Impact of Single and Mixed Heavy Metal Contamination on Accumulation Patterns and Organ Distribution in Sunflowers

Sunflowers, recognized for their exceptional tolerance and accumulation capacity for heavy metals, are widely used as a model plant in phytoremediation technologies. However, due to the physicochemical properties of heavy metals and the physiological differences among plant tissues, the accumulation of heavy metals in different plant organs exhibits significant variability. Considering that heavy metal contamination in natural environments often involves complex mixtures rather than single pollutants, investigating the accumulation and distribution characteristics of sunflowers in soils contaminated with multiple heavy metals is of critical importance. In this study, pot experiments were conducted to systematically compare the germination, biomass, heavy metal accumulation, and organ-specific distribution of sunflowers grown in soils contaminated with single heavy metals (As, Cd, Cu, Ni, Pb, and Zn) and those with mixed heavy metals. The results revealed no significant differences in germination rates or total biomass of sunflowers between single and mixed contamination conditions. Similarly, the total accumulation of heavy metals in sunflower plants did not differ significantly. However, the distribution of heavy metals among plant organs showed notable differences: under mixed contamination, the accumulation of As, Ni, and Pb in sunflower roots was significantly higher compared to single-contamination conditions, while the distribution ratios of Cd and Cu in plant organs were unaffected by the type of contamination. This study elucidates the impact of mixed contamination on heavy metal distribution and provides critical scientific insights for the practical application of phytoremediation in complex contamination scenarios, offering a framework for optimizing remediation strategies and improving efficiency.