Traffic-related platinum group elements (PGE) in soils from Mexico City

doi:10.1016/S0375-6742(01)00163-7

Journal of Geochemical Exploration

Volume 72, Issue 3, June 2001, Pages 223-227

https://doi.org/10.1016/S0375-6742(01)00163-7 Get rights and content

Abstract

The first evaluation of the distribution of platinum group elements (PGE) derived from automobile catalytic converters in urban soil samples in Mexico City was carried out. There are more than four millions cars in Mexico City and, at the present time, one third of them have catalytic converters. PGE concentrations in soils exposed to high traffic densities exceed the natural background values by upto two orders of magnitude and are directly influenced by traffic conditions. The highest concentrations of Pt, Pd and Rh in the analyzed samples are about 300, 70 and 40 μg/l, respectively. Although the PGE concentrations found in soil samples are relatively low, they represent an accumulation of only 10 yr. It is likely that the use of catalytic converters will dramatically change the distribution of these metals in the urban environment in the next decades.

Section snippets

Introducti1on

The use of catalytic converters on automobile exhaust has a significant effect by removing about 90% of the carbon monoxide, unburned hydrocarbons and nitrogen oxides from the exhaust. Platinum group elements (PGE) are considered exceptional catalysts for these reactions. Platinum (Pt) and palladium (Pd) together are used to oxidize carbon monoxide and hydrocarbons. Rhodium (Rh) must be present to reduce nitrogen oxides.

Modern catalytic converters consist of a wash-coated (γ-alumina)

Experimental and analytical methods

In order to evaluate the contribution of PGE to environmental pollution, soils exposed to different traffic conditions (low, high constant speed, high stop and go speed) and different intensities (60–200 cars/min), were sampled in the southwest area of Mexico City (see Table 3). A set of soil samples was obtained in areas close to heavily traveled roads and from side streets with lower traffic densities. Randomly selected samples of this set were analyzed.

Two pre-anthropogenic soil samples from

Results and discussion

The analytical results of PGE in soils are given in Table 3.

The PGE concentrations in analyzed soil samples with respect to background values (pre-anthropogenic soil samples S1 and S2) clearly depend on the traffic conditions, increasing on heavily used roads.

The highest concentrations (20–30 times background levels) are found in areas of high density traffic. Those samples that have been exposed to constant speed traffic (S14–S21) have generally lower concentrations than those related to stop

Conclusion

The analyses of PGE presented here are significant in the study of the distribution of these elements derived from automobile catalytic converters in urban soil samples in Mexico City.

The high PGE contents found in the soils analyzed, compared to the lower natural background values suggests a contribution of these elements from an anthropogenic source. The results indicate that the PGE concentrations in all soil samples are directly influenced by traffic conditions and distance, as far as one

Acknowledgements

We would like to thank Barbara Martiny for her critical revision of the manuscript.

References (18)

S. Artelt et al.
Engine dynamometer experiments: platinum emission from differently aged three-way catalytic converters
Atmos. Environ.
(1999)
S. Artelt et al.
Bioavailability of fine dispersed platinum as emitted from automotive catalytic converters: a model study
Sci. Total Environ.
(1999)
H. König et al.
Determination of Platinum Emissions from a three-way Catalyst-equipped Gasoline Engine
Atmos. Environ.
(1992)
S. Lustig et al.
Transformation behavior of different platinum compounds in a clay-like humic soil: speciation investigations
Sci. Total Environ.
(1996)
A.N. Rencz et al.
Platinum group elements and Au in Arctic vegetation growing on gossans, Keewatin District, Canada
J. Geochem. Explor.
(1992)
J. Schäfer et al.
Platinum-Group-Metals (PGM) emitted from automobile catalytic converters and their distribution in roadside soils
J. Geochem. Explor.
(1998)
J. Schäfer et al.
Uptake of traffic-related heavy metals and platinum group elements (PGE) by plants
Sci. Total Environ.
(1998)
F. Zereini et al.
Geochemical behavior of platinum-group elements (PGE) in particulate emissions by automobile exhaust catalyst: experimental results and environmental investigations
Sci. Total Environ.
(1997)
R.R. Barefoot
Determination of platinum at trace levels in environmental and biological material
Environ. Sci. Technol.
(1997)

There are more references available in the full text version of this article.

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Traffic-related platinum group elements (PGE) in soils from Mexico City

Abstract

Section snippets

Introducti1on

Experimental and analytical methods

Results and discussion

Conclusion

Acknowledgements

Atmos. Environ.

Sci. Total Environ.

Atmos. Environ.

Sci. Total Environ.

J. Geochem. Explor.

J. Geochem. Explor.

Sci. Total Environ.

Sci. Total Environ.

Determination of platinum at trace levels in environmental and biological material

Environ. Sci. Technol.