Overcoming pollution by ... grass

Broccoli, ferns, vetiver grass, betel nut grass . are used to overcome heavy metal pollution on ore mining and processing areas.

This is a new study of scientists from the Institute of Environmental Technology (Vietnam Academy of Science and Technology).

According to the research results, only after 2-3 years, the land has been mined, heavy metals in the soil will be fully absorbed by the plant. Experimental results at some ore mines in Thai Nguyen show that heavy metals such as arsenic, lead, cadmium and zinc (As, Pb, Cd and Zn) are treated significantly.

Prof. Dr. Dang Dinh Kim, Chairman of the Scientific Council of the Institute of Environmental Technology, chairman of the project, said since 2007, scientists from the Institute of Environmental Technology, Institute of Ecology and Biological Resources, Hanoi National University started to carry out the project 'Research on the use of plants to improve heavy metal contaminated soil in mineral exploitation areas' (under the key state-level Science and Technology Program on talents). Natural, environmental and natural disasters - KC 08.04 / 06-10).

In 2007 and 2008, scientists took hundreds of acres of land and trees in the mines (Mount Hong coal mine in Yen Lang commune, tin mine in Ha Thuong commune - Dai Tu district; Trai Cau iron mine and lead and zinc village mines). Hích - Đồng Hy district, Thái Nguyên province to analyze components and content of heavy metals.

The scientist examined the fern growing model in Ha Thuong, Dai Tu and Thai Nguyen communes.Photo: Manh Dong

The results show that Mount Hong coal mine is a hot spot for arsenic pollution in soil. Here, arsenic content reaches 202 - 3,690 ppm (1ppm = 1 part million), more than 300 times higher than the Vietnamese Standard for arsenic content in soil .

Tin mine in Ha Thuong commune has serious arsenic pollution, some places arsenic content in soil is 1.262 times higher than Vietnam Standard!

Besides, the researchers also collected 157 plant species on ore dumps and surrounding areas. Thereby, 33 species of plants can be survived on high contaminated soil.

Analysis results show that there are 2 species of fern family (scientific name: Pteris vittata and Pityrogramma calomelanos) and betel nut grass (scientific name Eleusine indica) capable of heavy metal accumulation, arsenic content to 5,876ppm and in the root is 2,642ppm. Betel grass can be used as a recovery solution for areas contaminated with lead and zinc.

Research has shown that vetiver grass is also resistant to very high levels of lead pollution (experimental planting in soil contaminated from 1,400ppm to 2,530ppm, grass still grows well).

This is the basis for scientists to study and experiment with these plants for the purpose of restoring areas of heavy metal pollution, especially in mining areas.

After selection and analysis, the scientists tested vetiver grass and Pteris vittata fern in Hich village with an area of ​​over 600m ² .

In Ha Thuong commune, scientists also experimentally tested the ability to absorb arsenic of two species of fern Pteris vittata, Pityrogramma calomelanos and vetiver grass on an area of ​​over 700m2.

Test results in Ha Thuong commune showed that after 4 months of trial planting, the arsenic content in soil decreased from 5,606.31 ppm to 4,521 ppm.

From this result, the research team continued to improve the technological process to propagate 2 native ferns, betel nut grass and vetiver grass to recover soil contaminated with heavy metals.

Currently, scientists propose to the Government and ore mining and processing units to early deploy the application of plants in soil pollution treatment.

Geological exploration results across the country show that there are about 5,000 mines and ore spots, of which about 1,000 mines have been exploited. Particularly, the land area has stopped exploiting up to 3,749ha. However, very few areas after being exploited are incomplete, or of poor quality, not suitable for cultivation.