Statistical processing of the selection of samples was performed using Microsoft Excel. For samples of metals in the sludge and bottom sediments of the background area, the mean values, median, and double median absolute deviations (MAD — (Lukashov, 2007)) were calculated. The median value + 2MAD was used as the threshold value of the background concentrations of metals.
The degree of contamination of the sediments in the watercourses of mines was calculated using the total pollution index (Guidelines for assessing the danger of soil contamination with chemicals, 1987) by the formula: