Background and threshold values of potentially toxic elements in soil at Central part of Republic of Serbia

The study used data from the project "Fertilization control and content determination of harmful and dangerous substances in the soil of the Republic of Serbia" (1993-2007). The soil samples were obtained from the surface horizon for content determination of heavy metals pseudo-total forms (HNO3 and H2O2). Based on 5,022 soil samples, the variations and limits of the background values for As, Cr, Cu, Ni, Pb and Zn were determined by the following methods: [Mean ± 2Sd], [Median ± 2MAD], and boxplot-Tukey upper threshold (TIF). The obtained values were the lowest with the employment of Median + 2MAD method, for most elements between 87 and 90%, which means that there was a significant number of locations with unusual values which needs special attention. The other two methods gave more approximate values, generally between 95-98%. Inside research it is considered the most appropriate method and relationship with the limit values inside Serbian regulations. Due to the significant difference in Ni and Cr by geological units in the Republic of Serbia, it is necessary to determine two background limits for these elements-for soils on serpentine rock (and on the material originating from them) and for other soils.