Differentiation of Nanoparticles Isolated from Distinct Plant Species Naturally Growing in a Heavy Metal Polluted Site

Leaves harvested from the plants of two different species (Dittrichia viscosa and Cichorium intybus) grown in their autogenous environment near a steel manufacturing company were characterized for naturally accumulated nanoparticles. These plant species are known to accumulate heavy metals. It was, however, unknown if these species would also accumulate these heavy metals in the form of nanoparticles. The isolated solid fractions were analyzed using dynamic light scattering, X-ray fluorescence, and transmission electron microscopy. These analyses revealed the presence of nanoparticles within the plants. The composition of nanoparticles found in each plant species is distinct: (i) for Dittrichia viscosa, the nanoparticle composition matched the heavy metal pollution anticipated from the surrounding industries; (ii) for Cichorium intybus, the nanoparticle composition was similar to the most abundant elements in the soil. The different behavior is a reflection of the phytoaccumulator characteristics of both species. This study provides the first evidence of sequestration of heavy metals in the form of nanoparticles by plants grown autogenously in polluted areas and will have implications in waste management of phytoremediation systems and in understanding the heavy metal life-cycle in the environment.