Environ. Sci. Techno/. 1988,22,956-962
Dickhut, R. M.; Andren, A. W.; Armstrong, D. E. Environ. Sci. Technol. 1986, 20, 807. Hutzinger, 0.;Safe, S.; Zitko, V. The Chemistry of PCB’s; R. E. Krieger: Malabar, FL, 1983; p 16. Braun, A. M.; Gilson, M.-A.; Krieg, M.; Maurette, M.-T.; Murasecco, P.; Oliveros, E. Organic Phototransformations in Nonhomogeneous Media; Fox, M. A,, Ed.; ACS Symposium Series 278; American Chemical Society: Wash-
(26) Ohashi, M.; Tsujimoto, K. Chem. Lett. 1983, 423. (27) Bunce, N. J.; Ravanal, L. J. Am. Chem. SOC.1977,99,4150. (28) Davidson, R. S.; Goodin, J. W. TetrahedronLett. 1981,22, 163. (29) Davidson, R. S.; Goodin, J. W.; Pratt, J. E. Tetrahedron Lett. 1982, 23, 2225. (30) Barltrop, J. A.; Bradbury, D. J. Am. Chem. SOC.1973, 95,
ington, DC, 1985; pp 79-97. Meuser, J. M.; Weimer, W. C. Amine-Enhanced Photodegradation of Polychlorinated Biphenyls;Report CS-2513, Electric Power Research Institute: Palo Alto, CA, 1982. Christensen, D. C.; Weimer, W. C. Proc. Ind. Waste Conf. 1979, 160. Bunce, N. J. J. Org. Chem. 1982,47, 1948. Ohashi, M.; Tsujimoto, K.; Seki, K. J . Chem. SOC.,Chem.
(31) Epling, G. A.; McVicar, W.; Kumar, A. Chemosphere 1987, 16, 1013. (32) Klinger, R. J.; Mochida, K.; Kochi, J. K. J. Am. Chem. SOC. 1979, 101, 6626.
Commun. 1973,384.
5085.
Received for review April 20,1987. Accepted January 28,1988. This study was financially supported by the National Institutes of Health (ES03527) and the Universityof Connecticut Institute for Hazardous Materials and Wastes.
Detailed Hydrocarbon and Aldehyde Mobile Source Emissions from Roadway Studies Roy B. Zweldlnger,” John E. Slgsby, Jr., Sllvestre B. Tejada, Fred D. Stump, David L. Dropkln, and William D. Ray Mobile Source Emissions Research Branch, Environmental Sciences Research Laboratory, US. Environmental Protection Agency, Research Triangle Park, North Carolina 2771 1
John W. Duncan Northrop Services, Inc., Research Triangle Park, North Carolina 27709
A field study was conducted along U.S.Highway 70 near Raleigh, NC, to evaluate methods for estimating emission factors and, in particular, for determining volatile organic carbon (VOC) species (i.e., individual hydrocarbons and aldehydes) emitted from traffic. Integrated samples were collected 1m from the roadway between 7:30 and 830 a.m. at four different roadside locations representing various combinations of traffic conditions (cruise, acceleration, deceleration, and idle). The light-duty traffic component (>go%) was classified by model year between 1975 and 1983. On a percent of total non-methane basis, the distribution of VOC’s varied little between sampling sites. The roadside VOC distribution was compared to dynamometer/dilution tube test results on in-use vehicles, which were weighted to reflect the same model year distribution observed on the roadway. Some of the differences seen were attributed to fuel effects, while others may reflect an insufficient data base. Mass emission rates calculated from release of a tracer gas by a pace car varied unpredictably and were higher than those calculated by the Mobile3 model or observed with the in-use vehicle dynamometer data. Introduction
Since the role of individual hydrocarbons (HC’s) in oxidant formation varies greatly, detailed speciation data can aid substantially in predicting ambient air quality. However, most data related to mobile source emissions are limited to measurements of total hydrocarbon (THC), CO, and oxides of nitrogen (NO,) derived from laboratory dynamometer/dilution tube studies in which vehicles are operated in a fixed, prescribed manner. For example, a current method for estimating mobile source emission factors (THC, CO, and NO, only) employs the Mobile3 model (1) and its associated data base (2),which is based on testing vehicles using the federal test procedure (FTP) (3). By comparison, only a minimal amount of data exists 956
Environ. Sci. Technol., Vol. 22, No. 8, 1988
for detailed HC speciation from mobile sources. Even less data exist for aldehydes and other carbonyls. Emission inventories of carbonyl compounds are of particular interest because these compounds play an important role in both the formation and perpetuation of atmospheric “smog”. The establishment of a detailed speciation data base is costly and time consuming when conducted on a vehicleby-vehicle basis in the laboratory. Furthermore, most laboratory testing is conducted on relatively new vehicles in proper operating condition, a situation which may not reflect the “real world”. An alternative is to conduct roadside sampling, which provides an opportunity to obtain integrated samples of vehicle types and ages under a variety of operating conditions. While a number of such roadside studies have been conducted in the past, they have frequently been limited to tunnels ( 4 ) or roadway situations where accurate emission rates could not be calculated (5). By employing tracer gas techniques (6),it is possible to determine dilution factors for samples collected in the field and to calculate mass emission rates. In 1983 we conducted a series of preliminary field studies to define and evaluate alternative procedures for collecting HC and aldehyde speciation data from mobile sources via roadway sampling. We sought (1)to determine if differences in emissions could be observed for sites influenced by cruise, acceleration, and deceleration traffic modes and (2) to compare the observed emissions with those measured in dynamometer/dilution tube experiments. In addition, we were curious to determine, under the conditions employed, what sort of mass emission rates could be obtained from the release of a tracer gas. Experimental Section
The field experiments reported here were conducted along a section of U.S. Highway 70 near Raleigh, NC, during May 1983.
0013-936X/88/0922-0956$01.50/0
0 1988 American
Chemical Society
I E
mar10
VEST BOUND - 3 LANES
MEDIAN
0 l m
A@<
