Browsing by Author "Maenhaut, W"

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Elemental composition and sources of atmospheric particulate matter in Dar es salaam, Tanzania
(Ethiopian Journal of Environmental Studies and Management, 2010) Mkoma, S. L; Tungaraza, C; Maenhaut, W; Raes, N
An intensive aerosol field campaign was carried out from 16 August to 16 September 2005 (dry season) at a kerbside in Dar es Salaam, Tanzania. A Gent PM 10 stacked filter unit sampler with coarse and fine Nuclepore polycarbonate filters, providing fine (0.4 μm) and coarse (8 μm) size fractions, was deployed. A total of 64 parallel collections were made. All samples were analysed for the PM mass by weighing. A further analysis was performed for 25 elements by particle-induced x-ray emission spectrometry. The PM 10 mass, as derived from the 3 stacked filter unit samples, was, on average, 58 μg/m . The concentrations of the heavy metals were lower than those for the elements of crustal origin. Nevertheless, some typical anthropogenic metals, such as Zn and Pb, exhibited much higher median PM 10 levels, suggesting strong local sources for these elements in Dar es Salaam. The results also showed very strong day/night differences for the crustal elements (Al, Si, Ca, Ti and Fe). Most elements exhibit strong correlations in the coarse size fraction and somewhat weaker ones in the fine size fraction suggesting that they may originate predominantly from the same source. Principal component analysis with VARIMAX rotation was applied to the data set. Five and four components were identified for the fine and coarse fractions and explained 86.5% and 90.8% of the variance in the data set respectively.
Seasonal variation of atmospheric composition of water-soluble inorganic species at rural Background site in Tanzania, East africa
(Ethiopian Journal of Environmental Studies and Management, 2010) Mkoma, S.L; Wang, W; Maenhaut, W; Tungaraza, C.T
Samples of coarse, fine and PM10 aerosols were collected at a rural Morogoro sites, during the 2005 dry season and 2006 wet season campaigns using a “Gent” PM10 stacked filter unit sampler with sequential Nuclepore polycarbonate filters. A total of 80 aerosol samples were analyzed for water-soluble inorganic ions components 2- + - - using Ion Chromatography. The mean concentration for the anions Cl , NO 3 , and SO 4 and the cations Na , + + 2+ 2+ NH 4 , K , Mg , Ca , showed seasonal variation in all size fractions with higher levels during the 2005 dry season campaign than the 2006 wet season campaign. The mean concentrations and associated standard deviation of 3 fine, coarse and PM10 mass were, 17±4, 52±27 and 69±29 μg/m during the 2005 dry season campaign and 3 2+ 13±5, 34±23 and 47±25 μg/m for the 2006 wet season campaign, respectively. Ca was the most important + 2- cation and the SO 4 was the main acidifying anionic component in PM10 while NH 4 was the most abundant - cation in the fine fraction and Cl the main anionic species in the coarse fraction. The ion balance ratios were all larger than 1.0; they range from 1.30 to 1.44 for the fine fraction and from 2.01 to 3.14 for the coarse fraction. The carbonates were not measured by Ion Chromatography therefore; these missing carbonates are thought to be largely responsible for the observed deviation from 1.0. The study suggests that primary sources such as soil dust dispersion and biomass burning made a significant contribution to the atmospheric particulate pollution in Morogoro.