The High-altitude Monte Curcio station is part of the Global Mercury Observations System (GMOS) as well as of the Global Atmospheric Watching (GAW) networks within which, since 2015, it produces quality controlled and high-temporal resolved data on atmospheric mercury, greenhouses gases and the physical-chemical properties of aerosols. Located within the Sila National Park (39.2° N 16.2°E; 1780 m a.s.l.) the station is not influenced by local anthropogenic sources being instead able to intercept long-range transported air masses. These last may include industrial pollutants from continental Europe, sea spray from the surrounding Mediterranean sea, volcanic ashes from the nearby Etna and Stromboli volcanoes as well as mineral dust from the Saharan desert. Among various atmospheric monitoring instruments, the station is equipped with the SWAM Dual Channel Monitor by which, based on the ?-ray attenuation method, 24-h PM10 and PM2.5 samples were simultaneously collected. In total, about 300 samples have been gained, for both the finer and coarser size fractions of PM, and then analyzed by the thermo-optical method to quantify their Organic and Elemental Carbon concentrations (OC and EC). Starting from April 2016 until June 2017, an extensive and quite continuous data series on PM levels and its carbonaceous content was thus obtained for the first time at the most southern part of Italy as representative for the regional area of the central Mediterranean basin. The new dataset together with the study of air-mass origin and the aerosol optical depth allowed to identify the occurrence of dust outbreaks and to assess their influence in terms of physical-chemical modification of PM. Over than 10% of our collected samples resulted to be affected by Saharan intrusions with a concurrently increase in PM levels, particularly relevant for the coarser aerosol fraction. Mean values of 5.6 ± 3.0 and 9.0 ± 6.0 ?gm-3 were recorded over background conditions for PM2.5 and PM10, respectively, while the same reached the averaged levels of 13.7 ± 8.4 and 43.3 ± 32.4 ?g m-3 in conjunction with dust outbreaks. A seasonal pattern was identified revealing the spring period like the one characterized by a major emphasis of Saharan intrusions in terms of both frequency and intensity, differently from the winter time during which not even a dust occurrence was observed. Synoptic and local wind fields were analyzed and discussed in terms of the observed PM seasonal variability. The availability of the carbon content provided insights about the possible association of OC to mineral dust contrarily to the EC component that was instead more influenced by wildfire events, widely occurred during summertime. The comparison of carbon species and their share between the fine and coarse PM fractions resulted useful in discriminating the prevailing sources at our monitoring station.
Seasonal patterns of Saharan Dust detected over the central Mediterranean basin, at the High-altitude Monte Curcio GAW Station
Mariantonia Bencardino;Virginia Andreoli;Jessica Castagna;Francesco D'Amore;Valentino Mannarino;Sacha Moretti;Attilio Naccarato;Antonella Tassone;Francesca Sprovieri;
2018
Abstract
The High-altitude Monte Curcio station is part of the Global Mercury Observations System (GMOS) as well as of the Global Atmospheric Watching (GAW) networks within which, since 2015, it produces quality controlled and high-temporal resolved data on atmospheric mercury, greenhouses gases and the physical-chemical properties of aerosols. Located within the Sila National Park (39.2° N 16.2°E; 1780 m a.s.l.) the station is not influenced by local anthropogenic sources being instead able to intercept long-range transported air masses. These last may include industrial pollutants from continental Europe, sea spray from the surrounding Mediterranean sea, volcanic ashes from the nearby Etna and Stromboli volcanoes as well as mineral dust from the Saharan desert. Among various atmospheric monitoring instruments, the station is equipped with the SWAM Dual Channel Monitor by which, based on the ?-ray attenuation method, 24-h PM10 and PM2.5 samples were simultaneously collected. In total, about 300 samples have been gained, for both the finer and coarser size fractions of PM, and then analyzed by the thermo-optical method to quantify their Organic and Elemental Carbon concentrations (OC and EC). Starting from April 2016 until June 2017, an extensive and quite continuous data series on PM levels and its carbonaceous content was thus obtained for the first time at the most southern part of Italy as representative for the regional area of the central Mediterranean basin. The new dataset together with the study of air-mass origin and the aerosol optical depth allowed to identify the occurrence of dust outbreaks and to assess their influence in terms of physical-chemical modification of PM. Over than 10% of our collected samples resulted to be affected by Saharan intrusions with a concurrently increase in PM levels, particularly relevant for the coarser aerosol fraction. Mean values of 5.6 ± 3.0 and 9.0 ± 6.0 ?gm-3 were recorded over background conditions for PM2.5 and PM10, respectively, while the same reached the averaged levels of 13.7 ± 8.4 and 43.3 ± 32.4 ?g m-3 in conjunction with dust outbreaks. A seasonal pattern was identified revealing the spring period like the one characterized by a major emphasis of Saharan intrusions in terms of both frequency and intensity, differently from the winter time during which not even a dust occurrence was observed. Synoptic and local wind fields were analyzed and discussed in terms of the observed PM seasonal variability. The availability of the carbon content provided insights about the possible association of OC to mineral dust contrarily to the EC component that was instead more influenced by wildfire events, widely occurred during summertime. The comparison of carbon species and their share between the fine and coarse PM fractions resulted useful in discriminating the prevailing sources at our monitoring station.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
