Scielo RSS <![CDATA[Clean Air Journal]]> vol. 29 num. 2 lang. en <![CDATA[SciELO Logo]]> <![CDATA[<b>Measurement of atmospheric black carbon in some South Mediterranean cities: Seasonal variations and source apportionment</b>]]> 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: BCff and wood burning: BCwb). The annual mean concentrations of BC, BCff and BCwb 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 BCff, 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 BCff, respectively. For BCwb, 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 BCwb 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. <![CDATA[<b>Aerosol characterisation including oxidative potential as a proxy of health impact: a case of a residential site in a highly industrialised area</b>]]> This study aimed to characterise aerosols sampled in the vicinity of a major industrialised area, i.e. the Vaal Triangle. It included the determination of oxidative potential as a predictive indicator of particle toxicity. Aerosol samples were collated through the cascade filtering during an eight-month period (12 h over three days in one week). Three size fractions were analysed for organic carbon (OC), black carbon (BC) and oxidative potential (OP), while ionic content was presented as monthly and seasonal concentrations. The continuous measurement of black carbon by an optical attenuation instrument was collated concurrently with cascade filtering. The carbonaceous content was low compared to the ionic one. Within the carbonaceous concentrations, the organic carbon was higher than concentrations of black carbon in both seasons in the ultra-fine fraction; the opposite was the case for the fine fraction, while the coarse fraction concentrations of organic carbon in the dry season had higher concentrations than black carbon in the wet season and organic carbon in the wet season. The OP tended to increase as the size was decreasing for wet season aerosols, whereas, for the dry season, the highest OP was exerted by the fine fraction. The ultrafine fraction was the one showing the most contrasting OP between the two seasons. Continuous monitoring indicated that the higher BC concentrations were recorded in the dry/winter part of the year, with the daily pattern of concentrations being typically bimodal, having both the morning and evening peaks in both seasons. Within the ionic content, the dominance of sulphate, nitrate and ammonium was evident. Multiple linear correlations were performed between all determined compounds. Strong correlations of carboxylic acids with other organic compounds were revealed. These acids point to emissions of VOC, both anthropogenic and biogenic. Since they were equally present in both seasons, a mixture of sources was responsible, both present in the wider area and throughout the year. <![CDATA[<b>Aerosol optical properties and direct radiative effect over Gobabeb, Namibia</b>]]> Atmospheric aerosols contribute significantly to the uncertainty in radiative forcing effects that influence the climate as well as posing a significant health risk to humans. The climatic implications of aerosols are dependent on many variables, including aerosol size, shape, chemical composition, and position in the atmospheric column. The radiative impact of aerosols transported over the west coast of southern Africa has been found, in particular, to be complicated by the aforementioned aerosol properties. This study investigated the columnar optical properties of aerosols over Gobabeb, Namibia (23.5621° S, 15.0409° E, 405 m asl) using sunphotometer data between December 2014 and November 2015. Aerosol mean optical depth AOD500 had its maximum and minimum values in 2015 August (0.37±0.30) and June (0.06±0.02), respectively. The Angström parameter was mostly above unity during the study period and indicated the prevalence of fine particles for the most part of the year with maximum and minimum values observed in August 2015 (1.44±0.19) and December 2014 (0.57±0.19), respectively. The columnar water vapor was highest in January (2.62±0.79) and lowest in June (0.76±0.27). The volume size distribution showed the fine particles having a mean radius of about 0.16 pm and the coarse mode had variation in sizes with a radius ranging between 3 pm and 7 pm. The single scattering albedo at visible wavelengths ranged between 0.83 and 0.91. The phase function was high at small angles but minimum at about 140° in all seasons. The radiative forcing showed a heating effect in all seasons with maximum and minimum in winter (9.41 Wm-2) and autumn (3.64 Wm-2), respectively. Intercomparison of the sunphotometer data with the Moderate Resolution Imaging Spectroradiometer (MODIS) showed that the satellite sensor overestimates the aerosol loading compared to the ground-based sunphotometer measurements. Both sets of observations were better correlated during the spring and winter seasons than for the summer and autumn.