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| Kourtidis K.A., Ziomas I., Zerefos C., Kosmidis E., Symeonidis P., Christophilopoulos E., Karathanasis S., Mploutsos A. | [abstract]
Benzene, toluene, sulphur dioxide, ozone and nitrogen dioxide were measured at a mean level of 13.5 m above ground in a narrow, four-lane street canyon (height 30 m, width 20 m) in Thessaloniki, Greece during the period January-July 1997 by means of a commercial differential optical absorption spectrometer (OPSIS DOAS). Primary pollutant levels were found to be 2.5-4.4 times higher during the cold part of the year than during the warm part of the year, the winter/summer ratio increasing with the reaction rate constant with OH for each of the measured species. Ozone, on the other hand exhibited, a winter/summer ratio of 0.36 NO2 originates from both primary and secondary sources; its winter/summer concentration ratio of 1.4 lies, therefore, between those of primary pollutants and ozone. Pollution levels were influenced considerably by wind speed, while for the street canyon under study wind direction did not influence pollutant levels considerably. While primary pollution was found to decrease with increasing wind speed, ozone increased. Benzene mean levels during the study period were around 6ppb and hence much higher than the EU annual limit value of 5μg m-3 (1.44ppb at STP). Toluene mean levels were around 14ppb and hence also several times above the WHO recommendation of 2ppb for 24h. The apportionment of traffic emissions in four time zones used in most inventories in urban airshed models was tested using benzene and toluene measurements at low (<1m s-1) wind speeds. The agreement between model emission and calculated emissions apportionment into the four time zones was good, except for Zone D (23:00 - 1:59), where model inventory emissions were somewhat too low. | [keywords]
Benzene, toluene, ozone, NO2, SO2 | | Atmos. Envir., 2002 | | |  back to publications list |
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