Impact of soil geochemical contamination on plant community stability in Zhezkazgan and Temirtau, Kazakhstan using X-ray fluorescence and granulometric analyses

Mining and metallurgical industrial activities often lead to the accumulation of heavy metals in the soil and create ecological pressure on adjacent ecosystems. This study aimed to assess the impact of soil geochemical pollution on the stability of plant communities in two industrial regions of Dzhezkazgan (copper deposit) and Temirtau (steel industry) in Kazakhstan. In each region, ۱۵ study plots were established and their soil samples were collected. Heavy metal concentrations (copper, lead, zinc, arsenic, and nickel) were measured with a portable X-ray fluorescence (XRF) device and soil texture was determined by hydrometry. In addition, the vegetation cover of each plot was fully recorded and diversity indices were calculated. The results showed that the soil in both regions is severely polluted. The average copper concentration in Dzhezkazgan was ۴۱۲.۵ ± ۱۸۵.۵ mg kg-۱ and the average lead concentration in Temirtau was ۲۵۵.۳±۱۱۰.۸ mg kg-۱. Correlation analysis showed a strong and significant negative relationship between the concentration of these metals and the Shannon-Wiener diversity index of plant communities (r = -۰.۹۲ for lead in Temirtau). By increasing pollution, sensitive species such as Stipa capillata and Festuca valesiaca completely disappeared, and resistant and roderal species such as Artemisia austriaca occupied up to ۳۸.۵% of the dominant cover. The diversity index in the most polluted plots was significantly reduced compared to the reference points. The rank-order analysis (RDA) confirmed that heavy metals explained ۶۸% of the variance in species composition. Also, the integrated soil quality index (SQI) showed that ۶۰% of the Temirtau plots and ۴۰% of the Dzhezkazgan plots were in a “degraded” state. Finally, this study showed that industrial soil pollution not only drastically alters the chemical composition of the soil, but also the structure, diversity, and stability of plant communities, leading to the formation of poor communities composed of resistant species.

کلیدواژه ها:

Soil pollution ، Heavy metals ، Plant biodiversity ، X-ray fluorescence (XRF) ، Industrial ecosystems