Efeito do rejeito de mineração de Mariana-MG sobre espécies arbóreas de diferentes estados sucessionais ecológicos e do vermicomposto como atenuante

Abstract

The accident involving the mining company Samarco, which released 50 million m³ of tailings with the collapse of the Fundão dam, on November 5, 2015, impacted on fauna, flora and society. Institutions are still monitoring the tailings’ properties, its flow and consequences in the area. However, much remains to be done to reduce environmental and socioeconomic impacts in the region of the Rio Doce watershed. Thus, the use of tree species alongside organic fertilizers, has great potential of revitalizing the locality, and decrease the concentration or immobilize the heavy metals released with the tailings, in addition to improving the structure of the resulting soil. Therefore, this work aimed to evaluate the performance of native plant species of Cerrado or Atlantic Forest and of different levels of ecological succession (Schinus terebinthifolius, Cedrela fissilis and Cariniana estrellensis) under the tailings of the Fundão dam, besides if the addition of vermicompost would improve its performance. The seedlings were transplanted in 2 L pots containing substrates for the treatments: soil, mining tailings and mining tailings with the addition of earthworm humus (2% w/w), conducted for 80 days, with data collection in 20-day intervals (C1: start of the experiment, C2: 20 days, C3: 40 days, C4: 60 days, C5: 80 days). During this period, biometric and morphological parameters, gas exchange and chlorophyll a fluorescence were evaluated. At the end of 80 days, the plants were collected, divided into leaves, stalk, and root. Part of the leaf material was tested for lipid peroxidation and the roots for morphology. Then, the plant material was dried in an oven with forced air circulation at 60ºC until constant weight. Mining tailings tend to worsen the performance of plant species that have different degrees of sensitivity according to their level of ecological succession. In this manner, as expected, each species presented a behavior regarding development under the tailings. Pioneer species such as S. terebinthifolius are important alternatives for revegetation since they are more robust and tolerant. However, secondary species, mainly C. fissilis, also show great potential; however, climax species, such as C. estrellensis, are the most sensitive and, in this case, do not show potential. The use of vermicompost to attenuate the effect of mining tailings was shown to have great potential, favoring S. terebinthifolius and, to a lesser extent, C. fissilis, but more studies should be carried out to assess its potential.