A spectroscopic study to assess heavy metals absorption by a combined hemp/spirulina system from contaminated soil

The efficiency of hemp (Cannabis sativa L.) in remediating sites contaminated with heavy metals has received great attention in recent years. The main advantage of this technology relies on its inherent sustainability with a potential re-utilization of the significant amount of produced biomass which acts as a valuable flow resource. In this study, a combined system consisting of Cannabis sativa L. (hemp) and the blue-green alga Arthrospira platensis (spirulina) was tested to clean up soils contaminated with cadmium, chromium, copper, nickel, lead, and zinc. The application of non-targeted NMR methods combined with ICP-AES quantification provided an efficient strategy for detecting residual heavy metals within plant tissues and soil. Importantly, non-targeted metabolomic analysis helped to reveal the relationships between metabolites distribution in hemp tissues and the sequestered metals. It was demonstrated that hemp accumulates copper, chromium, nickel, and zinc preferentially in the leaves, while lead is distributed mainly in the stems of the plant. Moreover, it was found that, at higher concentrations, spirulina acts as a growth promoter, contributing to an increase in the final generated biomass. Results reported in this work indicate that the hemp/spirulina system represents a suitable tool for remediation of metal contaminated soils by modulating biomass production and metals uptake.