Magnetic susceptibility as an indicator of heavy metal contamination of urban soils (Review)

Researchers have a particular interest in the assessment of magnetic susceptibility due to aerial contamination of soils by magnetite and heavy metals. The content of magnetite and other magnetic minerals in urban soils is tens and hundreds of times higher than their background values. The properties of technogenic magnetics are also different: whereas background soils are dominated by thin superparamagnetic and single-domain particles, large multidomain particles prevail in urban soils. Technogenic magnetics consist of micron-sized spherules. It has been proven that there is a correlation between magnetic susceptibility and the total content of heavy metals in soil. However, each city (or its district) has its own level, either positive or negative, which is determined by the nature of local contamination. Magnetic susceptibility maps have been created even for some countries (Poland, United Kingdom, etc.). Local surveys of urban areas, for example of a city or its vicinity, is of the greatest practical interest. Such maps reflect detailed contamination by heavy metals. Critical values of magnetic susceptibility above which soil is considered contaminated, differ between countries.