Case studies of the spatial variation of benzene and toluene concentrations in parks and adjacent built-up areas

The focus in the present study is the spatial variation of anthropogenic volatile organic carbon compounds (VOC), mainly benzene and toluene, in parks and their built-up surroundings. Case studies were located in two large Scandinavian cities and measurements were made two meters above ground level in maximum traffic periods. The results showed large variations in time and space but despite high pollution levels in the streets the air in parks and non-trafficked built-up areas are substantially cleaner. The pollutant concentration inside a large park decreased to a low level (i.e. 1/3 to 1/9 the concentration at the source) in a short distance (< 40 m). An analysis showed that measured VOC was associated with fresh emissions, suggesting that the local traffic intensity was the main governing parameter. It is, however, obvious that the spatial pattern of pollution is the result of a combination of many different factors and variables including traffic intensity, weather, local climate, land use and the character of park border.