Lead in Soils and Tolerant Herbs on Roadsides in Search of the Metal Accumulation Patterns in Diverse Species

Lead contamination in roadside soil is a global phenomenon, but Lead accumulation in roadside herbs is least reported. Lead accumulating species are rare; the success of phytoremediation of Lead contaminated soils depends on the discovery of new Lead hyper accumulators. In this context, Lead in the shoots and roots of about nineteen tolerant roadside herbs growing in soils close to one meter margin from the tar-edge of two busy roadsides in Kerala in South India was examined. Soil and plant samples were collected for two years from different sites differing in the degree of contamination. Lead in the shoots of all plant species and also in the roots of grasses, and in the soils where the plants grew was assessed, compared and statistically analyzed. The roadside soils were found moderately Lead contaminated. All the species were found accumulating Lead in shoots or roots in significantly different amounts. Positive correlations were found between Lead in plants and that in the different soils where they grew and in some of the species, the correlations were very strong. Lead in the shoots of Pilea microphylla (L.) Liebm., and that in the roots of Cynodon dactylon (L.) Pers., was found in quantities higher than the quantity of the metal in the soil.