Analysis of the radioecological situation in oil-contaminated areas: migration characteristics of heavy metals in soil

This study presents a comprehensive geochemical and radioecological assessment of oil-contaminated landscapes on the Absheron Peninsula, one of the most environmentally impacted regions in Azerbaijan due to extensive petroleum extraction. By employing an integrated methodological framework encompassing field surveys, soil profiling, multi-component chemical analysis, and biological monitoring, the research identifies the patterns of migration, accumulation, and bioavailability of heavy metals and macro-elements in various landscape components – including soils, rocks, surface waters, and vegetation. The findings reveal that long-term oil pollution has significantly altered the natural geochemical balance, resulting in both vertical and lateral migration of trace elements. Elevated concentrations of hydrocarbonates were detected in surface and subsurface waters, as well as in soils, where they influence the solubility, mobility and trasport of metals. Elements such as Cl, Sb, Cd, Tb, and Ag exhibit abnormally high concentrations in the upper soil layers, indicating anthropogenic enrichment, while elements like Fe, Sr, Rb, and Zr show increased accumulation in deeper soil horizons, suggesting delayed migration processes and sorption effects. Biological absorption coefficients (Kb) and Clarke concentration values (CC) were calculated to assess the biogeochemical behavior and mobility of these elements, highlighting the influence of both lithological composition and rather hydrologeological dynamics on element distribution. The study found that urban soils showed heavy metal concentrations up to 20 times higher than background levels. The order of metal mobility in soil decreased as follows: Cd > Mn > Pb > Zn > Ni = Cu > Co > Cr > Fe. In plants, the accumulation followed a different pattern: Fe > Zn = Mn > Pb > Cu > Cr > Co > Ni > Cd. The study also identifies specific zones of geochemical anomalies and heavy metal enrichment, emphasizing the ecological risks associated with these patterns. The results contribute to a better understanding of hydrocarbonate-metal interactions and element migration in disturbed landscapes, providing a scientific basis for remediation strategies and environmental monitoring protocols in oil-impacted areas.