Soil trace element status in an impouded vehicle scrapyard

Abstract

The number of motor vehicles has increased by 118% over the past decade in Brazil, which is transforming urban space regarding mobility, parking and disposal capacity of these vehicles. Impounded vehicle scrapyard overcrowding has become a challenge in many Brazilian regions. This now is considered a potential risk to soil quality, since vehicles are usually parked directly on the topsoil. The aim of this study was to evaluate topsoil samples from a scrapyard of impounded vehicles for Potentially Toxic Elements (PTEs), like As, Co, Cr, Cu, Mo, Ni, Pb, and Zn, and rare-earths. The area of study is in Ribeirão Pires, São Paulo, Brazil. For this purpose, forty samples were analysed by Instrumental Neutron Activation Analysis (INAA) and X-Ray Fluorescence Spectrometry (XRF). The obtained values were compared with literature data from Brazil and other regions around the world, as so with recommended values from environmental regulatory agencies. Some soil-geochemical variables [including pH, organic matter (OM), cation exchange capacity (CEC)], and texture (e.g. clay, silt and sand content) were used to interpret the behaviour of the studied elements in the soil. The PTEs contents ranged as follows: As (<3–15 mg kg–1), Co (2–30 mg kg–1), Cr (7–183 mg kg–1), Cu (3–73 mg kg–1), Mo (<1–6 mg kg–1), Ni (<3–38 mg kg–1), Pb (23–211 mg kg–1) and Zn (18–352 mg kg–1). In some hotspots, PTEs content exceeded continental crust and also international recommended values. The normalization of the rare-earth data by the Post-Archean Average Australian Shale (PAAS) indicated high anomalous values of Ce in some points that may suggest an anthropogenic source, such as vehicle exhaust catalysts (VEC). Total contents of PTEs rank in the following order: Cr>Zn>Pb>Cu>Ni>As>Co>Mo. This is the first study in scrapyards of impounded vehicles in Brazil. The results may be used to monitor soil contamination in these sites and for more effective environmental management.