UAE shrub could prove key to solving soil pollution

The auricula shrub, or Calotropis procera, is native to the Middle East

Professor Ali Al Keblawy with the auricular shrub. Courtsey: Professor Al Keblawy

Scientists have recommended planting more of a particular species of desert shrub to help clean up polluted areas of the Emirates.

Researchers found that the auricula shrub, already native to the Middle East, was especially effective at absorbing toxic heavy metals.

A recent study found the plant took in iron, manganese, strontium and zinc through its roots before channelling the metals to its leaves.

When the leaves shed naturally and fell to the ground, scientists suggested they be collected and incinerated, helping detoxify the surrounding soil.

“Plants can’t get rid of the things that they absorb from the ground or from the air easily, that’s why they accumulate,” said Dr Ahmed Al Mehdi, an associate professor at the University of Sharjah’s Department of Chemistry.

“The high accumulation of different heavy metals in a small volume of old leaves makes it easy to get rid of them directly by dumping in landfills or through incineration,” the study added.

The new UAE research was published in the International Journal of Phytoremediation and written by six researchers from the University of Sharjah and one from Banaras Hindu University in Varanasi, India.

The study took samples from the roots, stems, green leaves and old leaves of auricula shrubs growing alongside Emirates Road in Dubai.

The tissues were then analysed using microscopes and a technique known as spectroscopy, which measures electromagnetic radiation.

Prof Ali Al Keblawy, from the University of Sharjah’s Department of Applied Biology, said heavy metals were usually toxic to plants.

But he said some species had developed effective strategies to combat the issue, storing “limited” amounts of absorbed metals in leaf cells called vacuoles.

“That’s why the plant redirects them [toxic metals] from the general leaves to old leaves before they drop them,” he said.

“It seems it’s a strategy. In all cases, old leaves will be dropped. The plant will immediately get rid of the leaves.

“The main conclusion [is that] we can use these plants for cleaning our environment from heavy metals.”

Heavy metal contamination of soil can come from the air as well as a variety of other factors.

The wear and tear of road surfaces, for example, which contain nickel and zinc, can contribute to the issue, as can the vehicles which use them.

A car tyre — which is typically made up of between 1.3 and 1.7 per cent zinc — might lose 1.5 kilograms of weight in its lifetime.

And after rainfall, this and other metals left by brake and clutch wear, can be washed from motorways into nearby soil.

Prof Al Keblawy said that because the auricula shrub, also known by its Latin name Calotropis procera, was native to the Middle East, it was an ideal plant to help tackle polluted soil.

He argued the species was well adapted in coping with the country’s often severe climate, offering a more effective solution than other foreign plants.

The shrub is already relatively common in the UAE, although its exact distribution across the country is not known.

“It’s very important to use such plants rather than exotic plants coming from other countries which don’t tolerate the heat and use too much water,” he said.

“Why not use native plants that have the ability to clean the environment and at the same time they’re conserving water and they don’t need much nutrients?”