Glomalina e carbono orgânico do solo: atributos eficientes na avaliação da reabilitação de áreas impactadas pela deposição de rejeito de mineração de ferro

Abstract

The breach of the Fundão dam in Mariana, Minas Gerais, Brazil, caused severe environmental impacts, polluting soils and water bodies, and negatively affected local biodiversity and the population. Revegetation, as a means of rehabilitating areas affected by mining residues, has yielded positive results, including the promotion of some soil microorganisms, such as arbuscular mycorrhizal fungi (AMFs), which, in addition to their widespread spatial distribution, are involved in soil aggregation, water and nutrient absorption, and the synthesis of glomalin. Glomalin, also known as Glomalin-Related Soil Protein (GRSP), is a glycoprotein associated with soil carbon retention. In this context, two studies were conducted to clarify the role of GRSP in soil carbon storage (SOC). In the first article, original soils adjacent to technosols were sampled in 2017, 2019, and 2021, along the Gualaxo do Norte and Rio do Carmo rivers. The results showed that SSOC was 58% lower in the technosols compared to the original soil. The contents of EE-GRSP and SOC were positively correlated with basic soil fertility characteristics. There was also clustering of the technosols in 2017 and 2019 and a clear spatial separation from the original soils. In 2021, the conditions (Technosols and Undisturbed) grouped together. These findings suggest that after six years of the revegetation process, there may have been an accumulation of carbon and other forms, such as EE-GRSP, in the technosols. A second article was developed with the aim of investigating the concentrations of EE-GRSP in areas along the Gualaxo do Norte River with different reforestation processes and assessing the contribution of EE-GRSP to carbon and nutrient storage in technosols with different levels of initially deposited waste thickness: a deposition layer exceeding 1 m (Di), an area with a deposition layer less than 0.4 m (Pi), and an original soil area where no waste was deposited (Und), at two different depths (0- 3 and 10-13 cm). Three types of vegetation were also evaluated (Euc - eucalyptus planting area with anthropic reforestation; RF - forest area with anthropic reforestation through herbaceous plant seeding; NF - forest area with natural reforestation). The formed technosol had a more silty texture with less clay than the adjacent original soil. The low EE-GRSP levels in Di and Pi compared to Und can indicate that the rehabilitation time was insufficient for EE-GRSP accumulation in the affected areas. EE-GRSP contributes to SOC, and both are correlated with soil chemical and textural properties, suggesting that an increase in EE-GRSP and SOC content results in soil attribute improvement. The contributions of GRSP to the rehabilitation of areas impacted by iron mining and the detailed analysis of the Mariana case provide valuable insights for the development of more effective environmental rehabilitation strategies aimed at preserving ecosystems and essential ecosystem services for environmental sustainability. Thus, the deposition and accumulation of glomalin in the soil may be a promising strategy for the recovery of areas degraded by iron mining in Mariana, contributing to carbon storage and soil property improvement.