Sources and factors affecting PM10 levels in two European cities: Implications for local air quality management

Despite improvements in vehicle and fuel technology that have led to reductions in primary particle emissions, high PM10 levels have been observed in recent years in several European cities, including Athens (Greece) and Birmingham (UK). In certain cases, high PM10 concentrations have persisted over periods of several hours, resulting in exceedences of EU target values. In order to design effective PM10 control strategies, it is essential to develop an understanding of local and remote sources of particulate matter, as well as of the factors influencing its temporal and spatial variability in urban areas. In this study, PM10 data from Athens and Birmingham were analysed for relationships to other pollutants (NOx, CO, O3 and SO2) and meteorological parameters (wind velocity, temperature, relative humidity, precipitation, solar radiation and atmospheric pressure) during a 3-year period (2001–2003). Significant positive correlations between PM10 and NOx, CO, and solar radiation were observed at the selected monitoring sites during cold seasons. On the other hand, negative correlations between PM10 and O3, wind speed and precipitation were observed during the same seasons. However, these correlations became weaker during warm seasons, probably due to secondary aerosol formation and enhanced soil dust re-suspension. Furthermore, principal component and regression analyses were used to quantify the contribution of non-combustion sources to the observed PM10 background levels. This contribution ranged between 45% and 70% in Birmingham and 41–74% in Athens. Finally, several winter and summer PM10 episodes from each city were analysed using a back trajectory model, in order to identify the origin of the polluted air masses. It was found that long-range transport of particles from continental Europe had a marked effect on PM10 background levels in Birmingham, while the local weather had a stronger influence on PM10 levels in Athens.