How scientists use natural processes to detoxify the environment

Pollution is everywhere. The land, oceans, and atmosphere all feel the effects of human activity. Pollution can even make its way into the soil, with heavy, toxic metals accumulating in the earth and harming both the ecosystem and human health (1). One eco-friendly and cost-efficient method of dealing with polluted soil is phytoremediation (1, 2). Phytoremediation uses plants and microorganisms to extract pollutants and minimize the consequences of toxic contaminants on the environment. But how does phytoremediation work, and what makes it better than artificial alternatives?

Metal contamination in soil can have major consequences on the surrounding environment. 

Phytoremediation consists of planting specialized plants in contaminated areas to detoxify the surrounding biosphere. Many processes within plants are necessary for phytoremediation to occur. To remove metals from the soil, the plant first needs to make them soluble enough to be absorbed by secreting special compounds (1). Through diffusion and active transport, the metals enter the root cells. Once inside, the heavy metallic ions form new compounds with existing acids and are contained within both the cell walls and storage vacuoles (1). Some of these compounds may be transported through the xylem and into the leaves. However, the plant must be able to withstand the metal toxicity, so plants have developed defenses to withstand the presence of harmful substances in the soil. One such strategy is avoidance, where plants force metals to precipitate and restrict the transport system of toxic substances, limiting the uptake of metals from the roots to other plant cells (1). A second defense is tolerance, where proteins and amino acids within the plant cells detoxify metals (1). 

Phytoremediation can take many different forms that tap into different plant processes. Phytostabilization, for example, prevents contaminants from spreading by using plants with especially high tolerance against metals to trap the metals underground and prevent them from escaping into the surrounding environment (1, 2). This process can be facilitated by the use of microorganisms that make it easier for the plant to immobilize metals. Phytoextraction is another type of phytoremediation, in which plants transport metals from the soil up to harvestable plant tissues. Plant engineers select plants that mature quickly to ensure a continuous process and repeatedly harvest the plants to reduce the concentration of metals over time (1, 2). Phytoextraction offers advantages over phytostabilization by providing a more permanent solution that removes the metals from the ground (1). Various other methods of phytoremediation exist, such as phytovolatilization, which converts metals into gaseous states and releases them into the atmosphere, and phytodegradation, where plants release enzymes to break down metals directly (2). 

Diagram showcasing the different types of phytoremediation and what areas of the plant they focus on. 

https://en.wikipedia.org/wiki/Phytoremediation

Phytoremediation offers several advantages over other methods. Since phytoremediation is powered purely by solar energy, its cost and maintenance are low (1). Phytoremediation also reduces exposure of secondary pollutants and can be applied on a large scale (1). While other methods of managing soil pollution exist–including encapsulating contaminated soil with cement, separating metals with water, using landfills, and even applying electrical currents–phytoremediation remains the cheapest and most effective solution to detoxifying our world. Its only drawbacks are the time required and the limited depth of soil it can affect, but neither makes it inferior to synthetic alternatives. In some cases, humanity truly cannot create a solution superior to the one created by Mother Nature. 

Bibliography

1. Yan, A., Wang, Y., Tan, S. N., Mohd Yusof, M. L., Ghosh, S., & Chen, Z. (2020). Phytoremediation: A Promising Approach for Revegetation of Heavy Metal-Polluted Land. Frontiers in Plant Science, 11(359). https://doi.org/10.3389/fpls.2020.00359 

2. Greipsson, S. (2011). Phytoremediation | Learn Science at Scitable. Nature.com. https://www.nature.com/scitable/knowledge/library/phytoremediation-17359669/ 

3. Liu, N., Zhao, J., Du, J., Hou, C., Zhou, X., Chen, J., & Zhang, Y. (2024). Non-phytoremediation and phytoremediation technologies of integrated remediation for water and soil heavy metal pollution: A comprehensive review. Science of the Total Environment, 948, 174237. https://doi.org/10.1016/j.scitotenv.2024.174237