Lead and cadmium contamination in soils: impacts and phytoremediation strategies using ornamental plants, nanoparticles, and organic growth regulators

The contamination of agricultural land with toxic chemicals, such as lead (Pb) and cadmium (Cd), has become a major global concern, negatively affecting the ecosystem, public health, and food safety. This review highlights the sources of Pb and Cd into the environment, current knowledge of the severity of Pb and Cd contamination in soil and vegetables, documents their phytotoxicity and human toxicity, and then assesses effective remediation strategies that include phytoremediation, foliar application of nanoparticles, and organic growth hormones. The current study found that the toxicity of Pb and Cd in soils and vegetables from different countries exceeded the WHO permissible limit. For the phytoremediation process, ornamental plants are selected due to their genetic and phenotypic characteristics, as well as their widespread use. Since the sisal plant (Agave sisalana) is a rapidly growing plant that produces a high quantity of biomass, its products never compete with the food chain. Hence, these characteristics make it a suitable choice for phytoremediation of Pb- and Cd-contaminated soil. Furthermore, the fiber derived from sisal’s leaves has the capacity to sequester these toxic metals straight from the contaminated soil. Nanoremediation involves the foliar application of zinc oxide nanoparticles, and moringa leaf extract has been proposed to reduce the uptake of Pb and Cd in plants. However, more research is needed to understand better how the individual and combined effects of these remediation techniques effectively treat Pb- and Cd-contaminated and co-contaminated soil.