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Source Profiles for Nonmethane OrganicCompounds in the Atmosphere of Cairo, EgyptPaul V. Doskey a , Yoshiko Fukui a , Mohamed Sultan a , Ashraf Al Maghraby b & AmanyTaher ba Environmental Research Division , Argonne National Laboratory , Argonne , Illinois ,USAb Cairo University/Center for Environmental Hazard Mitigation, Cairo University ,Giza , EgyptPublished online: 27 Dec 2011.

To cite this article: Paul V. Doskey , Yoshiko Fukui , Mohamed Sultan , Ashraf Al Maghraby & Amany Taher (1999) SourceProfiles for Nonmethane Organic Compounds in the Atmosphere of Cairo, Egypt, Journal of the Air & Waste ManagementAssociation, 49:7, 814-822, DOI: 10.1080/10473289.1999.10463850

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Doskey et al.

814 Journal of the Air & Waste Management Association Volume 49 July 1999

ISSN 1047-3289 J. Air & Waste Manage. Assoc. 49:814-822

Copyright 1999 Air & Waste Management Association

TECHNICAL PAPER

Source Profiles for Nonmethane Organic Compounds in theAtmosphere of Cairo, Egypt

Paul V. Doskey, Yoshiko Fukui, and Mohamed SultanEnvironmental Research Division, Argonne National Laboratory, Argonne, Illinois

Ashraf Al Maghraby and Amany TaherCairo University/Center for Environmental Hazard Mitigation, Cairo University, Giza, Egypt

ABSTRACTProfiles of the sources of nonmethane organic compounds(NMOCs) were developed for emissions from vehicles, pe-troleum fuels (gasoline, liquefied petroleum gas [LPG], andnatural gas), a petroleum refinery, a smelter, and a castiron factory in Cairo, Egypt. More than 100 hydrocarbonsand oxygenated hydrocarbons were tentatively identifiedand quantified. Gasoline-vapor and whole-gasoline pro-files could be distinguished from the other profiles by highconcentrations of the C5 and C6 saturated hydrocarbons.The vehicle emission profile was similar to the whole-gaso-line profile, with the exception of the unsaturated andaromatic hydrocarbons, which were present at higher con-centrations in the vehicle emission profile. High levels ofthe C2-C4 saturated hydrocarbons, particularly n-butane,were characteristic features of the petroleum refinery emis-sions. The smelter and cast iron factory emissions weresimilar to the refinery emissions; however, the levels ofbenzene and toluene were greater in the former twosources. The LPG and natural gas emissions contained high

IMPLICATIONSPhotochemical smog in the world’s megacities can ad-versely affect the health of many inhabitants of these largeurban areas and can influence the chemistry of the globaltroposphere. Controls on emissions of nonmethane organiccompounds (NMOCs) may be necessary to reduce theformation of photochemical smog. To formulate effectivecontrol strategies, the critical tasks are identifying theNMOCs in the emissions from various source sectors anddetermining the contributions of those source sectors toambient levels of NMOCs. Profiles of NMOC sources canbe used in chemical mass-balance source-reconciliationmodels to provide an independent determination of sourcecontributions. Source profiles vary according to the com-position of petroleum fuels. Thus, deriving NMOC sourceprofiles that are specific to the area of study is critical.This paper describes a preliminary evaluation of thesources of NMOCs in Cairo, Egypt.

concentrations of n-butane and ethane, respectively. TheNMOC source profiles for Cairo were distinctly differentfrom profiles for U.S. sources, indicating that NMOC sourceprofiles are sensitive to the particular composition of pe-troleum fuels that are used in a location.

INTRODUCTIONThe world’s megacities commonly experience episodes ofair pollution. The health of the inhabitants of these largeurban centers is a concern, as is the effect of pollutant emis-sions on the global troposphere. Cairo, Egypt, a metropoliswith a population of over 10 million, frequently experi-ences episodes of photochemical smog, formed in a com-plex series of chemical reactions involving nonmethaneorganic compounds (NMOCs) and nitrogen oxides. Con-trols on some sources of the NMOC emissions may be nec-essary to reduce photochemical smog formation. Therefore,determination of the contributions of the various sourcesectors to ambient NMOC levels is critical.

The chemical mass-balance (CMB) source-reconciliationmodel has been widely applied to estimate the contributionof NMOC sources to their ambient levels in the atmospheresof various urban areas.1-11 The NMOC source profiles (i.e.,the concentrations of the individual NMOCs in the sourceemissions) are essential input data to the CMB model. Pro-files for NMOC sources have been developed for urban areasof the United States,8,11-13 Canada,10 Japan,4 and Australia.3

However, these profiles may not be applicable to urban ar-eas in other countries because of differences in the composi-tion of the petroleum fuels used in different areas.

The first measurements of NMOCs from various sourceswithin and around Cairo represent major consumers andproducers of coal and petroleum fuels. Emissions from ve-hicles, an oil refinery, users of liquefied petroleum gas (LPG)and natural gas, a lead smelter, and a cast iron factory werecollected in June 1997 for a preliminary evaluation of theNMOC sources. Samples of gasoline fuels were also obtained.The samples were analyzed by a cryogenic preconcentration/

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high-resolution gas chromatographic technique,14 and pro-files for each source were developed. The profiles for the Cairosources are compared with one another and with profilesfrom U.S. sources.

EXPERIMENTALSampling Strategies

The NMOCs are emitted during the production, refining,and use of petroleum fuels. To make a preliminary evalua-tion of the NMOC sources in Cairo, the emissions from ve-hicles, the use of LPG and natural gas, an oil refinery, a leadsmelter, and a cast iron factory were sampled. Samples ofliquid gasoline fuels were also obtained. Vehicles can be asource of NMOCs during starting (cold-start emissions), driv-ing (roadway emissions), immediately after the vehicle hasbeen stopped after driving (hot-soak emissions), and duringthe diurnal and resting phases. Cold-start and hot-soak emis-sion profiles were measured for an integrated sample of ve-hicles of various ages inside of the El Boston auto parkinggarage, which contained mainly light-duty vehicles, and in-side of the Egyptian Geological Survey (EGSMA) passenger-bus parking garage, which contained heavy-duty diesel en-gine vehicles. The auto parking garage has a capacity of 50vehicles and is about 200 m (l) × 30 m (w) × 2.5 m (h), withopenings on the east and west sides. The ambient air withinthe garage was sampled under nearly stagnant conditions0.5 hr after the lot had been filled to near capacity in themorning and immediately after half of the vehicles left inthe afternoon. The bus parking garage has a capacity of about20 vehicles and is about 40 m (l) × 30 m (w) × 7 m (h). Theambient air within the garage was sampled in the early morn-ing, when all the buses left the garage and 0.5 hr after fivebuses had returned on the same morning.

Roadway emissions were sampled along Salah SalemStreet, a major thoroughfare in downtown Cairo, at a heightof 1.2 m and a distance of 6 m from the roadway. A samplewas taken at 8:40 a.m., when the rates for traffic densitywere about 65 gasoline engine vehicles min-1 and 10 dieselengine vehicles min-1. Roadway emissions were also sampledin the Sheraton Tunnel (30° 02´50¨N, 31° 13´19¨E; altitude,21 m), which is situated near the west side of the RiverNile. A sample was collected from the pedestrian pavementmidway through the tunnel, when the traffic density wasabout 66 and 79 vehicles min-1 on each side of the tunnel,with about 17 diesel engine vehicles and two motorcyclesbeing included in the vehicle distribution. A backgroundsample of air entering the tunnel was also collected. Emis-sions from a motorcycle were independently sampled atabout 0.5 m from the exhaust pipe of an idling vehicle. A50/50 mixture of gasoline and motor oil is commonly usedas a motorcycle fuel in Cairo.

The NMOC emissions from a petroleum refinery, leadsmelter, and cast iron factory were sampled, and

uncombusted LPG and natural gas vapors were also col-lected. Samples of ambient air were collected at ground level1 km upwind and 0.5 km downwind of a major petroleumrefinery located to the northwest of Cairo. The emissionsfrom a lead smelter that uses Mazot, a heavy oil, as a fuelwere sampled within a visible smoke plume 50 m down-wind of the plant. Emissions from a cast iron factory thatuses coal as a fuel were collected in a similar manner. Toofew sampling canisters were available to collect ambient airsamples directly upwind of the lead smelter and cast ironfactory. Instead, a single ambient air sample was taken at anearby location upwind of the two sources. UncombustedLPG and natural gas samples were collected above a gasstove in a residential home.

Sampling and Analytic TechniquesWhole-air samples of the emissions were collected by pas-sively withdrawing air into preevacuated Summa passi-vated stainless steel canisters (Scientific InstrumentationSpecialists, Moscow, ID) over a period of about 30 sec. Thecanisters were cleaned in a series of pressurization/evacu-ation cycles at 105 °C by using humidified ultra zero air13,14

were evacuated to < 0.2 mm Hg, and were shipped to thefield. A total of 14 samples of the source emissions werecollected between June 5 and June 10, 1997, at variouslocations in Cairo (30° 04´N, 31° 17´E). Regular and high-grade liquid gasoline samples were sampled directly fromthe pump of a gas station into glass vials with caps con-taining Teflon-lined septa.

The air samples were cryogenically preconcentratedwith a Chemical Data Systems CDS 330 sample concen-trator (Autoclave Inc., Oxford, PA) and analyzed with aHewlett Packard 5890A high-resolution gas chromato-graph (Palo Alto, CA) with a flame ionization detector(FID). Details of the analytic technique have been describedelsewhere.14 Briefly, the whole-air samples werepreconcentrated at -100 °C in a 15-cm section of a glass-lined stainless steel tube (0.180-cm i.d.) packed with 60/80 mesh porous glass beads (Unibeads 1S; Alltech Associ-ates, Inc., Deerfield, IL), were thermally desorbed at 100°C for 2 min, and were transferred to either (1) a 60-m ×0.32-mm-i.d. fused-silica capillary column coated with a1-µm-thick film of polydimethylsiloxane (DB-1; J&W Sci-entific, Folsom, CA) for analysis of the C4-C12 hydrocar-bons and oxygenated hydrocarbons (OxHCs), or (2) a 30-m × 0.53-mm-i.d. porous-layer open tubular columncoated with alumina (GS-Alumina; J&W Scientific) foranalysis of the C2 and C3 hydrocarbons. The DB-1 columnwas held at -50 °C for 2 min during the thermal desorp-tion step, was temperature-programmed at a rate of 8 °Cmin-1 to 210 °C and then at 20 °C min-1 to 250 °C, and washeld at 250 °C for 5 min. The GS-Alumina column washeld at -50 °C for 2 min during the thermal desorption

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step. Then the temperature was increased at a rate of 8 °Cmin-1 to 135 °C, and then at 20 °C min-1 to 200 °C and washeld for 5 min at 200 °C.

Whole-air samples of uncombusted LPG and natu-ral gas and the motorcycle emissions were too concen-trated to be cryogenically preconcentrated and were di-luted by pressurizing the canisters to 2 atm with humidi-fied ultra zero air. The dilute samples were analyzed byinjecting 300-µL aliquots directly into the column injec-tion port of the CDS 330 with a gas-tight syringe. Whole-gasoline samples were prepared by injecting 1 µL of theliquid gasolines at 21 °C into 2-L static dilution bottlesfilled with high-purity helium gas at 65 °C. The whole-gasoline samples were analyzed by injecting 100-µLaliquots directly into the column injection port of theCDS 330 with a gas-tight syringe. Gasoline headspacesamples were prepared by injecting 1 mL of the headspacevapors from glass vials with Teflon-lined septa caps con-taining the gasolines at 21 °C into 500-mL static dilu-tion bottles filled with high-purity helium gas at 65 °C.The samples were analyzed by injecting 100-µL aliquotsdirectly into the column injection port of the CDS 330with a gas-tight syringe.

The FID was calibrated daily with a mixture of C2-C6

n-alkanes, benzene, and toluene at a level of 10 ppbveach (Scott Specialty Gases, Inc., Plumsteadville, PA). Re-sponse factors for the OxHCs were derived by using ef-fective carbon numbers to compensate for their dimin-ished responses in the FID.15 Tentative identifications ofthe NMOCs were made by comparing retention times ofstandards prepared in static dilution bottles with samplesinjected under identical chromatographic conditions.

RESULTS AND DISCUSSIONA total of 142 NMOCs were tentatively identified in thesamples. The numbers of saturated (alkanes), unsaturated(alkenes and alkynes), aromatic, oxygenated, and chlori-nated hydrocarbons were 50, 36, 23, 26, and 7, respectively.Source profiles were developed that were based on theweight fraction of each compound relative to the total massof the NMOCs in the source emission. The total mass ofthe NMOCs in each sample is estimated by correcting thetotal FID response for the diminished responses of theidentified OxHCs and assigning an average number of car-bon atoms of six and a molecular weight of 86 (equivalentto n-hexane) to the total NMOCs. The NMOCs in Table 1were all present at a level greater than 0.50% in at least oneof the source profiles, with the exception of cyclopentane,2,4-dimethylpentane, and methylcyclohexane, which werepresent at lower levels, but have been included in Table 1because they are routinely used in CMB modeling applica-tions. The chlorinated hydrocarbons are not included inthe source profiles because the concentrations in the

samples were similar, indicating that they were not emit-ted by the sources under study.

To facilitate the comparison of the source profiles fromCairo with one another and with profiles from U.S.sources, 23 NMOCs were chosen for the CMB profiles.These NMOCs have been used to determine the contribu-tion of NMOC sources to ambient levels because of theirstability with regard to reaction with the hydroxyl radi-cal (OH).8 Rate constants for the reaction of the 23 NMOCswith OH range from 0.31 × 10-12 cm3 molecule-1 sec-1 forethane to 10.4 × 10-12 cm3 molecule-1 sec-1 formethylcyclohexane.16 At an OH concentration of 1 × 107

molecules cm-3, which is typical of a heavily polluted at-mosphere, the lifetime of methylcyclohexane would beabout 3 hr. Four of the 23 NMOCs in the CMB profilesroutinely coelute under the conditions of the gas chro-matographic analysis. The authors found that 2-methylpentane coeluted with 4-methyl-2-pentene, as didn-hexane and 2-ethyl-1-butene, and 2- and 3-methylhexane and pentanal. They assumed that the 2-methylpentane and n-hexane gas chromatographic peakscontained only those compounds and that the othercoelution was a 50/50 mixture of 2- and 3-methylhexane.

Gasoline Vapor and Whole GasolineFugitive emissions from gasoline service stations and bulkterminals and hot-soak emission profiles are similar andcan be developed from an analysis of the headspace va-por of liquid gasoline.11,13 The headspace vapor of the regu-lar gasoline had a higher alkane and lower aromatic con-tent than did the high-grade gasoline (Table 1). The dataare consistent with other studies that found the aromaticcontent of the vapor of premium fuel to be larger thanthat of the regular grades.13,17,18 Evidently, OxHCs are addedto Cairo gasoline because the headspace vapor of the regu-lar and high-grade gasoline contained 3.38% and 9.46%,respectively, of methyl tert-butyl ether (MTBE). For CMBmodeling applications, deriving a single source profile forthe gasoline vapor that reflects the volume sales of thedifferent grades of gasoline is useful.13 However, this in-formation is not available for Cairo. The CMB gasoline-vapor profile for Cairo was calculated as an average of thetwo grades of gasoline and is compared with the profilefor the U.S. sources, which is an average calculated fromthe results of several studies (Figure 1).13,19-21 The gasolinevapor of the Cairo samples contained smaller amounts ofn-butane and larger amounts of the C5 and C6 alkanesthan did the samples from the United States; for example,the average ratios of n-pentane to n-butane in the Cairoand U.S. samples were 3.0 and 0.57, respectively. The Cairoheadspace samples also have larger amounts of aromat-ics; for example, the toluene contents of the Cairo andU.S. samples were 3.26% and 1.52%, respectively.

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Whole-gasoline profiles can be used to represent theemissions of unburned gasoline during cold-start condi-tions, rapid accelerations, and “running losses” from satu-rated fuel-injection systems. The high-grade gasoline hashigher aromatic and MTBE contents and a lower alkanecontent than the regular grade gasoline (Table 1). This char-acteristic is typical of gasoline that is produced in the UnitedStates.13 The whole-gasoline profile for Cairo was calculatedas an average of the two grades of gasoline and is comparedwith a profile for the U.S. sources, which was calculated asan average of the results from several studies (Figure 2).19-21

The Cairo samples have higher aromatic and C5-C8 alkane

contents than do the gasolines produced in the UnitedStates; for example, the n-butane/toluene ratios of Cairoand U.S. samples were 0.04 and 0.25, respectively.

Roadway EmissionsRoadway emissions were sampled adjacent to a major thor-oughfare and in a tunnel in Cairo. Motorcycle emissionswere sampled independently of the roadway emissions. TheNMOC emissions profiles for the major thoroughfare andthe tunnel were similar and were averaged to obtain theroadway emission profile presented in Table 1. Roadwayemissions consist of exhaust and evaporative losses from

Table 1. NMOC source profiles, % by weight.

Gasoline Headspace Whole Gasoline Bus Parking Garage Uncombusted FuelNMOC Regular High Regular High Roadway Hot- Cold- Motorcycle Petroleum Lead Cast Iron LPG Natural

Grade Grade soak start Emissions Refinery Smelter Factory Gas

Ethane 0.19 - a - 0.10 0.79 0.34 0.40 0.35 7.10 0.11 - 0.06 61.98Propane 0.33 1.51 - 0.06 0.32 0.48 1.26 0.13 10.24 4.98 0.73 4.67 26.152-Methylpropane 1.40 1.49 0.04 0.08 0.22 0.28 0.87 0.16 6.97 8.88 5.20 20.07 3.35n-Butane 6.81 6.80 0.53 0.51 0.94 0.85 2.89 0.81 36.85 25.60 18.07 69.59 3.292-Methylbutane 28.33 22.60 6.13 4.20 5.53 2.49 5.53 8.41 3.18 1.30 1.93 2.38 1.93n-Pentane 22.42 18.24 8.98 4.91 5.48 2.26 5.55 8.55 3.24 0.83 1.53 0.21 1.26Cyclopentane - 0.12 - - 0.03 0.01 0.09 - - 0.03 0.02 - -2,2-Dimethylbutane 0.50 0.71 0.17 0.26 0.24 0.08 0.18 0.29 0.09 0.03 0.09 - 0.062,3-Dimethylbutane - - - - 0.43 0.23 - 0.37 0.09 - - 0.01 -2-Methylpentane/4-Methyl-2-pentene 6.90 8.21 4.30 4.08 2.82 0.92 2.53 4.12 1.59 0.42 0.76 - 0.333-Methylpentane 3.22 3.96 2.26 2.50 1.95 0.63 1.65 2.77 1.09 0.29 0.52 - 0.16n-Hexane/2-Ethyl-1-butene 5.37 5.05 4.60 3.98 3.23 1.06 2.89 5.01 2.30 0.54 0.88 - 0.27Methylcyclopentane 2.28 1.51 2.19 1.30 1.19 0.43 1.20 2.04 1.25 0.23 0.38 - 0.15Cyclohexane 0.98 0.43 1.17 0.45 0.47 0.22 0.55 0.89 0.84 0.34 0.25 - 0.092,3-Dimethylpentane 0.49 0.54 0.90 0.82 0.55 0.18 0.46 0.76 0.27 0.07 0.18 - 0.022,4-Dimethylpentane 0.32 0.36 0.42 0.43 0.29 0.09 0.21 0.40 0.11 0.04 0.15 - 0.032- & 3-Methylhexane/Pentanal 1.53 1.49 2.97 2.71 1.91 0.70 1.50 2.62 0.83 0.45 0.58 - 0.05n-Heptane 1.55 1.09 4.01 2.64 2.00 0.75 1.60 2.94 1.76 0.42 0.66 - 0.07Methylcyclohexane - - 0.18 0.05 0.07 0.04 0.08 0.13 0.12 0.03 0.05 0.01 -2,2,4-Trimethylpentane 0.43 0.12 0.79 0.35 0.35 0.18 0.46 0.62 0.53 0.13 0.21 - -2,2-Dimethylhexane 0.68 0.24 1.97 0.57 0.66 0.65 0.82 1.04 1.79 0.52 0.79 - 0.092,4-Dimethylhexane 0.25 0.24 0.89 0.60 0.41 0.18 0.33 0.64 0.32 0.07 0.18 - -2-Methylheptane 0.28 0.35 1.90 1.24 0.84 0.49 0.67 1.29 0.72 0.24 0.36 - -4-Methylheptane 0.11 - 0.76 0.54 0.35 0.17 0.29 0.58 0.19 0.08 0.16 - -3-Methylheptane 0.33 0.31 2.26 1.65 0.85 0.47 0.67 1.69 0.50 0.20 0.31 - -n-Octane 0.26 0.13 2.42 1.37 0.98 1.29 0.94 1.43 1.44 0.70 0.89 - -Ethylcyclohexane/Chlorobenzene - - 0.60 0.36 0.27 0.60 0.30 0.37 0.41 0.39 0.43 - -n-Nonane - - 0.49 0.46 0.34 3.19 0.77 0.36 0.64 2.28 1.83 - -2,6-Dimethyloctane 0.08 - 0.12 0.12 0.08 1.64 0.40 0.05 0.19 1.10 0.88 - -2-Methylnonane - - - - 0.03 0.66 0.15 - 0.05 0.40 0.32 - -3-Methylnonane - - 0.07 0.12 0.06 0.56 0.15 0.05 0.04 0.35 0.27 - -n-Decane/m-Dichlorobenzene 0.31 0.27 0.32 0.32 0.13 3.82 0.90 0.10 0.19 2.78 2.22 - -n-Butylcyclohexane - - - - 0.13 0.93 0.23 0.01 0.03 0.51 0.25 - -Undecane - - - - 0.11 3.45 1.16 - 0.11 2.17 2.28 - -n-Dodecane - - 0.01 - 0.13 2.99 1.34 - 0.06 0.98 1.63 - -∑Other identified saturates 0.45 0.56 1.77 1.43 0.95 1.55 1.16 1.28 0.84 1.56 1.85 0.01 0.03

Ethene - - - - 4.44 1.04 3.94 3.10 - 0.15 0.38 - -Ethyne - - - - 5.48 1.27 1.71 3.38 0.03 0.12 0.40 - -Propene - - - - 1.85 0.44 1.39 1.59 - 0.17 0.28 - -Propyne - - - - 0.56 0.09 0.20 0.20 - 0.06 0.17 - -2-Methylpropene/1-Butene - 0.17 - - 1.21 0.24 0.72 1.03 0.34 0.70 1.51 1.98 -Isoprene - - - - 0.10 0.85 0.02 0.09 - - - - 0.064-Methyl-1-pentene 1.11 1.15 0.52 0.47 0.44 0.19 0.44 0.65 0.36 0.09 0.14 0.01 0.10beta-Pinene - - 0.36 0.77 0.49 0.60 0.29 0.30 0.07 0.23 0.23 - -∑Other identified unsaturates 0.12 1.07 0.21 0.56 1.61 1.44 1.82 1.89 0.24 2.28 3.13 0.90 0.05

a Hyphen indicates that the value is below detection limit. Continued on next page.

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vehicles. An analysis of data from the Cassiar tunnel studyindicated that evaporative losses represented approximately10% of the total NMOC on-road emission rate.21 About 33%and 57% of the remaining emissions were derived fromgasoline combustion and unburned gasoline, respectively,and were emitted in the vehicle exhaust. The same trendsare evident in the roadway emission profile from Cairo(Table 1). The unsaturated hydrocarbons, which are typicalproducts of fuel combustion, comprise 16% and 1.4% of theroadway and whole-gasoline profiles, respectively; however,

a strong similarity exists between the whole-gasoline androadway emission profiles, which are largely composed ofsaturated and aromatic hydrocarbons (Figures 2 and 3). Themotorcycle emission profile contains higher concentrationsof the C5-C8 alkanes than does the roadway emission pro-file; however, levels of the unsaturated and aromatic hy-drocarbons in the motorcycle emission profile are lower(Table 1). The heavier alkanes present in the motorcycleemissions reflect the use of a 50/50 mixture of gasoline andoil as a fuel in Cairo.

Table 1. NMOC source profiles, % by weight (continued).

Gasoline Headspace Whole Gasoline Bus Parking Garage Uncombusted FuelNMOC Regular High Regular High Roadway Hot- Cold- Motorcycle Petroleum Lead Cast iron LPG Natural

Grade Grade soak start Emissions Refinery Smelter Factory Gas

Benzene 1.88 3.03 1.93 3.20 3.63 1.04 2.16 2.77 0.37 0.68 3.61 - 0.08Toluene 2.77 3.74 10.03 13.50 9.46 2.68 4.95 9.06 1.46 3.74 3.52 - -Ethylbenzene/1-Hexanol 0.18 0.18 2.55 3.15 1.94 0.88 1.05 1.81 0.50 0.40 0.68 - -p- & m-Xylene 0.58 0.69 9.37 12.82 6.89 2.87 3.53 6.24 1.64 1.48 2.00 - -o-Xylene 0.11 0.17 3.17 4.39 2.33 1.11 1.20 2.04 0.52 0.47 0.56 - -i-Propylbenzene - - 0.03 0.06 0.05 0.64 0.15 0.04 0.10 0.41 0.29 - -n-Propylbenzene - - 0.43 0.77 0.46 0.61 0.31 0.30 0.09 0.35 0.23 - -m-Ethyltoluene - - 1.25 2.24 1.55 1.24 0.80 0.82 0.22 0.81 0.68 - -p-Ethyltoluene - - 0.82 1.45 0.71 0.62 0.39 0.50 0.10 0.32 0.25 - -1,3,5-Trimethylbenzene - - 1.00 1.91 0.91 1.09 0.71 0.58 0.18 0.76 0.59 - -1,2,3-Trimethylbenzene - - 0.25 0.50 0.45 1.14 0.40 0.16 0.07 0.62 0.54 - -1,2,4-Trimethylbenzene/t-Butylbenzene 0.09 - 1.92 3.47 2.40 2.27 1.37 1.15 0.28 1.38 1.11 - 0.011-Methyl-4-i-propylbenzene - - - - 0.03 0.90 0.22 - 0.04 0.46 0.46 - -n-Butylbenzene - - 0.15 0.27 0.54 0.80 0.35 0.08 0.04 0.46 0.40 - -1,2,3,4-Tetramethylbenzene - - 0.01 - 0.10 0.73 0.29 - 0.02 0.28 0.37 - -∑Other identified aromatics - - 0.15 0.11 0.56 2.66 1.01 0.08 0.07 1.17 1.15 - -

Ethanal - - - - 0.90 1.53 2.64 - 0.64 1.92 4.88 - -Methanol - - - - 1.28 2.50 3.02 0.03 0.20 1.45 3.50 0.03 -Ethanol - - - - 0.30 0.79 2.06 - 0.10 1.60 2.80 - -Propanal - - - - 0.15 0.32 0.58 0.02 0.04 0.40 0.96 - -Acetone - - - - 0.71 1.72 1.88 0.04 0.11 2.14 1.96 - -1-Propanol 1.09 1.37 0.65 0.70 0.75 0.26 0.65 1.05 0.43 0.12 0.22 - 0.19Butanal - - - - 0.10 0.26 0.39 - 0.02 0.33 0.34 - 0.042-Butanone - - - - 0.06 0.16 0.20 0.01 - 0.20 0.22 0.01 0.12MTBEb 3.38 9.46 1.37 4.85 3.71 0.78 2.97 2.05 - 0.40 0.72 - -ETBE/3-Methyl-2-pentenec - - - - 0.03 0.08 0.08 0.03 0.02 1.32 0.17 - -1-Butanol/Carbon tetrachloride 0.09 0.14 0.15 0.20 0.20 0.13 0.24 0.21 0.04 0.24 0.26 - -2-Pentanone/Cyclohexene 1.67 1.55 3.01 2.73 2.32 0.69 1.70 3.23 0.98 0.36 0.49 - 0.05Hexanal - - - - 0.04 0.24 0.26 0.02 - 0.42 0.89 - -Heptanal/Styrene - - - - 0.38 0.41 0.24 0.14 0.08 0.37 0.73 - -1-Heptanol - - - - 0.02 0.54 0.12 0.01 0.05 0.36 0.23 - -Benzyl alcohol/p-Cymene - - - - 0.06 0.48 0.18 0.01 0.02 0.29 0.32 - -1-Octanol - - - - 0.03 0.51 0.14 - 0.01 0.28 0.28 - -2-Heptanone/4-Methyloctane - - 0.81 0.65 0.37 0.86 0.36 0.51 0.29 0.40 0.41 - -Decanal/1-Dodecene 0.13 - - - 0.30 0.82 0.47 - 0.01 0.35 0.80 - -1-Decanol - - - - 0.01 0.58 0.23 - 0.01 0.11 0.18 - -∑Other identified OxHCs - - 0.32 0.38 0.53 1.48 0.70 0.21 0.34 0.77 1.15 - -

Total unknowns 0.97 0.93 6.34 2.61 4.46 22.59 11.32 4.31 3.89 10.05 9.88 0.07 -∑ Saturates 85.8 76.3 53.2 38.2 35.1 34.8 40.2 50.2 86.0 59.1 46.6 97.0 99.3∑ Unsaturates 1.2 2.4 1.1 1.8 16.2 6.2 10.5 12.2 1.0 3.8 6.1 2.9 0.2∑ Aromatics 5.6 7.8 33.0 47.8 32.0 21.3 18.9 25.6 5.7 13.8 16.4 - 0.1∑ OxHCs 6.4 12.5 6.3 9.5 12.2 15.1 19.1 7.6 3.4 13.4 21.0 0.0 0.4 Weight % Total 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0

Total NMOC concentration 139,000d 134,000d 281,000e 369,000e 8,620 1,810 2,230 2,020 4,120 918 325 3,840 755unit for NMOC concentration ppmC ppmC ppmC ppmC ppbC ppbC ppbC ppmC ppbC ppbC ppbC ppmC ppmC

aHyphen indicates that the value is below detection limit; bmethyl tert-butyl ether; cethyl tert-butyl ether; d1/500 dilution of gasoline headspace; e1 µL of whole gasoline diluted ina 2-L gas dilution bottle.

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A roadway emission profile for U.S. sources was calcu-lated as an average of the results from several studies.11,13,18-20,22

Major differences exist in the roadway emission profiles ofthe U.S. and Cairo sources (Figure 3). The ethyne contribu-tions are greater by nearly a factor of 2 in the Cairo profilethan in the U.S. profile. The mole ratio of ethene to ethynefor the Cairo profile is 0.75, characteristic of vehicles withoutcatalysts. Hoekman23 reported average ratios of 3.10 and 1.07for catalyst- and noncatalyst-equipped vehicles, respectively,evaluated with the 1975 U.S. Environmental Protection AgencyFederal Test Procedure. The n-butane, n-pentane, benzene, andtoluene contributions are dissimilar in the Cairo and U.S. pro-files, but the respective profiles are similar to the trends in thewhole-gasoline profiles for those locations (Figures 2 and 3).

Cold-Start and Hot-Soak EmissionsThe NMOCs are also released from vehicles during thecold-start and hot-soak phases of the driving cycle. Ahot-soak emission profile contains very low levels ofunsaturated hydrocarbons and can be sufficiently rep-resented by a gasoline-vapor profile, while unsaturated

hydrocarbons from combustion of the fuel comprise alarger fraction of the cold-start emissions.13 These trendswere not evident in the cold-start and hot-soak emis-sion profiles that were developed from the samples col-lected in a Cairo auto parking garage. Concentrationsof 2-methylbutane, n-pentane, and toluene were high-est in the hot-soak and cold-start profiles. Ethyne lev-els were higher in the hot-soak emission profile than inthe cold-start profile, indicating that vehicle exhaustwas included in the hot-soak sample. Concentrationsof the total saturated hydrocarbons were higher in thecold-start and hot-soak emission profiles than in theroadway emission profile, but they were much lowerthan the levels of saturated hydrocarbons in the gaso-line-vapor and whole-gasoline profiles. Toluene levelswere similar in all three profiles; however, the unsatur-ated hydrocarbons were lower in the cold-start and hot-soak emission profiles than in the roadway emissionprofile. These trends indicate that the hot-soak and cold-start emission samples were diluted by ambient air. Theauto parking garage was open on two sides, and, al-though the air was stagnant, significant mixing of out-side air into the garage must have occurred during sam-pling. Unfortunately, the profiles for the backgroundair could not be corrected because a sample of air out-side the parking garage was not obtained. Therefore,data for the cold-start and hot-soak emission profiles ofautomobiles in Cairo are not reported.

Emissions from diesel engine vehicles also contributeto the roadway emissions in Cairo. The hot-soak and cold-start emissions from diesel engine vehicles were sampledin a bus parking garage. The concentrations of hydrocar-bons with fewer than seven carbon atoms were lower inthe hot-soak and cold-start diesel engine vehicle emissionsthan in the gasoline engine vehicle emissions (Table 1). Thecontribution of the ∑C9-C12 n-alkanes was 13.5% and 4.2%of the total NMOCs in the hot-soak and cold-start diesel

Figure 2. Profiles of NMOCs in whole gasoline from U.S. and Cairo sources.

Figure 1. Profiles of NMOCs in gasoline vapor from U.S. and Cairo sources.Figure 3. Profiles of NMOCs in roadway emissions from U.S. and Cairo sources.

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engine emissions, respectively, and was 0.4% and 0.5% inthe hot-soak and cold-start gasoline engine emissions, re-spectively. Profiles of the diesel emissions also had highlevels of unidentified hydrocarbons with more than eightcarbon atoms: 23% and 11% of the hot-soak and cold-startemissions, respectively.

Diesel fuels contain higher concentrations of high-mo-lecular-weight hydrocarbons than do gasoline fuels. The re-sults from Cairo clearly indicate the influence of fuel com-position on the diesel engine emissions. The hydrocarbonemissions of diesel engine vehicles exhibit a maximum atabout C14.

24 Hampton et al.25 and Sagebiel et al.24 reportedmole ratios of dodecane to undecane of 0.99 and 1.2, respec-tively, for the Allegheny Mountain and Fort McHenry/Tuscarora Mountain Tunnel studies. These values are similarto the ratio of 1.1 that was observed for the cold-start dieselemissions in the bus parking garage. The hot-soak and cold-start emission profiles for Cairo are unique; however, to de-termine the contribution of diesel engine emissions to theroadway emissions, a roadway emission profile for diesel en-gine vehicles would be more applicable to a CMB analysisthan a cold-start emission profile.

Reconciling the gasoline and diesel engine emissionsources in Cairo may be critical because diesel emissionscould make significant contributions to photochemicalsmog formation. Sagebiel et al.24 evaluated the reactivity ofdiesel engine vehicle emissions for the Fort McHenry/Tuscarora Mountain Tunnel study on the basis of ozone-forming reactivity (mass of O3 produced) per (1) vehicle-mile, (2) mass of total hydrocarbons emitted, and (3) gal-lons of fuel consumed. The ozone-forming reactivity of thediesel emissions per vehicle-mile was greater than the reac-tivity of the emissions from gasoline engine vehicles, be-cause the diesel engine vehicles emitted more of the reac-tive olefinic and aromatic hydrocarbons. The diesel emis-sions were less reactive than the emissions from gasolineengine vehicles on the basis of (1) mass of total hydrocar-bons emitted and (2) gallons of fuel consumed. However,Sagebiel et al.24 stated that (1) uncertainties in emissionmeasurements and reactivity adjustment factors26 precludeany final judgments on the reactivity of diesel emissionsand (2) the contribution of diesel engine emissions to ozoneformation will depend greatly on the number of diesel en-gine vehicles.

Petroleum Refinery, Cast Iron Factory, and LeadSmelter Emissions

Saturated hydrocarbons comprised 86% of the NMOC emis-sions from the petroleum refinery, with 61% of the totalbeing composed of ethane, propane, 2-methylpropane, andn-butane (Table 1). The Cairo source profile is similar to theone developed from an average of the results for severalU.S. sources;13,27,28 however, the level of n-butane is much

higher in the Cairo refinery emissions than in U.S. refineryemissions (Figure 4). The NMOC emissions from the castiron factory and lead smelter contained lower levels of satu-rated hydrocarbons and higher levels of unsaturated andaromatic hydrocarbons than did the petroleum refineryemissions (Table 1); however, similar to the petroleum re-finery emissions, the C2-C4 saturated hydrocarbons accountfor most of the NMOC emissions from the cast iron factoryand the lead smelter (Figure 5). The concentrations of n-butane and C9-C11 saturated hydrocarbons were highest inthe refinery emission profile. Benzene levels in the cast ironfactory emissions were comparable with levels in the road-way emissions. Toluene levels in the cast iron factory andlead smelter emissions were about one-third of the levelsin the roadway emissions.

Liquefied Petroleum and Natural Gas ProfilesNearly all (97%) of the NMOC emissions from uncombustedLPG were composed of the saturated hydrocarbons, withn-butane comprising 70% of the emissions (Table 1). Low

Figure 4. Profiles of NMOCs in petroleum refinery emissions from U.S.and Cairo sources.

Figure 5. Profiles of NMOCs in petroleum refinery, lead smelter, andcast iron factory emissions from Cairo sources.

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levels of unsaturated and aromatic hydrocarbons were ob-served. The same trends were found in the NMOC emis-sions from uncombusted natural gas; however, ethane com-prised 62% of the emissions (Table 1). A comparison of LPGgas emissions for the United States,1 Mexico City,29 and Cairoindicates that propane levels are highest in the U.S. emis-sions, and that n-butane levels are highest in the Cairoemissions (Figure 6). The n-butane levels in the Mexico Cityemissions are about 10% lower than their propane levels.Natural gas profiles for Cairo and the United States1 aresimilar, with ethane dominating the emissions.

CONCLUSIONSOver 100 hydrocarbons were tentatively identified andquantified in several sources of NMOCs in Cairo. UniqueCMB source profiles were developed for source reconcili-ation modeling applications from the concentrations of23 NMOCs in the emissions from vehicles, petroleum fu-els, a petroleum refinery, a cast iron factory, and a leadsmelter. Characteristic features of the gasoline-vapor andwhole-gasoline profiles included high concentrations ofthe C5 and C6 saturated hydrocarbons. Ethyne and ben-zene levels were greatest in the roadway emission profile.Motorcycles and diesel engine vehicles are included inthe vehicle distribution of Cairo and were sampled inde-pendently. The NMOC emissions from the tailpipe of amotorcycle contained higher levels of the C5-C8 saturatedhydrocarbons than did the roadway emissions. Dieselemissions from the cold-start and hot-soak phases of thedriving cycle contained more of the C9-C12 saturated hy-drocarbons than did emissions from gasoline engine ve-hicles. Efforts should be made to reconcile these sourcesbecause emissions from the diesel engine vehicles maymake a significant contribution to the formation of pho-tochemical smog in Cairo. Methyl tert-butyl ether wasfound in the gasoline and vehicle emissions and shouldbe considered as an additional CMB fitting compound in

future studies. MTBE has a reaction rate of 2.83 × 10-12

cm3 molecule-1 sec-1 with OH16 and is stable enough to beincluded in a CMB source profile. Characteristic featuresof the petroleum refinery emissions included high con-centrations of the C2-C4 saturates, while the LPG and natu-ral gas emissions were dominated by n-butane and ethane,respectively. The lead smelter and cast iron factory emis-sions also exhibited high levels of the C3 and C4 saturatedhydrocarbons, but the emissions from these two sourcescould be distinguished from the petroleum refinery pro-file by the elevated concentrations of benzene and tolu-ene in the profiles of the former two sources.

The NMOC source profiles for Cairo were distinctlydifferent from profiles for U.S. sources, indicating thatNMOC source profiles are sensitive to the local composi-tion of petroleum fuels. The analysis of the emissions ofNMOCs from various sources in Cairo will permit a pre-liminary assessment of the contribution of the sources toambient levels of the NMOCs; however, a longer samplingprogram is needed to quantify the variability of the sourceprofiles. In addition, the collection of ambient air samplesand meteorological data from several locations in Cairo overthe course of a year will be needed to assess the impact ofthe various sources on ambient levels of the NMOCs. Thedevelopment of an NMOC emission inventory for Cairowould also be useful in interpreting the results from a CMBanalysis of the NMOC sources.

ACKNOWLEDGMENTSThe authors thank Eileen Brazelton for editing this manu-script and two anonymous reviewers for their insightfulcomments. This work was supported by Cairo Universitythrough contract 856F9-00-149 to Argonne National Labo-ratory and by the U.S. Department of Energy under con-tract W-31-109-Eng-38, as part of the Atmospheric Chem-istry Program of the Office of Energy Research, Office ofHealth and Environmental Research.

REFERENCES1. Mayrsohn, H.; Crabtree, J.H. “Source reconciliation of atmospheric

hydrocarbons,” Atmos. Environ. 1976, 10, 137-143.2. Mayrsohn, H.; Crabtree, J.H.; Kuramoto, M.; Sothern, R.D.; Mano,

S.H. “Source reconciliation of atmospheric hydrocarbons 1974,”Atmos. Environ. 1977, 11, 189-192.

3. Nelson, P.F.; Quigley, S.M.; Smith, M.Y. “Sources of atmospheric hy-drocarbons in Sydney: A quantitative determination using a sourcereconciliation technique,” Atmos. Environ. 1983, 17, 439-449.

4. Wadden, R.A.; Uno, I.; Wakamatsu, S. “Source discrimination of short-term hydrocarbon samples measured aloft,” Environ. Sci. Technol. 1986,20, 473-483.

5. O’Shea, W.J.; Scheff, P.A. “A chemical mass balance for volatile or-ganics in Chicago,” J. Air Pollut. Control Assoc. 1988, 38, 1,020-1,026.

6. Aronian, P.F.; Scheff, P.A.; Wadden, R.A. “Wintertime source-recon-ciliation of ambient organics,” Atmos. Environ. 1989, 23, 911-920.

7. Fujita, E.M.; Watson, J.G.; Chow, J.C.; Lu, Z. “Validation of the chemi-cal mass balance receptor model applied to hydrocarbon source ap-portionment in the Southern California air quality study,” Environ.Sci. Technol. 1994, 28, 1,633-1,649.

Figure 6. Profiles of LPG emissions from U.S., Mexico City, and Cairo sources.

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About the AuthorsP.V. Doskey (corresponding author, pvdoskey@anl.gov) is achemist and M. Sultan is a geologist in the EnvironmentalResearch Division of Argonne National Laboratory, 9700 S.Cass Ave., Argonne, IL 60439. Y. Fukui was a postdoctoralappointee at Argonne National Laboratory; she is now a re-search fellow at NASA/Ames Research Center in MoffettField, CA. A. Al Maghraby and A. Taher are assistant profes-sors in the Geology Department and senior scientists in theCenter for Environmental Hazard Mitigation at Cairo Univer-sity, Giza, Egypt.

8. Fujita, E.M.; Watson, J.G.; Chow, J.C. “Receptor model and emissionsinventory source apportionments of nonmethane organic gases inCalifornia’s San Joaquin Valley and San Francisco Bay area,” Atmos.Environ. 1995, 29, 3,019-3,035.

9. Kenski, D.M.; Wadden, R.A.; Scheff, P.A.; Lonneman, W.A. “A recep-tor modeling approach to VOC inventory validation in five U.S. cit-ies,” J. Environ. Eng. 1995, 121, 483-491.

10. McLaren, R.; Singleton, D.L.; Lai, J.Y.K.; Khouw, B.; Singer, E.; Wu, Z.;Niki, H. “Analysis of motor vehicle sources and their contribution toambient hydrocarbon distributions at urban sites in Toronto duringthe Southern Ontario Oxidants Study,” Atmos. Environ. 1996, 30,2,219-2,232.

11. Scheff, P.A.; Wadden, R.A.; Kenski, D.M.; Chung, J.; Wolff, G. “Recep-tor model evaluation of the Southeast Michigan Ozone Study ambi-ent NMOC measurements,” J. Air & Waste Manage. Assoc. 1996, 46,1,048-1,057.

12. Scheff, P.A.; Wadden, R.A.; Bates, B.A.; Aronian, P.F. “Source finger-prints for receptor modeling of volatile organics,” J. Air Pollut. Con-trol Assoc. 1989, 39, 469-478.

13. Doskey, P.V.; Porter, J.A.; Scheff, P.A. “Source fingerprints for volatilenon-methane hydrocarbons,” J. Air & Waste Manage. Assoc. 1992, 42,1,437-1,445.

14. Fukui, Y.; Doskey, P.V. “An enclosure technique for measuringnonmethane organic compound emissions from grasslands,” J.Environ. Qual. 1996, 25, 601-610.

15. Scanlon, J.T.; Willis, D.E. “Calculation of flame ionization detectorrelative response factors using the effective carbon number concept,”J. Chrom. Sci. 1985, 23, 333-340.

16. Atkinson, R. “Kinetics and mechanisms of the gas-phase reactions ofthe hydroxyl radical with organic compounds,” J. Phys. Chem. Ref.Data, Monograph. 1989, 1, 246 pp.

17. Lonneman, W.A.; Seila, R.L.; Meeks, S.A. “Non-methane organic compo-sition in the Lincoln tunnel,” Environ. Sci. Technol. 1986, 20, 790-796.

18. Sigsby, Jr., J.E.; Tejada, S.; Ray, W.; Lang, J.M.; Duncan, J.W. “Volatileorganic compound emissions from 46 in-use passenger cars,” Environ.Sci. Technol. 1987, 21, 466-475.

19. Conner, T.L.; Lonneman, W.A.; Seila, R.L. “Transportation-relatedvolatile hydrocarbon source profiles measured in Atlanta,” J. Air &Waste Manage. Assoc. 1995, 45, 383-394.

20. Gertler, A.W.; Fujita, E.M.; Pierson, W.R.; Wittorff, D.N. “Apportionmentof NMHC tailpipe vs non-tailpipe emissions in the Fort McHenry andTuscarora Mountain tunnels,” Atmos. Environ. 1996, 30, 2,297-2,305.

21. McLaren, R.; Gertler, A.W.; Wittorff, D.N.; Belzer, W.; Dann, T.; Single-ton, D.L. “Real-world measurements of exhaust and evaporative emis-sions in the Cassiar tunnel predicted by chemical mass balance mod-eling,” Environ. Sci. Technol. 1996, 30, 3,001-3,009.

22. Kirchstetter, T.W.; Singer, B.C.; Harley, R.A.; Kendall, G.R.; Chan, W.“Impact of oxygenated gasoline use on California light-duty vehicleemissions,” Environ. Sci. Technol. 1996, 30, 661-670.

23. Hoekman, S.K. “Speciated measurements and calculated reactivitiesof vehicle exhaust emissions from conventional and reformulatedgasolines,” Environ. Sci. Technol. 1992, 26, 1,206-1,216.

24. Sagebiel, J.C.; Zielinska, B.; Pierson, W.R.; Gertler, A.W. “Real-worldemissions and calculated reactivities of organic species from motorvehicles,” Atmos. Environ. 1996, 30, 2,287-2,296.

25. Hampton, C.V.; Pierson, W.R.; Schuetzle, D.; Harvey, T.M. “Hydro-carbon gases emitted from vehicles on the road—2: Determinationof emission rates from diesel and spark-ignition vehicles,” Environ.Sci. Technol. 1983, 17, 699-708.

26. Carter, W.P.L.; “Development of ozone reactivity scales for volatile or-ganic compounds,” J. Air & Waste Manage. Assoc. 1994, 44, 881-899.

27. Sexton, K.; Westberg, H. “Photochemical ozone formation from pe-troleum refinery emissions,” Atmos. Environ. 1983, 17, 467-475.

28. Rappaport, S.M.; Selvin, S.; Waters, M.A. “Exposures to hydrocarboncomponents of gasoline in the petroleum industry,” J. Applied Indust.Hygiene. 1987, 2, 148.

29. Blake, D.R.; Rowland, F.S. “Urban leakage of liquefied petroleum gasand its impact on Mexico City air quality,” Science 1995, 269, 953-956.

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