Total Petroleum Hydrocarbons and Trace Metals in Street Dusts from Tshwane Metropolitan Area, South Africa

Abstract

This study reports the level of total petroleum hydrocarbons (TPHs) and trace metals in dusts from some petroleum handling facilities (gasoline stations), selected high traffic density roads and residential areas within the Tshwane Metropolitan area in South Africa. Total petroleum hydrocarbons in dust samples were extracted using soxhlet extraction and isolated gravimetrically after column cleanup, while total trace metals in dust samples were digested using mineral acid digestion and analyzed using atomic absorption spectrometry (AAS). The mean TPH level from the residential sites ranged from 206 ± 20.3–300 ± 36.4 μg g−1 while those from gasoline stations and high traffic density roads varied between 562 ± 43.9–340 ± 62.6 μg g−1 and 404 ± 32.7–852 ± 55.4 μg g−1 respectively. Mean concentrations of analyzed trace metals at residential areas ranged from 0.04 ± 0.02–0.07 ± 0.03 μg g−1; ND; 0.21 ± 0.01–0.34 ± 0.02 μg g−1; 0.66 ± 0.06–2.11 ± 0.82 μg g−1; 18.7 ± 0.86–33.4 ± 0.83 μg g−1 and 0.07 ± 0.04–0.23 ± 0.01 μg g−1 for Cd, Pb, Cu, Zn, Mn and Cr respectively. Mean levels from gasoline stations ranged between 0.05 ± 0.02–0.17 ± 0.07; 0.08 ± 0.02—0.12 ± 0.04; 0.21 ± 0.04–4.34 ± 0.60; 7.44 ± 0.40—13.0 ± 0.56; 23.36 ± 4.37–131 ± 10.5 and 0.05 ± 0.02–0.17 ± 0.05 μg g−1 while those from high traffic density roads ranged from 0.07 ± 0.04–0.10 ± 0.04; ND—0.30 ± 0.05; 0.67 ± 0.05–3.80 ± 0.82; 2.40 ± 0.25–10.6 ± 0.96; 19.8 ± 1.03–108 ± 4.44 and 0.06 ± 0.02–0.12 ± 0.04 μg g−1 also in the above metal order. Contamination by TPH and trace metals both at gasoline stations and high traffic density roads is revealed by their significantly higher values compared to those of residential areas.