Measuring copper, lead and zinc concentrations and oral bioaccessibility as part of the Soils in Scottish Schools project

Determination of potentially toxic elements in soils with which children have regular contact can provide valuable information to support health risk assessment. It is also important to engage schoolchildren with soil science so that they become well-informed citizens. The Soils in Scottish Schools project involved pupils across Scotland in the collection of soil from school grounds for determination of copper, lead and zinc. Samples were subjected to microwave-assisted aqua-regia digestion to determine pseudototal analyte concentrations. The simplified bioaccessibility extraction test was applied to estimate bioaccessibility. Analysis was performed by inductively-coupled plasma mass spectrometry. Pseudototal analyte concentrations varied widely: Cu 15.6-220 mg kg-1; Pb 24.6-479 mg kg-1 and Zn 52.5-860 mg kg-1. Higher concentrations were measured in urban areas, which were historically home to heavy manufacturing industries, with lower concentrations in soils from more rural schools. Bioaccessible analyte concentrations also varied widely (Cu 3.94-126 mg kg-1; Pb 6.29-216 mg kg-1 and Zn 4.38-549 mg kg-1) and followed similar trends to pseudototal concentrations. None of the elements studied posed a significant health risk to children through accidental soil ingestion whilst at play during breaks in the school day, although the relatively high bioaccessible levels of lead at some locations are worthy of further investigation.