Dandelion Plants as a Biomonitor of Urban Area Contamination by Heavy Metals

To examine metal content of dandelion plants in relation to environmental metal levels, concentrations of Cd, Hg and Pb were analyzed in plant parts (leaves and roots) and soil samples from five sites in the city of Brno (Czech Republic), differentially impacted by pollution. Soils and plants were collected mid-April 2011. Atomic absorption spectrometry was used to determine concentrations of the studied elements. The amount of metals measured in soils and plants corresponded with the contamination load of the sampling place. The highest values of metals were found in the soil and plants sampled at Opuštěná Street, a heavily polluted locality with high traffic density situated in the city centre. Significant correlations were found between the amount of Cd in the soil and in the dandelion roots (r = 0.863) and between the amount of Pb (r = 0.870) and Hg (r = 0.828) in the soil and in the dandelion leaves. Higher Cd content was found in underground part of the plants, indicating soil contamination. The higher Hg and Pb content in leaves rather than in roots in all locations illustrated a contribution of significant atmospheric deposition. Washing the leaves before the analysis significantly reduced the measured metal concentrations. This indicated that substantial amount of metals was on the leaves surface as dry aerosol particles. Inter-metal correlations between soil, leaves and roots samples showed that the sources of Cd, Pb and Hg pollution in Brno urban areas were mainly of anthropogenic origin. The content of heavy metals both in the dandelion plant tissue and in the soil should be seen as a good indicator of natural urban environmental pollution.