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Benzene from Traffic. Fuel Content and Air Concentrations

Palmgren, F., Hansen, A.B., Berkowicz, R. & Skov, H.

NERI Technical Report No. 309

Abstract

Many pollutants are of importance for assessing the adverse impact of the air pollution, e.g. NO2, CO, lead, VOCs and  particulate matter. Aromatic VOCs are of special great concern due to their adverse health impacts. Measurements of benzene, toluene and xylenes have been carried out in central Copenhagen since 1994. Hourly mean concentrations of benzene were observed to reach values of up to 20 ppb, which is critically high according to WHO’s recommendations and the new EU limit values.

The emission of benzene is determined by petrol composition, driving conditions, composition of the car fleet and the percentage of catalytic converters. From year 2000 the content of benzene in petrol must be <1% in EU, a reduction from max. 5%.

Therefore it was decided to investigate this type of air pollution in more details, especially the relationship between the benzene content in petrol and the air concentration. This was supported by the Danish Environmental Protection Agency.

The following is a summary of the analysis of petrol sold in Denmark and the air quality measurements at two locations in Denmark, Jagtvej in Copenhagen and Albanigade in Odense. The objectives of the project were, to

  • determine the benzene content in petrol and follow the changes in benzene content in petrol produced in Denmark,
  • determine the air concentrations of benzene and other aromatic VOCs in Danish streets and determine the emissions from the Danish car fleet, and
  • analyse the relationship between benzene content in fuel and air concentrations.

Crude petrol samples from the two Danish refineries, Shell in Fredericia and Statoil in Kalundborg, which deliver petrol to most of the petrol companies in Denmark West and East of the Great Belt respectively, have been analysed. Retail petrol from different petrol companies in Roskilde were also analysed. Samples were collected twice a year in the period August 1997 to July 1999. The results were also compared with earlier data. The benzene content was before 1995 approx. 3.5% for 95 RON. Statoil reduced the benzene content to approx. 2 % in 1995 and further to approx. 1 % in 1998. Shell reduced the benzene content from approx. 3.5% to approx. 1 % in 1998.

Air quality measurements of aromatic VOCs were started at Jagtvej in Copenhagen in 1994 and at Albanigade in Odense in 1997. The air concentration is a result of the emissions and the dispersion (meteorology). The air quality data were analysed using air quality models, i.e. Operational Street Pollution Model (OSPM). The method used made it possible to remove the influence from the meteorology and determine the actual emissions.

The measurements of benzene showed very clear decreasing trends in the air concentrations and the emissions, especially at Jagtvej in Copenhagen, where long time series are available from 1994. At the same time the measurements of CO and NOx also showed a decreasing trend, but not so strong as for benzene. The general decreasing trend is explained by the increasing number of petrol vehicles with three way catalysts, 60-70% in 1999. The very steep decreasing trend for benzene at the beginning of the period from 1994 was explained by the combination of more catalyst vehicles and reduced benzene content in Danish petrol. The total amount of aromatics in petrol, including toluene, increased only weakly.

The concentration of benzene at Jagtvej in Copenhagen was still in 1998 above the expected new EU limit value, 5 µg/m3 as annual average. However, the reduced content of benzene in petrol from 1998 and increasing number of vehicles with catalysts will probably lead to compliance with this limit value.

The benzene contribution from diesel vehicles is small.

Bibliographic information: Palmgren, F., Hansen, A.B., Berkowicz, R. & Skov, H.  (2000): Benzene from Traffic. Fuel Content and Air Concentrations. National Environmental Research Institute, Denmark. NERI Technical Report No. 309. Available at www.dmu.dk

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