This study investigates sedimentation rates and historical trends of heavy metal concentrations in two lakes (Câşla and Somova), part of the Somova-Parcheş aquatic complex, located in the predeltaic sector of Danube Delta (Tulcea - Romania), based on sediment core analyses. The area was historically affected by intensive ferroalloy and alumina processing activities. Radiometric dating based on of 210Pb, 137Cs and the 226Ra radionuclides, provided results which were used to estimate the sediment accumulation rates and depositional dynamics. The results reveal distinct sedimentation regimes in both lakes, reflecting catchment-scale environmental changes, which may be linked to erosion and extreme hydrological events. A positive correlation was observed between sedimentation rate and metal accumulation rate, whereas metal concentrations exhibited an inverse relationship with sedimentation rate, suggesting a dilution effect linked to increased mineral input. The sediments from Somova Lake had a high content of Cd (0.26 - 13.37 mg/kg), Pb (293.65 - 3416.77 mg/kg), Cu (84.13 - 547.98 mg/kg) and Zn (468.98 - 4070.48 mg/kg), exceeding the national guideline values for these elements. Geo-accumulation index (Igeo) and enrichment factor (EF) assessments indicate moderate contamination in Câşla Lake, primarily driven by Cd, whereas Somova Lake exhibits strong to very strong contamination with Cd and Pb and significant enrichment in Zn and Cu. Overall, the findings highlight correlation between sediment dynamics and anthropogenic metal inputs and underscore the environmental vulnerability of the pre-deltaic lake systems.
Bican-Brişan et al. (Mon,) studied this question.