Measurement results
Comparison to EU values

Measurement results

Eight different components of VOC were analysed; benzene, toluene, octane, butylacetate, ethylbenzene, m+p-xylene, o-xylene and nonane.

The sites V4 - V9 were located in areas classified as B-sites, while V1, V2 and V3 can be characterized as source sites. A brief description of the sites is found in table below. V10 was a "moving" point, located at different places during the different campaigns.

Station number	Station name	Site type	Comments
V1	Trammi depoo	Source site	Located around furniture factory in the city centre
V2	Tehnikakooli hoov	- " -	- " -
V3	Magasini tänav	- " -	- " -
V4	Endla ristmik	High traffic crossroad
V5	Kadaka ringtee	- " -	Gasoline station located at the north side of the crossroad
V6	Järvevana/Pärnu mnt. ristmik	- " -	Gasoline station located at the south side of the crossroad
V7	Peterburi mnt. ringtee	- " -	3 gasoline stations around the crossroad
V8	Lasnamäe kanalis	8 lane highway	Relatively low traffic intensity
V9	Viru Väljak	City centre	Station situated in a high traffic intensity area
V10	Different sites	Different	9604, roof level 9701, living area, close to the oil heated power plant 9710, living area, near gasoline loading harbour

The results from the VOC measurements are presented in figures below, as site columns of monthly averages for the four months respectively. The third measurement period was performed during two weeks in January and two weeks in February 1997, here referred to as the January campaign.




The highest levels of VOC as a sum were observed in August 1996, and the lowest for most of the sites, in January 1997. The comparatively low levels in January/February were probably caused by a somewhat higher wind speed during that measurement period (table of meteorological conditions). There is a general negative correlation between measured VOC-levels and wind speed, as reported from measurements in urban areas in Sweden.

Generally there was a difference in pollution load regarding VOC, where site V4 consistently showed the highest levels, with V9 having the second highest levels. The source sites (V1 - V3), together with V8, an 8-lane highway with relatively low traffic intensity, and V10 at different locations, exhibited the lowest concentrations measured. Thus, the sites located at high traffic crossroads (V4-7), and at Virju väljak (V9) with high traffic intensity in the city centre, were the most polluted sites with regard to VOC.

In order to trace sources of the VOC measured the relation between individual VOC can be calculated. For the measurement sites in Tallinn the ratio of toluene:benzene and of xylenes:benzene have been calculated. In table below the ratios are presented, together with the average concentration of benzene and of total VOC at the different sites. The ratios of individual VOC depend both on the composition of the source, but also on the general pollution level of VOC, of the distance from the source etc. Comparisons among the sites in Tallinn do show that two of the source sites, V1 and V2, have a somewhat higher ratio for toluene:benzene than the other sites, and among the highest for xylenes:benzene. This might indicate influence from the furniture factory located close to these sites. The site V4, with the highest total load of VOC, is the only one with a higher xylene:benzene ratio. It has been observed in Swedish measurements that there is a correlation between higher total concentration and higher ratio of xylenes or toluene to benzene.

Ratio of toluene to benzene, and sum of xylenes to bensen, as well as average concentrations of benzene and total VOC at the different sites during four months measurements.

	Ratio		Average concentrations, µg/m3
	toluene/benzene	xylene/benzene	benzene	Total VOC
V1 V2 V3 V4 V5 V6 V7 V8 V9	3.5 3.2 2.4 3.1 3.1 2.9 2.8 2.2 3.0	2.3 2.3 1.7 2.5 2.2 2.1 2.1 1.6 2.2	3.6 3.5 3.1 12.9 7.1 6.8 6.9 3.4 7.7	31 28 19 95 50 48 46 20 55

Comparison to limit values and to VOC levels in other cities

There are presently no EU limit values regarding VOC. Within the EU commission discussions are held regarding a limit value for benzene. The suggested limit value, probably an annual average for benzene of 5 µg/m³ to be met everywhere in 2010, will be the second daughter directive to the EU directive EU 96/62/EC. The average levels of benzene measured in Tallinn, based on four months measurements, exceed this level at some of the sites. This is however also the case in other European countries. In Germany for example annual averages for benzene in a number of cities (urban background, expected to be less polluted than the measurement sites in Tallinn) vary between ca 2-6 µg/m³. In Göteborg, Sweden, measurements in a street with heavy traffic and poor ventilation conditions (approximately an A-site, more exposed than the Tallinn sites), weekly averages of benzene varied in the interval 6-25 µg/m³ during the winter season 1997/98. In Tallinn the weekly results varied between approximately 2-23 µg/m³ of benzene.