Biomonitoring of heavy metal contamination in Pongamia pinnata and Peltophorum pterocarpum growing in the polluted environment of Karachi, Pakistan

Determination of some of the important heavy metals like lead and cadmium was carried out in the city environment of Karachi. Foliage parts of two roadside trees, Pongamia pinnata (L.) Merrill and Peltophorum pterocarpum D.C. Backer ex K. were used to carry out such investigation. Five roadside points were selected for the study in different parts of the city. The investigations showed that high level of lead and cadmium was found in the foliage of P. pinnata and P. pterocarpum, which were growing along the busy roads of the city. The level of Pb and Cd in the foliage of the above mentioned trees was quite high at M.A. Jinnah road as compared to Shahrahe- Faisal, Nazimabad, Gulshan-e-Iqbal and Karachi University Campus. Low traffic activities at the University Campus showed lowest lead and cadmium levels in the foliage of both tree species than the other point of the city. In this study, P. pinnata showed more accumulations of lead and cadmium than P. pterocarpum. This difference might be due to large surface area of the foliage in P. pinnata that is available for exposure to any pollutants as compared to P. pterocarpum. P. pinnata is a useful plant species in removing different heavy metals from the urban environment of the city. It is therefore suggested, that P. pinnata should be given more preference for future plantation in the areas, particularly along the busy roads and highways.