Methods for the assessment of background limits of Cd and Cr in the soil of Moravicki district

This paper presents different approaches to background limits assessment of Cr and Cd content in the soil of the Moravicki district. The investigated elements have right-skewed asymmetrical distribution, with high dispersion, especially Cr. By using graphical methods (cumulative curve - CDF and boxplot ) the obtained background limits of the natural contents were Cd 1.40 mg kg-1 and Cr 230 mg kg-1. Natural and log-transformed data were used for empirical methods, and significantly higher values were obtained than in the natural simulation. The background limits obtained by empirical methods were different. The maps show that the largest part of the territory has a relatively low concentration of investigated elements, whose values are the most similar to the background limits calculated by [Median+2MAD] methods and below. In parts of the territory with an increased content the most suitable computational methods are [Mean ? 2SD] and boxplot - calculation of the upper threshold. Background limits are given for certain homogenous geochemical wholes.