Cote, E.A.

Dietz, R.N.

Ferber, G.J.

Dietz, R. N.

Cote, E. A.

Ferber, G. J.

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BNL 17478aNot for PublicationPresented Before the Division of Water, Air, and Waste ChemistryAmerican Chemical SocietyDallas, April 1973EVALUATION OF AN AIRBORNE GAS CHROMATOGRAPHFOR LONG DISTANCE METEOROLOGICAL TRACINGRussell N. Dietz, and Edgar A. CoteBrookhaven National LaboratoryDepartment of Applied ScienceUpton, L.I., New York 11973C;Q§ Gilbert J. Ferber^ c National Oceanic & Atmospheric AdministrationAir Resources LaboratoriesSilver Spring, Maryland 20910IntroductionAir pollution studies require an understanding of the mechanismsaffecting transport and diffusion of gaseous plumes over short dis-tances {to predict local effects of pollutant emissions) and alsolong distances (to evaluate regional and world-wide effects). A numberof urban air pollution models have been developed from studios ofexisting pollutant sources (1) or special tracers added to thesesources &) (for example, power plant stacks), but much remains to belearned about plume behavior in an urban environment. Even less isknown of pollutant plume behavior at great distances from the source.The chromatographic detection and analysis of selected gaseous tracersappears to offer a promising technique for studying plume behaviour todistances of thousands of kilometers from a source.The feasibility of such long-range tracer studies rests on theavailability of a non-toxic, inert tracer gas that can be detected atvery low concentrations using simple and inexpensive techniques.Ideally, the amount of tracer already present in the atmosphere shouldbe below the level of detectability. Several compounds are under in-vestigation as potential tracers including sulfur hexafluoride (SFg)and two halocarbons {C2F4Br2 and CF2Br2). All are detectable byelectron-capture gas chromatography at extremely low concentrations(parts in 10 i 2 of air, or less). Preconcentration of a sample maypermit detection down to 1 part in 10 1 4 or less. An experiment wasconducted last September, at the National Reactor Testing Station(NRTS) near Idaho Falls, Idaho, to test a variety of equipment and-NOTICE-This report m i preparedS ^ ! ? ? *h U i 3 Sppared „ an account of workto^! *? e nit=l  t"«C™mm«t.«Stte United Stitei nor the United States Atomic Energytteir eontnctors iubcontr*ctors or th i lHeiri co tr*ctors,  their employeeslegs lubiatjr or_̂  responsibility for Jhe accuracy, completeness or usefulness of «.y informition, .ppmtus1TI??"U d « ' ° * d , or represents thit " u s emfrinf e privately owned rights.THIS OOCUmhl JS 0NLJMJ7Otechniques for release, sampling, and analysis of these compounds.Several other tracers were also released to provide intercompari-sons and detailed data were obtained on plume behavior out toabout 90 km. This experiment was the first field trial in a Long-Range Transport and Diffusion Study being conducted by the NQAAAir Resources Laboratories (ARL) under sponsorship of the AdvancedResearch Projects Agency (DoD). Meteorological support provided byARL was funded by the AEC Division of Biomedical and EnvironmentalResearch. Complete results will be reported when analyses are com-pleted.This paper describes some preliminary sampling results obtain-ed with an aircraft-mounted SFg chromatograph at distances from 6 to90 km from the source. In an earlier paper (3) the development ofan improved electron-capture gas chromatographic technique for thelaboratory determination of the meteorological tracer gas, sulfurhexafluoride, was presented(3,4}. This effort was part of theAtmospheric Diagnostics program at Brookhavenf5). As a consequenceof this new method, a portable real-time SPg chromatograph based onfrontal elution chromatography was wade feasible (2)# it was esti-mated that plumes could be traced for 100 km or more during unstablemeteorological conditions.ExperimentalA complete description of the portable real-titr.e electron-capture gas chromatograph for sulfur hexafluoride determinations asdeveloped at BNL has been presented previously (2). calibration waspartially performed at the NRTS site with lecture bottles contain-ing 10"1" and 10"H parts of SPg per part of air. It was discover-ed, however, that the instrument response was sensitive to baro-metric pressure and iji a non-linear way. Since the atmosphericpressure at Idaho Falls was about 635 mm Hg at ground level (1.5 kmabove mean sea level) and analyses were performed at altitudes up to1.4 km above ground level (2.9 km MSL) where the pressure was535 mm Hg, additional calibration was found to be necessary. Thiswas performed in the High Altitude Test Chamber at the Health andSafety Laboratories (HASL) of the AEC in New York City. Simulatedbarometric pressures as low as 550 mm Hg were achieved duringanalyses with standard mixtures of 10"9 and 10"10 cm3/cm3.iThe combined results of the calibration at the NRTS site andat HASL were correlated by least squares approximation and plotted,for various altitudes, with the Hewlett-Packard computer-calculatorof conversion of the pollutant could be rapidly determined aswell as the relative contribution of a source to the pollutantlevel at a distant location.Further development of this instrument will allow continuousreal-time measurements over any desired time interval (by auto-matically switching chromat©graphic columns during backflush)thus enhancing its usefulness for meteorological tracer work.The use of SFg appears impractical for long-range (thousandsof kilometers) tracer experiments because of the very large re-lease amounts required to overcome the existing SFg background.Preliminary indications offer hope that the halocarbons (CF2BR2and C2F4Br2) tested in this experiment will prove to be feasiblelong-range tracers. Measurement of concentrations down to a fewparts in 10^5 m ay be possible by cryogenic concentration of samplesin the laboratory prior to chromatographic analysis. It should alsobe possible to adapt the portable real-time instrument to these halo-carbons by changing the column material (a prototype laboratorychromatograph was tested in this experiment). Such an airborne in-strument could provide useful data to a distance of at least severalhundred km as part of a long-range experiment.Reference31. Koch, R.C., Thayer, S.D. "Validation and Sensitivity Analysisof the Gaussian Plume Multiple-Source Urban Diffusion Model".Geomet Report #EF-60 Geomet, Inc., Rockville, Md., November 1971.2. Dietz, R.N., Cote, E.A., Brown, R.M., "A Portable ElectronCapture GC for Tracing Air Pollutants", 163rd ACS Meeting,Boston, Diy. Water, Air, and Waste chem. 12 (1), 29-35 (1972).3. Dietz, R.N., Cote, E.A., "GC Determination of Sulfur Hexa-fluoride for Tracing Air Pollutants", 162nd ACS Meeting,Washington,D.C., Div. Water, Air, and Waste Chem. 11 (2),208-15 (1971),4. Dietz, R.N., Cote, E.A., "Tracing Atmospheric Pollutants by GasChromatographic Determination of Sulfur Hexafluoride", BNL 16642,February 1972.5. Manowitz, B., Newman, L., Tucker, W.D., "The AtmosphericDiagnostics Prohram at Brookhaven National Laboratory" ThirdStatus Report, BNL 50280, December 1970; Fourth Status Report,BNL 50361, June 1972.CaptionsFigure 1 Portable chromatograph calibration curve at variousaltitudes.Figure 2 Crosswind SF6 concentration profiles versus analysisto 5 time at 6, 18, 48, and 90 km downwind;altitudes of460, 760, 150, and 460 meters, respectively.10" i11 mi • i n r i 111in r i nini • »10 102 iO3 I0 4DETECTOR RESPONSE, h t x att.I05Figure 1Portable Chromatograph Calibration Curve at Various Altitudes• f e « .50 55 60 65 70 75TIME, SECONDSFigure 2SO 65 9041 45 50 55 60 65 70 75TIME, SECONDS60 85 90Figure 31.8"§ 1.6I I I I I I IJ I 1 I I I J 1150 55 60 65 70 75 80TIME, SECONDSFigure 465 9041 45 50 55 60 65 70 75TIME, SECONDS80 85 90Figure 5

Evaluation of an airborne gas chromatograph for long distance meteorological tracing

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