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Assessment of ambient air quality in Eskişehir, Turkey
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Environment International 34 (2008) 678 – 687 www.elsevier.com/locate/envint
Assessment of ambient air quality in Eskişehir, Turkey Ö. Özden, T. Döğeroğlu ⁎, S. Kara Environmental Engineering Department, Faculty of Engineering & Architecture, Anadolu University, İki Eylül Campus, 26555 Eskişehir, Turkey Available online 4 March 2008
Abstract This paper presents an assessment of air quality of the city Eskişehir, located 230 km southwest to the capital of Turkey. Only five of the major air pollutants, most studied worldwide and available for the region, were considered for the assessment. Available sulphur dioxide (SO2), particulate matter (PM), nitrogen dioxide (NO2), ozone (O3), and non-methane volatile organic carbons (NMVOCs) data from local emission inventory studies provided relative source contributions of the selected pollutants to the region. The contributions of these typical pollution parameters, selected for characterizing such an urban atmosphere, were compared with the data established for other cities in the nation and world countries. Additionally, regional ambient SO2 and PM concentrations, determined by semiautomatic monitoring at two sites, were gathered from the National Ambient Air Monitoring Network (NAAMN). Regional data for ambient NO2 (as a precursor of ozone as VOCs) and ozone concentrations, through the application of the passive sampling method, were provided by the still ongoing local air quality monitoring studies conducted at six different sites, as representatives of either the traffic-dense-, or coal/natural gas burning residential-, or industrial/rural-localities of the city. Passively sampled ozone data at a single rural site were also verified with the data from a continuous automatic ozone monitoring system located at that site. Effects of variations in seasonal-activities, newly established railway system, and switching to natural gas usage on the temporal changes of air quality were all considered for the assessment. Based on the comparisons with the national [AQCR (Air Quality Control Regulation). Ministry of Environment (MOE), Ankara. Official Newspaper 19269; 1986.] and a number of international [WHO (World Health Organization). Guidelines for Air Quality. Geneva; 2000. Downloaded in January 2006, website: http://www. who.int/peh/; EU (European Union). Council Directive 1999/30/EC relating to limit values for sulfur dioxide, nitrogen dioxide and lead in ambient air. Of J Eur Communities L 163: 14–30; 29.6.1999; EU (European Union). Council Directive 2002/3/EC relating to ozone in ambient air. Of J Eur Communities. L 67: 14–30; 9.3.2002.; USEPA (U.S. Environmental Protection Agency). National Ambient Air Quality Standards (NAAQS). Downloaded in January 2006, website: http://www.epa.gov/ttn/naaqs/] ambient air standards, among all the pollutants studied, only the annual average SO2 concentration was found to exceed one specific limit value (EU limit for protection of the ecosystem). A part of the data (VOC/NOx ratio), for determining the effects of photochemical interactions, indicated that VOC-limited regime was prevailing throughout the city. © 2007 Elsevier Ltd. All rights reserved. Keywords: Urban air quality; Emission inventory; Air pollutants (sulphur dioxide, particulate matter, nitrogen dioxide, ozone, volatile organic carbons); Active/ passive sampling; Continuous monitoring
1. Introduction Urban air pollution, with its long- and short-term impacts on human health, well-being and the environment, has been a widely recognized problem during the last 50 years. Besides deleterious effects on human health, pollution causes serious negative effects on ecosystems (leading to injury to plants and reduction in crop yields), materials and the visibility (Fenger, 1999; Riga-Karandinos, 2005). ⁎ Corresponding author. Tel.: +90 222 321 35 50x6305; fax: +90 222 323 95 01. E-mail address: [email protected] (T. Döğeroğlu). 0160-4120/$ - see front matter © 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.envint.2007.12.016
In order to protect the atmosphere, governments promote policies and programmes in the areas of energy, environmentally sound and efficient transportation, industrial pollution control and management of toxic and other hazardous wastes. Many countries and different international organizations such as EPA (Environmental Protection Agency), WHO (World Health Organization), the European Union Air Quality Framework and Daughter Directives, World Bank, etc. published their own standards for this purpose (Lim et al., 2005). Monitoring studies are also of particular importance in this respect in order to improve air quality management efforts, detect long-term air quality trends, and observe the effectiveness of air quality control regulations. If the ambient air quality is unlikely to meet
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existing air quality standards, local authorities are required to devise, test and implement pollution control policies. In developed countries where more than 75% of all people now live in cities, their economical strength allows for effective pollution prevention and control against the pollutants impacts. Pollution prevention and control concepts in developing countries are also gaining increasing importance under stricter regulations, particularly in recent years (Fang and Chen, 1996; O'Malley, 1999; Bailey and Solomon, 2004; Mao et al., 2005), and there has been a growing concern about urban air quality in terms of the pollutants impacts (Wolf, 2002; Agrawal et al., 2003; Vargas, 2003; Brajer et al., 2006; Oudinet et al., 2006). However, air pollution in many urban areas of the developing countries is still a serious environmental problem, and many cities in the world are exposed to high levels of air pollution. There are many reasons of such local negative changes in the air quality in developing countries. Rapidly increasing population in those countries leads to unplanned urbanization and industrialization without taking the natural characteristics (such as meteorological and topographical conditions) of the region into account. Although, currently, only about 35% of the people live in cities in the developing countries, this ratio corresponds to twice as many people living in urban areas as 50 years ago (Baldasano et al., 2003). Rapid increase in population generally goes together with the increase in a variety of stationary and mobile facilities and products to supply for the increasing human needs and demands for energy, material and comfort, and hence with the increased resource consumption, including deforestation. Such broad range of sources as road traffic, mining, space-heating, industry, power plants, commercial activities, trade centres and many others, inevitably cause increased emissions of air pollutants in the urban areas. It is not easy, for the developing countries, to prevent and control these emissions under stricter international standards and regulations with limited economies. Air pollutants, once emerged from a variety of sources, are subject to mixing, dispersion, transport and complex series of chemical interaction and physical transformation processes in urban atmospheres. For example, atmospheric reactions between emitted nitrogen oxides (NOx = NO + NO2) and volatile organic compounds (VOCs) result in the formation of ground level ozone (Fenger, 1999). These primary and secondary pollutants, when combined with emitted sulphur compounds (including sulphur dioxide (SO2) and reduced sulphur compounds), may also lead to acid deposition and the formation of secondary particulate matter in urban atmospheres (Atkinson, 2000). Of the main air quality indicators, SO2 maintains, globally, a downward trend with the exception of some Central American and Asian cities (Fenger, 1999; Streets et al., 2000; Baldasano et al., 2003). Although nitrogen dioxide (NO2) generally maintains levels very close to those of WHO, the levels are approximately three times higher than the value of WHO guideline in some cities such as Kiev, Beijing and Guangzhou (Oduyemi and Davidson, 1998; Fenger, 1999; Baldasano et al., 2003; Han and Naeher, 2006). Particulate matter (PM) is still a major problem in almost all Asian countries with concentrations exceeding
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300 μg/m3 in many cities (Fenger, 1999; Baldasano et al., 2003; Han and Naeher, 2006). Average concentrations of ground level ozone (O3) are above the limits of WHO, EU and USEPA guidelines demonstrating that it is a global problem (Fenger, 1999; Guicherit and Roemer, 2000; Baldasano et al., 2003; Vingarzan, 2004). As is the case in many other developing countries, the most important contributions to air pollution in the Turkish cities originate from incorrect urbanization and industrialization. In addition to the topography of the site and the meteorological conditions, the quality of the air is influenced by usage of lowquality fossil fuels and improper combustion techniques, a shortage of green areas, and the increase in the number of motor vehicles and traffic load (Döğeroğlu, 2002). The Ministry of Environment and Forestry (MOEF) and the Ministry of Health (MOH) are the two main government sectors in Turkey responsible for the decision-making related to protection of the atmosphere and for transboundary atmospheric pollution control, respectively. Currently available historical information and data on the national air quality in Turkey is either limited to only a few pollutants or is not spatially and/or temporally representative of the current situation due to rapid growth of the urban areas. Currently, only the SO2 and PM parameters, monitored under the guidance of the MOH at multiple points in many cities, and the data are available from the Turkish National Ambient Air Monitoring Network (NAAMN) databank (TURKSTAT, 2006). Other pollutants, including NOx and O3, could have been monitored at only a limited number of points by, particularly, the universities, research institutes and the TUBITAK (Turkish Scientific & Technical Research Council). Existing ambient air quality statistics in Turkey, based on the average annual SO2 and PM levels supplied by the NAAMN, indicate that urban air quality in, particularly, those cities where low-quality coal is heavily used for heating activities and in the industry is quite poor. Although the annual concentrations (as high as 100 μg/m3) of SO2 and PM in those cities are below the national limits of the Air Quality Control Regulation (AQCR, 1986), they exceed the limit values of the WHO and EU (European Union) standards. Presently, air quality limits of this legislation, which suggests detailed technological alternatives for limiting the emissions from a large number of industrial activities and combustion systems, are subject to radical revisions by the MOEF for making it compatible with the EC directives. Although these revisions appear to provide stricter pollution limits for short- and long-term averages of SO2, PM10, NO2, NMVOC and CO (carbon monoxide), the proposed limits for SO2 and PM are still above those of WHO guideline (1996 version) and EC directives (Elbir et al., 2000). Emitted amounts of PM, NO2, VOC and CO originating from the city-traffic are not less important than the emissions from other sources such as residential heating systems and industrial activities. As in the most of the developing countries (Oduyem and Davidson, 1998; Mayer, 1999), the road traffic in Turkey appears to be the most important source group contributing to air pollution especially in city centres. In these central locations large traffic volumes and congestion commonly result in
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Fig. 1. Study area and sampling sites.
significant degradation of the air quality as a function of the rate of increase in population and urbanization. Thus, the particular aim of this study has been to assess the air quality of the rapidly urbanizing mid-northwestern Turkish city, Eskişehir. For this purpose, available SO2, PM, NO2 and VOC data from local emission inventories were combined with the national (for SO2, PM since 1986) and local (for NO2 and O3 since 2004) monitoring studies, all specific to Eskişehir. The emission inventory study was conducted by Çınar (2003) for Eskişehir for the year 2002, and its data were generated based on the emission factors of EPA (2003) and CORINAIR (EEA, 2003) for SO2, PM, CO, NOx and VOCs. Emission inventory and monitoring studies for VOC species for the city were also con-
ducted, discontinuously, for the years 2002 and 2003 (Döğeroğlu, 2003). NO2 and O3 measurements have been carried out continuously at different sites of the city since January 2004 by use of passive samplers (Özden, 2005). Passive sampling (Cadoff and Hodgeson, 1983; De Santis et al., 1997) is proved to be a methodology to fulfil the need of adopting inexpensive, simple and reliable methods for wide-spread air quality monitoring, simultaneously, at multiple points over large areas in Turkey. In addition to a set of NO2 measurements (based on the Saltzman method) during 1989–1993 (Kara, 1993), some discontinuous NO2 (Çokgürses, 2003), ozone (Canbaz, 2003) and BTX (Yurtsever, 2003) monitoring studies were also conducted during 2003 at two campuses of Anadolu University. Aside from the emission
Fig. 2. Source distribution of the air pollutants for Eskişehir.
Ö. Özden et al. / Environment International 34 (2008) 678–687 Table 1 Per capita emission rates of SO2 and NOx for different national and international cities Emission rate per capita (kg/capita-year)
Eskişehir Ankara (Turkey) İzmir (Turkey) Manisa (Turkey) Denizli (Turkey) Uşak (Turkey) Nuremberg (Germany) Helsinki (Finland) Rotterdam (Holland) Stockholm (Sweeden)
Population
SO2
NO x
504,724 2,977,546 2,250,149 214,435 273,515 136,879 500,000 491,000 582,000 667,000
4.89 4.08 54.15 811.90 12.79 90.87 8.2 44.6 81.8 3.6
6.02 2.82 5.32 99.77 2.46 21.43 22.4 72.7 66.2 16.2
inventory and monitoring activities in Eskişehir, a study on modelbased estimation of the dispersion of surface ozone was also carried out for the city by taking relevant meteorological parameters into account (Yay, 2006). 2. The study area and sampling sites Eskişehir, as a rapidly developing intermediate size city with a population of approximately 500,000 inhabitants, is located to the Northwest of the Central Anatolia in Turkey. Its topographical structure consists of plains, in general. A harsh terrestrial climate is dominant in the city. The weather is continually hard and cold in winter. Significant differences are observed between day-time and night-time temperatures (hot during the days but cool during the nights) in summer. Prevailing east-to-west wind direction in winter switches to northwest-to-northeast direction at the beginning of spring season. Towards the end of spring season, wind directions from southwest, west and northwest are dominant. In 1994, the community of Eskişehir started consuming natural gas in their fuel-mixes mostly for industrial utilization. Since then, mainly the residential heating activities and the traffic have been the subjects of complains about the pollution in the city. Residential heating by the natural gas started in 1996. With the gradual increase in its annual supply capacity, 50% of the population in
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the city now has become natural gas users. To combat with the congestion problems originating from motor vehicles and road traffic in Eskişehir, a railway system had been constructed couple of years ago as a partial replacement for public transportation. Çınar's (2003) emission inventory study shed light to determining proper locations of representative monitoring sites of this study. Fig. 1 shows the sampling sites selected in the study area. Among the air pollutants investigated in this study, SO2 and PM have been monitored simultaneously at, both, Site 1 and Site 2, since 1986. These MOH data are available from the Turkish NAAMN (TURKSTAT, 2006). Site 1 at the city centre is representative of a high traffic density region consuming natural gas for heating. Site 2, located in a residential area with low traffic density, represents a region consuming coal for heating. The lack of NO2 and ozone data within the monitoring network necessitated the use of passive sampling method for monitoring and determining the spatial and temporal distributions of both NO2 (since January 2004) and ozone (since November 2004). The pollutant NO2, as one of the main precursors for the ozone formation through photochemical reactions (Sillman, 1999; Atkinson, 2000), is known to mostly originate from the traffic. Therefore, a total of six sites (Site 3–Site 8) were selected in a way to collect ambient data for different levels of traffic density, in accordance with the results of the emission inventory study (Çınar, 2003). Sites 3–6 were the locations where high exposure to heavy traffic emissions was of concern. Daily vehicle numbers reported by Çınar (2003), as the representatives of the traffic densities in those sites, range between 20,500 for Site 1 and Site 4 and 5250 for Site 6. Site 7 characterized a suburban residential area south to the city. Site 8 can be defined as a rural area at the northern part of the city and is located nearly 8 km away from the city centre. 3. Data and methods The SO2 and PM data, corresponding to the period from 1986 to 2006, were gathered from the Turkish NAAMN (TURKSTAT, 2006). NO2 and ozone concentrations were obtained by collecting weekly average data at the six sampling sites of the city by use of passive samplers. These samplers, developed by the authors (Özden et al., 2005a,b) were the modified versions of the opentube design (Palmes and Gunnison, 1973; Palmes et al., 1976) and Analyst
Fig. 3. SO2 and PM trends in Eskişehir for the period 1986–2005.
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Fig. 4. Monthly average PM and SO2 concentrations in 2005.
Fig. 5. Monthly average NO2 concentrations at six sampling sites for the period 2004–2005.
(Bertoni et al., 2000; De Santis et al., 2002) type passive samplers. Collected samples (between the years from 2004 to 2006) were analyzed by using spectrophotometric method for NO2 and ion chromatographic method for ozone. Also, an automatic ozone analyzer was available at one of the sampling sites
(Site 8) to monitor hourly changes in the ozone concentrations continuously, to deduce diurnal, daily and seasonal variations. Relative contributions of the pollutants studied were evaluated based on the data of Çınar's (2003) emission inventory study. Average monthly, annual and
Fig. 6. Monthly average ozone concentrations at six sampling sites for the period 2004–2005.
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Fig. 7. Spatial variations of average NO2 and ozone concentrations in the city for the year 2005.
seasonal concentration variations of the studied pollutants were compared with the national air quality limits of AQCR (1986) as well as those of WHO (2000), EU (1999, 2002) and USEPA (2006).
4. Results and discussion Fig. 2 presents source contributions of the studied pollutants for the city based on the total annual emissions of SO2 (2467 ton), PM (881 ton), NOx (3131 ton) and VOCs (405 ton) for 2002 (Çınar, 2003). The results of the emission inventory study indicate that, the respective contributions of domestic heating to SO2 and PM pollution are 70% and 84%. Traffic is responsible for 60% of the total NOx emissions. Industrial contribution appears to be less important for the air pollution in Eskişehir. Table 1 provides a comparison of the SO2 and NOx data (emission rates per capita) for Eskişehir against those available for some other national and world cities (Çınar, 2003). The rates for Eskişehir are generally lower than the rates for other national and international cities compared. The particular similarity of the SO2 data for Eskişehir and Ankara may be attributed to the similarity of the large contributions of residential heating sources as well as that of climatic and topographical natures of both cities. Lower NOx value for Ankara may be explained by the heavier use of more efficient subway public transportation and smaller contribution of industry there relative to those in Eskişehir. The significant differences between the SO2 and NOx data for Eskişehir and for more industrialized western Turkish cities (such as İzmir, Manisa, Denizli, Uşak) and the world cities with nearly similar populations may be associated mostly with the differences in climatic and topographical conditions, and the ways the industry, transportation and residential heating contribute. Fig. 3 shows the temporal trends of the PM and SO2 concentrations during the period from 1986 to 2005. A sharp decline of the SO2 concentrations from 200 μg/m3 to below 50 μg/m3 after 1996 is noticeable.
Monthly variations in SO2 and PM concentrations, as presented in Fig. 4 for the year 2005, exhibit higher values in winter season due to domestic heating activities. The variations in the monthly average concentrations of NO2 and ozone at six sampling sites are indicated respectively in Figs. 5 and 6, for the years 2004 and 2005. Higher NO2 levels in Site 3–Site 6 during winter seasons may be related to higher traffic density and the formation of a temperature-inversion layer. Lower NO2 levels in summer may be due to its destruction by photochemical reactions. Higher ozone concentrations during summer season may be attributed to its formation in the presence of precursors and sunlight. In contrast to its higher levels at sites remote from the city centre, lower ozone concentrations were observed at the city centre. Depletion of the ozone by NO2 may have been the cause of the low ozone values in the central areas having high traffic densities. About 45% decrease during the period from the end of 2004 to the end of 2005 was recorded in NO2 concentrations at the traffic-dense central part of the city after the railway system was constructed for public transportation at the end of 2004. Average NO2 and ozone concentrations for each sampling site for the year 2005 are depicted in Fig. 7. This figure facilitates the observation of spatial distribution of these two related pollutants over the city. Table 2 Annual and seasonal averages of SO2, PM, NO2 and ozone concentrations for the year 2005 Pollutant
SO2 PM NO2 Ozone
Annual (μg/m3)
Seasonal (μg/m3)
Mean
Winter
Summer
47.13 ± 11.30 30.45 ± 10.73 22.57 ± 16.99 46.08 ± 23.62
56.79 ± 8.14 39.33 ± 7.71 29.45 ± 20.15 37.91 ± 21.60
37.47 ± 4.02 21.56 ± 1.87 15.69 ± 9.20 54.26 ± 22.96
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Fig. 8. Typical example for the relationship between NO2 and ozone for Site 5.
Fig. 9. Nonlinear and reverse relationship between atmospheric NO2 and ozone concentrations.
Average annual and seasonal concentrations of SO2, PM, NO2 and ozone are given in Table 2, for the year 2005. When the tabled values are compared with the data of other metropolitan cities in Turkey, SO2 levels in Eskişehir appear slightly higher than those in Ankara (30 μg/m3) and İzmir (38 μg/m3) (DRSCH, 2006). Much lower PM levels relative to those in Ankara (50 μg/m3) are nearly twice as high as of İzmir (15 μg/ m3) (DRSCH, 2006). Average NO2 concentrations in Eskişehir are lower than the annual data of Ankara (around 40 μg/m3) (MPAP, 2004) and the
monthly data of İstanbul (60–80 μg/m3) (Topçu et al., 2003). Lower winter season ozone data (20 μg/m3) of Ankara (MPAP, 2004) support the findings about the relationship between NO2 and ozone. The ratio of the atmospheric levels of NOx and VOCs, known to be the main precursors for the ozone formation (Sillman, 1999; Atkinson, 2000), is important for the understanding of the ozone formation process and its reduction methodology. Low VOC/NOx ratios in urban atmospheres correspond to VOC-limited chemistry (Sillman, 1999; Yay, 2006) in which any change in VOC levels will cause important changes in ozone levels. This ratio (about 0.13) of emissions for Eskişehir indicates that VOC-limited regime is prevailing in the city and, thus, ozone levels decrease with decreasing VOC and increasing NOx levels (Sillman, 1999). Fig. 8 shows a typical opposing relationship between NO2 and ozone concentrations recorded at one of the traffic-dense sites (Site 5) in the city. Corresponding behaviors of these two pollutants at the suburban (Site 7) and rural (Site 8) sites are not much different than that at Site 5. In fact, ozone formation is a highly nonlinear process regarding its interactions with NOx and VOC components. Fig. 9, which indicates the nonlinear and reverse relationship between NO2 and ozone concentrations in a different way is also confirmed by the studies conducted by Sillman (1999), Topçu et al. (2003) and Yay (2006). According to the Sillman's (1999) kinetics study, the changes in ozone formation rates are dependent on NOx levels. From Fig. 9, one can state that the slope of the curve is steeper at high NO2 concentrations, and
Fig. 10. Change in hourly ozone concentrations during the days 01.01.2005 and 13.06.2005.
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Fig. 11. Daily maximum ozone concentrations at the beginning of an ozone season (April 2005).
this steepness may be interpreted as higher ozone generation rates at higher NO2 concentrations. Fig. 10 illustrates typical trend of hourly changes in ozone values during two different days, one in winter (January) and the other in summer (June). The effects of sunlight, temperature, and other meteorological conditions may be responsible for the higher hourly values for the day in June, as compared to those in January. Of the two summer peaks, morning peaks (extend to noon hours) are observed when the weather is calm or northeast wind direction is dominant, and afternoon peaks correspond to northwest–west wind direction. As may be deduced from this information, local effects are dominating during morning hours, and transport of ozone to the region by the winds in northwest–west direction is of concern in the afternoon. As depicted in Fig. 11, maximum daily ozone concentrations varied between 96–140 μg/m3 during the start of an ozone season (April 2005), and increased up to a value of 155 μg/m3 in June. Much higher levels are observed during summer seasons. As may be observed from Table 3, measured concentrations of the majority of the pollutants studied in this work do not exceed the limits of the national AQCR and of the international regulations, considered for comparisons. Only the annual average SO2 concentration seems to exceed the limit of one international regulatory limit (the EU limit set for the protection of ecosystem).
5. Conclusion Local monitoring results, combined with the emission inventory data, provided suitable selection of the sites and, thus, the assessment of the quality of air prevailing in the urban Eskişehir. Apparently, domestic heating (for SO2 and PM) and traffic (for NOx and VOC), rather than the industry, are responsible for the pollution in the city. Regarding seasonal contributions, prevailing higher SO2 and PM concentrations in winter point out to the sites where coal is used heavily for heating. High winter season NO2 concentrations may be associated with those sites characterized by high traffic densities. Higher ozone concentrations in remote areas during summer season may be related to the complex photochemical reactions. As compared to the data of some cities in Turkey and in the world having similar populations, the air quality in Eskişehir may be considered moderate, and the differences in rates of pollutant emissions may be caused by the differences in their climatic and topographical conditions. Under the influence of the national as well as some international legislations, and implementations, air pollution in
Table 3 Comparison of SO2, PM, NO2 and ozone data (in the units of μg/m3 for the year 2005) with the national and international limits Pollutant
Monitored data from this work
Turkish limits Daily
Annual
SO2
47 a
400
150
PM10
31 b
300
150
NO2
23 c
300
100
Ozone
165 e
240 (1 h)
–
a,b c d e
Annual average measured at two sampling sites. Annual average measured at six sampling sites. Limit set for the protection of ecosystem. Maximum hourly ozone concentration measured in July at Site 8.
WHO guidelines
EU regulations
USEPA regulations
500 (1 h) 125 (24 h) 50 (annual) –
350 (1 h) 25 (24 h) 20 d (annual) 50 (24 h) 40 (annual) 200 (1 h) 30 d (annual) 180 (1 h) 120 (8 h)
1300 (3 h) 365 (24 h) 80 (annual) 150 (24 h) 50 (annual) 100 (annual) 30 d (annual) 235 (1 h) 157 (8 h)
200 (1 h) 40 (annual) 120 (8 h)
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Eskişehir has decreased significantly, particularly during the last 10 years. The use of natural gas for industry (since 1994) and for residential heating (since 1996) has been effective in the significant decrease (75%) in SO2 levels. Partly switching to public transportation by the railway system at the end of 2004, played an important role in the decrease in NO2 concentrations (45%) within, particularly, the central part of the city. The resulting data of this study and the methodology applied are expected to be useful not only for the future air pollution control applications in other urban areas, but also for the improvement of monitoring and evaluation systems, building air quality management strategies, and preparation of new clean air plans. Apparently, there is a need for expanding the existing national network, for monitoring additional air pollutants other than SO2 and PM; and such an expansion requires large investments and additional operational expenses for a developing country. Hence, an urgent action of adopting inexpensive, simple and reliable methods for wide-spread air quality monitoring, simultaneously, at multiple points over large areas is needed for Turkey. Passive sampling is proved to be one such methodology to fulfil this need in applications, as demonstrated by the authors of this study for Eskişehir. Certainly, the information on meteorological conditions has very important impacts, providing greater insight into the daily variations in air quality and the effects of past air quality management decisions. It allows for more effective decisions towards improving future air quality. Although some of the meteorological parameters (such as solar radiation, specific humidity, temperature, wind speed and wind direction, as monitored continuously in the study area) were monitored and found highly correlated with the pollutant concentrations determined, the results have not yet been published. Acknowledgements This work presents a part of the results from two research projects funded by Anadolu University. One of these projects (numbered 020237) is entitled “Use of Passive Sampling Method for the Determination of NOx and Ozone Pollution in Eskişehir and Preparation of Pollution Maps” and the other (numbered 030251) “Monitoring of Local Air Quality by Use of Passive Samplers”. References Agrawal M, Singh B, Rajput M, Marshall F, Bell JNB. Effect of air pollution on peri-urban agriculture: a case study. Environ Pollut 2003;126:323–9. AQCR (Air Quality Control Regulation). Ministry of Environment (MOE), vol. 19269. Ankara: Official Newspaper; 1986). Atkinson R. Atmospheric chemistry of VOCs and NOx. Atmos Environ 2000;34:2063–101. Bailey D, Solomon G. Pollution prevention at ports: clearing the air. Environ. Impact. Asses. Rev 2004;24:749–74. Baldasano JM, Valera E, Jimenez P. Air quality data from large cities. Sci Total Environ 2003;307:141–65. Bertoni G, Tappa R, Allegrini I. Assessment of a new device for the monitoring of benzene and other volatile aromatic compounds in the atmosphere. Annali di Chim. 2000;90:249–63.
Brajer V, Mead RW, Xiao F. Valuing the health impacts of air pollution in Hong Kong. J Asian Econ 2006;17:85–102. Cadoff BC, Hodgeson J. Passive sampler for ambient levels of nitrogen dioxide. Anal Chem 1983;55:2083–5. Canbaz S. B. Sc. Thesis: Monitoring of Tropospheric Ozone in Eskişehir and Evaluation of the Results. AnadoluUniversity, Faculty of Engineering&Architecture, Department of Environmental Engineering; Eskişehir, Turkey; 2003. Çınar H. Master of Science Thesis: Preparation of Emission Inventories and GIS-Supported Mapping of Air Pollution in Eskişehir. Anadolu University, Graduate School of Natural and Applied Sciences, Environmental Engineering Program; Eskişehir, Turkey; 2003. Çokgürses E.S. B.Sc. Thesis: Ambient Air Nitrogen Oxides Measurements and Their Assessment. Anadolu University, Faculty of Engineering&Architecture, Department of Environmental Engineering; Eskişehir, Turkey; 2003. De Santis F, Allegrini I, Fazio MC, Pasella D, Piredda R. Development of a passive sampling technique for the determination of nitrogen dioxide and sulphur dioxide in ambient air. Anal Chim Acta 1997;346:127–34. De Santis F, Dogeroglu T, Fino A, Menichelli S, Vazzana C, Allegrini I. Laboratory development and field evaluation of a new diffusive sampler to collect nitrogen oxides in the ambient air. Anal. Bioanal. Chem. 2002;373:901–7. Döğeroğlu T. Air pollution in Turkey. Global atmospheric change and its impact on regional air quality; 2002. p. 183–8. Döğeroğlu T. (Project leader). Ambient air volatile organic carbons (VOCs) measurements and prediction of the VOC emission potentials in Eskişehir. Scientific Research Project Report. No: 000213. Anadolu University, Environmental Engineering Department, Eskişehir, Turkey; 2003. DRSCH (Directory of Refik Saydam Center of Hygiene). Research Directorate of Environmental Health. Data downloaded in January; 2006). website: www.rshm.saglik.gov.tr. EEA (European Environmental Agency). EMEP/CORINAIR Atmospheric Emission Inventory Guide Book3rd Edition. ; 2003). Data downloaded in May http://reports.eea.eu.int/EMEPCORINAIR3/en/tab_content_RLR. Elbir T, Müezzinoğlu A, Bayram A. Evaluation of some air pollution indicators in Turkey. Environ Int 2000;26:5–10. EPA (Environmental Protection Agency). Compilation of air pollution emission factors; AP-42. Fifth Edition; Volume 1; 2003). Data downloaded in May website: http://www.epa.gov/ttn/chief/ap42/ch01. EU (European Union). Council Directive 1999/30/EC relating to limit values for sulfur dioxide, nitrogen dioxide and lead in ambient air. Of J Eur Communities 29.6.1999;L 163:14–30. EU (European Union). Council Directive 2002/3/EC relating to ozone in ambient air. Of J Eur Communities 9.3.2002;L 67:14–30. Fang S-H, Chen H-W. Air quality and pollution control in Taiwan. Atmos Environ 1996;30-5:735–41. Fenger J. Urban air quality. Atmos Environ 1999;33:4877–900. Guicherit R, Roemer M. Tropospheric ozone trends. Chemosphere-Glob Chang Sci 2000;2:167–83. Han X, Naeher LP. A review of traffic-related air pollution exposure assessment studies in the developing world. Environ Int 2006;32:106–20. Kara S. (Project leader). Investigation, review, modelling and evaluation of some quantitative and qualitative site-specific air quality indicators for determining the guiding-researches towards taking regional precautions. Research Fund Project Report. Anadolu University, Chemical Engineering Department, Eskişehir, Turkey; 1993. Lim LL, Hughes SJ, Hellawell EE. Integrated decision support system for urban air quality assessment. Environ Model Softw 2005;20:947–54. Mao X, Guo X, Chang Y, Peng Y. Improving air quality in large cities by substituting natural gas for coal in China: changing idea and incentive policy implications. Energy Policy 2005;33:307–18. Mayer H. Air pollution in cities. Atmos Environ 1999;33:4029–37. Oduyemi KOK, Davidson B. The impacts of road traffic management on urban air quality. Sci Total Environ 1998;218:59–66. O'Malley V. The integrated pollution prevention and control IPPC directive and its implications for the environment and industrial activities in Europe. Sens Actuators B 1999;59:78–82.
Ö. Özden et al. / Environment International 34 (2008) 678–687 Oudinet J-P, Méline J, Chelmicki W, Sanak M, Magdalena D-W, Besancenot J-P, et al. Towards a multidisciplinary and integrated strategy in the assessment of adverse health effects related to air pollution: the case study of Cracow (Poland) and asthma. Environ Pollut 2006;143:278–84. Özden Ö. Master of Science Thesis: Monitoring of Air Quality by Use of Passive Samplers. Anadolu University, Graduate School of Natural and Applied Sciences, Environmental Engineering Program; Eskişehir, Turkey; 2005. Özden Ö, Döğeroğlu T, Kara S. Determination of tropospheric ozone in Eskisehir by use of passive samplers. 1st International Conference on Air Pollution and Combustion. Ankara, Turkey; 2005a. Özden Ö, Döğeroğlu T, Kara S. Development of a new passive sampler for NO2 and field evaluation in the urban area of Eskisehir, Turkey. 9th International Conference on Environmental Science and Technology. Rhodos Island, Greece; 2005b. Palmes ED, Gunnison AF. Personal monitoring device for gaseous contaminants. Am Ind Hyg Assoc J 1973;34:78–81. Palmes ED, Gunnison AF, Di Mattio AF, Tomczyk C. Personal sampler for nitrogen dioxide, J. Am. Ind. Hyg. Assoc. 1976;37:570–7. Primair, Royal Haskoning, SRK. Preliminary Assessment of Ambient Air Quality for the Ankara Metropolitan Area. Matra Pre-accession Projects Program (MPAP); 2004. Riga-Karandinos AN, Saitanis C. Comparative assessment of ambient air quality in two typical Mediterranean coastal cities in Greece. Chemosphere 2005;59:1125–36. Sillman S. The relation between ozone, NOx and hydrocarbons in urban and polluted environments. Atmos Environ 1999;33:1821–45.
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Streets DG, Tsai NY, Akimoto H, Oka K. Sulfur dioxide emissions in Asia in the period 1985–1997. Atmos Environ 2000;34:4413–24. Topçu S, Kahya C, Demirhan D, İncecik S. The variations of surface ozone levels in ozone seasons in İstanbul (1998–2002). VI. National Symposium on Combustion and Air Pollution Control. İzmir, Turkey; 2003. TURKSTAT (Republic of Turkey, Prime Ministry Turkish Statistical Institute). Data downloaded in November; 2006. website: http://www.turkstat.gov.tr. USEPA (U.S. Environmental Protection Agency). National Ambient Air Quality Standards (NAAQS); 2006. Downloaded in January 2006, website: http:// www.epa.gov/ttn/naaqs/. WHO (World Health Organization). Guidelines for air quality. Geneva; 2000). Downloaded in January 2006, website: http://www.who.int/peh/. Wolf C. Urban air pollution and health: an ecological study of chronic rhinosinusitis in Cologne, Germany. Health & Place 2002;8:129–39. Vargas VMF. Mutagenic activity as a parameter to assess ambient air quality for protection of the environment and human health. Mutation Res 2003;544:313–9. Vingarzan V. A review of surface ozone background levels and trends. Atmos Environ 2004;38:3431–42. Yay O.D. PhD Dissertation: Estimation of the Dispersion of Surface Ozone at and Around Eskisehir with the Use of MM5-CAMx Models. Anadolu University, Graduate School of Natural and Applied Sciences, Environmental Engineering Program; Eskişehir, Turkey; 2006. Yurtsever D. B.Sc. Thesis: Measurement and Assessment of Volatile Organic Compounds (VOCs) in the Ambient Air. Anadolu University, Faculty of Engineering&Architecture, Department of Environmental Engineering; Eskişehir, Turkey; 2003.
Environment International 34 (2008) 678 – 687 www.elsevier.com/locate/envint
Assessment of ambient air quality in Eskişehir, Turkey Ö. Özden, T. Döğeroğlu ⁎, S. Kara Environmental Engineering Department, Faculty of Engineering & Architecture, Anadolu University, İki Eylül Campus, 26555 Eskişehir, Turkey Available online 4 March 2008
Abstract This paper presents an assessment of air quality of the city Eskişehir, located 230 km southwest to the capital of Turkey. Only five of the major air pollutants, most studied worldwide and available for the region, were considered for the assessment. Available sulphur dioxide (SO2), particulate matter (PM), nitrogen dioxide (NO2), ozone (O3), and non-methane volatile organic carbons (NMVOCs) data from local emission inventory studies provided relative source contributions of the selected pollutants to the region. The contributions of these typical pollution parameters, selected for characterizing such an urban atmosphere, were compared with the data established for other cities in the nation and world countries. Additionally, regional ambient SO2 and PM concentrations, determined by semiautomatic monitoring at two sites, were gathered from the National Ambient Air Monitoring Network (NAAMN). Regional data for ambient NO2 (as a precursor of ozone as VOCs) and ozone concentrations, through the application of the passive sampling method, were provided by the still ongoing local air quality monitoring studies conducted at six different sites, as representatives of either the traffic-dense-, or coal/natural gas burning residential-, or industrial/rural-localities of the city. Passively sampled ozone data at a single rural site were also verified with the data from a continuous automatic ozone monitoring system located at that site. Effects of variations in seasonal-activities, newly established railway system, and switching to natural gas usage on the temporal changes of air quality were all considered for the assessment. Based on the comparisons with the national [AQCR (Air Quality Control Regulation). Ministry of Environment (MOE), Ankara. Official Newspaper 19269; 1986.] and a number of international [WHO (World Health Organization). Guidelines for Air Quality. Geneva; 2000. Downloaded in January 2006, website: http://www. who.int/peh/; EU (European Union). Council Directive 1999/30/EC relating to limit values for sulfur dioxide, nitrogen dioxide and lead in ambient air. Of J Eur Communities L 163: 14–30; 29.6.1999; EU (European Union). Council Directive 2002/3/EC relating to ozone in ambient air. Of J Eur Communities. L 67: 14–30; 9.3.2002.; USEPA (U.S. Environmental Protection Agency). National Ambient Air Quality Standards (NAAQS). Downloaded in January 2006, website: http://www.epa.gov/ttn/naaqs/] ambient air standards, among all the pollutants studied, only the annual average SO2 concentration was found to exceed one specific limit value (EU limit for protection of the ecosystem). A part of the data (VOC/NOx ratio), for determining the effects of photochemical interactions, indicated that VOC-limited regime was prevailing throughout the city. © 2007 Elsevier Ltd. All rights reserved. Keywords: Urban air quality; Emission inventory; Air pollutants (sulphur dioxide, particulate matter, nitrogen dioxide, ozone, volatile organic carbons); Active/ passive sampling; Continuous monitoring
1. Introduction Urban air pollution, with its long- and short-term impacts on human health, well-being and the environment, has been a widely recognized problem during the last 50 years. Besides deleterious effects on human health, pollution causes serious negative effects on ecosystems (leading to injury to plants and reduction in crop yields), materials and the visibility (Fenger, 1999; Riga-Karandinos, 2005). ⁎ Corresponding author. Tel.: +90 222 321 35 50x6305; fax: +90 222 323 95 01. E-mail address: [email protected] (T. Döğeroğlu). 0160-4120/$ - see front matter © 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.envint.2007.12.016
In order to protect the atmosphere, governments promote policies and programmes in the areas of energy, environmentally sound and efficient transportation, industrial pollution control and management of toxic and other hazardous wastes. Many countries and different international organizations such as EPA (Environmental Protection Agency), WHO (World Health Organization), the European Union Air Quality Framework and Daughter Directives, World Bank, etc. published their own standards for this purpose (Lim et al., 2005). Monitoring studies are also of particular importance in this respect in order to improve air quality management efforts, detect long-term air quality trends, and observe the effectiveness of air quality control regulations. If the ambient air quality is unlikely to meet
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existing air quality standards, local authorities are required to devise, test and implement pollution control policies. In developed countries where more than 75% of all people now live in cities, their economical strength allows for effective pollution prevention and control against the pollutants impacts. Pollution prevention and control concepts in developing countries are also gaining increasing importance under stricter regulations, particularly in recent years (Fang and Chen, 1996; O'Malley, 1999; Bailey and Solomon, 2004; Mao et al., 2005), and there has been a growing concern about urban air quality in terms of the pollutants impacts (Wolf, 2002; Agrawal et al., 2003; Vargas, 2003; Brajer et al., 2006; Oudinet et al., 2006). However, air pollution in many urban areas of the developing countries is still a serious environmental problem, and many cities in the world are exposed to high levels of air pollution. There are many reasons of such local negative changes in the air quality in developing countries. Rapidly increasing population in those countries leads to unplanned urbanization and industrialization without taking the natural characteristics (such as meteorological and topographical conditions) of the region into account. Although, currently, only about 35% of the people live in cities in the developing countries, this ratio corresponds to twice as many people living in urban areas as 50 years ago (Baldasano et al., 2003). Rapid increase in population generally goes together with the increase in a variety of stationary and mobile facilities and products to supply for the increasing human needs and demands for energy, material and comfort, and hence with the increased resource consumption, including deforestation. Such broad range of sources as road traffic, mining, space-heating, industry, power plants, commercial activities, trade centres and many others, inevitably cause increased emissions of air pollutants in the urban areas. It is not easy, for the developing countries, to prevent and control these emissions under stricter international standards and regulations with limited economies. Air pollutants, once emerged from a variety of sources, are subject to mixing, dispersion, transport and complex series of chemical interaction and physical transformation processes in urban atmospheres. For example, atmospheric reactions between emitted nitrogen oxides (NOx = NO + NO2) and volatile organic compounds (VOCs) result in the formation of ground level ozone (Fenger, 1999). These primary and secondary pollutants, when combined with emitted sulphur compounds (including sulphur dioxide (SO2) and reduced sulphur compounds), may also lead to acid deposition and the formation of secondary particulate matter in urban atmospheres (Atkinson, 2000). Of the main air quality indicators, SO2 maintains, globally, a downward trend with the exception of some Central American and Asian cities (Fenger, 1999; Streets et al., 2000; Baldasano et al., 2003). Although nitrogen dioxide (NO2) generally maintains levels very close to those of WHO, the levels are approximately three times higher than the value of WHO guideline in some cities such as Kiev, Beijing and Guangzhou (Oduyemi and Davidson, 1998; Fenger, 1999; Baldasano et al., 2003; Han and Naeher, 2006). Particulate matter (PM) is still a major problem in almost all Asian countries with concentrations exceeding
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300 μg/m3 in many cities (Fenger, 1999; Baldasano et al., 2003; Han and Naeher, 2006). Average concentrations of ground level ozone (O3) are above the limits of WHO, EU and USEPA guidelines demonstrating that it is a global problem (Fenger, 1999; Guicherit and Roemer, 2000; Baldasano et al., 2003; Vingarzan, 2004). As is the case in many other developing countries, the most important contributions to air pollution in the Turkish cities originate from incorrect urbanization and industrialization. In addition to the topography of the site and the meteorological conditions, the quality of the air is influenced by usage of lowquality fossil fuels and improper combustion techniques, a shortage of green areas, and the increase in the number of motor vehicles and traffic load (Döğeroğlu, 2002). The Ministry of Environment and Forestry (MOEF) and the Ministry of Health (MOH) are the two main government sectors in Turkey responsible for the decision-making related to protection of the atmosphere and for transboundary atmospheric pollution control, respectively. Currently available historical information and data on the national air quality in Turkey is either limited to only a few pollutants or is not spatially and/or temporally representative of the current situation due to rapid growth of the urban areas. Currently, only the SO2 and PM parameters, monitored under the guidance of the MOH at multiple points in many cities, and the data are available from the Turkish National Ambient Air Monitoring Network (NAAMN) databank (TURKSTAT, 2006). Other pollutants, including NOx and O3, could have been monitored at only a limited number of points by, particularly, the universities, research institutes and the TUBITAK (Turkish Scientific & Technical Research Council). Existing ambient air quality statistics in Turkey, based on the average annual SO2 and PM levels supplied by the NAAMN, indicate that urban air quality in, particularly, those cities where low-quality coal is heavily used for heating activities and in the industry is quite poor. Although the annual concentrations (as high as 100 μg/m3) of SO2 and PM in those cities are below the national limits of the Air Quality Control Regulation (AQCR, 1986), they exceed the limit values of the WHO and EU (European Union) standards. Presently, air quality limits of this legislation, which suggests detailed technological alternatives for limiting the emissions from a large number of industrial activities and combustion systems, are subject to radical revisions by the MOEF for making it compatible with the EC directives. Although these revisions appear to provide stricter pollution limits for short- and long-term averages of SO2, PM10, NO2, NMVOC and CO (carbon monoxide), the proposed limits for SO2 and PM are still above those of WHO guideline (1996 version) and EC directives (Elbir et al., 2000). Emitted amounts of PM, NO2, VOC and CO originating from the city-traffic are not less important than the emissions from other sources such as residential heating systems and industrial activities. As in the most of the developing countries (Oduyem and Davidson, 1998; Mayer, 1999), the road traffic in Turkey appears to be the most important source group contributing to air pollution especially in city centres. In these central locations large traffic volumes and congestion commonly result in
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Fig. 1. Study area and sampling sites.
significant degradation of the air quality as a function of the rate of increase in population and urbanization. Thus, the particular aim of this study has been to assess the air quality of the rapidly urbanizing mid-northwestern Turkish city, Eskişehir. For this purpose, available SO2, PM, NO2 and VOC data from local emission inventories were combined with the national (for SO2, PM since 1986) and local (for NO2 and O3 since 2004) monitoring studies, all specific to Eskişehir. The emission inventory study was conducted by Çınar (2003) for Eskişehir for the year 2002, and its data were generated based on the emission factors of EPA (2003) and CORINAIR (EEA, 2003) for SO2, PM, CO, NOx and VOCs. Emission inventory and monitoring studies for VOC species for the city were also con-
ducted, discontinuously, for the years 2002 and 2003 (Döğeroğlu, 2003). NO2 and O3 measurements have been carried out continuously at different sites of the city since January 2004 by use of passive samplers (Özden, 2005). Passive sampling (Cadoff and Hodgeson, 1983; De Santis et al., 1997) is proved to be a methodology to fulfil the need of adopting inexpensive, simple and reliable methods for wide-spread air quality monitoring, simultaneously, at multiple points over large areas in Turkey. In addition to a set of NO2 measurements (based on the Saltzman method) during 1989–1993 (Kara, 1993), some discontinuous NO2 (Çokgürses, 2003), ozone (Canbaz, 2003) and BTX (Yurtsever, 2003) monitoring studies were also conducted during 2003 at two campuses of Anadolu University. Aside from the emission
Fig. 2. Source distribution of the air pollutants for Eskişehir.
Ö. Özden et al. / Environment International 34 (2008) 678–687 Table 1 Per capita emission rates of SO2 and NOx for different national and international cities Emission rate per capita (kg/capita-year)
Eskişehir Ankara (Turkey) İzmir (Turkey) Manisa (Turkey) Denizli (Turkey) Uşak (Turkey) Nuremberg (Germany) Helsinki (Finland) Rotterdam (Holland) Stockholm (Sweeden)
Population
SO2
NO x
504,724 2,977,546 2,250,149 214,435 273,515 136,879 500,000 491,000 582,000 667,000
4.89 4.08 54.15 811.90 12.79 90.87 8.2 44.6 81.8 3.6
6.02 2.82 5.32 99.77 2.46 21.43 22.4 72.7 66.2 16.2
inventory and monitoring activities in Eskişehir, a study on modelbased estimation of the dispersion of surface ozone was also carried out for the city by taking relevant meteorological parameters into account (Yay, 2006). 2. The study area and sampling sites Eskişehir, as a rapidly developing intermediate size city with a population of approximately 500,000 inhabitants, is located to the Northwest of the Central Anatolia in Turkey. Its topographical structure consists of plains, in general. A harsh terrestrial climate is dominant in the city. The weather is continually hard and cold in winter. Significant differences are observed between day-time and night-time temperatures (hot during the days but cool during the nights) in summer. Prevailing east-to-west wind direction in winter switches to northwest-to-northeast direction at the beginning of spring season. Towards the end of spring season, wind directions from southwest, west and northwest are dominant. In 1994, the community of Eskişehir started consuming natural gas in their fuel-mixes mostly for industrial utilization. Since then, mainly the residential heating activities and the traffic have been the subjects of complains about the pollution in the city. Residential heating by the natural gas started in 1996. With the gradual increase in its annual supply capacity, 50% of the population in
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the city now has become natural gas users. To combat with the congestion problems originating from motor vehicles and road traffic in Eskişehir, a railway system had been constructed couple of years ago as a partial replacement for public transportation. Çınar's (2003) emission inventory study shed light to determining proper locations of representative monitoring sites of this study. Fig. 1 shows the sampling sites selected in the study area. Among the air pollutants investigated in this study, SO2 and PM have been monitored simultaneously at, both, Site 1 and Site 2, since 1986. These MOH data are available from the Turkish NAAMN (TURKSTAT, 2006). Site 1 at the city centre is representative of a high traffic density region consuming natural gas for heating. Site 2, located in a residential area with low traffic density, represents a region consuming coal for heating. The lack of NO2 and ozone data within the monitoring network necessitated the use of passive sampling method for monitoring and determining the spatial and temporal distributions of both NO2 (since January 2004) and ozone (since November 2004). The pollutant NO2, as one of the main precursors for the ozone formation through photochemical reactions (Sillman, 1999; Atkinson, 2000), is known to mostly originate from the traffic. Therefore, a total of six sites (Site 3–Site 8) were selected in a way to collect ambient data for different levels of traffic density, in accordance with the results of the emission inventory study (Çınar, 2003). Sites 3–6 were the locations where high exposure to heavy traffic emissions was of concern. Daily vehicle numbers reported by Çınar (2003), as the representatives of the traffic densities in those sites, range between 20,500 for Site 1 and Site 4 and 5250 for Site 6. Site 7 characterized a suburban residential area south to the city. Site 8 can be defined as a rural area at the northern part of the city and is located nearly 8 km away from the city centre. 3. Data and methods The SO2 and PM data, corresponding to the period from 1986 to 2006, were gathered from the Turkish NAAMN (TURKSTAT, 2006). NO2 and ozone concentrations were obtained by collecting weekly average data at the six sampling sites of the city by use of passive samplers. These samplers, developed by the authors (Özden et al., 2005a,b) were the modified versions of the opentube design (Palmes and Gunnison, 1973; Palmes et al., 1976) and Analyst
Fig. 3. SO2 and PM trends in Eskişehir for the period 1986–2005.
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Fig. 4. Monthly average PM and SO2 concentrations in 2005.
Fig. 5. Monthly average NO2 concentrations at six sampling sites for the period 2004–2005.
(Bertoni et al., 2000; De Santis et al., 2002) type passive samplers. Collected samples (between the years from 2004 to 2006) were analyzed by using spectrophotometric method for NO2 and ion chromatographic method for ozone. Also, an automatic ozone analyzer was available at one of the sampling sites
(Site 8) to monitor hourly changes in the ozone concentrations continuously, to deduce diurnal, daily and seasonal variations. Relative contributions of the pollutants studied were evaluated based on the data of Çınar's (2003) emission inventory study. Average monthly, annual and
Fig. 6. Monthly average ozone concentrations at six sampling sites for the period 2004–2005.
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Fig. 7. Spatial variations of average NO2 and ozone concentrations in the city for the year 2005.
seasonal concentration variations of the studied pollutants were compared with the national air quality limits of AQCR (1986) as well as those of WHO (2000), EU (1999, 2002) and USEPA (2006).
4. Results and discussion Fig. 2 presents source contributions of the studied pollutants for the city based on the total annual emissions of SO2 (2467 ton), PM (881 ton), NOx (3131 ton) and VOCs (405 ton) for 2002 (Çınar, 2003). The results of the emission inventory study indicate that, the respective contributions of domestic heating to SO2 and PM pollution are 70% and 84%. Traffic is responsible for 60% of the total NOx emissions. Industrial contribution appears to be less important for the air pollution in Eskişehir. Table 1 provides a comparison of the SO2 and NOx data (emission rates per capita) for Eskişehir against those available for some other national and world cities (Çınar, 2003). The rates for Eskişehir are generally lower than the rates for other national and international cities compared. The particular similarity of the SO2 data for Eskişehir and Ankara may be attributed to the similarity of the large contributions of residential heating sources as well as that of climatic and topographical natures of both cities. Lower NOx value for Ankara may be explained by the heavier use of more efficient subway public transportation and smaller contribution of industry there relative to those in Eskişehir. The significant differences between the SO2 and NOx data for Eskişehir and for more industrialized western Turkish cities (such as İzmir, Manisa, Denizli, Uşak) and the world cities with nearly similar populations may be associated mostly with the differences in climatic and topographical conditions, and the ways the industry, transportation and residential heating contribute. Fig. 3 shows the temporal trends of the PM and SO2 concentrations during the period from 1986 to 2005. A sharp decline of the SO2 concentrations from 200 μg/m3 to below 50 μg/m3 after 1996 is noticeable.
Monthly variations in SO2 and PM concentrations, as presented in Fig. 4 for the year 2005, exhibit higher values in winter season due to domestic heating activities. The variations in the monthly average concentrations of NO2 and ozone at six sampling sites are indicated respectively in Figs. 5 and 6, for the years 2004 and 2005. Higher NO2 levels in Site 3–Site 6 during winter seasons may be related to higher traffic density and the formation of a temperature-inversion layer. Lower NO2 levels in summer may be due to its destruction by photochemical reactions. Higher ozone concentrations during summer season may be attributed to its formation in the presence of precursors and sunlight. In contrast to its higher levels at sites remote from the city centre, lower ozone concentrations were observed at the city centre. Depletion of the ozone by NO2 may have been the cause of the low ozone values in the central areas having high traffic densities. About 45% decrease during the period from the end of 2004 to the end of 2005 was recorded in NO2 concentrations at the traffic-dense central part of the city after the railway system was constructed for public transportation at the end of 2004. Average NO2 and ozone concentrations for each sampling site for the year 2005 are depicted in Fig. 7. This figure facilitates the observation of spatial distribution of these two related pollutants over the city. Table 2 Annual and seasonal averages of SO2, PM, NO2 and ozone concentrations for the year 2005 Pollutant
SO2 PM NO2 Ozone
Annual (μg/m3)
Seasonal (μg/m3)
Mean
Winter
Summer
47.13 ± 11.30 30.45 ± 10.73 22.57 ± 16.99 46.08 ± 23.62
56.79 ± 8.14 39.33 ± 7.71 29.45 ± 20.15 37.91 ± 21.60
37.47 ± 4.02 21.56 ± 1.87 15.69 ± 9.20 54.26 ± 22.96
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Fig. 8. Typical example for the relationship between NO2 and ozone for Site 5.
Fig. 9. Nonlinear and reverse relationship between atmospheric NO2 and ozone concentrations.
Average annual and seasonal concentrations of SO2, PM, NO2 and ozone are given in Table 2, for the year 2005. When the tabled values are compared with the data of other metropolitan cities in Turkey, SO2 levels in Eskişehir appear slightly higher than those in Ankara (30 μg/m3) and İzmir (38 μg/m3) (DRSCH, 2006). Much lower PM levels relative to those in Ankara (50 μg/m3) are nearly twice as high as of İzmir (15 μg/ m3) (DRSCH, 2006). Average NO2 concentrations in Eskişehir are lower than the annual data of Ankara (around 40 μg/m3) (MPAP, 2004) and the
monthly data of İstanbul (60–80 μg/m3) (Topçu et al., 2003). Lower winter season ozone data (20 μg/m3) of Ankara (MPAP, 2004) support the findings about the relationship between NO2 and ozone. The ratio of the atmospheric levels of NOx and VOCs, known to be the main precursors for the ozone formation (Sillman, 1999; Atkinson, 2000), is important for the understanding of the ozone formation process and its reduction methodology. Low VOC/NOx ratios in urban atmospheres correspond to VOC-limited chemistry (Sillman, 1999; Yay, 2006) in which any change in VOC levels will cause important changes in ozone levels. This ratio (about 0.13) of emissions for Eskişehir indicates that VOC-limited regime is prevailing in the city and, thus, ozone levels decrease with decreasing VOC and increasing NOx levels (Sillman, 1999). Fig. 8 shows a typical opposing relationship between NO2 and ozone concentrations recorded at one of the traffic-dense sites (Site 5) in the city. Corresponding behaviors of these two pollutants at the suburban (Site 7) and rural (Site 8) sites are not much different than that at Site 5. In fact, ozone formation is a highly nonlinear process regarding its interactions with NOx and VOC components. Fig. 9, which indicates the nonlinear and reverse relationship between NO2 and ozone concentrations in a different way is also confirmed by the studies conducted by Sillman (1999), Topçu et al. (2003) and Yay (2006). According to the Sillman's (1999) kinetics study, the changes in ozone formation rates are dependent on NOx levels. From Fig. 9, one can state that the slope of the curve is steeper at high NO2 concentrations, and
Fig. 10. Change in hourly ozone concentrations during the days 01.01.2005 and 13.06.2005.
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Fig. 11. Daily maximum ozone concentrations at the beginning of an ozone season (April 2005).
this steepness may be interpreted as higher ozone generation rates at higher NO2 concentrations. Fig. 10 illustrates typical trend of hourly changes in ozone values during two different days, one in winter (January) and the other in summer (June). The effects of sunlight, temperature, and other meteorological conditions may be responsible for the higher hourly values for the day in June, as compared to those in January. Of the two summer peaks, morning peaks (extend to noon hours) are observed when the weather is calm or northeast wind direction is dominant, and afternoon peaks correspond to northwest–west wind direction. As may be deduced from this information, local effects are dominating during morning hours, and transport of ozone to the region by the winds in northwest–west direction is of concern in the afternoon. As depicted in Fig. 11, maximum daily ozone concentrations varied between 96–140 μg/m3 during the start of an ozone season (April 2005), and increased up to a value of 155 μg/m3 in June. Much higher levels are observed during summer seasons. As may be observed from Table 3, measured concentrations of the majority of the pollutants studied in this work do not exceed the limits of the national AQCR and of the international regulations, considered for comparisons. Only the annual average SO2 concentration seems to exceed the limit of one international regulatory limit (the EU limit set for the protection of ecosystem).
5. Conclusion Local monitoring results, combined with the emission inventory data, provided suitable selection of the sites and, thus, the assessment of the quality of air prevailing in the urban Eskişehir. Apparently, domestic heating (for SO2 and PM) and traffic (for NOx and VOC), rather than the industry, are responsible for the pollution in the city. Regarding seasonal contributions, prevailing higher SO2 and PM concentrations in winter point out to the sites where coal is used heavily for heating. High winter season NO2 concentrations may be associated with those sites characterized by high traffic densities. Higher ozone concentrations in remote areas during summer season may be related to the complex photochemical reactions. As compared to the data of some cities in Turkey and in the world having similar populations, the air quality in Eskişehir may be considered moderate, and the differences in rates of pollutant emissions may be caused by the differences in their climatic and topographical conditions. Under the influence of the national as well as some international legislations, and implementations, air pollution in
Table 3 Comparison of SO2, PM, NO2 and ozone data (in the units of μg/m3 for the year 2005) with the national and international limits Pollutant
Monitored data from this work
Turkish limits Daily
Annual
SO2
47 a
400
150
PM10
31 b
300
150
NO2
23 c
300
100
Ozone
165 e
240 (1 h)
–
a,b c d e
Annual average measured at two sampling sites. Annual average measured at six sampling sites. Limit set for the protection of ecosystem. Maximum hourly ozone concentration measured in July at Site 8.
WHO guidelines
EU regulations
USEPA regulations
500 (1 h) 125 (24 h) 50 (annual) –
350 (1 h) 25 (24 h) 20 d (annual) 50 (24 h) 40 (annual) 200 (1 h) 30 d (annual) 180 (1 h) 120 (8 h)
1300 (3 h) 365 (24 h) 80 (annual) 150 (24 h) 50 (annual) 100 (annual) 30 d (annual) 235 (1 h) 157 (8 h)
200 (1 h) 40 (annual) 120 (8 h)
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Eskişehir has decreased significantly, particularly during the last 10 years. The use of natural gas for industry (since 1994) and for residential heating (since 1996) has been effective in the significant decrease (75%) in SO2 levels. Partly switching to public transportation by the railway system at the end of 2004, played an important role in the decrease in NO2 concentrations (45%) within, particularly, the central part of the city. The resulting data of this study and the methodology applied are expected to be useful not only for the future air pollution control applications in other urban areas, but also for the improvement of monitoring and evaluation systems, building air quality management strategies, and preparation of new clean air plans. Apparently, there is a need for expanding the existing national network, for monitoring additional air pollutants other than SO2 and PM; and such an expansion requires large investments and additional operational expenses for a developing country. Hence, an urgent action of adopting inexpensive, simple and reliable methods for wide-spread air quality monitoring, simultaneously, at multiple points over large areas is needed for Turkey. Passive sampling is proved to be one such methodology to fulfil this need in applications, as demonstrated by the authors of this study for Eskişehir. Certainly, the information on meteorological conditions has very important impacts, providing greater insight into the daily variations in air quality and the effects of past air quality management decisions. It allows for more effective decisions towards improving future air quality. Although some of the meteorological parameters (such as solar radiation, specific humidity, temperature, wind speed and wind direction, as monitored continuously in the study area) were monitored and found highly correlated with the pollutant concentrations determined, the results have not yet been published. Acknowledgements This work presents a part of the results from two research projects funded by Anadolu University. One of these projects (numbered 020237) is entitled “Use of Passive Sampling Method for the Determination of NOx and Ozone Pollution in Eskişehir and Preparation of Pollution Maps” and the other (numbered 030251) “Monitoring of Local Air Quality by Use of Passive Samplers”. References Agrawal M, Singh B, Rajput M, Marshall F, Bell JNB. Effect of air pollution on peri-urban agriculture: a case study. Environ Pollut 2003;126:323–9. AQCR (Air Quality Control Regulation). Ministry of Environment (MOE), vol. 19269. Ankara: Official Newspaper; 1986). Atkinson R. Atmospheric chemistry of VOCs and NOx. Atmos Environ 2000;34:2063–101. Bailey D, Solomon G. Pollution prevention at ports: clearing the air. Environ. Impact. Asses. Rev 2004;24:749–74. Baldasano JM, Valera E, Jimenez P. Air quality data from large cities. Sci Total Environ 2003;307:141–65. Bertoni G, Tappa R, Allegrini I. Assessment of a new device for the monitoring of benzene and other volatile aromatic compounds in the atmosphere. Annali di Chim. 2000;90:249–63.
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