Phytoavailability and uptake of arsenic in ryegrass affected by various amendments in soil of an abandoned gold mining site.

ABSTRACT

Abandoned gold mining spoils pose socio-environmental, human, and animal health impacts and threaten sustainability of mineral extraction. Green trials and ecological solutions are required to effectively remediate these contaminated soils and mitigate the associated risks. Here, we carried out a pot experiment using a highly contaminated soil (mean total As = 5104.0 mg/kg) collected from an abandoned mine spoil in Ghana. We aimed to quantify the impacts of compost, iron oxide, and poultry manure on the mobilization, fractionation, and uptake of As by ryegrass (Lolium perenne). The soil amendments were applied at a rate of 5% (w/w) each, separately or in combination. We extracted the mine spoil soil readily-bioavailable As and specific-sorbed As, and determined the As contents in plant and the uptake after harvest. The plant transfer indices for soil-to-root (bioconcentration factor, BCF), soil-to-shoot (bioaccumulation concentration- BAC), and root-to-shoot (translocation factor- TF) were also calculated. Addition of manure increased the mining readily-bioavailable As by 243% and specific-sorbed As by 38%, as compared to the control. Manure addition further aided root As-uptake by 134%, whilst its combination with compost increased uptake by 101%. Lone addition of manure and in combination with compost resulted in BCF above 1, indicating increased As-phytostability. The presence of carbon and iron in the roots of the ryegrass sorbed or precipitated As limited its soil-to-shoot and root-to-shoot transfer. These findings indicate that manure alone and in combination with compost can be used to augment the phytoremediation efficiency of ryegrass in the As-contaminated spoil.