The Dzhezkazgan region of Kazakhstan, with a long history of copper mining and smelting, is known as a potential heavy metal contaminated site. This study aimed to investigate the geochemical characteristics, assess the degree of contamination, and analyze the spatial variability of heavy metals in surface soils of this region. A total of ۵۰ soil samples were collected from a depth of ۰-۲۰ cm based on a systematic grid. The total concentration of heavy metals (copper, lead, zinc, nickel, arsenic, cadmium, chromium, and cobalt) was measured using X-ray fluorescence spectrometry. Geoaccumulation, pollution load, and potential ecological risk indices were used to assess contamination and risk. Multivariate statistical analyses and geostatistical methods (variogram and kriging) were used to identify the origin of metals and to map their spatial distribution, respectively. The results showed that the average concentrations of copper (۳.۴۵۲ mg kg-۱) and lead (۵.۹۸ mg kg-۱) were ۱۵ and ۴.۹ times the background concentrations of the area, respectively. The geoaccumulation index classified the soil contamination as “moderate to severe” for copper and “moderate” for lead and arsenic. The total potential ecological risk index (۸.۶۲۳) placed the area at “high ecological risk”. Principal component analysis showed that copper, lead, zinc and arsenic had a common anthropogenic origin related to mining activities, while nickel and chromium showed a geological origin. Variogram analysis indicated a strong spatial structure for copper (nugget/flood ratio: ۲۵%) with an influence range of ۳.۵ km. The equivalent maps obtained by Kriging interpolation showed a steep gradient of decreasing concentration by elevating distance from the main smelter, such that the copper concentration decreased from ۱۸۵۰ mg kg-۱ in the vicinity of the source to ۵۰ mg kg-۱ at a distance of ۱۴ km. As a result, the soils of the
Zhezkazgan region have experienced widespread and severe contamination by heavy metals, especially copper, the spatial pattern of which is mainly controlled by atmospheric emissions from industrial fixed points.
