Banca de DEFESA: GUSTAVO VIEIRA NUNES

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : GUSTAVO VIEIRA NUNES
DATE: 27/02/2026
TIME: 14:00
LOCAL: UFRPE/Sede, Departamento de Agronomia, Área de Solos
TITLE:

Carbon stocks and geochemistry of mining tailings-derived Technosols after four decades

KEY WORDS:

Anthropogenic soils; trace elements; inorganic carbon; Technosols; Brazilian semi-arid region; spatial variability.

PAGES: 64
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUBÁREA: Ciência do Solo
SPECIALTY: Química do Solo
SUMMARY:

Scheelite mining in the Brazilian semi-arid region generates large volumes of tailings rich in carbonates and trace elements, constituting a significant environmental liability. The construction of Technosols from these materials represents an alternative for restoring degraded areas; however, knowledge gaps remain regarding their geochemical stability and carbon storage potential. This study evaluated, at Mina Brejuí (Currais Novos, Rio Grande do Norte), the largest scheelite mine in South America, operating since the 1940s, the stocks of organic carbon (OC), inorganic carbon (IC), and total carbon (TC), as well as the spatial variability of physical and chemical attributes of Technosols after 40 years of development. The tailings-forming rocks exhibited strong mineralogical heterogeneity (marble, tactite, and gneiss), controlling soil alkalinity and geochemical composition. The Technosols maintained strongly alkaline pH (8.0–8.9) and predominantly sandy texture. Over four decades, OC increased from 0.02% to 0.63%, with a rise in surface stock from 0.89 to 25.80 Mg ha⁻¹ (≈30-fold). IC remained dominant and nearly stable (148.48 to 146.10 Mg ha⁻¹), reflecting carbonate inheritance. As a result, total carbon stock increased from 149.37 to 171.90 Mg ha⁻¹. Copper (0.1–4.5 mg kg⁻¹), Ni (0.05–0.35 mg kg⁻¹), and Co (0.16–0.50 mg kg⁻¹) showed low available concentrations, consistent with control exerted by high pH and carbonates. Geostatistical analysis revealed pronounced spatial heterogeneity, with distinct zones of nutrient and potentially toxic element accumulation. Despite geochemical stability, P and Mg remained agronomic constraints under the carbonate-rich environment. Overall, Technosols derived from scheelite tailings in the semi-arid region combine high total carbon stocks, dominance of stable inorganic carbon, and low metal mobility, highlighting their potential for environmental restoration and ecosystem service provision in post-mining landscapes.

COMMITTEE MEMBERS:
Presidente - YGOR JACQUES AGRA BEZERRA DA SILVA
Interno - VALDOMIRO SEVERINO DE SOUZA JUNIOR
Externo à Instituição - AIRON JOSE DA SILVA - UFS