Efficient phytoremediation of Cd-contaminated soils by Tagetes patula L.: Greenhouse experiment, field study and meta-analysis

Applying (hyper)accumulators to remediate Cd-contaminated agricultural soils is vital to safeguard food safety and human health. Tagetes patula L. (Marigold) − an omnipresent hyperaccumulator − has been extensively explored with artificially Cd-contaminated soils. Little is known about its feasibility and potential for remediating naturally Cd-contaminated soils and field applications. In this study, the Cd remediation potential of Marigold was assessed with greenhouse and field studies, with the control groups of Solanum nigrum L. (Black nightshade), Amaranthus Hypochondriacus L. (Amaranth) and Pennisetum purpureum K. Schumach. × P. thyphoideum Rich. (King grass). The results of greenhouse experiment showed that Marigold obtained the highest shoot Cd (4.69 mg·kg⁻¹), Cd uptake amount (93.47 μg·pot⁻¹), translocation factor (TF, 2.80) and bioconcentration factor (BCF, 2.67) while remediating naturally Cd-contaminated soils. Moreover, the field study validated its superior phytoremediation potential of Cd – Marigold achieved 150.80 g·ha⁻¹ while treating a Cd-contaminated farmland (1.72 mg·kg⁻¹). Further, the meta-analysis corroborated Marigold’s strength over other control plants in remediating Cd-contaminated soils, holding the mean effect size of BCF and TF of 1.54 and 0.61, respectively. Taken together, Marigold is promising for the remediation of Cd-contaminated fields. Knowledge gleaned from this study provides an effective approach for the practical phytoremediation of Cd-contaminated soils.