Potential of Ornamental Trees to Remediate Trace Metal Contaminated Soils for Environmental Safety and Urban Green Space Development

Heavy metals are notoriously toxic pollutants which can potentially harm living beings and are serious health hazards. The aim of the present study was to assess the levels of cadmium (Cd) and nickel (Ni) throughout the year in the urban areas of the densely populated industrial city of Faisalabad in eight commonly raised ornamental tree species with phytoremediation potential. High levels of Cd and Ni were recorded in all study areas, with spatio-temporal heterogeneity. Heavy metal uptake varied among plant species with Cd and Ni in soil ranging between 6.78-8.57 mgkg(-1) and 46.31-55.85 mg kg(-1) respectively. Plant species accumulated 6.73-8.98 mg kg(-1) Cd and 26.42-52.50 mg kg(-1) Ni with Conocarpus erectus, Dalbergia sissoo and Bismarckia nobilis showing higher accumulation potential than others. Dalbergia sissoo accumulated the highest levels of Ni and was shown to a good bio-indicator for this metal. The highest accumulation of Cd was recorded in Conocarpus erectus (9 mg kg(-1)), followed by Dalbergia sissoo (8.2 mg kg(-1)) and Bismarckia nobilis (8.1 mg kg(-1)) while the leaves of Azadirachta indica retained the lowest (6.3 mg kg(-1)) Cd levels. The highest levels of metals were accumulated by all species during the summer season while the second highest were observed in the autumn season. The study revealed that ornamental species can help in minimizing heavy metal pollution as well as providing green space in urban settings for maintaining a clean and healthy environment.

Automated summary

Heavy metals, such as cadmium and nickel, were found to be present at high levels in urban areas of Faisalabad. Different tree species showed variation in their uptake of these metals from soil. Certain species, like Conocarpus erectus, Dalbergia sissoo, and Bismarckia nobilis, had higher accumulation potential. The study suggests that ornamental tree species can play a role in reducing heavy metal pollution and creating a healthier urban environment.