Beneficial use of industrial by-products for phytoremediation of an arsenic-rich soil from a gold mining area

Abstract

This study investigated two industrial by-products – red mud (RM) and its mixture with phosphogypsum (RMG), as amendments in an As(5+)-contaminated soil from a gold mining area in Brazil in order to grow three plant species: Brachiaria decumbens, Crotalaria spectabilis, and Stylosanthes cv. Campo Grande. These amendments were applied to reach a soil pH of 6.0. Using RM and RMG increased shoot dry matter (SDM) and root dry matter (RDM) of most plants, with RMG being more effective. Adding RMG increased the SDM of Brachiaria and Crotalaria by 18 and 25% and the RDM by 25 and 12%, respectively. Stylosanthes was sensitive to As toxicity and grew poorly in all treatments. Arsenic concentration in shoots of Brachiaria and Crotalaria decreased by 26% with the use of RMG while As in roots reduced by 11 and 30%, respectively. Also, the activities of the plant oxidative stress enzymes varied following treatments with the by-products. The plants grew in the As-contaminated soil from the gold mining area. Thus, they might be employed for phytoremediation purposes, especially with the use of RMG due to its potential advantage in terms of nutrient supply (Ca2+ and SO42− from phosphogypsum).