Ambient Hydrocarbon and Ozone Measurements Downwind of a Large Automotive Painting Plant Ken Sexton' and Hal Westberg" Air Resources Section, Washington State University, Pullman, Wash. 991 64
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This paper describes the results of a n intensive ambient air monitoring program near t h e G M automotive assembly plant a t Janesvillk, Wis. Utilizing three ground level sampling stations and an instrumented aircraft, a three-dimensional monitoring network was employed to investigate t h e effects of airborne hydri)carlion emissions 011 local ozone levels. T h e study focused on characterizing the gaseous components of t h e G M plume, with particular emphasis on C + 2 1 ~ hydrol carbon identification. and investigating in-plume chemical transformation during transport. Measurements of t h e following were routinely pert'ormed: ozone. oxides of nitrogen. methane, carbon monoxide. individual C2-C 1 0 hydrocarbons. halocarbons. coiidensation nuclei, visual distance, and numer ous me t eor 01I )gica l par am e t e r s. Gaseous hydrocarbon emissions occur during surfacecoating operations associated with a variety of industries including automotive assembly plants, furniture manufacturers, a n d plastic products producers. Chemical species typically emitted during application and drying processes are aliphatic a n d aromatic h:r.drocarbons, alcohols. ketones, and esters. Smog chamber studies have suggested t h a t many of these same organic compounds are photochemically reactive and have t h e potential to form significant quantities of ozone (1-.3). On t h e b a s k of these laboratory results and published emissions rates for surface-coating facilities (41,it is reasonable to assume t h a t organic emissions from a large-scale painting plant may have considerable impact on local ozone concentrations. ICurrently, there is a critical lack of amhient air d a t a available to document hydrocarbon and ozone coilcentrations near major surface-coating operations. In order to in1:estigate the effect of painting emissions on ambient ozone levels, t h e Air Resources Section a t LVashington State University initiated an air monitoring program near t h e General Motors Assembly Division plant in danesville, LVis. Aerial and surface sampling was used to provide information on plume composition, dimensions. and chemical transformations. T h e G M plant selected for this study is one o f t h e largest in the United States and annually emits a n estimated 9200 tons of volatile hydrocarbons. T h e relatively isolated location of t h e plant, away from other major hydrocarbon sources, facilitated tracking of the GM effluent.
E.upc~rimenta1Procedure During t h e month-long sampling period in August 1977, a n instrumented trailer served as a field laboratory for the study. T h i s trailer was positioned near Vista P a r k , approximately 1 mile northeast o f t h e General Motors complex. From this location it was possible to gather d a t a on ambient "background" pollutant levels within the city of .Janesville and compare these values with measurements made when the G51 plume drifted over t h e field laboratory. Continuous measurements routinely accomplished at t h e field laboratory in-
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Present addres,s, Energy and Environmental Division, Acurex Corporation. 185 Clyde Avenue, Llountain View, Calif. 940.12.
cluded O:],NO, NO?, NO,, CHA, CO, total hydrocarhons ( T H C ) , halocarbons, and various meteorological parameters. Individual hydrocarbon identification and sulfur hexafluoride (SF,;) tracer analyses using gas chromatographic techniques were also performed a t t h e field laboratory. T h e ground monitoring network also included a fixed-base sampling station 2 miles southwest of t h e G h l plant and a mobile air monitoring laboratory. Both provided continuous O:i, NO, NO?, and NO, measurements that were used to augment d a t a from t h e field laboratory. Aerial sampling was accomplished using a Rockwell Aero Commander 680FL equipped to make continuous measurecondensation nuclei ( C N ) , ments of O,].NO, NO?, NO,, SO?, visual distance, and meteorological and navigational parameters. Hydrocarbon and/or SFt; grab samples were collected in 6-L stainless steel cans and returned to the field laboratory for GC analysis. A comprehensive discussion of instrumentation. measurement techniques, a n d calibration procedures has been reported elsehwere ( 6 ) .
Result,\ a n d Discussion Prevailing Meteorological Conditions. Unseasonably cool temperatures a n d above normal precipitation were recorded in southern Wisconsin during August 1977'.Meteorological conditions conducive to formation of high ozone levels were present on only a few days during the study. On each of t h e seven occasions when one or more of t h e ground monitoring sites recorded 0,jconcentrations in excess of80 ppb (1-h average), elevated ozone levels extended throughout southern LVisconsin. Episodic ozone conditions (>80p p b ) observed during t h e study were associated with the trailing edge of transient high-pressure systems. Considerable documentation exists elsewhere on the relationship between migratory anticyclones a n d air quality in t h e Midwest ( 7 ,8). Ground Level Characterization of the GM Plume. Several times during August 1977 t h e field laboratory recorded instances of fumigation by G M emissions. Figure 1 provides a graphical illustration of changes in ambient concentrations of nonmethane total hydrocarbons ( N M T H C ) , methane, carbon monoxide, and methylchloroform (CH:jCCl,J during periods when t h e G M plume fumigated the field laboratory. As shown in Figure 1, increased N h I T H C levels provided t h e best indicator of t h e G M plume with in-plume concentrations typically 2 to 2.3 ppm above background levels (
