Hyperaccumulation of lead using Agrostis tenuis

Abstract

In recent years the quest for a circular economy approach and the upcycling of secondary raw materials have been pushed in the global political agenda. Increased interest has been taken by the recovery of materials from sludges, brines, contaminated waters and other media, all included in the larger umbrella identified as “low-grade” mineralisation. Contaminated soils have an interesting role in this process, and various methodologies have been developed using chemical, bacteriological and pyrometallurgical cleaning procedures. However, these procedures all involve the movement of high volume of materials and the disruption of the industrial landscape; furthermore, they often require the use of hazardous solvents and high energy processes. This work proposes to identify less impactful methods aimed at the recovery of metals from mining areas while preserving the landscape and avoiding environmental impacts such as the increase of CO2 for transport and increase hazard through use of solvents, this takes particular importance in areas of industrial heritage status. In particular, this work focuses on the use of Agrostis tenuis, an autochthonous species in mining areas of the UK, as a “mining tool” for the removal of lead. The selection of this plant is due to its visually non-invasive nature, as the plant is already present in these areas, it doesn’t grow above 10/15 cm and it also grows very fast and can be easily harvested with existing agricultural equipment. The experiments and results presented in this paper indicate: (1) Agrostis Tenuis shows the ability to adjust to contamination and increase its accumulation capacity; (2) the metal collected by the plant is fully transposed in the aerial part of the plant in a stable compound form and can consequently be harvested and further processed.