Mass Concentrations And Metals Speciation Of Urban Atmospheric Aerosols In Addis Ababa Ethiopia

Air aerosol samples for TSP (total suspended particulate) and coarse particulatern(particle matter with aerodynamic diameter 2.5–10 μm, PM2.5–10) and metallicrnelements were collected during February 2008 to July 2008 in urban and peri-urbanrnareas of Addis Ababa, Ethiopia. The seasonal variation mean concentration of TSPrnand PM10 were in the range of 17-556 μg/m3 and 27-285 μg/m3 respectively. Thernhighest TSP and PM10 peak values were observed in February 2008 at Nefas SilkrnLafto and Kotebe Waste Water Treatment Plant sites respectively. The lowest TSPrnand PM10 peak values were observed in June and July 2008 at Kality substation andrnCOLTI sites respectively. The mean TSP concentration surpassed the WHO safernguideline value of 150 μg/m3 and 79 % of the PM10 values were below the WHOrnguideline value. The PM10 to TSP mass ratio was between (0.26 -0.59) and PM10rnmass contributed ~39% to the TSP mass. The average element concentration orderrnwas Ca > Na > K > Zn > Sb >B > Al > V > Mg > S > Fe in PM10 filter sample. All thernanalyzed elements contributed ~0.1% to the PM10 mass. Crustal elements havernstrong correlation as do anthropogenic sources emissions which suggest thernpresence of similar sources. SEM-EDAX analysis of PM10 filter mass showed that Si,rnAl, Na, Zn, Ba, K and C were the predominant species. Crustal materials contributedrn76-95% and C and Cu was from 5-24%. The size distribution of aerosol particles asrnderived from SEM analysis was in 0.43-9.3 μm range.

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