Trace element concentrations in schoolyard soils from the port city of Talcahuano, Chile

• Soil concentration seems differently influenced by their respective urban activities.
• Background values were estimated for trace metals in the schoolyard soils.
• An estimated 34% of the schoolyard soils can be considered as contaminated.
• The proportion of anomalous concentrations was largest for Zn and Cr.
• The underlying material nature is the main sources of trace elements in the soils.

It is well documented that infants and children have a greater intake per unit of body weight of soil, air and water. The objective of this study was to determine the occurrence and concentrations of potentially toxic metals/metalloids in soils to which children are exposed to during outdoor school activities. A total of 76 soil samples from 38 schoolyards throughout Talcahuano, Chile were collected. For each schoolyard site, a sample of the topsoil (ts, 0 to 10 cm) and subsurface soil (ss, 10 to 20 cm) was collected for analysis. The processed samples were analyzed by ICP-emission spectrometry following aqua regia digestion for the following elements: As, Cr, Cu, Ni, Pb and Zn. The median concentrations (mg kg− 1) obtained include: As 6 (range 1–24), Cr 29 (14–253), Cu 40 (11–190), Ni 30 (7–79), Pb 26.5 (3–349), and Zn 172 (29–1865). Different methods were evaluated in order to facilitate the best diagnosis of contamination. First, the trace element geochemical background was determined using basic descriptive statistics. Second, the basic descriptive statistics were then compared with Dutch guidelines, in order to evaluate whether the concentrations measured in soils were abnormally large. By comparing the results of the different methods, we estimate that 34% of the schoolyards demonstrate contamination.