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| 2. |
- Palacios, M.A., et al.
(författare)
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Platinum-group elements: quantification in collected exhaust fumes and studies of catalyst surfaces
- 2000
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Ingår i: The Science of the Total Environment. ; 257, s. 1-15
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Tidskriftsartikel (refereegranskat)abstract
- Automotive catalytic converters, in which Pt, Pd and Rh (platinum-group elements; PGEs) are the active components for eliminating several noxious components from exhaust fumes, have become the main source of environmental urban pollution by PGEs. This work reports on the catalyst morphology through changes in catalyst surface by scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) and laser-induced breakdown spectrometry (LIBS) from fresh to aged catalytic converters. The distribution of these elements in the fresh catalysts analysed (PtPdRh gasoline catalyst) is not uniform and occurs mainly in a longitudinal direction. This heterogeneity seems to be greater for Pt and Pd. PGEs released by the catalysts, fresh and aged 30 000 km, were studied in parallel. Whole raw exhaust fumes from four catalysts of three different types were also examined. Two of these were gasoline catalysts (PtPdRh and PdRh) and the other two were diesel catalysts (Pt). Samples were collected following the 91441 EUDC driving cycle for light-duty vehicle testing. The results show that at 0 km the samples collected first have the highest content of particulate PGEs and although the general tendency is for the release to decrease with increasing number of samples taken, exceptions are frequent. At 30 000 km the released PGEs in gasoline and diesel catalysts decreased significantly. For fresh gasoline catalysts the mean of the total amount released was approximately 100, 250 and 50 ng km−1 for Pt, Pd and Rh, respectively. In diesel catalysts the Pt release varied in the range 400800 ng km−1. After ageing the catalysts up to 30 000 km, the gasoline catalysts released amounts of Pt between 6 and 8 ng km−1, Pd between 12 and 16 ng km−1 and Rh between 3 and 12 ng km−1. In diesel catalysts the Pt release varied in the range 108150 ng km−1. The soluble portion of PGEs in the HNO3 collector solution represented less than 5% of the total amount for fresh catalysts. For 30 000 km the total amount of soluble PGEs released was similar or slightly higher than for 0 km.
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| 3. |
- Gomez, B., et al.
(författare)
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Levels and risk assessment for humans and ecosystems of platinum group elements in the airborne particles of some European cities
- 2002
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Ingår i: The Science of the Total Environment. ; 299, s. 1-19
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Tidskriftsartikel (refereegranskat)abstract
- Traffic is the main source of platinum-group element (PGE) contamination in populated urban areas. There is increasing concern about the hazardous effects of these new pollutants for people and for other living organisms in these areas. Airborne and road dusts, as well as tree bark and grass samples were collected at locations in the European cities of Göteborg (Sweden), Madrid (Spain), Rome (Italy), Munich (Germany), Sheffield and London (UK). Today, in spite of the large number of parameters that can influence the airborne PGE content, the results obtained so far indicate significantly higher PGE levels at traffic sites compared with the rural or non-polluted zones that have been investigated (background levels). The average Pt content in airborne particles found in downtown Madrid, Göteborg and Rome is in the range 7.313.1 pg m−3. The ring roads of these cities have values in the range 4.117.7 pg m−3. In Munich, a lower Pt content was found in airborne particles (4.1 pg m−3). The same tendency has been noted for downtown Rh, with contents in the range 2.22.8 pg m−3, and in the range 0.83.0 and 0.3 pg m−3 for motorway margins in Munich. The combined results obtained using a wide-range airborne classifier (WRAC) collector and a PM-10 or virtual impactor show that Pt is associated with particles for a wide range of diameters. The smaller the particle size, the lower the Pt concentration. However, in particles
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| 4. |
- Moldovan, M., et al.
(författare)
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Environmental risk of particulate and soluble platinum group elements released from gasoline and diesel engine catalytic converters
- 2002
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Ingår i: The Science of the Total Environment. ; 296, s. 199-208
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Tidskriftsartikel (refereegranskat)abstract
- A comparison of platinum-group element (PGE) emission between gasoline and diesel engine catalytic converters is reported within this work. Whole raw exhaust fumes from four catalysts of three different types were examined during their useful lifetime, from fresh to 80 000 km. Two were gasoline engine catalysts (PtPdRh and PdRh), while the other two were diesel engine catalysts (Pt). Samples were collected following the 91441 EUDC driving cycle for light-duty vehicle testing, and the sample collection device used allowed differentiation between the particulate and soluble fractions, the latter being the most relevant from an environmental point of view. Analyses were performed by inductively coupled plasma-mass spectrometry (ICP-MS) (quadrupole and high resolution), and special attention was paid to the control of spectral interference, especially in the case of Pd and Rh. The results obtained show that, for fresh catalysts, the release of particulate PGE through car exhaust fumes does not follow any particular trend, with a wide range (onetwo orders of magnitude) for the content of noble metals emitted. The samples collected from 30 00080 000 km present a more homogeneous PGE release for all catalysts studied. A decrease of approximately one order of magnitude is observed with respect to the release from fresh catalysts, except in the case of the diesel engine catalyst, for which PGE emission continued to be higher than in the case of gasoline engines. The fraction of soluble PGE was found to represent less than 10% of the total amount released from fresh catalysts. For aged catalysts, the figures are significantly higher, especially for Pd and Rh. Particulate PGE can be considered as virtually biologically inert, while soluble PGE forms can represent an environmental risk due to their bioavailability, which leads them to accumulate in the environment.
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