The use of the magnetic susceptibility index of soils for the assessment of the ecological state of the soils in Yakutsk
For the first time, the volume magnetic susceptibility (VMS) was determined for technogenically polluted soils of Yakutsk formed on permafrost and functioning in the cryoarid climate of Central Yakutia. Magnetometric survey was carried out over the territory of the modern city of Yakutsk using an arbitrary observation network, and 444 measurements of soil VMS were made using a small-sized KM-7 kappameter. The values of soil VMS in Yakutsk vary significantly, with the average value equal to 163.5·10<sup>-5</sup> Si units. This parameter varies within the range 13,2-1220,0·10<sup>-5</sup> Si units, that is, almost three orders of magnitude (10<sup>3</sup>), which points to its high variability while the variation coefficient is V = 64 %. The average values of VMS obtained for the soils of individual streets and districts of the city vary significantly, too: from 80,3 to 314,6·10<sup>-5</sup> Si units, which is almost 4 times. A histogram of the VMS of soils in Yakutsk was compiled, when the entire data array was divided into 7 ranks or classes with a step equal to 50·10<sup>-5</sup> Si units. As a result, the majority of all values (84 %) fit within the range up to 250·10<sup>-5</sup> Si units, while only 16 % of the total number of measurements were above 250·10<sup>-5</sup> Si units. According to the results of the study, it was also found that the total indicator of contamination of the studied soils with heavy metals (Zc) is associated with the VMS indicator with a strong positive (r = 0,937) statistically significant (n = 8, rst = 0,707, p = 0,95) correlation, almost approaching a linear relationship. The average VMS of the Yakutsk soils is comparable with the values determined for the industrial districts of Moscow (160-180·10<sup>-5</sup> Si units), Perm (183·10<sup>-5</sup> units Si), Mednogorsk (158·10<sup>-5</sup> Si units), but at the same time it is much larger than the values obtained for large industrial cities in China, such as Hangzhou and Luoyang (128·10<sup>-5</sup> Si units).