Phytoremediation of Metals

Using Plants for Bioremediation of Metals

Metal pollutants, such as those found in soil, water, or the air, can be removed, stabilized, or detoxified via a method known as phytoremediation. Numerous plant species have been investigated and used for their capacity to perform phytoremediation. Although phytoremediation's efficacy might vary depending on site-specific circumstances, the following 10 plant species are frequently known for their capacity to remove metals from soil:

1. One of the most well-known and extensively researched plants for metal phytoremediation is Indian mustard. It has the capacity to hyperaccumulate these metals at high quantities and can collect metals including cadmium, zinc, lead, and nickel in its tissues. “Indian mustard can be successfully grown under the heavy metal polluted sites and offers a great potential in reclamation of these soils through phytoextraction. It can uptake higher quantities of metals,

   sequester these contaminants in tissues and can even biodegrade them into less toxic forms.” (Rathore et al., 2017)

2. It is well known that sunflowers have the capacity to collect metals from contaminated soils, particularly lead. They can absorb more metal because of their extensive roots, which can go far into the ground.

3. Phytoremediation frequently employs willows because of their rapid development and deep root systems. They have the capacity to gather metals like cadmium, zinc, and nickel. Salix viminalis is one willow species that has been used to clean up water that has been contaminated with metals. “This species has been shown to take up and accumulate large quantities of zinc (Zn) and cadmium (Cd); it also has high biomass production. In comparison with species such as poplar, sunflower and tobacco, willow shows the highest uptake capacity in the field.” (Landberg et al., 2022)

4. In-depth research has been done on poplar trees' capacity to remove various pollutants, including metals. They have the capacity to gather metals like cadmium, copper, and zinc. Poplars are recognized for their quick growth and extensive root systems, which make them ideal for cleaning up soil and groundwater that have been poisoned with metals.

5. Because of its capacity to fix and immobilize metals in the soil, vetiver grass has been used in phytoremediation. “Phytoremediation of Cr and Ni is shown that heavy metal content in plant growth media were reduced during 28 days remediation by vetiver grass (C. zizanoides L.). The results showed heavy metal reduction were 61.10% and 95.65% in Cr-A treatment and Ni-A treatment respectively.” (Nugroho et al., 2021) Metal uptake and stability are aided by the plant's fibrous and thick root structure.

6. Athyrium yokoscense and Pteris vittata, popularly known as the "arsenic fern," are two fern species that are well-known for their propensity to hyperaccumulate elements like arsenic. They are capable of cleaning up soils that have been poisoned with arsenic. “The plant species (Athyrium yokoscense) best suited for phyto-extraction require the ability to accumulate large amounts of Cd in their shoots, extension of their roots into soil, rapid growth and a long growing period.” (Ogasawara, 2012)

7. The hyperaccumulator plant species known as alpine pennycress is capable of accumulating significant amounts of zinc, cadmium, and nickel. Its potential for phytoremediation of locations with metal contamination has been researched. ("Alpine pennycress, Thlaspi caerulescens, can concentrate cadmium in its leaves up to about 8,000 ppm (parts per million)…Harvesting the aboveground vegetation annually makes it possible to gradually reduce the soil concentration of cadmium to safe levels. The cost of this remediation method, called phytoextraction, is about $250 to $1,000 per acre per year.” (USDA.gov, 2004)

8. Water hyacynth, a floating aquatic plant, has been employed in the phytoremediation of metal-contaminated water bodies. Metals like cadmium, lead, and nickel can build up on it.

9. The capacity of Chinese brake fern to both accumulate and tolerate arsenic is well documented. It has been used in phytoremediation initiatives that aim to clean up water and soil contaminated by arsenic.

10. The potential of hemp plants for phytoremediation, including the uptake and buildup of metals like cadmium, lead, and nickel, has been investigated. “Since 1998, hemp has been successfully used to remove soil contaminants from agricultural lands that were heavily contaminated by the 1986 Chernobyl nuclear disaster [56]. In 2008, in an Italian farming region contaminated by a nearby steel plant, hemp was grown to leach pollutants, such as dioxin, from the soil [57].” (Placido & Lee, 2022)

It's important to remember that the individual pollutants, environmental factors, and site characteristics should all be considered when choosing plant species for phytoremediation. Phytoremediation operations frequently combine plant species to maximize metal removal and remediation results. Many of these studies also mention the effects of organic matter and microbes that aid in the remediation process.

Have you ever been involved in a phytoremediation project? If so, which plants did you use to remediate? And which compounds were you remediating?

Resources

Landberg T, Greger M. Phytoremediation Using Willow in Industrial Contaminated Soil. Sustainability. 2022; 14(14):8449. https://doi.org/10.3390/su14148449

Nugroho, A.P., Butar, E.S.B., Priantoro, E.A. et al. Phytoremediation of electroplating wastewater by vetiver grass (Chrysopogon zizanoides L.). Sci Rep 11, 14482 (2021). https://doi.org/10.1038/s41598-021-93923-0

Ogasawara, Masaru. Restoration of Cadmium (Cd) Pollution Soils by Use of Weeds. Weed Science Center (WSC), Utsunomiya University, 350 Mine-machi, Utsunomiya Japan. 2012. 15pp.

Placido, D. F., & Lee, C. C. (2022). Potential of Industrial Hemp for Phytoremediation of Heavy Metals. Plants (Basel, Switzerland), 11(5), 595. https://doi.org/10.3390/plants11050595

Rathore, Sanjay & Shekhawat, Kapila & Dass, Anchal & Kandpal, Bk & Singh, Vinod. (2017). Phytoremediation Mechanism in Indian Mustard (Brassica juncea) and Its Enhancement Through Agronomic Interventions. Proceedings of the National Academy of Sciences, India Section B: Biological Sciences. 89. 10.1007/s40011-017-0885-5.

USDA.gov. “Dainty Plant Outpowers Cadmium-Contaminated Soils.” Excerpt from Agricultural Research magazine. 2004.