The research focuses on the assessment of potential toxic elements (PTEs) contamination of the soils of the Kočani field (North Macedonia) due to the surrounding past and current polymetallic mining activities. The Zletovska River drains the untreated wastewater from the Pb-Zn mine in the Zletovo-Kratovo region and is unfortunately used to irrigate the surrounding rice fields. Elevated levels of molybdenum (Mo) and especially lead (Pb) and zinc (Zn) were found in the soil samples from the rice fields near the Zletovska River (in the western part of the Kočani field), which are well above the limit and critical emission values for PTEs content in soils. In addition, Mo was consistently bound to water soluble, exchangeable and oxidizable fractions in all samples, while reducible and residual fractions were predominated by Pb and Zn. According to the sum of the water-soluble and exchangeable fractions, the mobility and environmental bioavailability potential of the investigated PTEs in the soil-plant system decreased in the following order: Mo > Pb > Zn. It is therefore very important to emphasize that when assessing the environmental impact of PTEs on the respective surroundings, not only the commonly considered trace and minor PTEs (such as Pb and Zn) that occur in geological materials should be taken into account, but also in lower contents (such as Mo). The translocation of PTEs within the ecosystem does not depend on their total content in the primary geological materials, but on their individual mobility and binding capacity.
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