Banca de DEFESA: TAILA MILANE PEREIRA DA SILVA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : TAILA MILANE PEREIRA DA SILVA
DATE: 28/07/2023
TIME: 09:00
LOCAL: Auditório do prédio do PPGCS-UFRPE
TITLE:

Rare earth elements and available phosphorus in soil-saprolite systems developed from gneiss

KEY WORDS:

Geochemistry. Weathering. Phosphate minerals. Monazite. Regolith.

PAGES: 78
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUBÁREA: Ciência do Solo
SPECIALTY: Química do Solo
SUMMARY:

The regolith can be composed of soil, saprolite and/or sediments, covering the entire “mantle of weathering” present on the rocks. Regoliths formed by soil-saprolite systems are frequently observed in the pedosphere, the unified study of soil and saprolite makes it possible to understand the dynamics of several geochemical processes that occur in the soil, including those associated with rare earth elements (REE), whose behavior is influenced by the physical, chemical, mineralogical and biological attributes of the regolith. REEs move throughout regolith and are found in multiple minerals, which are released into the soil-saprolite system during weathering processes. Phosphate minerals, among which monazite is found, stand out among those that carry and release REE. Its dissolution releases, in addition to REE, phosphorus, which is one of the main sources of phosphorus readily available to plants. Although there is scientific evidence of the importance of saprolite for understanding the processes that occur in regolith, studies that approach saprolite as part of the regolith or that deeply investigate its properties and potentials are scarce. Therefore, seeking to understand the dynamics and associations that REE make up in the regolith, the present study aimed to investigate the REE geochemistry and its relationship with physical, mineralogical and chemical attributes of soil-saprolite systems, with emphasis on its relationship with the elevated levels of available P in these gneiss-derived regoliths. For this purpose, three points were selected for sampling soil-saprolite systems under a climatic gradient in the State of Pernambuco, in which deformed and undisturbed samples of soil and saprolite were collected for chemical, physical, mineralogical and micromorphological analyses. The three profiles were classified as Cambissolo Háplico Tb Eutrófico léptico over Gneiss Schistadap (Zona da Mata), Planossolo Nátrico sálico típico over Gneiss Schistadap (Agreste) and Luvissolo Crômico Órtico típico over Gneiss Schistarap (Sertão), with all regoliths presenting shallow soil. Physical analyzes showed limitations regarding porosity in the profiles, with all of them presenting low porosity and sand and silt content greater than clay in most horizons. Routine chemistry showed high levels of all plant nutrients, with emphasis on the sodium content observed in P2, and the available phosphorus found in the saprolite of all profiles. The three profiles showed higher proportions of Si, Al, Fe, Ca, Na, Mg and K, consistent with the characteristic geochemical composition of the source rock (Gneiss), these elements were also identified via scanning electron microscopy. The applied weathering indices showed values that indicate moderate weathering in all profiles, not being sensitive in detecting the effect of the climatic gradient, with the highest values being found in the diagnostic horizons and decreasing in depth. Various associations of REE with phosphate minerals such as possibly monazite and/or xenothym were detected by study with energy dispersive X-ray spectroscopy. A negative correlation was identified between well crystallized iron oxides and light rare earth elements, as well as organic matter with these same elements, a positive correlation was also identified between light rare earth elements and available phosphorus. Based on the analyzes carried out, it is possible to infer that the high level of available phosphorus is correlated with REE, especially the light ones, which are associated with phosphate minerals such as monazite.

COMMITTEE MEMBERS:
Presidente - JEAN CHEYSON BARROS DOS SANTOS
Interna - ***.067.914-** - MARILYA GABRYELLA FERNANDA DE SOUSA - UFRPE
Externo à Instituição - RODRIGO SANTANA MACEDO