Platinum and Lead in South African Road Dust - Highway and Urban Environment - page 153

Table 1 Pb and Pt concentrations in road dust in selected
South Africa cities. Concentrations are presented as average ±
standard deviation (standard deviation is presented in brackets
when it exceeds average concentration)
City Pb (mg/g) Pt (ng/g)

Cape Town 706 ± 271 4 ± 2

Port Elizabeth 434 ± 228 6 ± 1

Pretoria 775 (999) 23 ± 13

Rustenberg 345 ± 172 223 ± 116

2500

2000

1500

1000

500

0

Rust Rust Rust Rust Rust Rust PrePre PreCT T TPEPE

Fig. 2 Lead concentrations in road dust in Rustenburg (Rust), Pretoria (Pre), Cape Town (CT)
and Port Elizabeth (PE)

Platinum Concentrations

Average Pt concentrations range from 4 ng/g in Cape Town to 223 ng/g in
Rustenburg (Table 1 ) with a minimum concentration of 2 ng/g along highway N2
in Cape Town and a maximum concentration of 391 ng/g at Mandela Street in
Rustenburg (Fig. 3 ). For comparison, average Pt concentrations in Ghana ranged
from 1.5 ng/g at a background site to 55 ng/g near a heavy traffic road [11] .
Concentrations in Rustenburg and Pretoria range from 108 to 391 ng/g and from
13 to 37 ng/g, respectively, and are clearly higher than in other South African
cities where concentrations range from 2 to 7 ng/g. The relatively low concentra-
tions in Cape Town and Port Elizabeth indicate that automobile traffic is a minor
source of Pt in South Africa, possibly due to the currently limited number of vehicles
equipped with exhaust catalysts. Therefore, the relatively high Pt concentrations
found in Rustenburg and Pretoria are attributed to non-automobile sources. Since
Rustenburg is located on the edge of the Bushveld Igneous Complex, near major
Pt mines, mining activities are a likely source of Pt in road dust in Rustenburg.