Spatial distribution of trace elements in topsoils adjacent to main avenues of Sao Paulo city, Brazil

In the present study, the concentration and distribution of Ba, Cu, Mo, Pb, S, Zn and Zr in soils collected along two main avenues (Pinheiros River Highway and Tiete River Highway) with high traffic density in the metropolitan region of Sao Paulo, Brazil, are presented, and their possible sources are discussed. These elements are strongly considered as contaminants originated from vehicular emissions. The analytical technique employed was XRF. The data set was evaluated by a t test for independent samples (group: avenues) at a 0.05 significance level. According to t test, the average contents obtained from Pinheiros River Highways are significantly different than the Tiete River, except for Mo. Multivariate statistic approaches (Pearson Correlation, Cluster and Factorial Analysis - FA) were adopted for data treatment. FA identified two main factors which accounted for about 86% of the total variance. The behavior of Ba, Cu, Pb, S and Zn were explained by the Factor 1. This indicates that the elements may have similar sources, probably related to gas emissions escaping from the vehicle fuel system. Factor 2 included Mo and Zr, suggesting their origin in the sample soils may be associated with the deterioration process of some device in the vehicular engine system or may be associated with the chemical composition of the urban soil analyzed. (author)