocarbons Hlroyasu Yamasakl, * Kazuhlro Kuwata, and Hlroko Mlyamoto Environmental Pollution Control Center, 62-3, 1 Chome, Nakamichi, Higashinari-ku, Osaka City, 537, Japan ~ ~~~ Three- to six-ring polycyclic aromatic hydrocarbons in the vapor phase (PAHs,,,) and in the particulate phase (PAHs,,) and total suspended particulate (TSP) in am- bient air were sampled and determined year-round. At ambient temperature levels, substantial amounts of three- to five-ring PAHs were found in the vapor phase de- pending upon temperature (T, K) and the six-ring PAHs were all found in the particulate phase. For three- to five-ring PAHs, the Langmuir adsorption concept was in- troduced for PAHs,,~, and PAH$,t on the particulates. log [(PAHs,ap)/{(PAHs,at)/(TSP))] was related to 1/T, and a high correlation (r = -0.834 to -0.942) was obtained be- tween the two quantities. Thus, aspects of the three- to five-ring PAHs in ambient air were considered to be ex- plained by using the Langmuir adsorption concept. Introduction Polycyclic aromatic hydrocarbons (PAHs) have received much attention in studies of air pollution because some of these compounds are highly carcinogenic. In most cases, PAHs in the atmosphere have been collected as particulate matter on glass-fiber filters (GFs) by using conventional high-volume air samplers. However, as pointed out in several articles (1-4), three- to five-ring PAHs are found, or estimated to be to some extent, in the vapor phase at ambient temperature. Especially the three- and four-ring PAHs, which have relatively high vapor pressures, are not satisfactorily trapped on GFs. Some authors (I, 2) report that even benzopyrene, which has a low vapor pressure, is appreciably lost on a GF by sublimation and/or de- composition during ordinary sampling. The degree of loss seems to depend greatly upon the sampling temperature. In a previous study (3), we reported that three- to five-ring PAHs in the vapor phase can be effectively trapped on polyurethane foam plugs (PUFPs) and that a high volume of urban air can be sampled for simultaneous determina- tion of three- to six-ring PAHs by using a combination of a GF and PUFPs attached to a high-volume air sampler. From the results, substantial amounts of three- to five-ring PAHs are found in the vapor phase. The facts mentioned above suggest that it is important to investigate the state of the PAHs in the atmosphere in studies of air pollution. So far, few reports have been published concerning the determination of various PAHs in the vapor phase and in the particulate phase in urban air throughout the year. In this study, urban air was sampled throughout 1 year by using the apparatus previously reported (3), and the var- ious PAHs in the vapor phase and in the particulate phase were determined. Aspects of PAHs in ambient air are explained by using the Langmuir isothermal adsorption concept. Experimental Section Reagents and Materials. The PAHs as standard reagents were purchased from Wako Pure Chemical In- dustries (Osaka, Japan), Tokyo Kasei Kogyo (Tokyo, Ja- pan), R. K. Chemical (Hartville, OH) and Analabs (North Haven, CT). Benzene and n-hexane were pesticide-resi- due-analysis grade from Wako Pure Chemical Industries, and other solvents were either chromatographic or spectral grade from Wako Pure Chemical Industries. Davison Chemical No. 923 silica gel (Fuji Davison Chemical, Aichi, Japan) for a purification column (20 cm X 10-mm i.d., glass) was washed with benzene for 10 h in a Soxhlet ex- tractor and activated by heating at 140 "C for 4 h. The PUFP (5 X 10 cm, 0.021 g/cm3 density) was cut out from a polyurethane foam sheet (ether type) available from Bridge Stone Co. Inc. (Tokyo, Japan) and washed with acetone for 10 h in a Soxhlet extractor followed by similar washing with cyclohexane for 10 h. The GF was a Toyo Roshi (Tokyo, Japan) GB-100R which could trap 99.99% of 0.3-pm particulate matter. The GF was heated at 350 "C before use to eliminate organic compounds. Apparatus. The sampling apparatus for PAHs is shown in Figure 1. The apparatus was attached to a conventional high-volume air sampler. An Ogasawara Instrument Manufacturing Co. Ltd. (Tokyo, Japan) A-1250 automatic recording thermometer with a platinum ther- mosensor, which was set next to the sampling apparatus, was used. A Shimazu-LKB (Shimazu Co., Kyoto, Japan) 9OOO combined gas chromatograph-mass spectrometer was used to identify the PAHs. A Varian (Walnut Creek, CA) 2100 gas chromatograph with a flame ionization detector was used to determine quantitatively the PAHs identified. The working conditions were as follows: column, 1.5 m X 2-mm i.d. stainless-steel tube packed with 6% Dexil300 on 80-100 mesh Chromosorb W (HP); carrier gas, nitrogen 30 mL/min; injection temperature, 270 "C; column tem- perature, isothermal at 160 "C for first 2 min (when amounts of phenanthrene + anthracene are less, isothermal at 140 "C for first 10 min), programmed from 160 (or 140) to 320 "C at 6 "C/min; detector temperature, 350 OC; sample volume, 10 pL. Sampling. Urban air was sampled at 0.75-0.80 m3/min (30.6-32.6 cm/s of linear velocity on the GF) for 24 h (from 10 a.m. through 10 a.m. of the next day) by using the apparatus shown in Figure 1. Suspended particulate was 0013-936X/82/0916-0189$01.25/0 0 1982 American Chemical Society Environ. Sci. Technol., Vol. 16, No. 4, 1982 189Table I. Recovery of the PAHs from the PUFP and the GF PAH anthracene fluorant hene pyrene chrysene benzo[a]pyrene o-phenylenepyrene benzo [ghilperylene " Averaged value in 5 runs. PUFP PAH PAH found t SD," 15.0 10.7 i 0.51 15.0 12.5 i 0.43 15.0 12.4 t 0.30 15.0 12.5 t 0.32 15.0 12.1 t 0.41 15.0 12.7 f 0.54 15.0 12.8 i 0.60 added, pg I.rg 1 :ecovery,b % 71.3 (4.8) 83.3 (3.4) 82.7 (2.4) 83.3 (2.6) 80.7 (3.4) 84.7 (4.3) 85.3 (4.7) GF PAH found i SD," Pg recovery,b % 11.9 t 0.56 79.3 (4.7) 13.6 t 0.37 90.7 (2.7) 13.7 t 0.24 91.3 (1.8) 13.8 t 0.61 92.0 (4.4) 13.1 t 0.54 87.3 (4.1) 13.6 t 0.42 90.7 (3.1) 13.5 i 0.47 90.0 (3.5) SD = standard deviation. Relative standard deviation (%) is given in parentheses. $*IR Flgure 1. Sampling apparatus for atmospherlc PAHs: (A) OF, (8) stainless-steel net, (C) Teflon gasket, (D,) first PUFP, (D2) second PUFP, (E) stalnless-steel cylinder. simultaneously collected by an ordinary high-volume air sampler. The
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