A new quality control soil material for monitoring trace metals in accidentally polluted areas

The use of reference materials is an essential requirement for the quality control of measurements in environmental chemistry. This paper describes the preparation of a new quality control soil material for extractable trace element contents in aqua regia (ISO Norm 11466) and in 0.01 mol l−1 CaCl2. These two methods are useful for estimating total contents and for assessing element mobility, respectively. The bulk material was sampled in Seville (south of Spain), in an area affected by an accidental spill comprising arsenopyrite- and heavy metal-enriched sludge particles and acidic waste waters. After preparation, homogeneity and stability studies were performed at 20 and 40 °C over a period of 24 months. No significant differences (F-test) were observed for the within- and between-bottle results, and the material was considered homogeneous. In general, neither the storage temperature nor the time of element determination after bottling affected the results for either extraction procedure. Small changes in extractability were observed only for Cu in CaCl2 after storage at 40 °C, and therefore temperatures above 20 °C must be avoided to prevent such changes. The prepared material can be used in proficiency testing and in routine quality control of environmental laboratories for monitoring pseudo-total and extractable trace elements in heavily polluted soil samples.