| Summary: | The aims of this study were (i) to assess the soil Cu concentration in the mineral A horizon and cambic Bw horizon, (ii) to determine the background threshold value (BTV), and (iii) to quantify the differences between the horizons in terra rossa soil from Dalmatia. A total of 128 samples from 64 soil profiles located on terrains used for non-agricultural purposes were analysed for aqua regia soluble Cu concentration. The soils were classified according to the Croatian Soil Classification System and World Reference Base for Soil Resources as terra rossa soil and Chromic and Rhodic Cambisols. The median value of Cu concentration in A horizon (CuA) and cambic Bw horizon (CuB) were 34.9 and 36.1 mg/kg, respectively, and ranged between 16.2 and 69.5 mg/kg in the CuA and from 17.0 to 73.0 mg/kg in the CuB horizon. The estimated BTV for CuA varied between 43.6 and 58.4 mg/kg depending on the calculation method applied. The median ratio CuA/CuB of 0.96 was close to identical. The Wilcoxon matched pairs signed rank test and the Hodges-Lehmann estimator showed that the median difference in Cu concentration between the CuA and CuB was very small (-1.78 mg/kg). Mentioned statistical evidence on the small differences in Cu concentration between the horizons suggests that Cu concentrations measured in the Bw horizon can be considered a “local background” for the samples collected in A horizon and its utilization in screening terra rossa soil contamination can be suggested.
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