Saharan dust contributions to PM10 and TSP levels in Southern and Eastern Spain

Abstract

The analysis of PM10 and TSP levels recorded in rural areas from Southern and Eastern Spain (1996–1999) shows that most of the PM10 and TSP peak events are simultaneously recorded at monitoring stations up to 1000 km apart. The study of the atmospheric dynamics by back-trajectory analysis and simulations with the SKIRON Forecast System show that these high PM10 and TSP events occur when high-dust Saharan air masses are transported over the Iberian Peninsula. In the January–June period, this dust transport is mainly caused by cyclonic activity over the West or South of Portugal, whereas in the summer period this is induced by anticyclonic activity over the East or Southeast Iberian Peninsula. Most of the Saharan intrusions which exert a major influence on the particulate levels occur from May to September (63%) and in January and October. In rural areas in Northeast Spain, where the PM10 annual mean is around 18 μg PM10 m −3, the Saharan dust accounts for 4–7 annual daily exceedances of the forthcoming PM10-EU limit value (50 μg PM10 m −3 daily mean). Higher PM10 background levels are recorded in Southern Spain (30 μg PM10 m −3 as annual mean for rural areas) and very similar values are recorded in industrial and urban areas. In rural areas in Southern Spain, the Saharan dust events accounts for 10–23 annual daily exceedances of the PM10 limit value, a high number when compared with the forthcoming EU standard, which states that the limit value cannot be exceeded more than 7 days per year. The proportion of Sahara-induced exceedances with respect to the total annual exceedances is discussed for rural, urban and industrial sites in Southern Spain.