Abstract
A comparative research has been carried out to allow us to determine the quantities and the central points of accumulation of Pb, Zn and Cd in the vegetative organs of dandelion (Taraxacum officinale Web.), as well as to ascertain the possibilities of using dandelion as an indicator plant. The dandelion plants were collected from four selected sites with different anthropogenic activity in Plovdiv and the region of Plovdiv, Bulgaria. The contents of heavy metals in the plant material (roots, stems, leaves, and blossoms) were determined by the method of the microwave mineralization. To determine the heavy metal content in the samples, ICP was used. The distribution of heavy metals in the plant organs of Taraxacum officinale depends on the total content and quantity of available forms of the heavy metal in the soil. The number 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 a 0.1 km and 0.5 km distance from the source of pollution – the Non-Ferrous Metal Works (KCM) near Plovdiv, Bulgaria.
The lead and zinc translocation factors were greater than 1, whereas for cadmium it was less than 1. A clearly distinguished trend exists which describes the accumulation of heavy metals within the vegetative organs of the dandelion. The depots for accumulation were in the following order: for Pb and Zn: leaves >roots >blossoms > stems, and for Cd: roots >leaves > blossoms > stems. Higher Cd content was found in theunderground part of the plants, indicating soil contamination. As the level of contamination increased, thepotential of dandelion to uptake and accumulate Cd in the aerial parts of the plant increased. The higher Pband Zn content in the leaves rather than in the roots in all locations illustrated a contribution of significantatmospheric deposition. The content of heavy metals both in the dandelion plant tissue and in the soil shouldbe seen as a good indicator of environmental pollution.
Keywords: distribution, heavy metals, Taraxacum officinale, translation factor, uptake