African dust contribution to ambient aerosol levels across central Spain: Characterization of long-range transport episodes of desert dust

This work presents a summary of the results obtained from a study of the impact of African dust on levels of atmospheric suspended particulate matter registered among different monitoring sites in the Madrid Air Basin, in the centre of the Iberian Peninsula. African dust outbreaks were identified over the period 2001–2008. Lidar measurements helped to assess the temporal evolution of the dust layers and subsequent impact on the surface boundary layer. Monthly trends were analyzed, revealing a late spring/summer maximum occurrence of episodes. The most common synoptic meteorological situations causing the transport of the African dusty air masses were also identified over the seasons. Time series of particulate matter daily concentrations recorded across Air Quality Network monitoring stations and sampling campaigns were collected and analysed. Our results show the contribution of mineral dust to PM10 (particulate matter lower than 10 μm, aerodynamic diameter) during African dust outbreaks to be significantly high at rural and urban sites of the Madrid Air Basin, giving rise to exceedances of the PM10 daily limit value (50 μg/m3). This result is especially relevant since European directive 2008/50/EC on air quality, takes into account the potential exceedance of the PM10 daily limit value, due to the transport of natural particles from arid regions.