Saharan dust and forest fires in Southern Europe in the period 2001-2011: estimation and geographical distribution

Abstract

Aim. In the context of the MED-PARTICLES project (EU LIFE+ ENV/IT/327) African dust outbreaks and wildfires over southern Europe were studied from 2001 to 2011, devoted to quantify short-term health effects of particulate matter over the Mediterranean region by distinguishing particle sizes, chemical components and sources. Methods. PM10 data from 19 regional and suburban background sites in the Mediterranean area were compiled. Daily influence of African dust and wildfires was assessed for each area, African dust contributions to PM10 were estimated and wildfire smoke plumes were classified according to their intensity. Results and conclusions. African dust outbreaks are more frequent in southern Mediterranean sites (30-37% vs. 20% days/year). A decreasing south to north gradient of African dust contribution to PM10 is patent. Higher annual dust contributions are encountered in the eastern Mediterranean with significantly higher contributions in autumn-spring and occurrence of various severe episodes throughout the year (over 100 µg m-3 dust in PM10). Clear summer prevalence is observed in the western part, with low occurrence of severe episodes. African dust emerges as the largest PM10 source in regional background southern sites of the Mediterranean (35-50% of PM10) with peak contributions up to 80% of the total PM10 mass in the eastern side. The multi-year study of African dust episodes and their contributions to PM10 displays a consistent decreasing trend in the period 2006/2007 to 2011 in the NW Mediterranean, almost parallel to that of NAO (North Atlantic Oscillation) index for the summer period, progressively more negative since 2006. As a consequence, a sharp change in the atmospheric circulation over the last 5 years has affected the number of African dust episodes and consequently the annual dust inputs to PM10 observed. Wildfires are more frequent in the eastern Basin, mainly concentrated in the warm season. A progressive decrease of wildfire events is observed in the western Mediterranean Basin.