Measurement of atmospheric black carbon in some South Mediterranean cities

Seasonal variations and source apportionment

Abstract

This study aims to investigate, for the first time in Algeria, the atmospheric black carbon (BC) concentrations over one year measured at the Scientific Observatory of Algiers and to compare their concentration levels with other Mediterranean cities (i.e., Athens and Crete). The diurnal cycles as well as seasonal variations of BC concentrations were evaluated and attributed to their emission sources (fossil fuel: BC_ff and wood burning: BC_wb). The annual mean concentrations of BC, BC_ff and BC_wb were 1.113±2.030, 1.064±2.002 and 0.049±0.262 µgm^-3, respectively. The highest seasonal mean concentrations were recorded in summer and autumn with 1.283±1.346 and 1.209±1.149 µgm^-3 for BC and 1.217±1.431 and 1.177±1.151 µgm^-3 for BC_ff, respectively. However, the lowest mean concentrations were recorded in winter and spring with 1.023±1.189 and 0.966±0.964 µgm^-3 for BC and 0.933±1.177 and 0.956±0.874 µgm^-3 for BC_ff, respectively. For BC_wb, the highest mean concentrations were reached in winter and summer with 0.090±0.055 and 0.066±0.050 µgm^-3, respectively, very likely due to the forest fires and long-range transport of air pollution from Europe. The lowest mean concentrations of BC_wb were recorded in autumn and spring with 0.032±0.033 and 0.010±0.021 µgm^-3, respectively. Seggregating BC levels into eight wind sectors, showed that the prevailing BC pollution with concentrations reaching up to 5.000 µgm^-3 originated from the North-West wind sector. A source apportionment of BC for the wet and dry period was also perfomed followed by a back trajectory cluster analysis for long-range transport.