Assessment of Alternanthera sessilis and Aster philippinensis as excluders in a small-scale Cu–Au processing site at Kias, Benguet, Philippines

In unregulated mining and processing for Cu and Au, large amounts of heavy metals and metalloids are generated as tails. These wasted by-products could actually pose serious environmental problems. The objective of this study was to assess the potential ability of Alternanthera sessilis and Aster philippinensis thriving abundantly in a small-scale mine processing site at Kias, Benguet, for possible Cu, Pb, Zn, and As uptake. It also aimed to determine the cellular localization of the contaminants within the plant biomass. Alternanthera sessilis and Aster philippinensis exhibited low bioaccumulation factor (BF) and translocation factor (TF) values for Cu, Pb, Zn, and As. The BF and TF values could suggest possible exclusion mechanisms of the plants in avoiding phytotoxicity. SEM-EDX analysis of the Alternanthera sessilis roots indicated higher weight % of Cu, Pb, and As in the epidermis, and Zn in the cortex. On the other hand, Aster philippinensis roots showed high weight % of Zn and As in the epidermis and Cu and Pb in the cortex. The localization of the contaminants in the root epidermal and cortical cells signifies restriction of their mobility to the xylem, preventing migration to the shoot system. The findings of this study suggest that Alternanthera sessilis and Aster philippinensis are considered potential phytostabilizers capable of immobilizing contaminant toxicity in the soil and in the rhizosphere.