The objective of the study was to carry out high-resolution measurements of urban pollutant concentrations which are subject to considerable variation both in space and over time. The pollution measurement stations operated by the environmental authorities only measure point data with very low spatial resolution. Air hygiene measurement trips similar to the temperature and humidity measurement trips widely used in urban climatology would be one way of obtaining the high-resolution data required. The data recorded would then present a high-resolution image of the urban pollutant concentration structure.

Measurement trips of this type were made in the cities of Essen, Mülheim, Bottrop and Gelsenkirchen with land utilization structures typical of conurbations, located in the central Ruhr area (position: 51° N, 7° E, 1.2 million inhabitants) in North Rhine-Westphalia. The total length of the route was 86 km and trips were made between 9:00 and 15:00 (CET=UTC + 1 h) in the period from February 2000 to October 2001. The average speed of the mobile laboratory was 8 m/s (16 m/s on motorways) and the sampling rate of the analysers was 1 Hz.

Average values for each section of the route were calculated from the pollutant concentrations recorded (CO, NO, NOX and O3) and assigned to the land utilization types motorway, main road, secondary road, residential area and green space.

Apart from different concentration levels, different distribution patterns for pollutants from road vehicle emissions were found in areas with different land utilization types. A multiple regression analysis confirmed that these distribution patterns were significantly correlated with factors relevant to emissions. Cluster analyses demonstrated that pollutant concentrations were a function of exchange conditions and photochemical reaction conditions.

The data obtained by mobile measurements were compared with the figures from the air pollution measurement stations in the investigation area. These represent the urban background situation.