Platinum, palladium, and rhodium deposition to the Prunus laurus cerasus leaf surface as an indicator of the vehicular traffic pollution in the city of Varese area: an easy and reliable method to detect PGEs released from automobile catalytic converters.

BACKGROUND, AIM, AND SCOPE: The widespread use of some platinum group elements as catalysts to minimize emission of pollutants from combustion engines produced a constantly growing increase of the concentration of these elements in the environment; their potential toxicological properties explain the increasing interest in routine easy monitoring. We have found that leaves of Prunus laurus cerasus are efficient collectors of particulate with a dimension <60-80 mum, and a simple and reliable procedure was developed to reveal traces of platinum, palladium, and rhodium released from automotive catalysts. The analysis of the dust deposited on the foliage is a direct indicator of traffic pollution.
MATERIALS AND METHODS: Leaves of P. laurus cerasus were washed by sonication in a mixture of water and 2-propanol and the washings, to be discarded, were separated by centrifugation to yield typically 0.05-1.2 g of dust that, after mineralization, was directly submitted for atomic absorption analysis.
RESULTS: Comparison of the 2007 and 2004-2005 results showed a dramatic reduction of the platinum levels and revealed that palladium is now the main component of this traffic-related pollution. DISCUSSION: The results are consistent with the increasing diffusion of cars with a diesel engine whose catalysts are made up of Pt and/or Pd alone, and gives a significant insight into the recent evolution in catalyst design that replaces platinum for palladium.
CONCLUSIONS: The proposed analytical procedure is simple, with short preparation times, and greatly reduces matrix effects so that atomic absorption spectroscopy can easily detect the three noble metals at the ng/g level in the dust. RECOMMENDATION AND PERSPECTIVES: The results clearly show that Pd concentrations have increased over time, and must be cause for concern.