A review on sources identification of heavy metals in soil and remediation measures by phytoremediation-induced methods

The continuous release of toxic heavy metals (HMs) in the soil has made the soil vulnerable to the environment. Metals come into the soil through natural processes (geogenic and air-borne) and human-induced actions like agricultural, industrial and mining. Heavy metals are not suitable for the soil quality and agriculture-friendly microbes found in the soil. The quality of crop products will also be affected by these metals as metals adversely affect plant physiology. Furthermore, HMs enter the human body through the food web and build up in human tissues. Severe diseases have been reported due to metal toxicities, including carcinogenicity, neural disorders, brain damage, etc. Physicochemical methods, microbes and plants are commonly applied for HMs remediation from the soil. Immobilization, stabilization, verification and soil washing are popular techniques for soil remediation. The application of different types of nanomaterials for soil remediation is an advance and effective method. However, nowadays, phytoremediation has attracted increasing interest in the elimination of HMs present in the soil because of its on-site application benefits and eco-friendly nature. Phytoremediation includes plant extraction, plant stabilization, plant filtration, plant volatilization, photodegradation and plant degradation. In the current review, sources of HMs, their ecological impacts and recent advances in phytoremediation approaches for soil treatment have been critically described. Further, different types of hyperaccumulator plants are also compiled in this paper. Mechanisms and factors affecting phytoremediation are the new dimensions of the present study. Limitations, challenges and future prospective of phytoremediation are also part of this study.