Chemical characterization of urban park soils of the metropolitan region of São Paulo

Abstract

In the last years, urban soils have been increasingly subject of investigations concerning their description and composition. In several important cities all over the world, urban soils show a significant increase in metal levels, due to the rise of pollution originated from continuous urbanization and industrial development. This metal contamination can disturb the natural geochemical cycles and their depending ecosystems. The expected population growth during the next decades will concentrate in urban areas, which are already the predominant human habitat. Metal contamination is a key issue in São Paulo City, the biggest urban agglomeration in Latin America. There has been little research on metal levels in São Paulo urban soils and almost nothing related to the city’s parks. The present study presents the concentration of major and trace elements in soil samples of nine parks of the metropolitan region of São Paulo. Top soil samples (0-20 cm) were collected in lines across the parks in order to have representative samples of the entire park. Instrumental Neutron Activation Analysis (INAA) and X-ray Fluorescence (XRF) were used for whole elemental analysis. The outcome of this study showed that the soils of the public parks studied presented, in general, concentration levels higher than the reference values for soils in São Paulo State. For As, V and Ni, which showed significant enrichment factors in relation to reference values, there is an indication of anthropogenic source. Cluster analysis grouped the elements Zn, Sb, Pb and Cu, well known as traffic-related elements, which may indicate a vehicular source.