Strategies of Heavy Metal Uptake by Plants Growing under Urban Environment

Total concentration of iron, manganese, zinc, lead, copper, cadmium and chromium have been estimated in soil of residential, traffic and tannery sites at two depths (0-20 cm and 20-40 cm) and in leaves of plant species Azadirachta indica, Pongamia glabra and Delonix regia growing at traffic and industrial site in urban town of Dindigul. The metal concentrations were found to be higher at traffic and tannery sites compared to residential area. The heavy metal concentrations were found to be higher at 0-20 cm depth compared to (20-40 cm) depth. Delonix regia had higher concentration of Fe, Mn, Cu and Cr at traffic and tannery sites (318.4 mg/kg, 375.2 mg/kg, 71.6 mg/kg, 85.3 mg/kg and 290.2 mg/kg, 41.0 mg/kg and 1.25 mg/kg, 1.93 mg/ kg, respectively). Pongamia glabra showed the higher concentration of Zn and Cd at traffic and tannery site (75.8 mg/kg, 40.2 mg/kg and 2.28 mg/kg and 4.60 mg/kg, respectively). The concentration of Pb was higher for Azadirachta indica at traffic and Pongamia glabra at tannery site. The enrichment data indicated Cd was enriched in the soil compared to other elements. Cr was enriched more in the tannery site.The Enrichment factor of plants for heavy metals such as Mn, Zn, Cu, Pb and Cd has the EF value greater than 2 except for Fe and Cr. Mobility ratio for heavy metals was found to be greater than 2 except for chromium. Soil plant transfer data indicated that plant was enhanced with anthropogenic activities. Therefore, Azadirachta indica, Pongamia glabra and Delonix regia could be considered a more suitable to biomonitor the environmental pollution in the examined area. These plant species had potential use as a low cost tool in ecological restoration. Since they are tolerant to most of the pollutant in the area studied.