Results and analysis of ozone monitoring at station Sr| (46.25° N, 17.45° E, 412 m a.s.l.) near Dubrovnik from 1998 – 2005 are reported. It is confirmed that this is an unpolluted place despite of high summer solar radiation which could contribute to the photochemical air pollution formation. There is no significant trend in ozone levels found during this time and the overall aver­age ozone fraction is found to be 46 ppb for the summer periodsPrikazani su rezultati i analiza mjerenja ozona na postaji Srđ (46.25° N, 17.45° E,
412 m a.s.l.) blizu Dubrovnika u razdoblju od 1998 do 2005. Potvrđen je neonečišćeni
karakter ove lokacije unatoč jakom Sunčevom zračenju ljeti. Mjerenja nisu dala naznake
trenda u koncentracijama ozona, a prosječna vrijednost udjela ozona u ljetnom
periodu je bila 46 ppb

Glenda Šorgo

Leo Klasnic

Nenad Kezele

Tomislav Cvitaš

English

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Short communicationUDC 551.510.41Ozone Measurement on mount Sr|near Dubrovnik, CroatiaTomislav Cvita{, Nenad Kezele, Leo Klasinc and Glenda [orgoRu|er Bo{kovi} Institute, Zagreb, HrvatskaReceived 14 August 2006, in final form 22 November 2006Results and analysis of ozone monitoring at station Sr| (46.25° N, 17.45°E, 412 m a.s.l.) near Dubrovnik from 1998 – 2005 are reported. It is confirmedthat this is an unpolluted place despite of high summer solar radiation whichcould contribute to the photochemical air pollution formation. There is nosignificant trend in ozone levels found during this time and the overall averageozone fraction is found to be 46 ppb for the summer periods.Keywords: ozone measurements, photochemical air pollution, Dubrovnik1. IntroductionThe oxidation capacity of boundary layers of the Earth atmosphere isincreasing over the past hundred years (Volz and Kley, 1988; Lisac and Gru-bi{i} 1991; Cvita{ et al., 2005) and there is no way to slow it down in the nearfuture. Photochemical pollution (beside the greenhouse effect and particle(aerosol) pollution) is one of the greatest atmospheric environmental problemstoday.It is well known that anthropogenic activities through fossil fuel combus-tion (and consequent emissions of NO2 and VOC (volatile organic compounds))are changing the microconstituent content of the atmosphere causing sideeffects (Crutzen, 1998).Photochemical pollution is highly dependent on regional characteristicsalthough it also depends on long distance transport of pollutants and theirprecursors. The state of pollution and its effect on the environment is muchbetter investigated in central and western Europe than in Croatia where suchinvestigations are needed due to different climate and emission conditions.At the Ru|er Bo{kovi} Institute we have 30 years of experience in moni-toring and investigation of air quality (predominantly of photochemical origin)in Croatia and abroad. Our team participated in the EUREKA environmentalproject EUROTRAC (environmental project on the transport and chemicalGEOFIZIKA VOL. 23 No. 2 2006transformation of pollutants in the troposphere over Europe) on troposphericozone research (subproject TOR and TOR–2) from 1988 till 2002 (Cvita{ andKley, 1994).Within this project the measurements at Sr| started in the summer of1998 and represent the first investigation of this type for the southern Adria-tic region in Croatia.2. ExperimentalMonitoring equipment has been placed inside a van located near the sum-mit of mount Sr| (Fig. 1a) (46.25° N, 17.45° E) above Dubrovnik from 1998 –2005. Mount Sr| rises steeply to a height of 412 m a.s.l. On its top there is aruin of an impressive 19th century Austrian military fortress, part of whichwas renovated into a TV-transmitter facility accompanied with a 150 m highantenna tower. The fortress and studio buildings with a height of approxi-mately 10 m and length of 200 m effectively screen the plateau behind fromevery direct effect from the city of Dubrovnik on the southern foothills of themountain (Fig. 1b and c).The monitoring site was chosen to be at the plateau to measure preferablythe remote and long range atmospheric characteristics. Actually, the distribu-tion of wind directions measured there exclusively corresponds to the direc-tions parallel with the mentioned buildings (Fig.3). The only exception was2005 when the ozone monitor was placed within the studio building (Fig 1band c) with the aim of sample collection oriented toward the city.Ozone has been monitored with a commercial instrument DASIBI 1008AHbased on UV absorption photometry which has been regularly checked andcalibrated. Wind speed and direction was measured with an AMES KVT–60Aanemometer.3. Results and discussionAfter careful check and selection of data, coverage for the whole period ofmeasurement is very low mainly due to frequent instrumental malfunction.The best consecutive data coverage is obtained for the months of June. This isalso the most interesting time for a year-to-year comparison because of in-tense solar irradiation, the main prerequisite for photochemical pollution.Obtained ozone data are summarized in Table 1.Local wind direction measurements which have been performed duringthe years 1998 and 1999 (wind rose is shown on Fig. 2) confirm the hypothesisthat the buildings (Fig. 1) effectively screen the plateau behind from directinfluence from the city. Wind measurements were discontinued after they hadbeen found not to represent the state within broader area. The mentioneddisplacement of the instruments in 2005 to the nearby studio building on the166 T. CVITA[ ET AL.: OZONE MEASUREMENT ON MOUNT SR\ ...top of the hill aimed to see such influence did not result in any significantincrease of measured ozone concentration and its diurnal variation. Namely, itwas expected that data from the new location may be affected by the city ofGEOFIZIKA, VOL. 23, NO. 2, 2006, 165–171 167a)c)b)Figure 1. a) View of the monitoring van situated on the summit plateau of Mount Sr| from 1998to 2004. (open to the air from the countryside to the North-East), b) view from the studiobuildings where the instruments were placed in 2005 (open to the air from the sea side) andc) satellite picture of Dubrovnik showing the monitoring site with respect to the city.Dubrovnik and the busy Adriatic coastal road which passes below along theslopes of Sr| from Dubrovnik towards the airport and further to the south.Consequently we can conclude that the city of Dubrovnik and the roadbelow do not substantially contribute to photochemical air pollution at the Sr|plateau. This is interesting in view of the planned sport activities there (e.g. golf).The maximum to minimum of the diurnal ozone concentrations ratios(Table 1, column 6), which were previously used for characterizing monitoringsites (Cvita{ et al., 1995), are used to assess the level of photochemical pol-lution. High values are representative for sites with significant local photo-chemical production as well as for ozone consumption. Index values below 2168 T. CVITA[ ET AL.: OZONE MEASUREMENT ON MOUNT SR\ ...Table 1. Data coverage during the period of measurements, yearly and June mean values, pollutionindex (daily max/min ratio)6 and the number of hours exceeding the hourly average of 80 ppb(AOT80 values).Year Datacoverage %June datacoverage %Meanozone volumefraction/ppbJune meanozone volumefraction/ppbJune indexmax/minAOT80value1998 8.6 0 34.1 – – 01999 28.5 40.3 48.3 48.1 1.62 02000 45.1 59.2 48.9 57.8 1.37 472001 48.0 59.9 36.9 39.5 1.47 02002 36.0 44.3 28.1 48.2 1.43 02003 – – – – – –2004 35.0 21.9 39.5 49.4 1.47 02005 25.0 74.9 40.0 39.3 1.77 0Figure 2. Wind rose for 1998 and 1999 at Sr| station.which were found at Sr| for June are a reliable indication that this is arelatively clean area with negligible local photochemical production. Photos-mog episodes exceeding the air quality standard for ozone given by an hourlyaverage of 80 ppb are scarce as indicated by the sum of hourly volume frac-tions in excess of 80 ppb the so called accumulated ozone time (AOT80)(Wayne, 2000) in Table 1, column 7.The average diurnal variation of ozone volume fractions depicted as a boxand whiskers plot for Junes 1999 – 2005 is given in Figure 3. The diurnalbehaviour is typical for an elevated site such as Mount Immitos above Athens(Cvita{ et al., 1988) or Puntijarka above Zagreb (Cvita{ et al., 1997). MountSr| is of about half the altitude of Mt Immitos and Medvednica (Puntijarka).The city of Dubrovnik has less than a tenth of the population of Athens andZagreb and no industry.It is interesting to note that the scattering of values around the median(Fig. 3) during night-time is greater than that during day-time. This indicatesthat the ozone at the monitoring site is not produced locally, but that its origincan be attributed to a displaced source requiring the air some 8 hours to reachMt Sr|. Taking the average wind speed this would amount to 180 km.Average summer (May to September, 1998 – 2005) ozone concentration atSr| was 46 ppb which is lower than published summer values at around 50GEOFIZIKA, VOL. 23, NO. 2, 2006, 165–171 169Figure 3. Box and whiskers plot of ozone volume fraction for the measurements in Junes from1999 to 2005. The line denotes the median, small square the mean, the box edges the 1st and 3rdquartile, and the bars the 10th and 90th percentile.ppb for Croatia elevated sites Puntijarka and Zavi`an (Cvita{ et al., 1997;Scheel et al., 1997) and similar to that found on the island of Lo{inj at MaliLo{inj 44 ppb.The period of ozone measurements from 1998 to 2005 was too short for astatistical long-term trend analysis. The data for the June averages are listedin Table 1 and do not show any noticeable trend over the 8 years.4. ConclusionsOzone measurements at the location Sr|, near Dubrovnik show that thisregion is substantially free of photochemical pollution episodes in spite ofintense solar radiation during the summer months. Ozone concentration va-lues are comparable with other Croatian coastal locations and somewhat lowerthan found at two elevated Croatian locations Puntijarka and Zavi`an.ReferencesCrutzen, J. P. (1998): How the Atmosphere keeps itself clean and how this is affected by humanactivities, Pure Appl. Chem.,70, 1319–1326.Cvita{, T., Kezele, N., Klasinc, L. and Lisac, I. (1995): Ozone Measurements in Croatia. Pure Appl.Chem., 67, 1450–1453.Cvita{, T., Kezele, N. and Klasinc, L. (1997): Boundary Layer Ozone in Croatia, J. Atmos. Chem.,28, 125–134.Cvita{, T., Kezele, N., Klasinc, L., McGlynn, S. P. and Pryor, W. A. (2005): New Directions: Howdangerous is ozone?, Atmos. Environ., 39, 4607–4608.Cvita{, T. and Kley, D., eds. (1994): The TOR network. A description of TOR measurementstations, Garmisch-Partenkirchen, EUROTRAC.Güsten, H., Heinrich, G., Cvita{, T., Klasinc, L., Ru{~i}, B., Lalas, P. D. and Petrakis, M. (1988):Photochemical formation and transport of ozone in Athens, Greece, Atmos. Environ., 22,1855–1861.Lisac, I. and Grubisic, V. (1991): An analysis of surface ozone data measured at the end of the19th-century in Zagreb, Yugoslavia, Atmos. Environ. A, 25, 481–486.Scheel, H. E., Areskoug, H., Geiss, H., Gomi{~ek, B., Granby, K., Haszpra, L., Klasinc, L., Kley, D.,Laurila, T., Lindskog, A., Roemer, M., Schmitt, R., Simmonds, P., Solberg, S. and Toupance, G.(1997): On the Spatial Distribution and Seasonal Variation of Lower-Troposphere Ozone overEurope, J. Atmos. Chem., 28, 1–3, 11–28Volz, A. and Kley, D. (1988): Ozone Measurements in the 19th Century: An Evaluation of theMontsouris Series, Nature, 332, 240–242.Wayne, R. P. (2000): Chemistry of the atmospheres, 3rd edn., Oxford University Press, Oxford, pp.422–439.170 T. CVITA[ ET AL.: OZONE MEASUREMENT ON MOUNT SR\ ...SA@ETAKMjerenja ozona na brdu Sr| blizu Dubrovnika, HrvatskaTomislav Cvita{, Nenad Kezele, Leo Klasinc i Glenda [orgoPrikazani su rezultati i analiza mjerenja ozona na postaji Sr| (46.25° N, 17.45° E,412 m a.s.l.) blizu Dubrovnika u razdoblju od 1998 do 2005. Potvr|en je neone~i{}enikarakter ove lokacije unato~ jakom Sun~evom zra~enju ljeti. Mjerenja nisu dala nazna-ke trenda u koncentracijama ozona, a prosje~na vrijednost udjela ozona u ljetnomperiodu je bila 46 ppb.Klju~ne rije~i: mjerenja ozona, fotokemijsko one~i{}enje zraka, DubrovnikCorresponding author’s address: Tomislav Cvita{, Ru|er Bo{kovi} Institute, Bijeni~ka 54, HR-10000 Zagreb.GEOFIZIKA, VOL. 23, NO. 2, 2006, 165–171 171

Mjerenja ozona na brdu Srđ blizu Dubrovnika, Hrvatska

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