GAW Report No. 205 - IGAC Project

CHAPTER 6 - EUROPEExceptionally high ozone concentrations up to 310µg . m −3 have been observed in Istanbul inthe early morning hours [Im et al., 2006]. The high ozone concentrations can be explained bydecreasing inversion heights during the early hours of the day that led to suppression of pollutantsclose to surface and thus an increase in ozone concentrations [Im et al., 2006]. During thisexceptionally high ozone event, high levels of NO 2 from traffic and CO, locally exceeding 100 µg . m -3and 1.5 mg . m -3 , were also reported.High correlations between NO and NO X were calculated for both stations suggesting thatNO X emissions originated locally. Vrekoussis et al. [2009] have also computed the annual levels ofthe vertical column densities of NO 2 (VCD NO2 ) based on SCIAMACHY observations during theperiod 2003-2007 and over a region of 0.5 o x0.5 ο (4 grids) around the city centre. The calculatedannual mean NO 2 VCDs over Istanbul are ~1 . 10 16 molecules . cm -2 . Satellite observations[Vrekoussis et al., 2009] indicate an increase in the tropospheric columns of NO 2 over recent years(Figure 34).Airborne particulate matter - Some regions of Istanbul are continuously exposed to high pollutionlevels during the heating season (November–March) [Gülsoy et al., 1999]. Since 1966, severalstations run by the Istanbul Municipality monitor PM 10 concentrations. At the end of the 1980s andthe beginning of the 1990s, sulphur dioxide (SO 2 ) and PM concentrations exceeded the short-termair quality standards 1 on many days [Tayanç, 2000]. The levels of SO 2 over Istanbul increased from1985 to 1991 reflecting the use of low quality fossil fuels during that period. In 1995-1996, there wasa considerable decrease in air pollution for 3 reasons: 1) increasing ventilation of the City, 2)switching to natural gas for heating and 3) treatment of coal before its entrance into the city.Karaca et al. [2005] found that the annual (July 2002-July 2003) arithmetic mean of PM 10was 47.1 µg m −3 , higher than the European Union air quality annual PM 10 standard of 40 µg . m −3 .The annual mean concentration of PM 2.5 (20.8 µg m −3 ) was also higher than United States EPAannual PM 2.5 standard of 15 µg m −3 . Ozdemir et al. [2009] reported average PM 10 levels of about 66µg . m -3 observed at 10 Istanbul municipality stations during the last 10 years with values rangingfrom 47 µg . m -3 to 115 µg . m -3 . Karaca and Camci [2010] have analyzed the episodes of high PM 10levels in Istanbul and attributed 52% of them to distant source contributions, massive anthropogenicactivity over all of Europe, and southwestern airflow most likely carrying PM 10 originating from theSahara Desert and other global dust generation regions located in the northern part of Africa.Recently, the first complete chemical characterization measurements of aerosol in GIAbecame available from the Bogaziçi University sampling station. The station is located at an urbanbackground site in Bosporus straight coast in Istanbul, and 9 different water-soluble ions, watersoluble organic carbon (WSOC), organic and elemental carbon (OC, EC) and several trace metalswere measured between November 2007 and June 2009. Theodosi et al. [2010] found that traceelements related to human activities (as Pb, V, Cd and Ni) reached peak values during winter due todomestic heating, whereas natural origin elements like Al, Fe and Mn peaked during the springperiod due to dust transport from Northern Africa. Organic carbon was found to be mostly primaryand elemental carbon was strongly linked to fuel oil combustion and traffic. Both OC and ECconcentrations increased during winter due to domestic heating, while the higher WSOC to OC ratioduring summer can be mostly attributed to the presence of secondary, oxidised and more solubleorganics. Source apportionment analysis of these observations using PMF indicates thatapproximately 80 % of the PM 10 in Istanbul is anthropogenic in origin [secondary, refuse incineration,fuel oil and solid fuel combustion and traffic, Koçak et al., 2010].Guelsoy et al. [1999] analyzed precipitation samples in Istanbul from January to October1996. They observed high sulphate and nitrate concentrations in the precipitation of up to 150 mg . l -1and 70 mg . l -1 , respectively, during the heating period, associated with high pH values due toneutralization of the acidity by calcium and ammonium observed at sufficient levels in these1 The current Turkish legislation sets SO2 and PM10 limits as follows (Ministry of Environment and Forest, Turkey, 2008): SO2 hourlylimit: 360 ug/m 3 ; SO2 24-hour limit: 125 ug/m 2 ; annual SO2 limit: 20 ug/m 3 . PM10 24-hour limit: 50 ug/m 3 ; annual PM10 limit: 40 ug/m 3 .237