Decontamination of pollutants present in water, air, and soil through phytoremediation: a critical review

Phytoremediation is a technique that uses plants to decontaminate polluted environments, such as soil, water and even air. Plants employ several mechanisms to remove, stabilize or degrade contaminants, depending on the nature of the pollutant and the environmental conditions. The main mechanisms include: phytoextraction, phytodegradation, phytovolatilization, phytostabilization and rhizofiltration. The uptake of heavy metals by plants is influenced by several key factors. Soil characteristics such as soil properties such as pH, organic matter content, cation exchange capacity (CEC), and texture significantly affect the mobility and bioavailability of heavy metals. For example, soil pH influences metal solubility, and acidic conditions generally increase the availability of metals. Conversely, higher organic matter and CEC can bind heavy metals, reducing their bioavailability. Different plant species and even varieties within a species exhibit varying capacities to take up and accumulate heavy metals. Some plants, known as hyperaccumulators, can tolerate and concentrate high levels of heavy metals in their tissues, making them useful for phytoremediation. In contrast, other plants may restrict the uptake or translocation of metals to aerial parts. And environmental conditions such as factors such as temperature, humidity, and the presence of other contaminants can influence the uptake of heavy metals. For example, waterlogging conditions can alter the redox state of metals, affecting their solubility and availability to plants. Furthermore, interactions with other pollutants, such as microplastics, can modify the adsorption and mobility of heavy metals in the soil-plant system. The main soil contaminants that can be treated include heavy metals (such as lead, cadmium and mercury), pesticides, solvents, hydrocarbons and explosives. In water, phytoremediation is applied to remove heavy metals, excess nutrients (such as nitrogen and phosphorus), pesticides and organic compounds. Although less common, phytoremediation can also be used to treat air pollutants, such as volatile organic compounds (VOCs) and certain gases. These can be of anthropogenic or natural origin, the former being more evident due to industrial activities, agricultural practices and low removal efficiency of conventional treatments present in water treatment plants. This study aims to analyze the potential of using phytoremediation as a way of recovering ecosystems and ensuring a healthy environment. While nanomaterials and similar compounds can enhance phytoremediation, high doses may harm plants. Further research is needed to improve phytoremediation's efficiency and feasibility for restoring contaminated soil, water, and air.