22.214.171.124 City characteristics, geography, population, meteorology
Greece has one of the most aged populations in Europe with almost one fifth to be over 65 years old. In 2004 the annual deaths of 104 000 inhabitants were slightly higher than the 101 000 births. In 2004, the life expectancy of the total population at birth is 79 years with the male population which constitutes 50% of the national total population having a lower life expectance (77 years) than the females (82 years), one of the highest in Europe (WHO, 2006). The Greater Athens Area (GAA) currently gathers a population exceeding 4 million inhabitants which is about 40% of the total population of Greece and has experienced a population growth rate of 0.6% per year over the last decade.
The climate of Athens is typically Mediterranean with hot dry summers and wet mild winters. The mean daily summer and winter temperatures are 25.8oC and 10.1oC, respectively. The mean annual total precipitation height is about 400 mm, and 85% of it occurs from October to March (Kalabokas et al., 1999a). The mean wind pattern in the atmospheric boundary layer in Athens during the warmer part of the year is a persisted northeasterly flow of relatively high constancy. The Athens basin is exposed to the summer monsoon circulation of the Eastern Mediterranean. The city of Athens is located in a basin on the west coast of the Attica peninsula (Fig 4). It is surrounded by moderately high mountains forming a channel with only one major opening toward the sea to the southwest. The mountains act as physical barriers with only small gaps between them. The most important is the channel between Hymmetus and Pendeli leading to the northeast coast of the Attica peninsula which gives the Athens basin access to the Etesians, a system of semi persistent northerly winds. During the appearance of the Etesians, good ventilation of the basin is favored and thus pollution episodes do not appear. The weakening of the synoptic wind allows the development of local circulation systems, such as sea/land breezes along the axis of the basin (NE to SW) and anabatic/catabatic flows from the surrounding mountains. In such a case the ventilation of the basin is poor, the boundary layer is shallow and the air pollution potential increases (Melas et al., 1995 and references therein).
Figure 4. Map of Greater Athens Area with altitude contours at 200 m intervals (from Melas et al., 1995)
Air pollution episodes may occur in Athens during all seasons of the year but most of these episodes are associated with the development of sea-breeze (Kallos et al., 1993).
126.96.36.199 Emissions of pollutants and their precursors in the area
The massive number of registered vehicles in circulation (over 2.5 million, growing at a rate of 7% yearly) is allegedly the major cause of air pollution related problems in the area, taking into account that a large proportion of these vehicles are non-catalytic (0.8 million) or are powered by old technology diesel engines (0.2 million). Although the use of natural gas for domestic heating purposes has increased lately, combustion of fuel oil is still primarily used for central heating.
An anthropogenic emissions inventory was compiled for Greece and the Greater Athens Area (GAA) for the reference year 2003 (Markakis et al., 2009b; Markakis et al., 2009c), spatially allocated in a 10 km spatial grid over Greece projected in Lambert Conformal Conic (LCC) and in 2 km resolution grids over GAA. The emission inventory has monthly, weekly and hourly temporal analysis. Total annual emissions for the GAA were estimated to be 473 kt for CO, 78 kt for NOx, 31 kt for SO2, 93 kt for NMVOCs and 20 kt for PM10. Approximately 75% of CO, 70% of NMVOCs and almost half of NOx emissions originate from the road transport sector while the most important SO2 emitter is the industrial sector. The majority of PM emissions stem from the industrial sector but the large industrial complexes are located several kilometres outside the Athens basin where the majority of the population resides. Inside the basin the road transport is again the most important emission source. Almost 20% of PM emissions originate from non-exhaust sources like tire and break wear as well as road abrasion. The annual variation of emissions shows that although the central heating operations do not account for more than a few percent in the annual totals (with an exception of SO2 – 15% contribution) in the winter months they make a significant contribution. In comparison to the Greek national totals Athens gathers almost half of the road transport CO emissions and 70% of the NOx emissions. Taking into account that almost half of the county’s population inhabits the GAA as well as the fact that Athens experiences very severe congestion phenomena with the average speed not to exceed 12 km/h during rush hours, the results are not surprising.
188.8.131.52 Air pollution levels and abatement measures
The GAA has been subject of intensive field campaigns like MECAPHOT-TRACE in summer 1994 (Ziomas, 1998 and references therein) and PAUR I and II (in summer 1996; Zerefos et al., 2001 references therein). For the GAA, the air quality reports have showed that there has been a great improvement in the latest years regarding the pollution levels. This is mostly due the fact that the large industries were reallocated from inside the Athens basin to the greater area while more strict legislation were enforced with a number of large units to be equipped with filters. In addition, pollution abatement measures taken by the state authorities during the period 1990-1994, consisting in the replacement of the old technology gasoline-powered private cars and the reduction of the sulfur content in diesel oil, seem to be the primary cause of the improvement in air quality in Athens during the recent years.
Kalabokas et al. (1999a,b) analyzing 11-year observations from the automated local air pollution network operating by the Ministry of Environment since 1987, found a significant downward trend for almost all primary pollutants in all stations. Comparison between the 3-year periods 1988-1990 and 1995-1997 gives the highest reduction in the center of GAA of 52%, 34%, 26% and 20% decreases for sulfur dioxide, carbon monoxide, nitrogen oxides and black smoke, respectively, whereas the concentrations of the secondary gaseous pollutants (especially Ox = sum of ozone and nitrogen dioxide) seem to have remained essentially at the same levels since 1990. Observations of O3 prior 2000 (Kalabokas and Repapis, 2004) at three stations in the GAA and the surroundings were found to exhibit characteristic seasonal variation of rural ozone concentrations with lowest winter afternoon values at about 50μg.m-3 in December–January and average summer afternoon values at about 120μg.m-3 in July–August, indicating that high summer values were observed all over the area.
The latest air quality report of the ministry of environment concludes that except from PM concentration the gaseous pollutants are generally below the EU limits.
In the GAA, PM still presents large exceedences, in contrast to gaseous pollutants. In 3 urban stations the daily limit value was exceeded almost half of the year with the average annual value to range from 48 μg.m-3 to 57 μg.m-3. Based on one year (2005-2006) observations of PM10 at two locations in Athens, Koulouri et al. (2008) reported for both about 44% of exceedances of the 24-h limit value of 50 μg m-3 while compliance with the air quality standard demands a maximum proportion of 9.6 % yearly. Furthermore, PM2.5 concentrations in both stations exceed the long-existing US-EPA limit value of 15 μg m-3.