INTEGRATED ENVIRONMENTAL ASSESSMENT OF IRON ORE TAILINGS IN FLOODPLAIN SOILS AND IN PLANT AFTER THE FUNDÃO DAM DISASTER IN BRAZIL.

Previous studies in Doce river basin (Brazil) seem to be contradictory regarding the contamination of soils with potentially harmful elements (PHE). This research aimed to perform an integrated assessment of PHE in the soil-plant-tailing system from the area most impacted by the iron waste, after the Fundão Dam disaster in 2015. Different fractions of PHE (exchangeable, non-exchangeable, reducible, and pseudo total) were determined on deposited iron waste (DIW), soil waste mixture (SWM), and control soil (CS) samples. Total contents of PHE in Poaceae were also determined, and Allium cepa bioassays were performed to determine DIW and CS cyto-/genotoxicity to plants. The Fe and Mn contaminations were the only ones related to the deposition of DIW on floodplains, and other harmful element contents (such as As, Hg, Ni, Cd, Cr, and Pb) were not found above baseline values for soils. In addition, a significant part of the Fe and Mn in DIW is readily available, or subject to acidification and prolonged flood reduction processes. The high available content of Fe favored its excessive accumulation by Brachiaria. The DIW chemical conditions reduced biological functions of A. cepa under a controlled environment. However, more drastic effects, such as genetic damage, were not seen. The post-disaster action of covering DIW with CS resulted in undesirable enrichment of Pb on the floodplain soils. The integrated results allow the conclusion that the iron waste is not a time-bomb for PHE contamination of soils between Fundão and Risoleta Neves Hydroelectric Dam (distant approximately 100 km of Fundão).