Brazilian PGE research data survey on urban and roadside soils

Abstract

Since the 1990s, investigations on the increase of platinum (Pt), palladium (Pd), and rhodium (Rh) levels in urban environments of big cities all over the world due to catalytic converters emissions have increased enormously, mainly in developed countries. Nevertheless, relatively few studies were performed in developing countries, such as Brazil. The state of São Paulo is the most populous and richest Brazilian state, and the city of São Paulo is the largest city in South America, and the 7th largest metropolitan region of the world. In this article, a discussion about the results obtained for the platinum group elements (PGE) Pt, Pd and Rh concentrations in soils adjacent to a major road in São Paulo state and in soils adjacent to seven main high density traffic avenues in the metropolitan region of São Paulo City are presented. Pt, Pd and Rh were found in much higher concentrations than PGE geogenic background, showing a catalytic converter origin. The platinum group elements levels obtained in São Paulo urban soils were much higher than those obtained for the roadside soils. Pd levels about seven times higher than the results obtained for the roadside soils were observed. The highest concentrations obtained for Pt (208 ng g−1) and Rh (45 ng g−1) were of about 12 and 5 times higher than the results obtained for the roadside soils. The results indicate that the PGE concentrations in São Paulo soils are directly influenced by traffic conditions. The concentrations of traffic-related elements such as Pb, Zn and Cu were also determined in the studied soils. Factorial analysis and cluster analysis discriminated the traffic related metals from PGE in the urban soils. However, in the roadside soils PGE were well correlated with Pb, Cu and Zn. The results obtained at present for PGE levels in São Paulo soils demonstrate the importance of continuous monitoring, since the rapid increase of the vehicular fleet in Brazil should also increase PGE emissions.