Soil contamination by heavy metals and their translocation in spring and winter wheat at sites distant from the Alaverdi Copper Smelting Plant, Armenia

An investigation was conducted into variations in concentrations of selected heavy metals (HMs) in soil and in spring- and winter-wheat crops cultivated near the Alaverdi Copper Smelting Plant (ACSP). The study aimed to elucidate the relationship between their agrochemical indicators and distance from the pollution source, specifically the ACSP. Soil samples were collected from private farm sites at specified distances from the primary pollution source, including 3, 5, 10, and 30 km, reflecting the prevailing wind direction gradient in each region. Changes in the concentration of HMs in soil are largely due to alternation between accumulation within the soil layer and subsequent migration away from the immediate source of pollution. In areas close to the main source of pollution (3 km), intensive accumulation and passive scattering of HMs in the soil were observed, as the ratios Cc > 1 and Sc < 1 were maintained for all elements. The total pollution index analysis revealed that within 3 km, only Cu and Pb exhibited fifth-degree contamination, while Zn and Mo showed third-degree contamination. The overall soil contamination indicated a dangerous hazard level up to 3 km and a moderate risk level up to 5 km. The accumulation potential of HMs was observed in the following order: Mo < Pb < Cu < Zn. The mobility index was calculated as the ratio of HMs concentrations in roots-to-straw and straw-to-grain for both plants. Uptake increases several times as total HM concentrations in soil rise.