Banca de DEFESA: RAYANNA JACQUES AGRA BEZERRA DA SILVA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : RAYANNA JACQUES AGRA BEZERRA DA SILVA
DATE: 07/03/2023
TIME: 08:00
LOCAL: Auditório do Prédio Prof. Mateus Rosas Ribeiro
TITLE:

Early pedogenesis of technosols originating from scheelite mining tailings in the Brazilian semi-arid region

KEY WORDS:

Anthropogenic soils. Soil micromorphology. Soil mineralogy. Taxonomic classification of soils.

PAGES: 111
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUBÁREA: Ciência do Solo
SUMMARY:

Studying technosols is crucial to understanding their potential for waste management, recovering degraded areas, agricultural production, carbon sequestration, and sustainable use of natural resources. The largest scheelite mine in South America is located in the tropical semiarid region of Northeast Brazil. However, the tailings from this mining activity have been accumulating in the open since the 1940s, causing several environmental problems. Although technosols derived from mining tailings are widely studied in the world, information on the pedogenesis of these soils is scarce in Brazil, especially in the Brazilian semi-arid tropical environment. In this scenario, the objectives of this study were: to understand the pedogenesis of technosols originated from scheelite mining over a chronossequence (0, 2, 5, 10, and 40 years) in the Brazilian tropical semiarid region; ii) to understand the macro and micromorphological evolution of these technosols; iii) investigate changes in their physical, chemical and mineralogical properties of the evaluated technosols; iv) identify the main pedogenetic processes in the studied technosols; v) classify the technosols taxonomically, according to the WRB, with a proposition to the SiBCS. The profiles of technosols constructed from scheelite mining tailings showed macromorphological evolution over the 40-year chronossequence, with increased thickness of surface horizons, clear development of colors and structures, and a more advanced stage of homogenization of their horizons. These results demonstrate the rapid pedogenesis of technosols derived from scheelite mining in the Brazilian semi-arid tropical environment. According to the WRB, the 2-, 5-, and 10-year-old profiles of technosols were classified as Spolic Technosol (Loamic, Alcalic, Calcic, Humic), while the 40- year-old profile was described as Spolic Technosol (Loamic, Alcalic, Calcic, Hyperhumic). Based on micromorphological investigations, substantial developments of specific pedogenetic processes were observed, such as bioturbation, melanization, and pedalization. Over the four decades, there was a progressive increase in the melanization process, accompanied by a high accumulation of organic carbon. Regarding the 0-30 cm depth range, the technosol profile derived from scheelite mining, with 40 years old, showed a carbon stock (131.38 Mg ha-1) superior to the main classes of natural soils in the Brazilian semi-arid region and stored three times more carbon than the average of Brazilian soils. Therefore, the studied technosols have great potential to sequester carbon in the Brazilian tropical semi-arid region and may play an important role in reducing atmospheric CO2 levels and mitigating climate change. he high natural reserve of nutrients in the primary minerals of the fine sand, coarse sand, and clay fractions, such as biotite, feldspars, actinolite, and talc, demonstrates the high potential of these technosols in providing essential elements to plants in the medium term and overcoming the main limitations nutrients for the development of the agricultural activity. Furthermore, the great diversity of minerals (biotite, plagioclase, apatite, microcline, actinolite, epidote, vesuvianite, powellite, carbonate minerals, titanite, and opaque minerals) in the waste-forming materials (tactite, marble, and gneiss) used to build technosols also can be important sources of slow release of nutrients, capable of maintaining the fertility of technosols in the long term. The presence of kaolinite and smectite in all technosols of the chronossequence, including the initial tailings, indicates that the profiles began their development enriched in these phyllosilicates. The formation of goethite was associated with reduced iron activity in the solution, with increased moisture and high concentrations of organic carbon in technosol horizons. Linear discriminant analysis showed a high potential for discriminating technosols originating from scheelite mining tailings, corroborating the rapid pedogenesis of the profiles over the 40-year chronossequence. In light of the scarcity of information on the construction of technosols derived from mining activity in a tropical semi-arid environment, this work provides promising results not only for the scientific community, but also for policy makers on the importance of efficient management of mining tailings. to recover degraded areas, agricultural production and manage waste in semi-arid environments.

COMMITTEE MEMBERS:
Externa à Instituição - MARILYA GABRYELLA FERNANDA DE SOUSA
Externo à Instituição - TIAGO OSORIO FERREIRA - USP
Presidente - VALDOMIRO SEVERINO DE SOUZA JUNIOR