A study of the composition of mobile compounds of heavy metals (HM) in the area of aerosol contamination by a heat supply company showed an increase in the number of these compounds near the source of contamination. In the group of loosely bound compounds, the largest part is represented by specifically sorbed compounds. Sample preparation (the degree of sample grinding) had a noticeable effect on the extractability of Zn, Cu, and Pb from the soil. During the sifting of a soil sample through a 0.25 mm sieve, the extraction of mobile forms of HM increases significantly (by 7-16 %). Thus, with an increase in the specific surface of soil particles, the extracting ability of the reagents increases. It is necessary to take into account the sample preparation used in each fractionation method to evaluate the results and compare them.