Brunke, E.G.

Labuschagne, C.

Mkololo, T.

Scheel, H.E.

English

Brunke, E. G.

Scheel, H. E.

KITopen

ANALYSIS OF OZONE FROM THREE AIR INTAKE HEIGHTS AT CAPE POINTE.-G. Brunke(1), T. Mkololo(1), C. Labuschagne(1), and H.-E. Scheel(2)(1) South African Weather Service, Stellenbosch 7599, South Africa; (ernst.brunke@weathersa.co.za)(2) Forschungszentrum Karlsruhe, IMK-IFU, 82467 Garmisch-Partenkirchen, GermanyOverviewSurface ozone measurements have been made atCape Point since 1982 from the top of a 30‐m airintake mast. In 1996 measurements were also startedfrom a 4 m high air intake and from September 2008onwards, they were extended to 14‐m elevation aswell. Seven months of ozone data from 3 air intakelevels: 4 m, 14 m and 30 m, respectively, are beingd d d d h h d h bCape Point GAW station: 34oS, 18oE; 230 m a.s.l.compare an iscusse ere. T e ata ave eenanalysed for background conditions as well as for airsampled during urban pollution episodes and biomassburning events.Ozone  AnalyserSchematic flow diagram for 3 Ozone analysersSchematic flow diagram for three O3 analysersAnalytical technique and data processingThe instruments in use comprise Thermo Electron (Teco)analysers based on an UV detection technique. An O3calibrator (TEI 49i‐PS) is being used to calibrate the threeinstruments every four months. Daily zero and sensitivityResultsPlume of veld fire (17‐02‐08) moving over Cape Point (http://modis.gsfc.nasa.gov).30 ‐mDust filterTeco_1Dust filter14‐mTeco_2Teco_34‐mcompressorAmbient intakeMoisture High volume fanexhaustConnect toTeco analysers2‐way solenoid2‐waysolenoid2‐way solenoidDustfilDustfilDustfil49i CDust filterAmbient intakeAmbient intakechecks are conducted automatically. Monthly zero‐calibration levels are factored into the data processingroutine, which yields 30‐min. averages, while the SPANsensitivity values provide information on long‐terminstrument stability. For the purpose of this study, ozonelevels in unpolluted air (30‐min. averages) were selectedvia a filtering technique based on carbon monoxide (CO)background data.The seven months of comparative ozone datashow on average good agreement (within 0.5ppb) for the three intake levels under most of theprevailing conditions. Significant deviations occurduring pollution episodes, which are particularlypronounced when biomass burning events areobserved.pumpActivated charcoalcalibratorSilica geltrapMolecular sieveterter terOzone shows either positive or negative correlations with theSummary and Conclusions O3 values from 3 analysers measuring air from 4, 14 and 30 m height, respectively,agreed within the analytical error margin of 0 5 ppb under backgroundFive pollution episodes were selected from the periodFebruary‐March 2009 (most of these were associatedwith biomass burning plumes). The O3 levels observed atthe three intakes, with differences sometimes > 65 ppb,do not reflect a consistent upward or downward gradient.It is speculated that these levels are haphazard and are afunction of the individual fire plume.CO mixing ratios. These are indicative of conditions favourablefor photochemical O3 production or O3 removal in polluted airmasses, respectively. In most cases positive correlations andslope values of a linear regression (Δ[O3]/Δ[CO]) wereobserved for daylight hours. However, there are cases wheresuch ratios have persisted into the night hours.The five pollution events are characterized by (Δ[O3]/Δ[CO]ratios ranging from +1.14 to – 0.11. Some episodes such asthe one from the 4th – 6th of March encompass the wholerange (day and night processes), whilst others (e.g. the 24thof February) indicate neither production nor destruction(Δ[O3]/Δ[CO] ≈ 0).Average diurnal O3 cycles (Sep 08 till Mar09) for the 3 air intakes agree within theexperimental error margin of 0 5 ppbAcknowledgements: Thanks are due to all Cape Point staff members who have contributed over the years through maintenance of instrumentation, calibrations, and data processing.September 2009.conditions. During pollution episodes (especially fire plumes) differences of > 60 ppb couldbe observed between the intakes. These differences are haphazard and do notrepresent a uniform upward or downward concentration gradient. Δ[O3]/Δ[CO] slope values during episodes varied between +1.14 and – 0.11. Diurnal O3 cycles showed amplitudes of only 1.2 ppb during background, but upto 4.4 ppb for non‐background conditions, thus reflecting different air‐chemicalconditions on local to regional scales.. .Shown here is O3 (4‐m intake) filtered viabackground and non‐background CO. Theformer shows smaller diurnal cycling (1.2ppb peak‐to‐peak) than the non‐back‐ground data (4.4 ppb peak‐to‐peak). Thelatter is indicative of photochemical O3production during the day and possible O3loss (NO chemistry) at night.

Analysis of ozone from three air intake heights at Cape Point

https://publikationen.bibliothek.kit.edu/220078049/3815602

Analysis of ozone from three air intake heights at Cape Point

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