Assessing Spatial Distributions of Total Trace Elements Content in Bottom Sediments of Dzierżno Duże Water Reservoir – Geostatistics-Based Studies

The aim of this study was to assess the spatial distributions of total trace elements content in the bottom sediments of Dzierżno Duże water reservoir, along with the comparison of the accuracy and characteristics of Kriging and IDW interpolations. On the basis of regular measurement grid consisting of 53 points, bottom sediments samples were collected. Mean values of total trace elements content in bottom sediments of Dzierżno Duże were as follows: Zn – 410 mg/kg, Pb – 57 mg/kg, Cr – 36 mg/kg, Cu – 40 mg/kg, Cd – 5 mg/kg, Ni – 16 mg/kg and Ba – 267 mg/kg. According to the geochemical quality classification, the concentrations of Cd in 32% of samples were assigned to class IV (heavily contaminated), 45% to class III (contaminated), Zn in 42% samples to class III with 1 sample in class IV and 26% to class II (slightly contaminated), Pb in 9% to class III and 58% to class II, Cu in 4% to class III and 68% to class II, Cr in 17% to class II, Ni in 55% to class II, Ba in 8% to class III and 61% in class II. Coefficient of determination was determined between each case of trace elements content. The highest correlation (R2 in range from 0.81 to 0.96) was observed between Zn and Pb, Zn and Cu, Zn and Cr, Zn and Ni, Pb and Cu, Pb and Cr, Cu and Cr, Cr and Ni. Significant correlation (R2 in range from 0.70 to 0.80) occurred between: Zn and Cd, Pb and Ni, Cu and Ni, Cd and Ni. The lowest correlations (R2 in range from 0.25 to 0.70) were observed between concentration of Ba and the rest of trace elements. Two different interpolation methods were chosen for the purpose of generating spatial distributions – Inverse Distance Weighted and Ordinary Kriging. These methods were chosen for purpose of obtaining optimal accuracy result of spatial distributions. The distributions of trace elements content were classified by means of geochemical criteria. In the case of accuracy comparison between IDW and Ordinary Kriging, the former had slightly better results in terms of mean value and root mean square. The generated spatial distributions allowed to determine the most contaminated areas, which were mainly northern-central and southern-central parts of water Dzierżno Duże reservoir.