Some city trees quietly soak up heavy metal pollution from soil
Adhikari P, Shrestha A, Shrestha U, Rijal S, Acharya BD
Phytoremediation
That scraggly street tree outside your window might be doing double duty as a pollution gauge, since certain species pull far more lead, copper, and cadmium out of urban soil than others.
Researchers compared trees growing in a clean part of a Nepali city with trees near heavy traffic and factories, and found the polluted-area trees had soaked up noticeably more toxic metals like copper, zinc, lead, and cadmium from the soil. Some species were much better at this than others: jackfruit trees pulled in the most cadmium, while a type of fig grabbed the most zinc. Because these trees act like sponges for pollution, scientists think planting the right species along busy roads could help track, and maybe even soak up, urban contamination.
Key Findings
Heavily polluted site soil showed severe copper contamination, with copper, zinc, and nickel traced to industrial and vehicle emissions via enrichment factor analysis.
Species-specific accumulation varied widely: Syzygium cumini took up the most copper (53.00 mg/kg), Ficus benghalensis the most zinc (143.33 mg/kg), and Artocarpus heterophyllus the most cadmium (5.33 mg/kg).
Artocarpus heterophyllus bark showed the highest metal accumulation index (17.28), and both it and Ficus benghalensis showed high bioaccumulation factors, marking them as strong candidates for pollution monitoring.
chevron_right Technical Summary
Trees growing near heavy traffic and industry in a Nepali city soak up copper, zinc, lead, and cadmium from polluted soil, and certain species like jackfruit and Indian rubber tree build up especially high levels, making them useful living pollution monitors.
Abstract Preview
Original paper
Heavy metal accumulation in soil and trees of Bhairahawa, a tropical urban city of Nepal: implications for pollution monitoring.
Heavy metals (HMs), including copper (Cu), zinc (Zn), nickel (Ni), lead (Pb), and cadmium (Cd), accumulation in the soil and trees of less polluted (LP) and heavily polluted (HP) sites in the tropi...
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