Concentration and translocation of trace metals in Solidago gigantea in urban areas: a potential bioindicator

Invasive species usually grow in human-disturbed habitats including urban areas where they face numerous pollutants, including metals that attract special attention due to their non-degradability and high accumulation potential. In this study we evaluated the contents of potentially toxic metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) in the invasive species Solidago gigantea. The strategy adopted by S. gigantea in response to excess trace metals in the soil was assessed. Metal contents were determined using atomic absorption spectrometry in leaves, stems and roots of S. gigantea collected from 30 sites located in areas affected by various human activities. Metal concentrations (total and bioavailable fraction) were also determined in corresponding soil samples. Results showed that S. gigantea was able to inhabit strongly polluted sites. High Bioaccumulation Factor but low Translocation Factor values for Cd, Cu, Cr, Fe, Ni show that S. gigantea takes up metals from soil but reduces their transport to the aboveground parts and could be classified as a metal-tolerant species with exclusion strategy. The Bioaccumulation Factor values for Cd, Cu, Cr, Pb and Zn were remarkably higher in plants growing in areas characterized by low metal concentrations in soil compared to the ones affected by industry, with high metal concentrations. This suggests that S. gigantea that grows in polluted areas can reduce the uptake of potentially toxic metals. Regardless of the limited transport of metals to the aboveground organs, the content of metals in S. gigantea leaves differed between areas differing in human impact and the species can be used as a biomonitor.