Ozone pollution and ozone biomonitoring in European cities. Part I: Ozone concentrations and cumulative exposure indices at urban and suburban sites

ARTICLE IN PRESS

Atmospheric Environment 40 (2006) 7963–7974 www.elsevier.com/locate/atmosenv

Ozone pollution and ozone biomonitoring in European cities. Part I: Ozone concentrations and cumulative exposure indices at urban and suburban sites Andreas Klumppa,, Wolfgang Ansela, Gabriele Klumppa, Vicent Calatayudb, Jean Pierre Garrecc, Shang Hec,1, Josep Pen˜uelasd, A`ngela Ribasd, Helge Ro-Poulsene, Stine Rasmussene, Marı´ a Jose´ Sanzb, Phillippe Vergnef a

Institute for Landscape and Plant Ecology and Life Science Center, University of Hohenheim, 70599 Stuttgart, Germany b Fundacio´n CEAM, Parque Tecnolo´gico, c/ Charles Darwin 14, 46980 Paterna (Valencia), Spain c INRA Nancy, Laboratoire Pollution Atmosphe´rique, 54280 Champenoux, France d Unitat d’Ecofisiologia CSIC-CEAB-CREAF, Centre de Recerca Ecolo`gica i Aplicacions Forestals (CREAF), Universitat Auto`noma de Barcelona, 08193 Bellaterra (Barcelona), Spain e Botanical Institute, University of Copenhagen, Øster Farimagsgade 2D, 1353 Copenhagen K, Denmark f ENS Lyon and Lyon Botanical Garden, 46 Allee d’Italie, 69364 Lyon Cedex 07, France Received 16 December 2005; accepted 4 July 2006

Abstract In the frame of a European research project on air quality in urban agglomerations, data on ozone concentrations from 23 automated urban and suburban monitoring stations in 11 cities from seven countries were analysed and evaluated. Daily and summer mean and maximum concentrations were computed based on hourly mean values, and cumulative ozone exposure indices (Accumulated exposure Over a Threshold of 40 ppb (AOT40), AOT20) were calculated. The diurnal profiles showed a characteristic pattern in most city centres, with minimum values in the early morning hours, a strong rise during the morning, peak concentrations in the afternoon, and a decline during the night. The widest amplitudes between minimum and maximum values were found in central and southern European cities such as Du¨sseldorf, Verona, Klagenfurt, Lyon or Barcelona. In the northern European cities of Edinburgh and Copenhagen, by contrast, maximum values were lower and diurnal variation was much smaller. Based on ozone concentrations as well as on cumulative exposure indices, a clear north–south gradient in ozone pollution, with increasing levels from northern and northwestern sites to central and southern European sites, was observed. Only the Spanish cities did not fit this pattern; there, ozone levels were again lower than in central European cities, probably due to the direct influence of strong car traffic emissions. In general, ozone concentrations and cumulative exposure were significantly higher at suburban sites than at urban and traffic-exposed sites. When applying the newly established European Union (EU) Directive on ozone pollution in ambient air, it was demonstrated that the target value for the protection of human health was regularly surpassed at urban as well as suburban sites, particularly in cities in Austria, France, northern Italy and southern

Corresponding author. Tel.: +49 711 4593043; fax: +49 711 4593044.

E-mail address: [email protected] (A. Klumpp). Permanent address: Chinese Academy of Forestry, Research Institute of Forest Ecology and Environmental Science, Wan Shou Shan, Beijing 100091, PR China. 1

1352-2310/$ - see front matter r 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2006.07.017

ARTICLE IN PRESS 7964

A. Klumpp et al. / Atmospheric Environment 40 (2006) 7963–7974

Germany. European target values and long-term objectives for the protection of vegetation expressed as AOT40 were also exceeded at many monitoring sites. r 2006 Elsevier Ltd. All rights reserved. Keywords: Air quality; AOT40; Thresholds; EU Directive; Urban air pollution

1. Introduction In most European cities, air quality has substantially improved over the last decades due to stricter legal regulations, the adoption of less-polluting technologies and the relocation of industry from the city centres. Nevertheless, air pollution remains one of the most urgent environmental problems in Europe. The enduring unsatisfactory situation of urban air quality originates mainly from the steadily increasing road traffic. According to the European Environment Agency (EEA) (2003), air pollution in Europe continues to pose risks and to have adverse effects on human health and on natural and manmade environments. Considerable fractions of urban populations are regularly exposed to peak air pollution in excess of current limit values. In particular, health effects caused by suspended particulate matter and by ozone and other photooxidants are presently the focus of public and scientific interest. Projections from the Auto-Oil II air quality study (De Leeuw, 2002) indicate that reductions in the emissions of ozone precursors will significantly reduce regional ozone production and peak concentrations. Air quality is therefore expected to improve in the period until 2010, but the improvements will be insufficient to meet the air quality targets all over Europe. On the other hand, there is growing evidence that sources outside Europe are becoming more important and that background ozone concentrations are generally increasing on the northern hemisphere (Prather et al., 2003; Grennfelt, 2004). Moreover, due to the complex chemical reactions and vertical transport processes in the atmosphere, a strong temporal and spatial variability of ozone pollution exists; this leads to rapidly alternating episodes of elevated and low ozone levels and often to significant differences in ozone load of urban vs. suburban and rural areas (Garland and Derwent, 1979; Fenger, 1999). In view of these special features, ozone and its potential impact on human health and the environment will stay on the agenda of European environmental policy in the future.

The assessment and management of air quality in Member States of the European Union is regulated by the Air Quality Framework Directive (European Union (EU), 1996) and its so-called Daughter Directives. Limit values for the protection of human health and for the protection of vegetation from harmful ozone concentrations have been settled by Directive 2002/3/EC relating to ozone in ambient air (European Union (EU), 2002), which was implemented in 2003. Measurements of atmospheric pollutant concentrations as prescribed by European directives and national legislation, however, provide no direct information regarding the possible pollution effects on man and the environment because the reaction of an organism depends not only on pollutant concentrations and exposure duration, but is also influenced by a range of predisposing or accompanying factors. Hence, biomonitoring using highly sensitive plant species and cultivars is an appropriate means to detect and to monitor air pollution effects; this supplements information gained from conventional pollution measurements and modelling. EuroBionet, the ‘European Network for the Assessment of Air Quality by the Use of Bioindicator Plants’ was established in 1999 as a network of research institutes and municipal environmental authorities from 12 urban agglomerations in eight EU Member States. It aimed at promoting environmental awareness of the urban population and at assessing and evaluating air quality by applying highly standardised bioindication methods. To this end, about 100 biomonitoring sites were established and operated over a period of up to 3 years. In order to comparatively evaluate air quality based on air pollution as well as on biological effects data, some bioindicator stations were established close to automated air monitoring stations (Klumpp et al., 2002, 2004). The present paper reports on ambient ozone pollution in urban and suburban areas using data obtained by conventional monitoring of atmospheric ozone concentrations as well as by standardised exposure of ozone-sensitive tobacco plants. Part I focuses on data gained by routine measurements of

ARTICLE IN PRESS A. Klumpp et al. / Atmospheric Environment 40 (2006) 7963–7974

ozone concentrations and evaluates them based on current European legislation. In an anticipatory approach, we used the new Ozone Directive (EU, 2002) for this purpose although it came into force only after the project’s end. This approach enabled us to determine whether the new target values and longterm objectives for human health and protection of vegetation can be met in European cities and where these limits are exceeded. This also improves our knowledge about the occurrence of ozone episodes in large agglomerations. In Part II (Klumpp et al., 2006b), we report on the intensity and geographical distribution of ozone-induced injuries to bioindicator plants and on the relationship between ambient ozone levels and ozone-induced effects on plants. 2. Material and methods 2.1. The city network The present study was part of the European bioindicator programme EuroBionet (www.eurobionet. com), which aimed at assessing and evaluating air quality in 12 urban agglomerations throughout Europe using various bioindicator species (Klumpp et al., 2002, 2004). To this end, a network of municipal administrations and research institutes was established under the coordination of the University of Hohenheim in 1999. The project started with the following cities and regions as participants: Copenhagen (Denmark), Edinburgh (UK), Klagenfurt (Austria), Greater Lyon (France), Sheffield (UK), and Verona (Italy). The City of Du¨sseldorf (Germany), the City of Ditzingen/ Greater Stuttgart (Germany), Greater Nancy (France) and the regional government of Catalonia/ Barcelona (Spain) joined the network in 2000, the cities of Valencia (Spain) and Glyfada/Greater Athens (Greece) in 2001. In each city, local bioindicator networks including urban, suburban, industrial, traffic and reference sites were implemented, totalling about 100 stations in operation during 1999–2002 (cp. Klumpp et al., 2006b). Classification and location of sampling points were in conformity with the criteria established by EU (2002). 2.2. Measurement and evaluation of ambient ozone concentrations In order to comparatively evaluate air quality using air pollution and biomonitoring data within the local networks, some bioindicator stations were

7965

established close to continuously working air monitoring stations (Table 1) run by the local and regional authorities in charge of air pollution monitoring. Ozone concentrations were measured at 2.5–3.5 m above ground by the UV photometric method according to EU (2002) using automated analysers from different manufacturers and were provided as hourly or half-hourly mean values. The paper focuses on 2001 because in that year almost complete data sets were available from 11 out of 12 cities. No data on atmospheric ozone concentrations in Glyfada were available: the values from neighbouring Athens were not used as they were not considered representative for the Glyfada suburb. 24-h mean and maximum ozone concentrations were calculated based on the hourly mean values. Additionally, mean and mean daily maximum values as well as average daily profiles of ozone concentrations were computed for the eight biweekly exposure periods of tobacco plants (cp. Klumpp et al., 2006b) and for the periods May–July and April–September. A cumulative ozone exposure index, the Accumulated exposure Over a Threshold of 40 ppb (AOT40; expressed as ppb*h), was calculated as the sum of the differences between the hourly ozone concentrations exceeding 40 ppb and 40 ppb using only the hourly values measured between 08:00 and 20:00 h CET daily for the periods between May–July and April–September according to the Ozone Directive (EU, 2002). Since sensitive plant species and cultivars may develop characteristic injuries even at ambient levels below 40 ppb, the AOT20 was also determined (correspondingly to the AOT40 calculation). Additionally, annual mean values of NO2 concentrations are given in order to describe the general air pollution situation at the monitoring sites (cp. Table 2). The evaluation of ozone concentrations and exposure characteristics included the count of exceedances of: (i) target values and long-term objectives for the protection of the vegetation (9000 and 3000 ppb*h during May–July, respectively) and forests (10,000 ppb*h during April– September); (ii) the target value for the protection of human health (60 ppb as maximum daily 8-h mean, not to be exceeded at more than 25 days/ year); and (iii) the information and alert thresholds (90 and 120 ppb hourly means), as prescribed by EU (2002). The AOT40 values of 3000 and 10,000 ppb*h correspond to the ‘Critical Levels’ for the protection of crops and forests established by United Nations Economic Commission for

ARTICLE IN PRESS A. Klumpp et al. / Atmospheric Environment 40 (2006) 7963–7974

7966

Table 1 Location and characteristics of ozone monitoring stations and corresponding bioindicator sites City/code

Name of air monitoring/bioindicator station

Distance between both stations (m)

Type

Edinburgh/Ed Sheffield/Sh Copenhagen/Co

Princes Street/Donaldson’s College City Centre/Heeley Farm Jaegersborg/Jaegersborg Jagtvej/Assistens Kirkegard Lille Valby/Lille Valby Lo¨rick/Strandbad Lo¨rick Brabois/Airlor Tomblaine/Me´te´o France Viaduc Kennedy/Parc Ste. Marie Hohenheim/Hohenheim Plochingen/Plochingen KoschatstraXe/KoschatstraXe St. Just/St. Just Croix Luizet/Croix Luizet Gerland/Gerland Torricelle/San Mattia ZAI/Liceo Galilei Bellaterra/Bellaterra Gra´cia/Gra´cia Hospitalet/Sants Avda. Arago´n/Avda. Arago´n Nuevo Centro/Prof. Beltra´n Ba´guena GVF Cato´lico/GVF Cato´lico

2000 1500 20 400 10 70 70 70 600 5 450 o5 o5 o5 800 700 40 5000 o5 o5 o5 o5 o5

Urbanb Urbanb Suburban Urbanb Suburban Suburbanb Suburban Suburban Urbanb Suburban Suburban Urbanb Urban Urban Urbanb Suburban Suburbanb Suburban Urban Urbanb Urban/street Urban/streetb Urban/street

Du¨sseldorfa/Du¨ Nancy/Na

Stuttgarta/St Klagenfurt/Kl Lyon/Ly

Veronaa/Ve Barcelona/Ba

Valencia/Va

a

No O3 concentrations from urban air monitoring stations available. Sites considered for presentation of diurnal profiles in Fig. 1.

b

Europe (UNECE) (Ka¨renla¨mpi and Ska¨rby, 1996) and World Health Organization (WHO) (2000), whereas the 8-h mean of 60 ppb corresponds to the critical level for human health (WHO, 2000). 2.3. Quality assurance and control Ozone monitoring equipment was maintained and calibrated by the responsible authorities according to the state-of-the-art. Following the Ozone Directive (EU, 2002), at least 75% of valid data are required to calculate mean values and 90% to compute cumulative indices and number of threshold exceedances. In our study, the proportion of valid data was generally between 90% and 100%, except from one station where a proportion of about 85% was accepted. Missing data were not estimated when computing AOT40 values. Monitoring sites with less than 85% valid data were excluded from the calculations. 3. Results and discussion 3.1. Diurnal ozone cycles The diurnal profiles of ozone concentrations showed a characteristic pattern in most city centres,

with minimum values in the early morning, a strong rise during the morning with increasing solar radiation, peak concentrations in most cities in the afternoon between 15.00 and 17.00 h, and a decline due to ozone destruction by nitrogen oxide during the night (Fig. 1). This feature can be explained by the activating role of solar radiation in photochemical ozone generation in the mixing layer and ozone transport from upper atmospheric layers. Once the nocturnal inversion layer has been established, no major changes in ozone concentrations occur until rupture of inversion layers and photochemical reactions start again with beginning of the daylight period (Coyle et al., 2002; Duen˜as et al., 2002). The widest amplitudes between minimum and maximum concentrations were found in central and southern European cities such as Du¨sseldorf, Verona, Klagenfurt, Lyon or Barcelona. Maximum values were lower and diurnal variation was much smaller in the northern European cities of Edinburgh and Copenhagen. There, slightly higher ozone values were also measured in the night and early morning hours before start of the rush hour. In Edinburgh, the mean daily maximum even occurred at 04:00 h. With low total photochemical activity in northern cities, vertical

1152 3350 5757 11,631 10,846 10,370 15,722 16,173 13,838 7094

Suburban sites Co Lille Valby Co Jaegersborg Du¨ Lo¨rick Na Brabois Na Tomblaine St Hohenheim St Plochingen Ve ZAI Ve Torricelle Ba Bellaterra 16,475 19,962 18,696 29,268 28,557 27,506 31,689 34,871 30,690 21,731

2816 6004 10,036 18,608 29,162 25,432 24,094 19,124 19,653 8420 10,765 4581 3714 29.674.6 33.576.2 27.978.3 35.8710.2 35.279.1 35.179.2 30.4711.8 37.3710.7 45.0712.0 29.376.7

17.876.2 20.976.2 24.876.5 29.1710.0 35.378.0 32.9710.2 32.4710.6 28.279.4 28.476.7 19.176.7 22.375.9 18.774.5 15.574.5 39.976.8 46.478.3 50.3716.0 56.1717.5 55.3716.2 55.6716.9 64.7723.4 65.5715.5 62.9714.3 54.7711.3

29.678.6 33.378.7 36.777.3 47.3715.8 56.6710.8 56.4718.6 56.2717.7 50.9716.4 50.5710.3 40.0711.4 40.7710.7 33.677.6 29.379.2 2306 5650 8071 15,403 15,024 14,832 19,428 25,292 21,837 9723

91 411 598 8301 17,219 13,722 13,172 9136 6881 1548 2452 278 243 29,236 34,450 29,008 45,771 45,767 45,508 44,970 57,423 51,685 37,848

4860 9360 13,798 29,051 49,320 40,358 37,297 31,723 34,688 13,310 20,166 8332 7290 28.575.4 31.277.6 24.279.6 32.4710.0 31.479.3 31.1710.1 24.4712.1 32.2713.0 40.7715.0 26.477.1

16.876.6 19.377.0 21.677.4 26.479.3 31.2710.4 29.2710.7 28.6710.9 24.979.6 26.977.0 17.976.4 21.976.0 17.674.5 15.175.1

39.378.1 44.279.9 44.1718.3 50.5717.0 50.2716.2 50.5716.8 54.0723.3 59.7718.2 56.8718.1 49.7711.0

28.478.8 31.079.0 33.878.0 43.6715.7 52.9713.9 50.8718.2 51.1717.7 46.5716.0 47.279.8 36.6710.1 40.7710.1 32.177.2 28.979.3

Mean7s.d. (ppb) Mean daily maximum7s.d. (ppb)

5.2 n.d. 15.6 12.0 9.4 n.d. 18.7 31.2 9.4 n.d.

22.4 19.2 20.8 21.3 14.0 19.8 23.9 21.8 20.8 33.3 26.0 33.3 41.1

Annual mean (ppb)

NO2

Exceedances of EU ozone target values for the protection of vegetation (9000 ppb*h) and forests (10,000 ppb*h) in bold; sd ¼ standard deviation; n.d. ¼ not determined.

80 387 540 5 866 10,644 9660 9392 6023 4926 1373 1413 242 120

AOT20 (ppb*h)

AOT40 (ppb*h)

Mean7s.d. (ppb) Mean daily maximum7s.d. (ppb)

AOT40 (ppb*h)

AOT20 (ppb*h)

Ozone: April–September

Ozone: May–July

Urban sites Ed Princes Street Sh City Centre Co Jagtvej Na Viad. Kennedy Kl KoschatstraXe Ly St. Just Ly Gerland Ly Croix Luizet Ba Hospitalet Ba Gra´cia Va Nuevo Centro Va GVF Cato´lico Va Avda. Arago´n

Site characteristics and names

Table 2 Mean and mean daily maximum O3 concentrations as well as AOT20 and AOT40 values during May–July and April–September 2001; annual mean values of NO2

A. Klumpp et al. / Atmospheric Environment 40 (2006) 7963–7974

ARTICLE IN PRESS 7967

ARTICLE IN PRESS A. Klumpp et al. / Atmospheric Environment 40 (2006) 7963–7974

7968

Edinburgh Sheffield Copenhagen Düsseldorf Nancy Klagenfurt Lyon Verona Barcelona Valencia

70

Ozone concentration [ppb]

60 50 40 30 20 10

24:00

23:00

22:00

21:00

20:00

19:00

18:00

17:00

16:00

15:00

14:00

13:00

12:00

11:00

9:00

10:00

8:00

7:00

6:00

5:00

4:00

3:00

2:00

1:00

0

Fig. 1. Mean daily profile of ozone concentrations at selected urban and suburban (Du¨sseldorf/Verona) monitoring sites (cp. Table 1) over the period April–September 2001.

exchange processes and onshore breezes in coastal regions that entrain ozone-polluted airmasses during the night and consequently lead to little nighttime depletion of ozone (Garland and Derwent, 1979; Coyle et al., 2002) play a comparatively greater role than they do in central and southern Europe, where higher photochemical ozone production rates and re-circulation of ozone-rich airmasses prevail (Duen˜as et al., 2002; Milla´n et al., 2002; Sanz et al., 2004). Within the local networks, suburban districts generally featured higher concentrations during the daylight hours than did the city centres; ozone breakdown by nitrogen oxide at night and during the early morning was less evident than at the urban stations (data not shown). 3.2. Ozone concentrations and cumulative ozone exposure 24-h mean ozone concentrations over the period May–July varied between 15.5 ppb at the site ‘Avenida Ara´gon’ in Valencia and 45 ppb at ‘Torricelle’ in Verona, whereas the mean daily maximum values ranged between 29.4 ppb at the same Spanish site and 65.5 ppb at ‘ZAI’ in Verona (Table 2). Lowest mean and maximum concentrations were generally registered in northern Europe (UK and Denmark) and at several Spanish sites; the highest levels occurred in Germany, France, Austria and northern Italy. The highest hourly mean value

Table 3 Results of one-way ANOVA using site type (urban/suburban) as a factor Ozone parameter

Significance (p)

Mean value May–July Mean maximum May–July AOT40 May–July Mean value April–September Mean maximum April–September AOT40 April–September

o0:01 o0:01 o0:001 o0:01 o0:01 o0:01

of the whole network (149.5 ppb) was measured at ‘Plochingen’ southeast of Stuttgart on 31 July 2001. This was also the highest value measured in Germany in that year. Mean and maximum values from April to September were somewhat lower than from May to July due to the relatively low ozone levels in early spring and autumn, but they followed a similar geographical pattern. Urban and suburban sites differed significantly concerning ozone pollution, with average values of 25.4 and 34.4 ppb and average maximum values of 43.0 and 56.8 ppb at urban and suburban sites, respectively; this was valid for the 3-month period and the longer monitoring period (Table 3). This well-known phenomenon reflects the higher emissions of nitrogen oxides in urban centres (cp. Table 2) and the consequently more intense ozone quenching during nighttime.

ARTICLE IN PRESS A. Klumpp et al. / Atmospheric Environment 40 (2006) 7963–7974

Differences between monitoring sites were much more pronounced when cumulative exposure indices were used for comparison. Accordingly, the AOT40 (May–July) varied between 80 ppb*h at ‘Princes Street’ in Edinburgh and 10,644 ppb*h at ‘KoschatstraXe’ in Klagenfurt for urban stations, and between 1152 ppb*h at ‘Lille Valby’ in Copenhagen and 16,173 ppb*h at ‘ZAI’ in Verona for the suburban stations (Table 2). Again, sites differed significantly depending on their location within the agglomerations (Table 3). Suburban sites featured AOT40 values that were nearly three times higher than those determined at urban sites. The AOT40 values for the period April–September 2001 revealed the same geographical pattern as that in the already described shorter calculation period (Table 2). When compared to the period May–July, the cumulative ozone exposure increased by up to 102%. At the urban sites in the northern European cities Edinburgh, Sheffield and Copenhagen and at some Spanish sites, AOT values increased only minimally (6–14%) when extending the calculation period to the spring and late summer months. A relatively high increase, by contrast, was found at suburban sites in Copenhagen and Verona and at some urban sites in Klagenfurt, Lyon, and Valencia. The monthly data revealed that the strong increases in long-term cumulative values were mostly due to high ozone concentrations in August (Du¨sseldorf, Nancy, Klagenfurt, Lyon, Verona). In Valencia, on the other hand, comparably high ozone pollution already appeared in April, while in Barcelona both months (April and August) showed similarly high values (data not shown). Because of the high ozone sensitivity of tobacco cultivar Bel–W3, AOT20 values were also determined. As Table 2 shows, the geographical pollution pattern was still evident when the lower cut-off value was employed, even though the differences between the individual cities were clearly reduced. Based on ozone concentrations as well as on cumulative exposure indices, ozone pollution showed a clear north–south gradient, with increasing levels from northern and northwestern sites to central and southern European sites. Only the two Spanish cities of Barcelona and Valencia were exceptions (Table 2): their ozone levels were again lower than in central European cities like Verona or Klagenfurt. Fig. 2 illustrates the AOT40 values from May to July 2001 at urban and suburban sites in various cities. The observed latitudinal gradient of ozone concentrations and cumulative exposure indices was

7969

further investigated by Pearson correlation and linear regression analyses. Table 4 shows the results using data of both urban and suburban sites but excluding the two Spanish cities. Linear regression fitted best to the data, and correlation coefficients were significant for concentration as well as for AOT40 values. Highest correlation coefficients (R40.8) were obtained when maximum concentrations and AOT40 were computed against latitude of sites. Similar results were published by Sanz et al. (2004), who analysed ozone concentrations at rural sites in SW Europe during 2000–2002. In their investigations, however, rural sites from various Spanish regions also fitted well into the exponential model they used. The monitoring data from our network—with low ozone levels at the Spanish sites—seem to contradict not only Sanz et al. (2004) but also various papers and reports from environmental agencies that relate strong ozone pollution along the Spanish east coast. The western Mediterranean basin, with its intense solar radiation and high emission rates of ozone precursors, is known to suffer from chronic ozone episodes during the summer and is frequently described as a ‘large natural photo-chemical reactor’ (Milla´n et al., 2000). This is due to the specific topographical situation and circulation dynamics of the region, where high mountain ranges surrounding the coastal cities favour the isolation from frontal systems and the creation of closed re-circulation processes driven by sea breezes. The result is a system of stacked layers of airmasses with high photochemical activity and comparatively long residence time of the polluted air (Milla´n et al., 2000, 2002; Gangoiti et al., 2001). Consequently, prolonged ozone episodes and exceedances of limit values for both human health and vegetation are frequently reported from urban and rural areas along the Iberian coast (Gimeno et al., 1995; EEA, 2001; Tobia´s and Scotto, 2005). Strong ozone pollution exceeding threshold values was also observed for example at several rural sites near Valencia during summer 2001 (Mantilla et al., 2002) and in Catalonia (Ribas and Pen˜uelas, 2003, 2004). The urban monitoring sites in our study, however, are located in the city centres of Barcelona and Valencia, quite close to heavy-trafficked roads and junctions. Such sites are directly influenced by high car traffic emissions (Gimeno et al., 1995; Mantilla et al., 2002) and partly also by NOx emissions from major industrial sources (Toll and Baldasano, 2000)

ARTICLE IN PRESS A. Klumpp et al. / Atmospheric Environment 40 (2006) 7963–7974

7970

18000

___

EU Target Value --- WHO-Guideline EU Long-term Objective

AOT40 [ppb*h]

15000 12000

10644 9660 9392

9000 6023

5866

6000

4926

3000 0

120 242

Ja

ity

in

St

en C

s

ce

.

18000

a

o

C

Pr

o ic ól at C VF G ón a Va rag uen A ág Va f. B o Pr Va cia t ra G ale Ba spit t o ze H ui Ba ix L ro C d Ly rlan e G t Ly us J tr. St ts Ly cha s Ko Kl GN U C j ve gt tre

N

C

Sh

Ed

(a) ___

15000 AOT40 [ppb*h]

1373 1413

387 540

80

EU Target Value --- WHO-Guideline EU Long-term Objective

12000

10846

16173

15722 13838 11631 10370

9000 7094 5757

6000 3350 3000

1152

0 Ba

Ve

Ve

St

St

lle

rra

te

lla

Be

I

ZA

ce

en

im

he

ng

hi

rri

oc

To

Pl

en

s

ne

g

or

sb

y

lb

ai

oi

ab

oh

Br bl

m

er

k

ric

To

Lö

Va

eg

Ja

lle

Li

H

a

N

a

N

ü

D

o

C

o

C

(b)

Fig. 2. AOT40 values at urban (a) and suburban (b) monitoring stations (cp. Table 1) for the period May–July 2001 as well as target and threshold values relating to vegetation protection as established by EU and WHO (cities listed from north to south).

Table 4 Results of regression analyses of the relationships between latitude of monitoring sites and ozone exposure indices Ozone parameter

Correlation coefficient R

R2

Significance of R

Mean value May–July Mean maximum May–July AOT40 May–July Mean value April–September Mean maximum April–September AOT40 April–September

0.643 0.831 0.813 0.558 0.832 0.829

0.413 0.690 0.661 0.311 0.692 0.687

po0:01 po0:001 po0:001 po0:05 po0:001 po0:001

resulting in elevated ambient levels of nitrogen oxides (cp. Table 2). The significant influence of traffic emissions at these sites has also been demonstrated by exposure of various bioindicator species in our studies (Klumpp et al., 2004, 2006a).

Consequently, ozone is rapidly being depleted by the high NO levels at those sites, and higher ozone levels can only be found at more distant sites like the suburban station ‘Bellaterra’ in Barcelona.

ARTICLE IN PRESS A. Klumpp et al. / Atmospheric Environment 40 (2006) 7963–7974

3.3. Exceedance of European target values and longterm objectives Analysis of ozone data according to the new European Ozone Directive (EU, 2002) demonstrated that the target value for protection of human health (60 ppb as running 8-h mean) was surpassed at urban as well as suburban sites in many cities, particularly in central and southern Europe, at least once a year (Table 5). In Lyon, Nancy, Klagenfurt, Stuttgart and Verona, this target value was exceeded on more than 25 days, which is the limit permitted by the directive. At the sites ‘ZAI’ and ‘Torricelle’ (Verona) and ‘Plochingen’ (Stuttgart) the limit was even exceeded on more than 50 days in the study year. Only at the urban sites of Edinburgh, Sheffield, Copenhagen and Valencia and at one of the urban sites in Barcelona did the running 8-h average always remain below 60 ppb over the whole period April–September 2001.

7971

The threshold for information to the public (90 ppb as 1-h mean) was also regularly exceeded at the monitoring sites in France, Italy, and Germany, and once at the Austrian site. The highest number of exceedances (57 times) was registered at ‘Plochingen’ (Stuttgart), where additionally the alert threshold (120 ppb as 1-h mean) was surpassed during 5 h in summer 2001 (Table 5). Our data are consistent with the evaluation of ozone pollution in summer 2001 published by EEA (2001). There, the number of exceedances of information and alert threshold values increased from zero in Scandinavia to a maximum in central Europe. The Mediterranean region showed no consistent spatial pattern, with many stations reporting no exceedances and other stations reporting more than 10. Weather conditions are important for the occurrence of prolonged ozone episodes with repeated exceedance of limit values. In southern European countries, transgression of the information threshold already

Table 5 Exceedances of the thresholds for information and warning of the population (days and total number of hours) and of the target value for the protection of human health (bold: surpassing the limit of 25 days as permitted by the directive) according to the new Ozone Directive (EU, 2002) Site characteristics and names

Urban sites Ed Princes Street Sh City Centre Co Jagtvej Na Viaduc Kennedy Kl KoschatstraXe Ly St Just Ly Gerland Ly Croix Luizet Ba Hospitalet Ba Gra´cia Va Nuevo Centro Va GVF Cato´lico Va Avda. Arago´n Suburban sites Co Lille Valby Co Jaegersborg Du¨ Lo¨rick Na Brabois Na Tomblaine St Hohenheim St Plochingen Ve ZAI Ve Torricelle Ba Bellaterra

Information threshold 90 ppb (days/hours)

Alert threshold 120 ppb (days/hours)

Target value for the protection of human health 60 ppb (max. 8-h mean) (days)

0 0 0 2/2 1/1 5/19 5/11 1/4 0 0 0 0 0

0 0 0 0 0 0 0 0 0 0 0 0 0

0 0 0 17 35 32 33 21 10 0 0 0 0

0 0 4/13 4/18 2/10 3/9 11/57 7/21 8/27 0

0 0 0 0 0 0 2/5 0 0 0

2 5 21 34 36 35 52 63 59 15

ARTICLE IN PRESS 7972

A. Klumpp et al. / Atmospheric Environment 40 (2006) 7963–7974

occurred in April and early May, whereas in central Europe this threshold was surpassed mostly between June and August. According to EEA (2001), the geographically most extended episode was late June (24–27 June), with exceedances in Germany, France, Italy, Benelux countries, Austria, Switzerland, Czech Republic, northern Spain and even southern UK. A so-called anti-episode with no exceedances throughout Europe, by contrast, occurred on 16–20 July during a spell of bad weather. Our own data show that most exceedances of the human health target and the information threshold in central Europe (Germany, France, Austria, Italy) occurred during five episodes in late May (23–31/ 05), late June (21–27/06), late July (22/07–02/08), mid-August (13–18/08), and late August (23–29/08), whereby the onset and duration varied with latitude and local weather conditions. No exceedances were registered during September 2001. The target value for protection of the vegetation (9000 ppb*h; AOT40 over the period May–July) was exceeded in Klagenfurt, Lyon, Nancy, Stuttgart, and Verona (Fig. 2 and Table 2). AOT40 values above this threshold were mainly registered at suburban sites, but also occurred at some urban sites in Nancy and Klagenfurt. The highest value was 16,173 ppb*h at ‘ZAI’ in Verona, followed by ‘Plochingen’ with 15,722 pph*h. The AOT40 values from suburban sites reported here are comparable to data obtained at rural sites in Austria, Switzerland or Italy within the UNECE ICP Vegetation network in the same year (Buse et al., 2002). The highest value in those studies (29,500 ppb*h) was registered in Rome. The AOT40 of 3000 ppb*h defined as an EU Long-Term Objective and WHO Threshold for the protection of vegetation was surpassed in all central and southern European cities except for Valencia and one site in Barcelona. Even the suburban site ‘Jaegersborg’ in Copenhagen surpassed this limit. Note, however, that the AOT40 limit values in the EU Directive are defined as 5year means in order to compensate for annual variations, while the statements here are based on a single study year only. On the other hand, the target values and long-term objectives of the directive refer to suburban and rural monitoring stations, where ozone pollution levels are usually higher than near the centre. It might actually be questioned whether it makes sense to apply AOT40, which was developed as a critical level for crops, for comparison of air quality in city centres. Short-term critical levels aiming to avoid visible injury on sensitive

plant species have been developed recently (Pihl Karlsson et al., 2003; UNECE, 2004). However, it must be emphasised that the AOT40 of 9000 ppb*h is currently the only legal threshold in force. The same sites that exceeded the threshold for the period May–July also clearly exceeded the target value of 10,000 ppb*h from April to September for the protection of forests. Moreover, this threshold was nearly reached at suburban sites in Du¨sseldorf and Barcelona (Table 2). If we consider recent work recommending an AOT40 value of 5000 ppb*h or even lower during the growing season to protect sensitive broadleaf and conifer species from harmful ozone effects (Karlsson et al., 2004), then all suburban sites, except for ‘Lille Valby’ in Copenhagen, and many urban sites of our network would not meet such a threshold. 4. Conclusions Photochemical processes regularly lead to elevated concentrations of tropospheric ozone in rural and remote regions of many European countries surpassing national and European threshold values and presumably contributing to vegetation damage and health problems (Buse et al., 2002; EEA, 2003). Our studies conducted in 11 European cities demonstrated that current ozone concentrations are also high enough to jeopardise human health and vegetation particularly at suburban sites, but also at some urban sites. The concentrations measured during summer 2001 exceeded the new European target values for the protection of human health at many sites, and thresholds of cumulative exposure indices established to protect vegetation from harmful ozone effects were also surpassed at many locations. There was a clear gradient with increasing ozone levels from northern and northwestern Europe to central and southern European cities; only the Spanish sites did not fit the pattern due to specific local characteristics. Strong ozone problems were detected primarily in the cities in eastern and southern France, southern Germany, Austria and northern Italy. This is in agreement with frequently observed ozone episodes over eastern France/southwestern Germany and with similar phenomena in the region influenced by the high precursor emissions from the Po Valley in Italy. On a local scale, the extent of ozone pollution depended very much on the exact location of the monitoring stations. Due to higher NO levels, which help destroy photochemically produced ozone, ozone

ARTICLE IN PRESS A. Klumpp et al. / Atmospheric Environment 40 (2006) 7963–7974

concentrations were significantly lower at urban sites and particularly at strongly traffic-exposed measuring stations than at suburban or even rural stations. Note that our study assessed data of a single year, whereas the new European target values are to be calculated as multi-annual averages. Moreover, these recently established thresholds shall only be met in 2010 (or even in 2020 for the long-term objectives). Otherwise, the year 2001 was a ‘normal’ year in terms of meteorological conditions and ozone pollution (EEA, 2001) with exception of Scandinavia where unusually low ozone levels were registered. In most other countries, values were not as high as in the hot summer 2003, but higher than during the relatively wet and cool summer months of 2002. Our data support the conclusion that even in urban areas it will remain difficult to meet the legal threshold values. The implementation of measures to reduce emissions of precursor substances may lower the risk of short-term peak concentrations. A future increase of background ozone in the northern hemisphere, as assumed by several authors (Prather et al., 2003; Grennfelt, 2004), however, would aggravate the situation. This is particularly true with regard to cumulative indices such as AOT40, where even small increases of background levels may strongly increase the number of exceedances. Acknowledgements This study was supported by the LIFE Environment Programme of the European Commission, DG Environment, under the Grant LIFE/99/ENV/ D/000453. We thank the following local and regional authorities and their respective project leaders and co-workers for their valuable support: Landeshauptstadt Du¨sseldorf, Umweltamt (H.-W. Hentze, M. Wiese), Communaute´ urbaine de Lyon, Ecologie urbaine (O. Laurent), Comune di Verona, Servizio Ecologia (T. Basso, N. Belluzzo, S. Oliboni, S. Pisani, R. Tardiani), The City of Edinburgh Council, Air Quality Section (T. Stirling), Sheffield City Council, Environment & Regulatory Services (G. McGrogan, N. Chaplin), Landeshauptstadt Klagenfurt, Abt. Umweltschutz (H.-J. Gutsche), City of Copenhagen, EPA (J. Dahl Madsen), Generalitat de Catalunya, Dept. Medi Ambient, Barcelona (X. Guinart), Communaute´ Urbaine du Grand Nancy (F. Perrollaz), and Ayuntamiento de Valencia, Oficina Te`cnica de la Devesa-Albufera

7973

(A. Vizcaino, A. Quintana) as well as the municipalities of Ditzingen, Plochingen, Deizisau and Altbach (Germany). We acknowledge provision of data sets on ambient pollutant concentrations by the Institute for Physics and Meteorology of the University of Hohenheim, Landesanstalt fu¨r Umwelt, Messungen und Naturschutz (LUBW) Baden-Wu¨rttemberg, Landesumweltamt (LUA) Nordrhein-Westfalen, Landesregierung Ka¨rnten, DMA Generalitat de Catalunya, Airlor Nancy, Coparly Lyon, and EEA AirBase. Gratitude is also expressed to the staff of all institutions involved in the present studies, and to M. Stachowitsch for proof-reading the English manuscript.

References Buse, A., Mills, G., Hayes, F., Ashenden, T., and participants of the ICP Vegetation, 2002. Air pollution and vegetation. UNECE ICP Vegetation. Annual Report 2001/2002, CEH Bangor, UK, 55pp. Coyle, M., Smith, R.I., Stedman, J.R., Weston, K.J., Fowler, D., 2002. Quantifying the spatial distribution of surface ozone concentration in the UK. Atmospheric Environment 36, 1013–1024. De Leeuw, F., 2002. European air quality—past, present and future. In: Klumpp, A., Fomin, A., Klumpp, G., Ansel, W. (Eds.), Bioindication and Air Quality in European Cities— Research, Application, Communication. Heimbach, Stuttgart, pp. 19–28. Duen˜as, C., Ferna´ndez, M.C., Can˜ete, S., Carretero, J., Liger, E., 2002. Assessment of ozone variations and meteorological effects in an urban area in the Mediterranean Coast. The Science of the Total Environment 299, 97–113. European Environment Agency (EEA), 2001. Air pollution by ozone in Europe in summer 2001. Topic Report 13/2001, Copenhagen, 24pp. European Environment Agency (EEA), 2003. Europe’s environment: the third assessment. Environmental Assessment Report 10, Copenhagen, 343pp. European Union (EU), 1996. Council Directive 96/62/EC on ambient air quality assessment and management. Official Journal of the European Communities 21.11.1996, L296/ 55–63. European Union (EU), 2002. Directive 2002/3/EC of the European Parliament and of the Council relating to ozone in ambient air. Official Journal of the European Communities 9.3.2002, L67/14–30. Fenger, J., 1999. Urban air quality. Atmospheric Environment 33, 4877–4900. Gangoiti, G., Milla´n, M.M., Salvador, R., Mantilla, E., 2001. Long-range transport and re-circulation of pollutants in the western Mediterranean during the project Regional Cycles of Air Pollution in the West-Central Mediterranean Area. Atmospheric Environment 35, 6267–6276. Garland, J.A., Derwent, R.G., 1979. Destruction at the ground and the diurnal cycle of concentration of ozone and other

ARTICLE IN PRESS 7974

A. Klumpp et al. / Atmospheric Environment 40 (2006) 7963–7974

gases. Quarterly Journal of Royal Meteorology Society 105, 169–183. Gimeno, B.S., Pen˜uelas, J., Porcuna, J.L., Reinert, R.A., 1995. Biomonitoring ozone phytotoxicity in eastern Spain. Water, Air, and Soil Pollution 85, 1521–1526. Grennfelt, P., 2004. Recent research findings may change ozone control policies. Atmospheric Environment 38, 2215–2216. Ka¨renla¨mpi, L., Ska¨rby, L. (Eds.), 1996. Critical Levels for Ozone in Europe: Testing and Finalising the Concepts. UNECE Workshop Report. University of Kuopio, Kuopio, Finland. Karlsson, P.E., Uddling, J., Braun, S., Broadmeadow, M., Elvira, S., Gimeno, B.S., Le Thiec, D., Oksanen, E., Vandermeiren, K., Wilkinson, M., Emberson, L., 2004. New critical levels for ozone effects on young trees based on AOT40 and simulated cumulative leaf uptake of ozone. Atmospheric Environment 38, 2283–2294. Klumpp, A., Ansel, W., Klumpp, G., Belluzzo, N., Calatayud, V., Chaplin, N., Garrec, J.P., Gutsche, H.-J., Hayes, M., Hentze, H.-W., Kambezidis, H., Laurent, O., Pen˜uelas, J., Rasmussen, S., Ribas, A., Ro-Poulsen, H., Rossi, S., Sanz, M.J., Shang, H., Sifakis, N., Vergne, P., 2002. EuroBionet: a Pan-European biomonitoring network for urban air quality assessment. Environmental Science & Pollution Research 9, 199–203. Klumpp, A., Ansel, W., Klumpp, G., 2004. European network for the assessment of air quality by the use of bioindicator plants. Final Report, University of Hohenheim, Germany, 168pp. (download from /www.eurobionet.comS). Klumpp, A., Ansel, W., Klumpp, G., Calatayud, V., Garrec, J.P., Shang, H., Pen˜uelas, J., Ribas, A., Ro-Poulsen, H., Rasmussen, S., Sanz, M.J., Vergne, P., 2006a. Tradescantia micronucleus test indicates genotoxic potential of traffic emissions in European cities. Environmental Pollution 139, 515–522. Klumpp, A., Ansel, W., Klumpp, G., Vergne, P., Sifakis, N., Sanz, M.-J., Rasmussen, S., Ro-Poulsen, H., Ribas, A., Pen˜uelas, J., Kambezidis, H., Shang, H., Garrec, J.P., Calatayud, V., 2006b. Ozone pollution and ozone biomonitoring in European cities. Part II. Ozone-induced plant injury and its relationship with descriptors of ozone pollution. Atmospheric Environment, in press, doi:10.1016/j.atmosenv. 2006.07.001. Mantilla, E., Castell, N., Die´guez, J.J., Palau, J.L., 2002. Previozono 2001. Programa especial de vigilancia del ozono troposfe´rico en la Comunidad Valenciana. Fundacio´n CEAM, vol. 1, 121pp. Milla´n, M.M., Mantilla, E., Salvador, R., Carratala´, A., Sanz, M.J., Alonso, L., Gangoiti, G., Navazo, M., 2000. Ozone

cycles in the Western Mediterranean Basin: interpretation of monitoring data in complex coastal terrain. Journal of Applied Meteorology 39, 487–508. Milla´n, M.M., Sanz, M.J., Salvador, R., Mantilla, E., 2002. Atmospheric dynamics and ozone cycles related to nitrogen deposition in the western Mediterranean. Environmental Pollution 118, 167–186. Pihl Karlsson, G., Karlsson, P.E., Danielsson, H., Pleijel, H., 2003. Clover as a tool for bioindication of phytotoxic ozone— 5 years of experience from southern Sweden—consequences for the short-term critical levels. The Science of the Total Environment 301, 205–213. Prather, M., Gauss, M., Berntsen, T., Isaksen, I., Sundet, J., Bey, I., Brasseur, G., Dentener, F., Derwent, R., Stevenson, D., Grenfell, L., Hauglustaine, D., Horowitz, L., Jacob, D., Mickley, L., Lawrence, M., von Kuhlmann, R., Muller, J.-F., Pitari, G., Rogers, H., Johnson, M., Pyle, J., Law, K., van Weele, M., Wild, O., 2003. Fresh air in the 21st century? Geophysical Research Letters 30 (2), 1100, 72/ 1–72/4. Ribas, A., Pen˜uelas, J., 2003. Biomonitoring of tropospheric ozone phytotoxicity in rural Catalonia. Atmospheric Environment 37, 63–71. Ribas, A., Pen˜uelas, J., 2004. Temporal patterns of surface ozone levels in different habitats of the North Western Mediterranean basin. Atmospheric Environment 38, 985–992. Sanz, M.J., Calatayud, V., Sanchez-Pen˜a, G., 2004. Ozone concentrations measured by passive sampling at the Intensive Monitoring Plots of South Western Europe. In: Ferretti, M., Sanz, M.-J., Schaub, M. (Eds.), Ozone and the Forests of South-West Europe. Final Report, pp. 51–73. Tobı´ as, A., Scotto, M.G., 2005. Prediction of extreme ozone levels in Barcelona, Spain. Environmental Monitoring and Assessment 100, 23–32. Toll, I., Baldasano, J.M., 2000. Modeling of photochemical air pollution in the Barcelona area with highly disaggregated anthropogenic and biogenic emissions. Atmospheric Environment 34, 3069–3084. United Nations Economic Commission for Europe (UNECE), 2004. Mapping Manual. Mapping Critical Levels for Vegetation. UNECE ICP Vegetation, Bangor, UK, 53pp. (Chapter 3). World Health Organization (WHO), 2000. Air Quality Guidelines for Europe, second ed. WHO Regional Office for Europe, Copenhagen, WHO Regional Publications, European Series, No. 91, 288pp.