Long-term measurements of carbonaceous aerosols in the Eastern Mediterranean: evidence of long-range transport of biomass burning

Abstract

Abstract. Long-term (5-year) measurements of Elemental Carbon (EC) and Organic Carbon (OC) in bulk aerosols are presented here for the first time in the Mediterranean Basin (Crete Island). A multi-analytical approach (including thermal, optical, and thermo-optical techniques) was applied for these EC and OC measurements. Light absorbing dust aerosols were shown to poorly contribute (+12% on a yearly average) to light absorption coefficient (b abs ) measurements performed by an optical method (aethalometer). Long-range transport of agricultural waste burning from European countries surrounding the Black Sea was shown for each year during two periods (March-April and July-September). The contribution of biomass burning to the concentrations of EC and OC was shown to be rather small (20 and 14%, respectively, on a yearly basis), although this contribution could be much higher on a monthly basis and showed important seasonal and interannual variability. By removing the biomass burning influence, our data revealed an important seasonal variation of OC, with an increase by almost a factor of two for the spring months of May and June, whereas BC was found to be quite stable throughout the year. Preliminary measurements of Water Soluble Organic Carbon (WSOC) have shown that the monthly mean WSOC/OC ratio remains stable throughout the year (0.45±0.12), suggesting that the partitioning between water soluble and water insoluble organic matter is not significantly affected by biomass burning and secondary organic aerosol (SOA) formation. A chemical mass closure performed in the fine mode (Aerodynamic Diameter, A.D.<1.5µm) showed that the mass contribution of organic matter (POM) was found to be essentially invariable during the year (monthly average of 26±5%).

Synoptic conditions favouring the occurrence of aerosol episodes over the broader Mediterranean basin

“…Lelieveld et al, 2002). The fine-mode aerosol load is larger in spring, and especially in summer, when wet removal is practically absent, fires are intensive (more so than in spring: Sciare et al, 2008) and photochemical reactions are at full strength, while it exhibits a clear north-to-south gradient (Barnaba and Gobbi, 2004;Basart et al, 2009). …”

“…These episodes are: (i) desert dust (e.g. Dayan et al, 1991;Moulin et al, 1997a;Tsidulko et al, 2002;Kubilay et al, 2003;Papayannis et al, 2005;Kalivitis et al, 2007;Toledano et al, 2007;Meloni et al, 2008), (ii) fine pollution aerosols (Kukkonen et al, 2005;Ladstätter-Weißenmayer et al, 2007;Sciare et al, 2008), (iii) forest fires Niemi et al, 2005;Pace et al, 2005), and (iv) sea-salt aerosols (Marenco et al, 2007). Nevertheless, most of these studies either focus on episodes of specific aerosol types or they refer to the local scale only.…”

Sources and mixing state of summertime background aerosol in the north-western Mediterranean basin

“…Less nitrate, or weaker signals for these species, relative to sulfate was expected given the high ambient temperatures. Nitrate is usually mixed with EC in the form of ammonium nitrate, which is more volatile than ammonium sulfate (Querol et al, 2009;Sciare et al, 2008). A smaller signal for MSA, 95 CH 3 SO − 3 (Neubauer et al, 1997) relative to sulfate was found in the K-EC-SO x class, indicating processing with marine emissions .…”

Long-range transport and mixing of aerosol sources during the 2013 North American biomass burning episode: analysis of multiple lidar observations in the western Mediterranean basin

“…The focus of biomass burning emission impact on the atmospheric composition is often on the effect of these fires on the aerosol distribution in North America and Siberia (Eck et al, 2009;Warneke et al, 2010). Long-range transport of biomass burning plumes has been also recognized as a significant source of aerosol in the mid-latitude free troposphere over Europe Fiebig et al, 2003;Sciare et al, 2008;Adler et al, 2011). Air mass aging related to long-range…”