Environ. Sci. Technol. 1985, 19, 968-974
(28) Betlach, M. R.; Tiedje, J. M. Appl. Environ. Microbiol. 1981, 42, 1074. (29) Knowles, R. Microbiol. Rev. 1982, 46, 43. (30) Jeter, R. M.; Ingraham, J. L. In “The Prokaryotes”; Starr, M. P.; Stolp, H.; Triiper, H. G.; Balows, A.; Schlegel, H. G., Eds.; Springer: Berlin, 1981; p 913. ( 3 1 ) Gibson, T.; Venkiteswaran, S. In “Microbial Degradation of Organic Compounds”; Gibson, T., Ed.; Marcel Dekker: New York, 1984; p 181. (32) Evans, W. C. Nature (London) 1977,270, 17. (33) Aftring, R. P.; Chalker, B. E.; Taylor, B. F. Appl. Environ. Microbiol. 1981, 41, 1177.
(34) Braun, K.; Gibson, D. T. Appl. Enuiron. Microbiol. 1984, 48, 102. ( 3 5 ) Young, L. Y. In “Microbial Degradation of Organic Compounds”; Gibson, T., Ed.; Marcel Dekker: New York, 1984; p 487.
Received for review October 1,1984. Revised manuscript received March 13,1985. Accepted April 9,1985. This project was funded by the Swiss National Science Foundation (Project 3.855-0.81) and by t h e Swiss Federal I n s t i t u t e of Technology (“Schulratsmillion”).
Reactions of o-Cresol and Nitrocresol with NO, in Sunlight and with Ozone-Nitrogen Dioxide Mixtures in the Dark Daniel Grosjean
Daniel Grosjean and Associates, Inc., 350 N. Lantana Street, Camarillo, California 93010 Studies relevant to the atmospheric chemistry of o-cresol were carried out using FEP Teflon outdoor chambers. These studies included sunlight irradiations of o-cresol-NO and nitrocresol-NO mixtures in purified air, reactions of o-cresol and of nitrocresol with 03-NOz mixtures in the dark, and photolysis as well as NO, photooxidation of the dicarbonyls pyruvic acid (CH,COCOR, R = OH) and biacetyl (R = CH,). Products identified included gas-phase nitrocresols in both cresol-NO-sunlight and cresol-0,NOz-dark experiments and dinitrocresol as an aerosol product+ofnitrocresol-NOx reactions. Yields of gas-phase and aerosol products, including gas-aerosol partition of nitrocresol isomers, are presented and are discussed in terms of reactions with NO, (dark) and with OH (sunlight). Photolysis rates for pyruvic acid and biacetyl were determined, and the corresponding product yields were measured.
Introduction Owing to their abundance in urban air (1,2),aromatic hydrocarbons continue to receive substantial attention as major precursors of ozone and organic aerosol formation. Several critical aspects of the atmospheric transformations of aromatic hydrocarbons are still poorly understood. Reactions of their polar aromatic products (cresols, nitrocresols) have received limited attention (3). The nature, yields, and subsequent reactions of the aliphatic dicarbonyls produced following opening of the aromatic ring are, for both aromatic hydrocarbons and their polar aromatic products, the object of considerable uncertainty (4). In a recent study (3),we have carried out sunlight irradiations of o-cresol-NO, mixtures in air and obtained some information on the nature of gas-phase and aerosol products. We present here additional results relevant to specific aspects of the atmospheric chemistry of o-cresol. Because o-cresol may react with both OH and NO, radicals, we attempted to separate the two chemistry regimes and carried out experiments with cresol-NOz-03 mixtures in the dark (N03-Nz05 chemistry) and cresol-NO in sunlight (mostly OH chemistry). Nitrocresols were formed in both cases, and their gas/aerosol-phase partition was investigated. Subsequent reactions of nitrocresols were also studied in the dark (0,-NO, mixtures) and in sunlight (NO, photooxidation). Experiments were also carried out with the dicarbonyl pyruvic acid (CH,COCOR, R = OH), 968
Envlron. Sci. Technol., Vol. 19, No. 10, 1985
a product of o-cresol photooxidation (3, 5 ) , and with its structural homologue biacetyl (R = CH,).
Experimental Methods Experiments were carried out in outdoor chambers constructed from FEP 200A Teflon film. Experimental protocols and measurement methods have been described before ( 3 , 5 1 0 )and are only listed here in summary form (Table I). New methods and protocols are described below. Gas-Phase Measurements. The ultraviolet photometer (Dasibi 1003 AH) we employed in previous studies of organic-NO, reactions responds to polar aromatics such as cresols and nitrocresols in purified, ozone-free air (11). In this work, we employed an ethylene chemiluminescence instrument (McMillan 1100-2) that is not subject to these interferences. The instrument was calibrated on test ozone atmospheres against a “transfer standard UV photometer (Dasibi 1008 PC), which in turn, was periodically checked against the UV photometer maintained by the California Air Resources Board at their El Monte, CA, laboratory. Biacetyl was measured by electron capture gas chromatography using conditions identical with those previously described for peroxyacetyl nitrate (PAN) (8). The two compounds are well resolved when present together at ppb levels in air. Experiments with Ozone and NOz in the Dark. The chamber containing purified air was covered with black plastic film which removed 299% of the incident sunlight. Ozone was introduced first from the diluted output of an 0, generator. The hydrocarbon was injected next by using a glass bulb flushed with dry Nz. Bulb and Teflon carrier gas lines were heated to facilitate injection. NOz (from 100 ppm in a Nz cylinder and using two nylon filters in series to remove nitric acid impurity, if any) was introduced last by syringe injection. Control experiments were conducted with cresol alone in purified air and with mixtures of NO2 and 0, (no o-cresol added) in purified air. Nitroeresols. The isomer selected for study was 4hydroxy-3-nitrotoluene. The two nitrocresol isomers formed as major products of o-cresol photooxidation ( 3 ) are not commercially available. Of the available isomers, the one selected has the lowest melting point, 32 “C, an important consideration for ease of injection into the chamber and for minimizing loss to the chamber walls. This isomer is also relevant to atmospheric chemistry as
0013-936X/85/0919-0968$01.50/0
0 1985 American Chemical Society
Table I. Summary of Parameters Measured a n d Analytical Methods method
parameter
instrument
comments (ref)
NO, NOz, NO,
chemiluminescence
TECO 14 B/E
ozone o-cresol
ethylene chemiluminescence gas chromatography, photoionization detection gas chromatography, electron capture detection
McMillan 1100-2 Varian 2440 with HNU detector
PAN
sensor dew-point hygrometer sensor derivatization-liquid chromatography ion chromatography, conductivity pyruvic acid detection GC-electron capture biacetyl aerosol molecular composition mass spectrometry temperature humidity Ultraviolet radiation intensity formaldehyde, acetaldehyde
ion chromatography, ultraviolet detection
Nitrocresols
calibration by gas-phase titration with NBS-traceable standards
Varian 2440 with EC detector
SP-1240 column calibration with PAN prepared from irradiated acetaldehyde-chlorine-NOz mixtures (8)
YSI 741-A-10 EG&G 8804-1 Eppley ultraviolet radiometer Altex 332 with ultra violet detector (9) Dionex 10
(10)
same conditions as for PAN (8) Kratos MS-25 with electron impact (3) and chemical ionization Dionex 10
Table 11. Summary of o-Cresol-NO, Irradiations run chamber size, m3 run time, h initial T, “C initial dew point, “C initial o-cresol, ppm NO, ppb NOz, PPb NO,, PPb maximum ozone, ppb o-cresol, final/initial NO,, finallinitial* “OH”, X106 ~ m -
~
~
153O
173
175
196
197
201
203
204
4 5 22 -19 1.0 0 0 0 0 1.00
4 3 18 -20 1.18 350 0 350 0 0.77 0.88 0.50
4 4.5 21 -18 1.35 443 5 448 0 0.62 0.53 0.50 0.86
80 4 18 +2 1.16 214 67 281 0 0.84 0.61 0.26
30 4 23 +7 0.45 115 33 148 25 0.58 0.26 0.87
80 5.5 23
80 4 19 -5 0.46 67 84 151 114 0.33 0.18 0.50 2.7 148
80 4.5 21 +2 0.40 200 127 327 30 0.38 0.36
50.07
max aerosol volume concn, pm3 cm-3
105
22
-1
0.61 161 38 199 90 0.56 0.12 1.27 204
1.1
2.1 117
a Control experiment. Final “NOz”may include nitric acid and other nitrogenous products. Calculated from plots of In [cresol]/ [cresol], vs. time, corrected for cresol loss to the chamber walls, and using k(creso1 + OH) = 4.7 X lo-” cm3 molecule-1 s-l. Two values are given for several runs and are for the early and latter phases of the run, respectively. The “OH” thus calculated from experimental data may include a contribution of NO3 to cresol decay in some runs; see text.
the major nitrocresol expected to form in the photooxidation of p-cresol. In our previous study (3),nitrocresol measurements were limited to aerosol samples and to qualitative analysis by mass spectrometry. A new analytical protocol was developed for quantitative analysis of gas-phase and particulate nitrocresols. Aerosol samples collected on Teflon filters were extracted by sonication with 5 X lo-, N aqueous KOH, and analyzed by nonsuppressed ion chromatography with ultraviolet detection (IC-UV). Gas-phase samples were collected in impingers containing 10 mL of 5X N aqueous KOH and analyzed directly by IC-UV following sample collection. Collection efficiency was 297% as verified with two KOH impingers in series. Analytical detection limits were 0.15 pg/mL for mononitrocresols and 0.25-1.0 pg/mL for dinitrocresols. Results Experimental conditions, initial concentrations, and other pertinent information are summarized in Table I1 for eight 0-cresol-NO, irradiations and in Table I11 for four experiments with o-cresol-03-N02 mixtures in the dark. Initial o-cresol concentrations were in the range 0.4-1.3 ppm. NO, concentrations were -150-450 ppb. NO/N02
Table 111. Summary of o-Cresol-N02-0, Experiments run chamber size, m3 run time, h initial temp, “C initial dew point, “C initial o-cresol, ppm NOz, ppb 0 3 , PPb. o-cresol, final/initial Os reacted ppb NOz reacted, ppb O1
154”
174
176
202
4 2 19 -20 1.0 0 0 1.0
4 4 17 -23 1.07 280 170 0.54 140 242
4 3 18 -20 1.15 280 187 0.86 116 250
4 3.5 25 -16 1.42 600 575 0.60 400 545
Control run.
ratios were selected so as to obtain a range of ozone concentrations including several runs where no ozone was produced (this in order to minimize NO, formation and NO, chemistry). The dark reaction of o-cresol with OsNO2 mixtures was studied with NO2 at -300-600 ppb and O3at -170-600 ppb. The experiments with nitrocresol also involved sunlight irradiations with NO,, dark reaction with N02-03 mixEnviron. Sci. Technol., Vol. 19, No. 10, 1985
969
Table IV. Summary of Nitrocresol Experiments"
run time, h initial temp, "C initial dew point, "C initial nitrocresol, PPm 0 2 , PPb NOz, PPb NO, ppb
control (pure air, dark), run 182 183
03-NO2 (dark), run 184 188
3 3 20 25 - 10
2.5 19
-
0.81 0 28.gb 44.5 9.2 >21.8b 0.6
186
333
584
57.0
a Aerosol volume concentration, corrected for wall loss (20, 21) and converted to mass concentration by using a density of 1.3 (nitrocresol density = 1.24; density of dinitro- and hydroxynitrocresols unknown and estimated to be 1.3 f 0.5). bAerosol volume concentration was still increasing rapidly at the end of the run.
Table XI. Summary of Dicarbonyl Photolysis Results run (ref)
102k, m i d
kl, rnin-'"
pyruvic acid, this work (sunlight)
161 162 117 (5) 118 (5)
1.34 1.24 1.62 1.62
0.38 0.41 0.49 0.49
biacetyl, this work (sunlight)
200 165 166 167
1.28 1.27 1.30 1.25
0.41 0.41 0.35 0.40
biacetyl, literature data (artificial light)
(23)
1.371.68 0.3 0.78
(24)
(25)
-0.35 0.084 0.35
+
-
k/kl 0.035 0.030 0.033 0.033 0.033 f 0.002 (la) 0.031 0.031 0.037 0.031 0.032 f 0.003 (la) 0.0390.048 0.036 0.022
From Eppley UV radiometer measurements and theoretical values for NO, photolysis rates.
The nitrocresol-OH reaction rate constant has not been measured. With OH addition being the major reaction pathway, substituent effects for nitrocresols should be similar to those for nitrotoluenes. Substitution of a nitro
-
Table XII. Products of Pyruvic Acid
photolysis run 117 run 161 photooxidation run 118 run 162
" From NO,
irradiation time, min
reacted pyruvic acid, PPb
HCHO, PPb
CH3CH0, PPb
116 213 45 108 178
280 330 136 230 277
94 124 81 49 54
17 17 32
116 230 45 105 165 225
370 440 317 534 634 680
50 74 36 215 41 61
impurities in matrix air.
'
PAN, PPb
NDb
3" 6" 0 0
66
0
9 12 43 52 63 45
30 36
