Ambiental dust speciation and metal content variation in TSP, PM₁₀ and PM_2.5 in urban atmospheric air of Harare (Zimbabwe)

Abstract

Levels of TSP, PM₁₀ and PM_2.5 as well as levels of Pb, Co, Ni and Cd in TSP, PM₁₀ and PM_2.5 have been determined in atmospheric particulates collected at Loius Mountbatten School (Harare). The samples were collected for a period of 6 months from July to December 2002. The average levels of TSP, PM₁₀ and PM_2.5 measured at the site are 106.11, 59.70 and 40.55 mg m^− 3 respectively. The average level of TSP at Loius Mountbatten School is 106.11 mg m^− 3, which is higher than the annual WHO guideline limit of 90 mg m^− 3. The average level of PM₁₀ measured at Loius Mountbatten School is 59.70 mg m^− 3, and is higher than the US-EPA and UK-EU guideline limit of 50 mg m^− 3. The average level of PM_2.5 measured at the site are also higher than the WHO and US-EPA annual guideline limit of 15 mg m^− 3. The analysis of metal concentrations in TSP, PM₁₀ and PM_2.5 was done using Graphite Furnace Atomic Absorption Spectrometry (GFAAS). The analysis showed the following average elemental concentrations: 0.157 mg Pb m^− 3 in TSP, 0.166 mg Pb m^− 3 in PM₁₀, 0.185 mg Pb m^− 3 in PM_2.5, 0.009 mg Co m^− 3 in TSP, 0.007 mg Co m^− 3 in PM₁₀, 0.011 mg Co m^− 3 in PM_2.5, 0.223 mg Ni m^− 3 in TSP, 0.166 mg Ni m^− 3 in PM₁₀, 0.180 mg Ni m^− 3 in PM_2.5 and 0.005 mg Cd m^− 3 in TSP, 0.006 mg Cd m^− 3 in PM₁₀, 0.005 mg Cd m^− 3 in PM_2.5. The levels of Pb and Ni were generally higher than those of Co and Cd and this could have been due to high traffic volumes and various industrial activities in the Workington Industrial Area.