Evaluation of the phytoremediation effect and environmental risk in remediation processes under different cultivation systems

• The remediation effect of different cultivation systems is assessed.
• Nitrogen fixers can improve the remediation effectiveness of target plants.
• Environmental risks during phytoremediation processes are assessed.
• A suitable cultivation system for phytoremediation is recommended.

Remediation effectiveness and environmental risks caused by phytoremediation processes under different cultivation systems were assessed at an electronic waste dismantling site. Non-nitrogen-fixing Eucalyptus globulus Labill. and nitrogen-fixing Cicer arietinum (chickpea) were selected for phytoremediation, while Eisenia foetida and Gus gallus were chosen as impacted receptors. Chickpea monoculture was least effective for soil remediation, and soil cadmium under this cultivation system had the most potential threats to the environment. The chickpea monoculture cultivation system needs 132 years to reduce the initial soil cadmium concentration to the quality guidelines of China. The environmental risk index of receptors was greater than in other cultivation systems. The greatest remediation effectiveness occurred in the E. globulus monoculture with earthworm addition. This approach decreases the decontamination time of cadmium in the soil by 80% compared to chickpea monoculture without earthworms. In addition to a favorable phytoremediation effect, this cultivation system was accompanied by a more acceptable environmental risk index value because E. globulus are evergreen trees, unpalatable by livestock, with less litterfall production than chickpeas. E. globulus monoculture with an earthworm addition system is especially suitable for remedying cadmium-polluted soil, as it causes the least environmental risk and reduces the time required to decontaminate the cadmium in the soil by 30% compared to the next most effective system. The decision of which cultivation system is more suitable for an anthropogenically influenced site should be balanced between the capacity of the plant to remove pollution and environmental preservation. Data from the present research have provided a new methodology of efficient phytoremediation with relatively low environmental risks.