Environmental Engineering Reference
In-Depth Information
elements such as Zn and Cu; residues of Zn and Cu also decrease rapidly as
distance from the traffic lanes increase. The work of Sutherland (2003) shows that
roadside soils exhibited a significant decrease in Pt concentration with depth of soil
sampling.
Very high concentration levels of PGMs reside in road and tunnel dusts.
However, they are expected to rise further as the use of PGMs in catalytic converters
grows. Leœniewska et al. (2004) conducted studies in polluted and nonpolluted
areas, and produced results showing enhanced levels of Pt, Rh, and Pd in road and
tunnel dust, or in grass growing near roads, compared to the geochemical back-
ground levels (samples collected from nonpolluted areas).
Schäfer and Puchelt (1998) demonstrated that PGMs emitted near roads accu-
mulate in the vicinity, and are subject to transport by wind and washoff; subse-
quently PGM residues can be measured in airborne particulate matter and
sediments.
Comparing the sampling yr 1993-1994 with 1995-1996, the latter showed a
detectable increase in airborne Pt levels (Schierl and Fruhmann 1996). Schäfer and
Puchelt (1998) revealed that people, residing particularly in urban areas, may be
exposed to particles containing PGMs with enhanced reactivity because of cluster
sizes in the nanometer range
The highest level of PGEs, in wetland sediment samples, was generally found at
basin low points, and these concentrations may be related to the area of road surface
drained and the traffic volume on proximate roads. Moreover, the results indicate
that fractionation is occurring during transport through the drainage system, and
suggest that a small portion of Pd in the road dust can be solubilized under natural
conditions (Whiteley and Murray 2005).
Traffic-emitted PGEs can enter plants, under natural growing conditions, and
show transfer coefficients similar to those of Cu, Ni, or Cd (cadmium), and much
higher than those of Pb (Schäfer et al. 1998).
Pt was also detected in biota sampled from moderately polluted sites (Haus et al.
2007). More Pt was absorbed by
Asellus aquaticus
and
Gammarus pulex
than were
other traffic-related heavy metals; uptake rates were more similar to those of essential
metals such as Zn. By analyzing Sb (antimony) and Pt concentrations in tissues of
those organisms, it could be shown that traffic-related heavy metals influenced
most of the investigated aquatic. Pt was found in a majority of biota samples, and
it emerged as being among the most widespread of the PGEs, even in moderately
polluted water bodies.
Table 3 presents data on the PGE concentrations found in an array of environ-
mental samples (Dubiella-Jackowska et al. 2007).
7
Summary
PGEs (Pt, Pd, Ru, Ir, and Os) are a relatively new group of anthropogenic pollut-
ants. Specific useful properties of these metals (high resistance to chemical corro-
sion over a wide range of temperatures, high melting point, high mechanical
Search WWH ::
Custom Search