Platinum and Lead in South African Road Dust - Highway and Urban Environment - page 150

Platinum and Lead in South African Road Dust
Sebastien Rauch and Olalekan S. Fatoki
Introduction
Automobile traffic is an important source of pollutants into the environment.
Elevated Pb concentrations have been attributed to the use of tetraethyllead as an
anti-knocking additive in gasoline. The recognition of human health effects, espe-
cially in children, has resulted in a progressive worldwide phase out of leaded gaso-
line [1] . Leaded gasoline was banned in South Africa in 2006. Until the ban, Pb was
added to gasoline at a concentration of 0.33 g/l. Combined with a gasoline
consumption of 7,000 Mt/year, this equates to a Pb consumption of 2,300 t/year,
making South Africa the second largest consumer of Pb gasoline additives in Africa
[2] . Lead concentrations are now expected to decrease in the South African envi-
ronment owing to the ban of leaded gasoline.
Catalytic converters are placed in the exhaust system of cars to reduce the
amount of gaseous pollutants (CO, hydrocarbons and NO x ) emitted as by-products
of fuel combustion in the engine. Because these catalysts are poisoned by the pres-
ence of Pb, the ban of leaded gasoline and the subsequent availability of unleaded
gasoline support the introduction of exhaust catalysts in South Africa. Platinum and
other Pt group elements are the main active components in catalysts and some Pt is
emitted into the environment [3] . As a consequence, Pt concentrations are increas-
ing in the urban and roadside environment [4] , and elevated Pt concentrations are
now found in airborne particles, road dust, as well as in roadside soil, plants, and
biota [5, 6] . Therefore, environmental Pt concentrations are expected to increase in
South Africa as a result of automobile emissions. However, South Africa is the