Аннотация
The biogeochemical distribution of trace elements in desert soil–plant systems is of considerable importance for understanding element migration, nutrient cycling, and ecological adaptation in arid ecosystems. The aim of this study was to investigate the vertical distribution of Cr, Sc, Co, and Cs in desert soils and to evaluate their biological absorption by the medicinal plant Silybum marianum (L.) Gaertn. Soil samples collected from two profile horizons (0–28 and 28–48 cm) and leaf samples of S. marianum were analyzed using the neutron activation analysis method. The biological absorption coefficient (BAC) was calculated to evaluate the transfer of trace elements from soil to plant tissues. The results showed that the concentrations of Cr, Sc, Co, and Cs increased with soil depth, indicating limited vertical migration and the predominant influence of parent material on trace-element distribution. Chromium exhibited the highest concentration in plant leaves, whereas scandium showed the lowest accumulation. The calculated BAC values followed the sequence Cr -0.039 > Co-0.015 > Cs- 0.013 > Sc- 0.010, with all values remaining below 0.1, indicating weak biological uptake under desert conditions. The findings demonstrate that trace-element distribution in the studied soil–plant system is controlled by the combined effects of soil geochemical characteristics and plant physiological selectivity. The low biological absorption coefficients indicate limited phytoavailability of the investigated elements and suggest that Silybum marianum can serve as a suitable bioindicator for assessing trace-element mobility and soil–plant biogeochemical interactions in desert ecosystems. These results provide a scientific basis for ecological monitoring and the sustainable management of medicinal plant resources in arid regions.