Depth distribution of trace elements in urban soil profiles

Abstract

Soils are an important component of urban ecosystems, but their ecosystemic functions may be negatively affected by the growth in urban population projected for the next decades. Among the problems that affect urban soils, the accumulation of inorganic contaminants such as heavy metals is one of the most challenging. In this study we analized the concentrations of Pb, Cu, Zn, Ni and Cr in six soil profiles of the city of Santiago de Compostela (northwestern Spain). Three of them are developed under natural conditions, and the other three are developed over human altered and transported materials. In two of the natural soils, trace metal concentrations show a clear trend to decrease with depth, suggesting that metals come from the environmental pollution. In the other natural soil, developed from amphibiles, this trend is only true for Pb , while Cu, Zn, Ni and Cr increase in depth, which can be explained by the particular lithology of this soil. On the contrary, in none of the three artificial soils a clear trend in the distribution of trace element concentrations with depth is observed.