Desempenho de sementes e plântulas de espécies arbóreas no rejeito oriundo do rompimento da Barragem de Fundão (Mariana, MG)

Abstract

The worlds biggest environmental accident in the mining sector, both in terms of dumped tailing volume and magnitude of damage, occurred in the Mariana municipality, MG, Brazil. This accident impacted the Rio Doce basin, which occurs in the Atlantic Rainforest Biome, considered one of the worlds hotspots of biodiversity. The aim of this study was to investigate the performance of arboreal species native to the Rio Doces basin under influence of the iron ore tailing dumped. The initial stages of development such as germination and initial growth were studied. The species used were: Albizia polycephala, Bowdichia virgilioides, Mimosa bimucronata, Parapiptadenia rigida, Peltophorum dubium, Cybistax antisyphilitica, Handroanthus heptaphyllus, Handroanthus impetiginosus, Bixa orellana e Dictyoloma vandelianum. Physicochemical analysis were performed on substrates (tailing and control soil) and germination assays, growth measurements and photosynthesis or early growing plants were assessed. The analysis showed that the concentrations of the toxic elements were below the recommended Brazilian Regulation. Although iron and manganese were found in higher concentrations these elements were not totally available to the plants. All species were capable to germinate in the iron ore tailing. For seedling experiment, were used four treatments (tailing control, soil control, fertilized tailing and fertilized soil). The tailing control and the soil control restricted the growth of the plants, and the fertilization treatment was able to correct this effect and promote plant growth. Even though the seedlings still growing less in the tailing treatment compared to the soil treatment. All seedlings, except for A. polycephala, allocated more biomass in the roots when grown in the tailing treatment; when the tailing waste was fertilized, plants allocated more biomass in the shoots, especially in leaves. The tailing did not suppress the soil microbiota, allowing for nodulation. Root length was highly variable among species and could not be related to any physical characteristics of the treatments, but with nutritional ones. All species showed a reduction in total leaf area when grown in the tailing treatment, although fertilization inverted this trend. Less leaf chlorophyll content was observed in plants grown in the tailing treatment, as well as lower maximum PSII quantum efficiency, in most species. Despite the fact that the plants grew more in the fertilized tailing treatment compared to the non-fertilized soil treatment most species showed better performance in the fertilized soil compared to the fertilized tailing. The species P. dubium and H. impetiginosus showed the same performance in both fertilized treatments. These species could be strong candidates to revegetation management of the impacted area. This data highlight that the main component impeding the initial growth of arboreal plant species is nutritional stress, though more in-depth studies are needed to investigate any possible metabolic interference due to the tailing.