This review briefly elucidates the research undertaken and benefits of using aromatic plants for remediation of heavy metal polluted sites. A sustainable approach to mitigate heavy metal contamination of environment is need of the hour. Phytoremediation has emerged to be one of the most preferable choices for combating the metal pollution problem. Aromatic plants can be used for remediation of contaminated sites as they are non-food crops thus minimizing the risk of food chain contamination. Most promising aromatic plants for phytoremediation of heavy metal contaminated sites have been identified from families - Poaceae, Lamiaceae, Asteraceae, and Geraniaceae. They act as potential phytostabilisers, hyper accumulators, bio-monitors, and facultative metallophytes. Being high value economic crops, monetary benefits can be obtained by growing them in tainted areas instead of food crops. It has been observed that heavy metal stress enhances the essential oil percentage of certain aromatic crops. Research conducted on some major aromatic plants in this context has been highlighted in the present review which suggests that aromatic plants hold a great potential for phytoremediation. It has been reported that essential oil from aromatic crops is not contaminated by heavy metals significantly. Thus, aromatic plants are emerging as an ideal candidate for phytoremediation. Highlights • Aromatic plants hold a great potential for phytoremediation of heavy metal contaminated sites. • Being high value economic crops, monetary benefits can be obtained by growing them in contaminated areas instead of food crops. • Research done on some major aromatic plants in this context has been highlighted in the present review.

The pollution of soil by heavy metals and organic pollutants has become a significant issue in recent decades. For the last few years, nanobiotechnology has been used to bio-remediate or reclaim soil contaminated with organic and inorganic pollutants. The removal of pollutants from industrial wastes is a major challenge. The utilization of nanomaterials is gaining popularity, which might be accredited to their enhanced physical, chemical, and mechanical qualities. The development of advanced nanobiotechnological techniques involving the use of nanomaterials for the reclamation of polluted soils has indicated promising results and future hope for sustainable agriculture. By manufacturing environment-friendly nanomaterials, the industrial expenditure on decreasing the load of pollution might be reduced. A potential emerging domain of nanotechnology for eco-friendly production and cost reduction is “green biotechnology”, alongside the utilization of microorganisms in nanoparticle synthesis.

One of the most sustainable approaches for reclamation of heavy metal contaminated sites is by phytoremediation. Cultivation of aromatic plants in such areas has been proposed by a number of researchers as it fulfills the purpose of phytoremediation alongside monetary benefits. A pot experiment was conducted to screen out most potential candidate among different lemongrass varieties which can be recommended to be grown in tannery effluent contaminated sites. Four consecutive harvests of nine varieties of lemongrass were tested. Translocation factor (TF) < 1 for chromium and cadmium whereas >1 for nickel and lead was observed in all varieties. Bioconcentration factor (BF) > 1 was observed for chromium in Suwarna variety. Photosynthetic pigments, growth parameters, antioxidants, oil content, and yield were highly correlated. Neighbor joining (NJ) cluster analysis was performed to predict the relationship between varieties according to their chromium uptake potential. Endurance of varieties towards metal stress was assessed using chlorophyll a fluorescence kinetics. Maximum reduction potential of chromium (70.07%), lead (85.29%), and cadmium (77.36%) was observed in Suwarna variety. Our study indicated that lemongrass acts as potential phytoextractor for nickel and lead. Suwarna variety appeared to be the best candidate among all the varieties tested owing to its higher biomass and metal uptake potential.

A field experiment was conducted to observe the effect of TS amendments on soil enzymes and phytoremediation potential of two economically important cultivars of geranium. Different doses of TS were applied in soil to examine threshold limit of HMs where geranium cultivars can be grown successfully in contaminated sites. Treatment variation significantly affected pH, EC, OC, N, P, K and HM content in soil after 50 days of incubation. After harvest, both cultivars were examined to assess the impact of various treatments on their fresh herb, dry matter, essential oil yield and HM accumulation. C/G ratio close to 1 was observed at 50 tha⁻¹ sludge treatment in both cultivars. Urease and β-glucosidase activities in soil were maximum at 50 tha⁻¹ whereas dehydrogenase and phosphatase activities were maximum at 100 tha⁻¹ in both cultivars. β-glucosidase, acid and alkaline phosphatase, urease and dehydrogenase activities were relatively high after 85 days over 45 days in both cultivars. Maximum metal uptake was found in roots of cv. Bourbon followed by leaves. Geranium was observed to be a good candidate for phytoremediation as it mitigates metal toxicity by root absorption and cv. Bourbon is better candidate for the same.