Distribution of heavy metals in Phragmites australis growing in constructed treatment wetlands and comparison with natural unpolluted sites

The study is aimed at the distribution of heavy metals in Phragmites australis growing in constructed wetlands as well as in natural stands. Three full-scale constructed wetlands and five natural wetlands were selected. The shoots of P. australis were analysed for Cu, Cd, Cr, Ni, Pb and Zn. The results revealed that the highest biomass was recorded in base parts of the shoots - 38% in constructed and 42% in natural wetlands. On the other hand, the lowest biomass occurred in top part of the shoots - 30% in constructed wetlands and 24% in natural wetlands. The highest amount of heavy metals was accumulated in the base parts of stems followed by top part of leaves. The only exception was the highest accumulation of Cu and Zn in top leaves in constructed wetlands. The accumulation of heavy metals decreases from the base to the top in stems and in the same direction the accumulation in leaves increases. Sequestration of heavy metals followed the same pattern in both constructed and natural wetlands. The average heavy metal standing stock in stems amounted to 56% in both constructed and natural wetlands, In leaves, the respective standing stocks amounted to 43.9% and 44%.

Automated summary

The study found that the base of the Phragmites australis had the highest biomass, while the top had the lowest. Heavy metals mainly accumulated in the base of the stems and the top of the leaves, with the highest accumulation of Cu and Zn in the constructed wetlands. The accumulation of heavy metals decreased from the base to the top in stems, while increasing in leaves.