Toxic Metals Extracted From Contaminated Soils by Wheat and Wheatgrass

Irina Shtangeeva, a researcher at the Department of Soil Science and Soil Ecology, St. Petersburg State University, studied the ability of wheat and wheatgrass to accumulate toxic substances. It turned out that both plants are capable of absorbing various chemical elements from the contaminated soil.

Interestingly, the plants do not die at the same time, but they accumulate toxicants in the shoots. These properties make wheatgrass and wheat especially effective for removing metals from soil by phytoextraction.

Today, ecologists often use phytoremediation methods to purify contaminated soils and wastewater - this is the name of a complex of remedial measures in which green plants play the main role. Phytoextraction is one of the directions of this method, which allows using hyperaccumulator plants to almost completely remove individual toxic microelements from contaminated soil. This method is quite inexpensive, and also does not destroy the soil, however, most often one hyperaccumulator plant is able to effectively accumulate only one element in the shoots.

“In my opinion, the search for new plants-hyperaccumulators of one metal is a dead-end path,” says Irina Shtangeeva, a researcher at the Department of Soil Science and Soil Ecology, St. Petersburg State University. “The fact is that usually the soil is not polluted with just one toxic microelement, but immediately with a group of metals, metalloids and organic pollutants.”

The scientist's experiments have shown that wheat and wheatgrass can become promising candidates for the role of such plants. The first representative of the flora, as Irina Shtangeeva notes, is able to survive in the most unfavorable conditions, and it also effectively accumulates various substances from the soil. Wheatgrass is one of the most common weeds in vegetable gardens, it also grows well in the immediate vicinity of roads with heavy traffic, is distinguished by its vitality and the ability to accumulate a large amount of various trace elements.

“Today you can find a lot of research on how plants accumulate cadmium, nickel, selenium and a number of other trace elements, the so-called heavy metals. However, almost no one is researching many other potentially toxic metals, the researcher said. “That is why I chose for my work“ unpopular ”trace elements, which are still little known in the context of phytoremediation: bromine, europium, scandium, thorium and uranium. It turned out that wheat and wheatgrass are able to efficiently absorb all these microelements simultaneously. At the same time, their content in the soil decreases ”.

What happens to plants after they have absorbed metals from the soil? As Irina Shtangeeva explains, they can be used in the future. There are commercial companies in Germany, Switzerland, the United States and some other countries that accept these plants for processing and extract toxic trace elements from them for use in industry.

In addition, the scientist emphasizes, it is important to take into account the specific time of cutting the plants. As her other  studies show, flora is affected by the circadian rhythm - the concentration of metals in plants can change depending on the time of day, so, for example, plants harvested at noon may contain more harmful substances than plants harvested in the morning or evening. ...

Another important factor that helps to make the phytoextraction process more efficient is the use of bacteria. Irina Shtangeeva's experiments demonstrate that wheat and wheatgrass seeds treated with Cellulomonas bacteria allow plants to accumulate more metals from contaminated soil. Apparently, they are able to “transform” metals into a more “digestible” form for plants.

Reference
Shtangeeva, I. About plant species potentially promising for phytoextraction of large amounts of toxic trace elements. Environ Geochem Health (2020). https://doi.org/10.1007/s10653-020-00633-z

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